阅读说明：本技术 光电传感器及其驱动方法、显示模组和显示装置 (Photoelectric sensor, driving method thereof, display module and display device ) 是由 姚绮君 于 2021-09-16 设计创作，主要内容包括：本发明提供一种光电传感器及其驱动方法、显示模组和显示装置。光电传感器包括光感电路；光感电路包括光电二极管、复位晶体管、电压转换晶体管、读取控制晶体管、读取晶体管,至少读取晶体管为p型晶体管；复位晶体管、光电二极管的第一极、以及电压转换晶体管的控制极均与第一节点电连接；电压转换晶体管、读取控制晶体管、以及读取晶体管的控制极均与第二节点电连接；复位晶体管用于在其控制极的控制下开启以对第一节点进行复位；电压转换晶体管和读取控制晶体管用于分别在其各自控制极的控制下开启、以对第二节点的电压进行控制；读取晶体管用于在其控制极的控制下输出检测信号。本发明实施例能够实现光感电路具有较宽的动态范围。(The invention provides a photoelectric sensor, a driving method of the photoelectric sensor, a display module and a display device. The photoelectric sensor comprises a light sensing circuit; the light sensing circuit comprises a photodiode, a reset transistor, a voltage conversion transistor, a reading control transistor and a reading transistor, wherein at least the reading transistor is a p-type transistor; the reset transistor, the first electrode of the photodiode and the control electrode of the voltage conversion transistor are all electrically connected with the first node; the control electrodes of the voltage conversion transistor, the reading control transistor and the reading transistor are electrically connected with the second node; the reset transistor is used for being turned on under the control of a control electrode of the reset transistor so as to reset the first node; the voltage conversion transistor and the reading control transistor are respectively turned on under the control of respective control electrodes thereof to control the voltage of the second node; the read transistor is used for outputting a detection signal under the control of a control electrode of the read transistor. The embodiment of the invention can realize that the light sensing circuit has a wider dynamic range.)

1. A photoelectric sensor is characterized by comprising a light sensing circuit; the light sensing circuit comprises a photodiode, a reset transistor, a voltage conversion transistor, a reading control transistor, a reading transistor, a first node and a second node, wherein at least the reading transistor is a p-type transistor; wherein the content of the first and second substances,

the reset transistor, the first electrode of the photodiode, and the control electrode of the voltage conversion transistor are all electrically connected with the first node; the voltage conversion transistor, the read control transistor and the control electrode of the read transistor are all electrically connected with the second node;

the reset transistor is used for being turned on under the control of a control electrode of the reset transistor so as to reset the first node;

the voltage conversion transistor and the reading control transistor are respectively turned on under the control of respective control electrodes thereof to control the voltage of the second node;

the reading transistor is used for outputting a detection signal under the control of a control electrode of the reading transistor.

2. The photosensor according to claim 1,

a control electrode of the reset transistor receives a reset control signal, a first electrode of the reset transistor receives a reset signal, and a second electrode of the reset transistor is electrically connected with the first node;

a first pole of the voltage conversion transistor receives a first voltage signal, and a second pole of the voltage conversion transistor is electrically connected with the second node;

a control electrode of the reading control transistor receives a reading control signal, a first electrode of the reading control transistor receives a second voltage signal, and a second electrode of the reading control transistor is electrically connected with the second node;

the first pole of the reading transistor receives the second voltage signal, and the reading transistor is started to output the detection signal under the control of the voltage of the control pole of the reading transistor.

3. The photosensor according to claim 2,

the control electrode of the reset transistor is electrically connected with a reset control line, and the reset control line is used for providing the reset control signal;

a first pole of the reset transistor is electrically connected with a reset signal line, and the reset signal line is used for providing the reset signal;

a first pole of the voltage conversion transistor is electrically connected with a first voltage line, and the first voltage line is used for providing the first voltage signal;

the control electrode of the reading control transistor is electrically connected with a reading control line, and the reading control line is used for providing the reading control signal;

a first pole of the read control transistor and a first pole of the read transistor are both electrically connected to a second voltage line for providing the second voltage signal;

the second pole of the reading transistor is electrically connected with a reading data line, and the reading data line is used for collecting the detection signal.

4. The photosensor according to claim 3,

the reset control line, the read control line, and the second voltage line extend in a first direction, the read control line is between the reset control line and the second voltage line; the first voltage line, the reset signal line, and the read data line extend in a second direction; the first direction and the second direction intersect;

the control electrode of the voltage conversion transistor and the control electrode of the reading transistor are positioned on a first virtual straight line; the reset transistor and the reading control transistor are respectively positioned at two sides of the first virtual straight line;

in the second direction, the reset transistor, the voltage conversion transistor, the read control transistor, and the read transistor are all located between the reset control line and the second voltage line; in the first direction, the reset transistor, the voltage conversion transistor, the read control transistor, and the read transistor are all located between the first voltage line and the read data line.

5. The photosensor according to claim 4,

the photoelectric sensor comprises a substrate, a semiconductor layer, a first metal layer and a second metal layer, wherein the semiconductor layer, the first metal layer and the second metal layer are sequentially far away from the substrate;

the active layer of each transistor in the photosensitive circuit is positioned on the semiconductor layer; the control electrode of each transistor in the light sensing circuit, the reset control line, the reading control line and the second voltage line are positioned in the first metal layer; the first voltage line, the reset signal line, and the read data line are located at the second metal layer.

6. The photosensor according to claim 2,

the control electrode of the reset transistor is electrically connected with a reset control line, and the reset control line is used for providing the reset control signal;

the first pole of the reset transistor and the first pole of the voltage conversion transistor are electrically connected with a first voltage signal line; the first voltage signal line is used for providing the reset signal to the first pole of the reset transistor in a first period and is also used for providing the first voltage signal to the first pole of the voltage conversion transistor in a second period, and the voltage value of the reset signal is different from that of the first voltage signal;

the control electrode of the reading control transistor is electrically connected with a reading control line, and the reading control line is used for providing the reading control signal;

the first pole of the reading control transistor and the first pole of the reading transistor are both electrically connected with the second voltage line, and the second voltage line is used for providing the second voltage signal;

the second pole of the reading transistor is electrically connected with the reading data line, and the reading data line is used for collecting the detection signal.

7. The photosensor according to claim 6,

the reset control line and the read control line extend along a first direction; the first voltage line, the second voltage line, and the read data line extend in a second direction, and the read data line is between the first voltage line and the second voltage line; the first direction and the second direction intersect;

the control electrode of the voltage conversion transistor and the control electrode of the reading transistor are positioned on a first virtual straight line; the reset transistor and the reading control transistor are respectively positioned at two sides of the first virtual straight line;

in the second direction, the reset transistor, the voltage conversion transistor, the read control transistor, and the read transistor are all located between the reset control line and the read control line; in the first direction, the reset transistor, the voltage conversion transistor, the read control transistor, and the read transistor are all located between the first voltage line and the second voltage line.

8. The photosensor according to claim 7,

the photoelectric sensor comprises a substrate, a semiconductor layer, a first metal layer and a second metal layer, wherein the semiconductor layer, the first metal layer and the second metal layer are sequentially far away from the substrate;

the active layer of each transistor in the photosensitive circuit is positioned on the semiconductor layer; the control electrode of each transistor in the light sensing circuit, the reset control line and the reading control line are positioned on the first metal layer; the first voltage line, the second voltage line, and the read data line are located at the second metal layer.

9. The photosensor according to claim 2,

the read control signal and the second voltage signal are the same voltage signal, and the first electrode of the read control transistor is electrically connected with the control electrode of the read control transistor.

10. The photosensor according to claim 9,

the control electrode of the reset transistor is electrically connected with a reset control line, and the reset control line is used for providing the reset control signal;

a first pole of the reset transistor is electrically connected with a reset signal line, and the reset signal line is used for providing the reset signal;

a first pole of the voltage conversion transistor is electrically connected with a first voltage line, and the first voltage line is used for providing the first voltage signal;

the control electrode of the reading control transistor, the first electrode of the reading control transistor and the first electrode of the reading transistor are all electrically connected with a reading control line, and the reading control line is used for providing the reading control signal and the second voltage signal;

the second pole of the reading transistor is electrically connected with a reading data line, and the reading data line is used for collecting the detection signal.

11. The photosensor according to claim 10,

the reset control line and the read control line extend in a first direction, the first voltage line, the read data line, and the reset signal line extend in a second direction, and the first direction and the second direction cross; wherein the content of the first and second substances,

the control electrode of the voltage conversion transistor and the control electrode of the reading transistor are positioned on a first virtual straight line; the reset transistor and the reading control transistor are respectively positioned at two sides of the first virtual straight line;

in the second direction, the reset transistor, the voltage conversion transistor, the read control transistor, and the read transistor are all located between the reset control line and the read control line;

in the first direction, the reset transistor, the voltage conversion transistor, the read control transistor, and the read transistor are all located between the first voltage line and the read data line.

12. The photosensor of claim 11,

the photoelectric sensor comprises a substrate, a semiconductor layer, a first metal layer and a second metal layer, wherein the semiconductor layer, the first metal layer and the second metal layer are sequentially far away from the substrate;

the active layer of each transistor in the photosensitive circuit is positioned on the semiconductor layer; the control electrode of each transistor in the light sensing circuit, the reset control line and the reading control line are positioned on the first metal layer; the first voltage line, the reset signal line, and the read data line are located at the second metal layer.

13. A driving method of a photoelectric sensor is characterized in that the photoelectric sensor comprises a light sensing circuit; the light sensing circuit includes: the photoelectric conversion device comprises a photodiode, a reset transistor, a voltage conversion transistor, a reading control transistor, a reading transistor, a first node and a second node, wherein at least the reading transistor is a p-type transistor;

the reset transistor, the first electrode of the photodiode, and the control electrode of the voltage conversion transistor are all electrically connected with the first node;

the voltage conversion transistor, the read control transistor and the control electrode of the read transistor are all electrically connected with the second node;

the driving method includes: controlling the working cycle of the light sensing circuit to comprise a reading stage; wherein, in the read phase:

the first node provides voltage to the control electrode of the voltage conversion transistor to control the voltage conversion transistor to be started, and simultaneously provides voltage to the control electrode of the reading control transistor to control the reading control transistor to be started, and the voltage of the second node is controlled by the voltage conversion transistor and the reading control transistor together;

the read transistor outputs a detection signal under the control of the second node.

14. The driving method according to claim 13,

controlling a voltage of the second node by the voltage conversion transistor and the read control transistor in common, including: controlling the voltage of the second node to change along with the voltage change of the first node;

the read transistor outputting a detection signal under the control of the second node, comprising: the reading transistor is turned on, so that the detection signal output by the reading transistor is changed along with the voltage change of the second node.

15. The driving method according to claim 14,

controlling the voltage of the second node to vary with the voltage of the first node, comprising: controlling the voltage of the second node to increase as the voltage of the first node decreases.

16. The driving method according to claim 14,

the reading transistor is turned on under the control of the second node, so that the detection signal output by the reading transistor is changed along with the voltage change of the second node, and the method comprises the following steps: the detection signal output by the read transistor decreases as the voltage of the second node increases.

17. The driving method according to claim 14,

the first node providing a voltage to the control electrode of the voltage conversion transistor to control the voltage conversion transistor to turn on while providing a voltage to the control electrode of the read control transistor to control the read control transistor to turn on, comprising:

the first node provides voltage to a control electrode of the voltage conversion transistor to control the voltage conversion transistor to work in a linear region, wherein the on-resistance of the voltage conversion transistor is changed along with the voltage change of the first node;

and providing a constant voltage signal to a control electrode of the reading control transistor to control the reading control transistor to work in a linear region.

18. The driving method according to claim 17, wherein the second pole of the voltage conversion transistor and the second pole of the read control transistor are both electrically connected to the second node;

the first node provides a voltage to the control electrode of the voltage conversion transistor to control the voltage conversion transistor to operate in a linear region, and the method comprises the following steps: the first node provides a voltage to the control electrode of the voltage conversion transistor, and provides a first voltage signal to the first electrode of the voltage conversion transistor so as to control the voltage conversion transistor to work in a linear region;

providing a constant voltage signal to a control electrode of the read control transistor to control the read control transistor to operate in a linear region, comprising: and providing a reading control signal to the control electrode of the reading control transistor, and providing a second voltage signal to the first electrode of the reading control transistor so as to control the reading control transistor to work in a linear region.

19. The driving method according to claim 18,

controlling the voltage of the second node to vary with the voltage of the first node, further comprising: and controlling the voltage magnitude of the second node to be between the voltage value of the first voltage signal and the voltage value of the second voltage signal.

20. The driving method according to claim 18,

the voltage value of the first voltage signal is greater than the voltage value of the second voltage signal.

21. The driving method according to claim 14,

the reading transistor is turned on under the control of the second node, so that the detection signal output by the reading transistor is changed along with the voltage change of the second node, and the method comprises the following steps: and controlling the reading transistor to work in a saturation region under the control of the second node.

22. The driving method according to claim 13,

the driving method further includes: controlling the working cycle of the light sensing circuit to comprise a reset stage;

in the reset phase:

and providing a reset control signal for the control electrode of the reset transistor, providing a reset signal for the first electrode of the reset transistor, and controlling the reset transistor to be started and then reset the first node through the reset signal.

23. The driving method according to claim 22,

a second pole of the photodiode receives a common voltage signal,

the voltage value of the common voltage signal is smaller than that of the reset signal.

24. A display module comprising the photoelectric sensor of any one of claims 1 to 12.

25. A display device comprising the display module of claim 24.

Technical Field

The invention relates to the technical field of photoelectric sensors, in particular to a photoelectric sensor, a driving method of the photoelectric sensor, a display panel and a display device.

Background

The fingerprint identification is mainly used for identifying the identity of an operator or an operated person according to the information of lines, detail characteristics and the like of human fingerprints. Thanks to modern electronic integrated manufacturing technology and fast and reliable algorithm research, fingerprint identification has gone into our daily life, becoming the most deep research, the most widely used, and the most mature technology in the current biological detection science.

The fingerprint identification technology applied to the display field comprises pressure-sensitive fingerprint identification, ultrasonic fingerprint identification, light-sensitive fingerprint identification and the like. With the proposal of the comprehensive screen concept, the under-screen fingerprint identification technology becomes a pursuing hotspot for people, and the development of the light sensation fingerprint identification technology is promoted.

Disclosure of Invention

The embodiment of the invention provides a photoelectric sensor, a driving method thereof, a display panel and a display device, which are used for ensuring that a light sensing circuit still has a wider dynamic range when a reading transistor is a p-type transistor and improving the fingerprint identification accuracy.

In a first aspect, an embodiment of the present invention provides an optical sensor, including a light sensing circuit; the light sensing circuit comprises a photodiode, a reset transistor, a voltage conversion transistor, a reading control transistor, a reading transistor, a first node and a second node, wherein at least the reading transistor is a p-type transistor; wherein the content of the first and second substances,

the reset transistor, the first electrode of the photodiode and the control electrode of the voltage conversion transistor are all electrically connected with the first node; the control electrodes of the voltage conversion transistor, the reading control transistor and the reading transistor are electrically connected with the second node;

the reset transistor is used for being turned on under the control of a control electrode of the reset transistor so as to reset the first node;

the voltage conversion transistor and the reading control transistor are respectively turned on under the control of respective control electrodes thereof to control the voltage of the second node;

the read transistor is used for outputting a detection signal under the control of a control electrode of the read transistor.

In a second aspect, an embodiment of the present invention provides a driving method for driving a photosensor, where the driving method for driving a photosensor includes: controlling the working cycle of the light sensing circuit to comprise a reading stage; wherein, in the reading phase:

the first node supplies voltage to the control electrode of the voltage conversion transistor to control the voltage conversion transistor to be started, simultaneously supplies voltage to the control electrode of the reading control transistor to control the reading control transistor to be started, and controls the voltage of the second node through the voltage conversion transistor and the reading control transistor together;

the read transistor outputs a detection signal under the control of the second node.

In a third aspect, an embodiment of the present invention provides a display module including the photoelectric sensor provided in any embodiment of the present invention.

In a fourth aspect, an embodiment of the present invention provides a display device, including the display module provided in any embodiment of the present invention.

The photoelectric sensor, the driving method thereof, the display panel and the display device provided by the embodiment of the invention have the following beneficial effects: the light sensing circuit is provided with a voltage conversion transistor, a control electrode of the voltage conversion transistor is connected with a first node, the starting state of the voltage conversion transistor is directly influenced by the voltage of the first node, a second electrode of the voltage conversion transistor is electrically connected with a second node, and the voltage of the second node is influenced by the voltage of the first node. In addition, the reading control transistor is electrically connected with the second node, and the voltage of the second node can be controlled together when the control transistor and the voltage conversion transistor are simultaneously started, so that the voltage for controlling the working state of the reading transistor can be converted along with the change rule of the voltage change of the first node. The potential of the first node is lower as the light receiving time of the photodiode is longer, and the potential of the second node is higher, the voltage supplied to the control electrode of the reading transistor is higher, so that the working characteristic of the p-type transistor can be adapted, the p-type reading transistor can be ensured to continuously work in a saturation region, and the light sensing circuit is ensured to have a wider dynamic range.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without inventive labor.

FIG. 1 is a diagram of a light sensing circuit in the prior art;

FIG. 2 is a schematic diagram of a light sensing circuit according to an embodiment of the present invention;

FIG. 3 is a timing diagram illustrating an operation of a light sensing circuit according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a characteristic curve of a p-type transistor;

FIG. 5 is a schematic diagram of a layout design of a light sensing circuit according to an embodiment of the present invention;

FIG. 6 is a schematic cross-sectional view taken along line E-E' of FIG. 5;

FIG. 7 is a schematic diagram of another light sensing circuit according to an embodiment of the present invention;

FIG. 8 is a timing diagram illustrating an operation of the photo sensing circuit of the embodiment of FIG. 7;

FIG. 9 is a schematic diagram of a layout design of a light sensing circuit according to an embodiment of the present invention;

FIG. 10 is a schematic cross-sectional view taken along line F-F' of FIG. 9;

FIG. 11 is a schematic diagram of another light sensing circuit according to an embodiment of the present invention;

FIG. 12 is a timing diagram illustrating an operation of the photo sensing circuit in the embodiment of FIG. 11;

fig. 13 is a schematic diagram of layout design of a light sensing circuit according to an embodiment of the present invention;

FIG. 14 is a schematic cross-sectional view taken along line G-G' of FIG. 13;

fig. 15 is a schematic view of a display module according to an embodiment of the invention;

FIG. 16 is a schematic view of another display module according to an embodiment of the present invention;

fig. 17 is a schematic view of a display device according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Fig. 1 is a schematic diagram of a photo sensing circuit in the prior art, as shown in fig. 1, the photo sensing circuit includes a reset transistor T1, a read transistor T2, a read control transistor T3, and a photodiode T4, wherein each transistor is an n-type transistor. Also illustrated in fig. 1 are a reset signal terminal D1, a reset control terminal D2, a read control terminal D3, a common voltage terminal D4, a first voltage terminal D5, and a signal output terminal D6. After the photodiode T4 is illuminated, a leakage current from the node C to the common voltage terminal D4 is generated, the potential of the node C drops, the voltage of the output terminal of the read transistor T2 changes along with the voltage change of the node C, and a detection signal is output to the signal output terminal D6 by controlling the read control transistor T3 to be turned on. In order to make the voltage at the output terminal of the read transistor T2 follow the voltage variation at the node C, i.e. the voltage at the output terminal of the read transistor T2 has a correlation with the voltage at the control electrode thereof, it is required to ensure that the read transistor T2 operates in the on-state saturation region after being turned on. The read transistor T2 is an n-type transistor, when the condition is satisfied: and Vgs is greater than Vth, and Vgs-Vds < Vth, wherein Vgs is the voltage difference between a control electrode and a source electrode of the transistor, Vds is the voltage difference between a source electrode and a drain electrode of the transistor, Vth is the threshold voltage of the transistor, and Vth is a positive value.

Compared with the p-type transistor, the n-type transistor requires at least one additional LDD (Lightly Doped Drain) process during the fabrication, i.e., the fabrication process of the n-type transistor is relatively complicated. If all the transistors of the photosensitive circuit in fig. 1 are made into p-type transistors, the process can be relatively simplified, and the cost can be reduced. However, the inventor analyzes that the potential of the N electrode of the photodiode decreases after the photodiode senses light in the light sensing circuit, the reading transistor connected with the N electrode of the photodiode is an N-type transistor, and the normal working range can be ensured. The dynamic range is understood to be the range between the maximum and minimum signal values of the detection signal to be detected.

In the circuit illustrated in fig. 1, the photodiode T4 receives different illumination intensities, generates different leakage currents, and the potential of the node C is lowered due to the existence of leakage current after illumination, wherein the longer the illumination time is, the lower the voltage of the node C is, the lower the control voltage of the reading transistor T2 is, that is, the smaller the transistor control voltage Vg is, and the smaller Vgs is. If the read transistor T2 is a p-type transistor, the conditions to be satisfied when it operates in the on-state saturation region are: vgs < Vth, and Vgs-Vds > Vth, which is negative. When the Vg voltage is too low, Vgs is smaller, then Vgs-Vds is also smaller, and the operating condition that Vgs-Vds > Vth cannot be continuously satisfied, at this time, the reading transistor T2 cannot operate in an on-state saturation region, the voltage at the output terminal of the reading transistor T2 cannot change along with the gate voltage thereof, and finally the detection signal output by the signal output terminal D6 of the photo sensing circuit cannot reflect the voltage change at the node C, which affects the operation of the photo sensing circuit. That is to say, after each transistor in the circuit is set as a p-type transistor, the dynamic range of the light sensing circuit is narrowed, and the fingerprint identification accuracy is affected when the light sensing circuit is applied to fingerprint identification detection.

Based on the problems in the prior art, embodiments of the present invention provide a photoelectric sensor, in which a structure of a light sensing circuit is designed, so that when a reading transistor is a p-type transistor, the light sensing circuit can still have a wider dynamic range, and when the photoelectric sensor is applied to fingerprint identification detection, the fingerprint identification accuracy can be ensured.

The embodiment of the invention provides a photoelectric sensor which can be used for optical fingerprint identification and detection. The photoelectric sensor comprises a plurality of light sensing circuits. Fig. 2 is a schematic diagram of a light sensing circuit according to an embodiment of the invention, as shown in fig. 2, the light sensing circuit includes a photodiode PD, a reset transistor M1, a voltage conversion transistor M2, a read control transistor M3, a read transistor M4, a first node a and a second node B, and at least the read transistor M4 is a p-type transistor. In one embodiment, the photodiode PD is a PIN photodiode. Wherein the content of the first and second substances,

the reset transistor M1, the first pole of the photodiode PD, and the control pole of the voltage conversion transistor M2 are all electrically connected to the first node a; the control electrodes of the voltage conversion transistor M2, the read control transistor M3, and the read transistor M4 are all electrically connected to the second node B;

the reset transistor M1 is used for turning on under the control of a control electrode thereof to reset the first node a;

the voltage conversion transistor M2 and the read control transistor M3 are respectively turned on under the control of their respective control electrodes to control the voltage of the second node B;

the read transistor M4 is used to output a detection signal under the control of its control electrode. The control electrode of the read transistor M4 is electrically connected to the second node B, that is, the read transistor M4 is capable of outputting a detection signal under the voltage control of the second node B.

In the prior art as shown in fig. 1, the gate of the read transistor T2 is directly connected to the node C, and as the photodiode T4 is illuminated for a longer time, the potential of the node C is lower, the voltage applied to the gate of the read transistor T2 becomes smaller, so that the p-type read transistor T2 cannot continuously satisfy the operating condition of Vgs-Vds > Vth, and the dynamic range of the light sensing circuit is too narrow.

In the embodiment of the present invention, the first pole of the photodiode PD is electrically connected to the first node a, and the control pole of the p-type read transistor M4 is not directly connected to the first node a, that is, the control pole of the read transistor M4 is not directly connected to the first pole of the photodiode PD, so that the on state of the read transistor M4 is not directly affected by the voltage of the node a. The voltage of the first node A is prevented from dropping too much in the application, so that the voltage of the control electrode of the read transistor M4 exceeds the voltage range required to be satisfied by the working condition, and the detectable dynamic range of the light sensing circuit is prevented from being influenced.

A voltage conversion transistor M2 is provided in the light sensing circuit, a control electrode of the voltage conversion transistor M2 is connected to a first node A, the on state of the voltage conversion transistor M2 is directly influenced by the voltage of the first node A, a second electrode of the voltage conversion transistor M2 is electrically connected to a second node B, and the voltage of the second node B is influenced by the voltage of the first node A. In addition, the reading control transistor M3 is electrically connected to the second node B, and the voltage of the second node B can be commonly controlled when the control transistor M3 and the voltage conversion transistor M2 are simultaneously turned on, so that the voltage for controlling the working state of the reading transistor M4 can be converted according to the change rule of the voltage of the first node a. The potential of the first node A is lower and the potential of the second node B is higher as the illumination time of the photodiode PD is longer, the voltage supplied to the control electrode of the reading transistor M4 is higher, so that the operating characteristics of the p-type transistor can be adapted, the p-type reading transistor M4 can be ensured to continuously work in a saturation region, and the wider dynamic range of the light sensing circuit is ensured.

The embodiment of the invention can control the voltage change range of the second node B to be within the voltage range required to be met by the working condition of the reading transistor M4, so as to ensure that the light sensing circuit has a wider dynamic range, and can ensure the fingerprint identification accuracy when being applied to fingerprint identification detection. The embodiment of the present invention further provides a driving method, which can be used for driving the light sensing circuit provided by the embodiment of the present invention, and the driving method includes: controlling the working cycle of the light sensing circuit to comprise a reset stage and a reading stage; wherein the content of the first and second substances,

in the reset phase: a signal is provided to the control electrode of the reset transistor M1 to control the reset transistor M1 to turn on to reset the first node a.

In the reading phase: the photodiode PD generates a leak current after being illuminated, and the voltage of the first node a drops. The first node A provides voltage to the control electrode of the voltage conversion transistor M2 to control the voltage conversion transistor M2 to be turned on, and provides voltage to the control electrode of the read control transistor M3 to control the read control transistor M3 to be turned on, after the voltage conversion transistor M2 and the read control transistor M3 are both turned on, the voltage of the second node B is controlled by the voltage conversion transistor M2 and the read control transistor M3 together; the control electrode of the read transistor M4 is electrically connected to the second node B, and the read transistor M4 outputs a detection signal under the control of the second node B.

The photodiode PD has different illumination intensities and generates different leakage currents, and the stronger the illumination intensity is, the larger the leakage current is, the more the voltage drop of the corresponding first node a is. The gate of the voltage converting transistor M2 is electrically connected to the first node a, and the voltage at the first node a affects the on state of the voltage converting transistor M2, and thus affects the voltage at the second node B. That is, the voltage of the second node B has a correlation with the voltage of the first node a.

In the read phase, the read control transistor M3 is controlled to be turned on, the read control transistor M3 and the voltage conversion transistor M2 jointly control the voltage of the second node B, and the voltage of the second node B influences the on state of the read transistor M4, and further influences the detection signal output by the photo sensing circuit.

In the embodiment of the present invention, the on state of the read transistor M4 is indirectly influenced by the voltage of the first node a, so as to ensure that the on state of the read transistor M4 has a correlation with the voltage of the first node a; meanwhile, the voltage of the second node B is controlled by the voltage conversion transistor M2 and the reading control transistor M3 together, the voltage for controlling the working state of the reading transistor M4 can be converted along with the change rule of the voltage change of the first node A, and the voltage change range of the second node B is controlled within the voltage range which needs to be met by the working condition of the reading transistor M4, so that the light sensing circuit is ensured to have a wide dynamic range, and the fingerprint identification accuracy can be ensured when the light sensing circuit is applied to fingerprint identification detection.

In one embodiment, each transistor in the photosensitive circuit is a p-type transistor, so that the manufacturing process does not need to be performed by an LDD process, thereby simplifying the process and reducing the cost.

As shown in fig. 2, the control electrode of the Reset transistor M1 receives the Reset control signal Reset, the first electrode of the Reset transistor M1 receives the Reset signal Vreset, and the second electrode of the Reset transistor M1 is electrically connected to the first node a; a first pole of the voltage converting transistor M2 receives the first voltage signal Vdd, and a second pole of the voltage converting transistor M2 is electrically connected to the second node B; the control electrode of the read control transistor M3 receives the read control signal read, the first electrode of the read control transistor M3 receives the second voltage signal, and the second electrode of the read control transistor M3 is electrically connected to the second node B; the first electrode of the read transistor M4 receives the second voltage signal Vcc, and the read transistor M4 turns on the output detection signal Vout under the control of the voltage of the control electrode thereof. A first pole of the photodiode PD is electrically connected to the first node a, and a second pole receives a common voltage signal Vcom.

In an embodiment, fig. 3 is a timing diagram illustrating an operation of a photo sensing circuit according to an embodiment of the invention. As shown in fig. 3, the operation process of the photo sensing circuit includes a first reading phase t1, a reset phase t2 and a second reading phase t 3.

At the reset phase t 2: a Reset control signal Reset is provided to the control electrode of the Reset transistor M1, wherein the Reset control signal Reset is a pulse signal, and a low level signal in the Reset control signal Reset is an enable signal for controlling the Reset transistor M1 to be turned on. At this stage, the control electrode of the reset transistor M1 receives the enable signal to control the reset transistor M1 to turn on, the first electrode and the second electrode of the reset transistor M1 are turned on, and the reset signal Vreset received by the first electrode of the reset transistor M1 is provided to the first node a to reset the first node a. In one embodiment, the voltage value of the reset signal Vreset is-3V.

The voltage value of the common voltage signal Vcom is set to be smaller than that of the reset signal Vreset, the electric potential of the first node a is higher than that of the second pole of the photodiode PD in the reset period t2, and the photodiode PD is in a reverse bias off state when the photodiode PD is not illuminated with light.

In the first reading phase t 1: the disable signal in the Reset control signal Reset is supplied to the control electrode of the Reset transistor M1, and the Reset transistor M1 is turned off. The photodiode PD generates a leakage current from the first pole to the second pole under the irradiation of light, and the potential at the position of the first node a is lowered. The control electrode of the voltage converting transistor M2 is electrically connected to the first node a, and the voltage converting transistor M2 is turned on under the control of the voltage signal at the first node a. The read control signal read is a pulse signal as illustrated in fig. 3, and the low signal in the read control signal read is an enable signal for controlling the turn-on of the read control transistor M3. At this stage, the enable signal is provided to the gate of the read control transistor M3 to control the read control transistor M3 to turn on. That is, the voltage conversion transistor M2 and the read control transistor M3 collectively control the voltage of the second node B at this stage. And the read transistor M4 outputs a detection signal under the voltage control of the second node B.

The voltage of the second node B is controlled by the voltage conversion transistor M2 and the reading control transistor M3 together, so that the voltage of the second node B is controlled to change along with the voltage change of the first node A; the read transistor M4 is turned on under the control of the second node B, so that the detection signal output by the read transistor M4 varies with the voltage variation of the second node B. It is achieved that the detection signal has a correlation with the voltage of the first node a.

As the time for which the photodiode PD receives light increases, the potential of the first node a continuously decreases.

In the second read phase t 3: the disable signal in the Reset control signal Reset is supplied to the control electrode of the Reset transistor M1, and the Reset transistor M1 is turned off. The voltage conversion transistor M2 is turned on under the control of the voltage signal at the first node a, and at the same time, the enable signal in the read control signal read is provided to the control electrode of the read control transistor M3 to control the turn-on of the read control transistor M3. The voltage conversion transistor M2 and the read control transistor M3 control the voltage of the second node B in common, and the read transistor M4 outputs the detection signal again under the voltage control of the second node B.

The detection signal obtained at the first reading stage t1 can be regarded as an initial detection value. As the time for which the photodiode PD is illuminated increases, the potential at the position of the first node a continues to decrease. In the second reading phase t3, a detection signal after a certain illumination time is detected. The detection signal obtained in the two reading stages can reflect the potential drop condition of the first node a, and also can reflect the illumination intensity condition received by the photodiode PD.

The fingerprint sensor is applied to fingerprint detection, and different fingerprint areas correspond to different light sensing circuits in the photoelectric sensor. Whereas the intensity of illumination of the photodiode PD varies in the unused fingerprint area. A plurality of light sense circuits in the photoelectric sensor respectively execute the working stages, and the overall illumination intensity condition of the fingerprint identification area can be obtained, so that the fingerprint graph is determined according to the illumination intensity, and the fingerprint identification is realized.

In one embodiment, as illustrated in fig. 3, the reset signal Vreset is a constant voltage signal.

In one embodiment, as shown in fig. 3, the first voltage signal Vdd and the second voltage signal Vcc are both constant voltage signals, and the voltage value of the first voltage signal Vdd and the voltage value of the second voltage signal Vcc are different.

In one embodiment, during the read phase: the turning on of the read transistor M4 under the control of the second node B, such that the detection signal outputted by the read transistor M4 varies with the voltage variation of the second node B, includes controlling the operation of the read transistor M4 in the saturation region under the control of the second node B. According to the characteristics of the field effect transistor, when the transistor works in a saturation region, the output voltage of the transistor changes along with the change of the control voltage of the transistor. When the light sensing circuit is driven to work in the reading stage, the reading transistor M4 is controlled to work in the saturation region by the voltage of the second node B, so that the detection signal can be output by the reading transistor M4, and the detection signal and the illumination intensity of the photodiode PD have correlation.

In one embodiment, the driving light sensing circuit operates during the read phase: the voltage of the second node B is controlled by simultaneously turning on the voltage conversion transistor M2 and the read control transistor M3 to control the voltage of the second node B to increase as the voltage of the first node a decreases. In the reading phase: as the light irradiation time of the photodiode PD increases, the voltage of the first node a decreases, and the voltage of the second node B increases as the voltage of the first node a decreases, that is, as the light irradiation time of the photodiode PD increases, the voltage of the second node B gradually increases. And the voltage at the second node B can control the on state of the read transistor M4.

For the read transistor M4, in the case where Vs (the source voltage of the transistor, here, the first voltage of the corresponding read transistor M4) and Vth are fixed, as the time of the photodiode PD receiving light is prolonged, the voltage of the second node B will become gradually larger, and then the Vgs of the read transistor M4 will be larger, so that the read transistor M4 can continuously satisfy the operating condition of Vgs-Vds > Vth, and the read transistor M4 is controlled to operate in the saturation region. In the embodiment of the invention, the voltage of the second node B is controlled by the voltage conversion transistor and the reading transistor together, so that the voltage for controlling the working state of the reading transistor M4 can be converted along with the change rule of the voltage change of the first node A, and the voltage supplied to the control electrode of the reading transistor M4 is gradually increased along with the prolonging of the illumination time of the photodiode PD, so that the working characteristic of the p-type transistor can be adapted, the reading transistor M4 of the p-type transistor can be ensured to continuously work in a saturation region, and the wide dynamic range of the light sensing circuit is ensured.

Fig. 4 is a schematic diagram of a characteristic curve of a p-type transistor, fig. 4 is only for explaining the operating characteristic of the p-type transistor, and the numerical parameters illustrated in fig. 4 are not intended to limit the characteristic parameters of the transistor in the present invention. The linear, saturation, and cut-off regions are illustrated in fig. 4. Wherein, the abscissa U_DSRepresenting the voltage difference between the drain and the source of the transistor, U_GSRepresenting the voltage difference between the gate and the source of the transistor, I_DRepresenting the drain flow of the transistor. The threshold voltage of the transistor illustrated in FIG. 4 is-2V, that is, at U_GSabove-2V, the transistor is in an off state. As can be seen from fig. 4, when the p-type transistor operates in the saturation region, the on-state leakage current generated by the p-type transistor becomes smaller as the voltage of the gate of the p-type transistor becomes larger.

In the embodiment of the present invention, the read transistor M4 is a p-type transistor. When the light sensing circuit is driven to work in the reading stage: the read transistor M4 is turned on under the control of the second node B, so that the detection signal output by the read transistor M4 decreases as the voltage of the second node B increases. Therefore, the reading transistor M4 is controlled to work in a saturation region through the voltage of the second node B, the correlation between the detection signal output by the reading transistor M4 and the voltage of the second node B is realized, and the correlation between the detection signal output by the reading transistor M4 and the voltage of the first node A is further realized, so that the illumination intensity condition of the photodiode PD can be reflected through the output detection signal.

In one embodiment, the driving the photo sensing circuit in the read phase when the voltage converting transistor M2 and the read controlling transistor M3 are turned on simultaneously and jointly control the voltage at the second node B comprises: the control voltage conversion transistor M2 and the read control transistor M3 both operate in the linear region. Wherein the content of the first and second substances,

the first node a provides a voltage to the control electrode of the voltage conversion transistor M2 to control the voltage conversion transistor M2 to operate in a linear region, and the on-resistance of the voltage conversion transistor M2 varies with the voltage variation of the first node a;

a constant voltage signal is supplied to the control electrode of the read control transistor M3 to control the read control transistor M3 to operate in a linear region.

As can be seen from the characteristic curve of the p-type transistor illustrated in fig. 4, when the transistor operates in the linear region, the on-resistance of the transistor has a correlation with the voltage of its gate, wherein the on-resistance of the transistor has a positive correlation with the voltage of its gate. When the voltage of the control electrode of the transistor is constant, the on resistance of the transistor is also constant, and the transistor is equivalent to a resistor with a fixed resistance value.

In the embodiment of the present invention in which the voltage converting transistor M2 is a p-type transistor, the voltage converting transistor M2 is controlled by the voltage at the first node a to operate in a linear region, so that the on-resistance of the voltage converting transistor M2 decreases as the voltage at the first node a decreases, and the on-resistance of the corresponding voltage converting transistor M2 increases as the voltage at the first node a increases. The voltage of the first node a varies with the illumination condition of the photodiode PD in application, and the voltage conversion transistor M2 can be regarded as a variable resistor under the influence of the voltage of the first node a in application.

Meanwhile, the read control transistor M3 is a p-type transistor, and a constant voltage signal is provided to the control electrode of the read control transistor M3 to control the read control transistor M3 to operate in a linear region, so that the on-resistance of the read control transistor M3 is a constant resistance, and the read control transistor M3 is equivalent to a fixed resistance resistor.

In view of the circuit structure diagram shown in fig. 2, the second pole of the voltage converting transistor M2 and the second pole of the read control transistor M3 are both electrically connected to the second node B; the first node a provides a voltage to the control electrode of the voltage converting transistor M2 to control the voltage converting transistor M2 to operate in a linear region, including: the first node a provides a voltage to the control electrode of the voltage conversion transistor M2, and provides a first voltage signal Vdd to the first electrode of the voltage conversion transistor M2 to control the voltage conversion transistor M2 to operate in a linear region; supplying a constant voltage signal to a control electrode of the read control transistor M3 to control the read control transistor M3 to operate in a linear region, including: the read control signal is supplied to the control electrode of the read control transistor M3, and the second voltage signal Vcc is supplied to the first electrode of the read control transistor M3 to control the read control transistor M3 to operate in the linear region.

When the on-resistance of the voltage converting transistor M2 is a variable resistance and the on-resistance of the read control transistor M3 is a fixed resistance, the voltage at the second node B changes with the change of the on-resistance of the voltage converting transistor M2 by setting the first voltage signal Vdd and the second voltage signal Vcc to be constant voltages at least during the read phase. The on-resistance of the voltage conversion transistor M2 has a correlation with the voltage of the first node a, so that it can be achieved that the voltage of the second node B has a correlation with the voltage of the first node a. And the voltage of the second node B can be controlled to be between the voltage value of the first voltage signal Vdd and the voltage value of the second voltage signal Vcc, so that the voltage range of the control electrode of the read transistor M4 can be controlled, and the operating state of the read transistor M4 can be controlled.

Wherein, when the voltage of the first node a is smaller, the on-resistance of the voltage conversion transistor M2 is smaller, and the voltage value at the position of the second node B is closer to the voltage value of the first voltage signal Vdd.

By setting the voltage value of the first voltage signal Vdd to be greater than the voltage value of the second voltage signal Vcc, the embodiment of the present invention can control the voltage of the second node B to vary with the voltage of the first node a by controlling the voltage converting transistor M2 and the read controlling transistor M3 to operate in the linear region, and the voltage of the second node B increases as the voltage of the first node a becomes smaller. Then, as the illumination time of the photodiode PD is longer, the potential of the first node a is lower, and the potential of the second node B is higher, the voltage applied to the control electrode of the reading transistor M4 is higher, so as to adapt to the operating characteristics of the p-type transistor, and ensure that the p-type reading transistor M4 can continuously operate in the saturation region under the control of the second node B, thereby ensuring that the light sensing circuit has a wider dynamic range.

In one embodiment, the voltage of the first voltage signal Vdd is 0V and the voltage of the second voltage signal Vcc is-7V.

In an embodiment, fig. 5 is a layout diagram of a light sensing circuit according to an embodiment of the present invention, and fig. 6 is a cross-sectional diagram of a position of a tangent line E-E' in fig. 5.

Fig. 5 shows four transistors in a light sensing circuit, and signal lines for driving the light sensing circuit. As shown in fig. 5, the photosensor includes a reset control line X1, a reset signal line X2, a first voltage line X3, a read control line X4, a second voltage line X5, and a read data line X6.

The control electrode of the Reset transistor M1 is electrically connected to a Reset control line X1, and the Reset control line X1 is used to supply a Reset control signal Reset. A first pole of the reset transistor M1 is electrically connected to a reset signal line X2, and the reset signal line X2 is used to supply a reset signal Vreset. The first pole of the voltage conversion transistor M2 is electrically connected to a first voltage line X3, and the first voltage line X3 is used for providing a first voltage signal Vdd. The control gate of the read control transistor M3 is electrically connected to the read control line X4, and the read control line X4 is used to provide a read control signal read. The first pole of the read control transistor M3 and the first pole of the read transistor M4 are both electrically connected to a second voltage line X5, and the second voltage line X5 is used to provide a second voltage signal Vcc. The second pole of the read transistor M4 is electrically connected to the read data line X6, and the read data line X6 is used for collecting the detection signal.

It should be noted that, in the embodiment of the present invention, the pattern filling is located in the same film layer of the photosensor.

In one embodiment, as shown in fig. 5, the reset control line X1, the read control line X4, and the second voltage line X5 extend in the first direction X, and the read control line X4 is located between the reset control line X1 and the second voltage line X5; the first voltage lines X3, the reset signal line X2, and the read data line X6 extend in the second direction y; the first direction x and the second direction y intersect. It should be noted that, in the embodiment of the present invention, the limitation on the extending direction of each signal line is only to describe the approximate routing direction of each signal line, and the line type of each signal line is not limited. In the embodiment of the present invention, each signal line is not limited to be a straight line, and taking the read control line X4 illustrated in fig. 5 as an example, the extending direction of the read control line X4 is the first direction y, and a partial line segment of the read control line X4 in the extending direction thereof may be a broken line.

The control electrode of the voltage conversion transistor M2 and the control electrode of the read transistor M4 are located on the first virtual straight line XX; the reset transistor M1 and the read control transistor M3 are respectively located on both sides of the first virtual straight line XX; the first virtual straight line XX in fig. 5 is only schematically shown, and it is understood that in an actual structure, the gate of the voltage converting transistor M2 and the gate of the reading transistor M4 are not one point, but both have a certain area size. In the embodiment of the present invention, the straight line passing through the gate of the voltage converting transistor M2 and the read transistor M4 at the same time is considered as the first virtual straight line XX.

In the embodiment of the invention, the light sensing circuit comprises four transistors, the reset transistor M1 and the reading control transistor M3 are respectively arranged at two sides of the first virtual straight line XX, the arrangement mode of the four transistors is designed according to the mutual connection relation of the four transistors, the four transistors are relatively closely arranged, and the area occupied by the light sensing circuit can be saved.

As shown with continued reference to fig. 5, in the second direction y, the reset transistor M1, the voltage conversion transistor M2, the read control transistor M3, and the read transistor M4 are all located between the reset control line X1 and the second voltage line X5; in the first direction X, the reset transistor M1, the voltage conversion transistor M2, the read control transistor M3, and the read transistor M4 are all located between the first voltage line X3 and the read data line X6. The reset control line X1 and the second voltage line X5 extend in the same direction and cross insulated from the first voltage line X3 and the read data line X6, respectively, and the four signal lines as shown in fig. 5 define a rectangular-like space in which the four transistors in the light sensing circuit are located. So set up, can make arranging of light sense circuit regular more and compact, be favorable to further reducing the area occupied of light sense circuit.

The layout design in the embodiment of the invention can increase the number of the light sensing circuits and improve the resolution of the photoelectric sensor under the condition that the size of the photoelectric sensor is fixed. The fingerprint identification device is applied to fingerprint identification detection, and can improve the precision of fingerprint detection.

As shown in fig. 5, for the first voltage line X3, the reset signal line X2, and the read data line X6 for driving one photo sensing circuit to operate, the read data line X6 is located between the first voltage line X3 and the reset signal line X2. In another embodiment, for the first voltage line X3, the reset signal line X2, and the read data line X6 for driving one photo sensing circuit to operate, the reset signal line X2 is located between the first voltage line X3 and the read data line X6, which is not illustrated in the drawings.

Fig. 6 illustrates a film layer structure of a photosensor, and as shown in fig. 6, the photosensor includes a substrate 10, and a semiconductor layer 20, a first metal layer 30, and a second metal layer 40, which are sequentially distant from the substrate 10. The photodiode PD is located on a side of the second metal layer 40 remote from the substrate 10. The photodiode PD includes a first pole 51, an active layer 52, and a second pole 53.

As will be understood from fig. 5 and 6, the active layer (not labeled in fig. 6) of each transistor in the light sensing circuit is located in the semiconductor layer 20. It will be understood that for a transistor, the region of the semiconductor layer 20 that overlaps the gate of the transistor is the active layer of the transistor. The control electrode (not labeled in fig. 6) of each transistor in the photo sensing circuit, the reset control line X1, the read control line X4 and the second voltage line X5 are located in the first metal layer 30; the first voltage line X3, the reset signal line X2, and the read data line X6 are located at the second metal layer 40.

Also illustrated in fig. 5 and 6 are a first connecting line L1, a second connecting line L2, a third connecting line L3 and a fourth connecting line L4. The first connection line L1, the second connection line L2, the third connection line L3, and the fourth connection line L4 are all located on the second metal layer 40.

The first pole 51 of the photodiode PD is connected to the first connection line L1 through the first via V1, one end of the first connection line L1 is electrically connected to the control electrode of the voltage conversion transistor M2 through the second via V2, and the other end of the first connection line L1 is electrically connected to the second pole of the reset transistor M1 through the third via V3. That is, the provision of the first connection line L1 realizes electrical connection between the first pole 51 of the photodiode PD, the control pole of the voltage conversion transistor M2, and the second pole of the reset transistor M1.

As can be seen from fig. 5, the second pole of the voltage conversion transistor M2 and the second pole of the read control transistor M3 are both located in the semiconductor layer 20 and directly connected. It can be seen from fig. 6 that one end of the second connection line L2 is connected to the semiconductor layer 20 through a via, and the other end of the second connection line L2 is connected to the gate of the read transistor M4 through a via. By the arrangement of the second connection line L2, electrical connection between the second pole of the voltage conversion transistor M2, the second pole of the read control transistor M3, and the control pole of the read transistor M4 is achieved.

A first end of the third connection line L3 is connected to the second voltage line X5 through a via, and the other end is connected to the first pole of the read control transistor M3 through a via, thereby enabling the second voltage signal Vcc to be supplied to the first pole of the read control transistor M3 through the second voltage line X5.

A first end of the fourth connection line L4 is connected to the second voltage line X5 through a via, and the other end is connected to the first pole of the read transistor M4 through a via, thereby enabling the second voltage signal Vcc to be supplied to the first pole of the read transistor M4 through the second voltage line X5.

In this embodiment, in the fabrication of the photosensor, a patterned semiconductor layer 20 and a patterned first metal layer 30 are sequentially formed on a substrate 10; then, a punching process for manufacturing the insulating layer is carried out; then, the patterned second metal layer 40 is fabricated, and the first to fourth connection lines L1 to L4, and the first voltage line X3, the reset signal line X2, and the read data line X6 are formed. Only one punching process is required before the process of the photodiode PD.

Also illustrated in fig. 6 is a planarization layer 61, wherein the planarization layer 61 is made of an organic material, the planarization layer 61 is located between the second metal layer 40 and the photodiode PD, and the planarization layer 61 is made after the second metal layer 40, and the planarization layer 61 can provide a relatively flat substrate for making the photodiode PD.

In another embodiment, fig. 7 is a schematic diagram of another light sensing circuit according to an embodiment of the invention, and fig. 8 is a timing diagram of an operation of the light sensing circuit according to the embodiment of fig. 7.

As shown in fig. 7, the control electrode of the Reset transistor M1 is electrically connected to a Reset control line X1, and the Reset control line X1 is used to provide a Reset control signal Reset. As illustrated in fig. 8, the Reset control signal Reset is a pulse signal, and a low level signal in the Reset control signal Reset is an enable signal that controls the Reset transistor M1 to be turned on.

A first pole of the reset transistor M1 and a first pole of the voltage conversion transistor M2 are both electrically connected to the first voltage signal line X3; the first voltage signal line X3 is used to supply the reset signal Vreset to the first pole of the reset transistor M1 in the first period and also to supply the first voltage signal Vdd to the first pole of the voltage conversion transistor M2 in the second period, the voltage value Vreset of the reset signal and the voltage value of the first voltage signal Vdd being different.

The control gate of the read control transistor M3 is electrically connected to the read control line X4, and the read control line X4 is used to provide a read control signal read. As illustrated in fig. 8, the read control signal read is a pulse signal, and the low signal in the read control signal read is an enable signal for controlling the turn-on of the read control transistor M3.

The first pole of the read control transistor M3 and the first pole of the read transistor M4 are both electrically connected to a second voltage line X5, and the second voltage line X5 is used to provide a second voltage signal Vcc. The second voltage signal Vcc is a constant voltage signal.

The second pole of the read transistor M4 is electrically connected to the read data line X6, and the read data line X6 is used for collecting the detection signal.

The first voltage signal line X3 in the embodiment of the present invention provides different voltage signals having different voltage values at different periods. As shown in fig. 8, the operation process of the photo sensing circuit includes a reset phase t2 and two reading phases (a first reading phase t1 and a second reading phase t 2). In the Reset phase t2, that is, the first period, in the Reset phase t2, the first voltage signal line X3 provides the Reset signal Vreset to the first electrode of the Reset transistor M1, and at the same time, the Reset control line X1 provides the Reset control signal Reset to the control electrode of the Reset transistor M1 to control the Reset transistor M1 to turn on, so that the Reset transistor M1 resets the first node a through the Reset signal Vreset. The read phase is a second period, in which the first voltage signal line X3 provides the first voltage signal Vdd to the first electrode of the voltage converting transistor M2, and in which the voltage converting transistor M2 operates in the linear region after being turned on under the voltage control of the control electrode thereof.

The signal provided on the first voltage signal line X3 in this embodiment is a pulse signal. The low-level signal portion of the pulse signal is the reset signal Vreset, and the high-level signal portion is the first voltage signal Vdd. In the reset phase t2, the first voltage signal line X3 provides the reset signal Vreset to the first pole of the reset transistor M1; during the read phase, the first voltage signal line X3 provides the first voltage signal Vdd to the first pole of the voltage converting transistor M2.

The first voltage signal line X3 is used for providing different voltage signals in a time-sharing manner, so that the number of signal lines in the photoelectric sensor can be reduced, and the wiring space is saved. The resolution of the photoelectric sensor can be improved.

In an embodiment, fig. 9 is a layout diagram of a light sensing circuit according to an embodiment of the present invention, and fig. 10 is a cross-sectional diagram of a position of a tangent line F-F' in fig. 9. Fig. 9 shows the connection relationship between each transistor and the signal line in the circuit for clarity, and does not show the photodiode PD.

As shown in fig. 9, the reset control line X1 and the read control line X4 extend in the first direction X; the first voltage line X3, the second voltage line X5, and the read data line X6 extend in the second direction y, and the read data line X6 is located between the first voltage line X3 and the second voltage line X5.

The control electrode of the voltage conversion transistor M2 and the control electrode of the read transistor M4 are located on a first virtual straight line; the reset transistor M1 and the read control transistor M3 are located on both sides of the first virtual straight line, respectively. The first virtual straight line is not illustrated in fig. 9, and reference may be made to the description of the embodiment of fig. 5 for understanding of the first virtual straight line.

In the second direction y, the reset transistor M1, the voltage conversion transistor M2, the read control transistor M3, and the read transistor M4 are all located between the reset control line X1 and the read control line X4; in the first direction X, the reset transistor M1, the voltage conversion transistor M2, the read control transistor M3, and the read transistor M4 are all located between the first voltage line X3 and the second voltage line X5.

In the embodiment of the invention, the light sensing circuit comprises four transistors, the reset transistor M1 and the reading control transistor M3 are respectively arranged at two sides of the first virtual straight line, the arrangement mode of the four transistors is designed according to the mutual connection relation among the four transistors, the four transistors are relatively closely arranged, and the area occupied by the light sensing circuit can be saved. The reset control line X1 and the read control line X4 extend in the same direction and cross over the first voltage line X3 and the second voltage line X5 in an insulated manner, respectively, and the four signal lines as shown in fig. 9 define a rectangular-like space in which the four transistors in the light sensing circuit are located. So set up, can make arranging of light sense circuit regular more and compact, be favorable to further reducing the area occupied of light sense circuit. The layout design in the embodiment of the invention can increase the number of the light sensing circuits and improve the resolution of the photoelectric sensor under the condition that the size of the photoelectric sensor is fixed. The fingerprint identification device is applied to fingerprint identification detection, and can improve the precision of fingerprint detection.

In the embodiment of the present invention, the photoelectric sensor includes a substrate 10, and a semiconductor layer 20, a first metal layer 30, and a second metal layer 40 sequentially separated from the substrate. As will be understood in conjunction with fig. 9 and 10, the active layer of each transistor in the light sensing circuit is located in the semiconductor layer 20; the control electrode of each transistor in the light sensing circuit, the reset control line X1 and the reading control line X4 are positioned on the first metal layer 30; the first voltage line X3, the second voltage line X5, and the read data line X6 are located at the second metal layer 40.

The photosensor further includes a first connection line L1 and a second connection line L2, wherein the first connection line L1 and the second connection line L2 are located on the second metal layer 40. The functions of the first connecting line L1 and the second connecting line L2 are the same as those in the embodiment of fig. 5, and are not described again.

In some embodiments, the read control signal read and the second voltage signal Vcc are the same voltage signal, and the first pole of the read control transistor M3 is electrically connected to the control pole of the read control transistor M3. Therefore, signals can be simultaneously provided for the first electrode of the reading control transistor M3 and the control electrode of the reading control transistor M3 through one signal line, the number of signal lines in the photoelectric sensor can be reduced, and the photoelectric sensor is beneficial to saving wiring space and improving the resolution of the photoelectric sensor.

Optionally, the read control signal read and the second voltage signal Vcc are both pulse signals.

FIG. 11 is a schematic diagram of another photo sensing circuit according to an embodiment of the invention, and FIG. 12 is a timing diagram illustrating an operation of the photo sensing circuit according to the embodiment of FIG. 11.

As shown in fig. 11, the control electrode of the Reset transistor M1 is electrically connected to a Reset control line X1, and the Reset control line X1 is used to supply a Reset control signal Reset. As shown in fig. 12, the Reset control signal Reset is a pulse signal, and a low level signal in the Reset control signal Reset is an enable signal for controlling the Reset transistor M1 to be turned on.

A first pole of the reset transistor M1 is electrically connected to a reset signal line X2, and the reset signal line X2 is used to provide a reset signal Vreset; as shown in fig. 12, the reset signal Vreset is a constant voltage signal.

The first pole of the voltage conversion transistor M2 is electrically connected to a first voltage line X3, the first voltage line X3 is used for providing a first voltage signal Vdd; the first voltage signal Vdd is a constant voltage signal.

The control electrode of the read control transistor M3, the first electrode of the read control transistor M3, and the first electrode of the read transistor M4 are electrically connected to a read control line X4, and the read control line X4 is used to provide a read control signal read and a second voltage signal Vcc.

The second pole of the read transistor M4 is electrically connected to the read data line X6, and the read data line X6 is used for collecting the detection signal.

In this embodiment, the signal provided by the read control line X4 is a pulse signal, wherein the low-level signal portion in the pulse signal is an enable signal for controlling the turn-on of the read control transistor M3. When the photo sensing circuit operates in the read phase (the first read phase t1 or the second read phase t3 illustrated in fig. 12), the read control line X4 provides a low level signal, that is, both the read control signal read and the second voltage signal Vcc are low level signals during this period. Supplying a low level signal to the control electrode of the read control transistor M3 can control the read control transistor M3 to turn on, while supplying a low level signal to the first electrode of the read control transistor M3 can control the read control transistor M3 to operate in a linear region. Moreover, the first pole of the read transistor M4 also receives the second voltage signal Vcc, and when the second voltage signal Vcc is a pulse signal, the second voltage signal Vcc is a high level signal in the non-read phase, so that the influence of leakage current generated by the read transistor M4 on the output of the detection signal can be avoided in the non-read phase.

In an embodiment, fig. 13 is a layout diagram of a light sensing circuit according to an embodiment of the present invention, and fig. 14 is a cross-sectional diagram of a position of a tangent line G-G' in fig. 13. Fig. 13 does not show the photodiode PD for clarity of connection between each transistor and a signal line in the circuit.

As shown in fig. 13, the reset control line X1 and the read control line X4 extend in the first direction X, and the first voltage line X3, the read data line X6, and the reset signal line X2 extend in the second direction y.

The control electrode of the voltage conversion transistor M2 and the control electrode of the read transistor M4 are located on a first virtual straight line; the reset transistor M1 and the read control transistor M3 are respectively located on both sides of the first virtual straight line; the first virtual straight line is not illustrated in fig. 13, and reference may be made to the description of the embodiment of fig. 5 for understanding of the first virtual straight line.

In the second direction y, the reset transistor M1, the voltage conversion transistor M2, the read control transistor M3, and the read transistor M4 are all located between the reset control line X1 and the read control line X4; in the first direction X, the reset transistor M1, the voltage conversion transistor M2, the read control transistor M3, and the read transistor M4 are all located between the first voltage line X3 and the read data line X6.

In the embodiment of the invention, the light sensing circuit comprises four transistors, the reset transistor M1 and the reading control transistor M3 are respectively arranged at two sides of the first virtual straight line, the arrangement mode of the four transistors is designed according to the mutual connection relation among the four transistors, the four transistors are relatively closely arranged, and the area occupied by the light sensing circuit can be saved. The reset control line X1 and the read control line X4 extend in the same direction and cross insulated from the first voltage line X3 and the read data line X6, respectively, and the four signal lines as shown in fig. 13 define a rectangular-like space in which the four transistors in the light sensing circuit are located. So set up, can make arranging of light sense circuit regular more and compact, be favorable to further reducing the area occupied of light sense circuit. The layout design in the embodiment of the invention can increase the number of the light sensing circuits and improve the resolution of the photoelectric sensor under the condition that the size of the photoelectric sensor is fixed. The fingerprint identification device is applied to fingerprint identification detection, and can improve the precision of fingerprint detection.

In the embodiment of the present invention, the photoelectric sensor includes a substrate 10, and a semiconductor layer 20, a first metal layer 30, and a second metal layer 40 sequentially separated from the substrate. As will be understood in conjunction with fig. 13 and 14, the active layer of each transistor in the light sensing circuit is located in the semiconductor layer 20; the control electrode of each transistor in the light sensing circuit, the reset control line X1 and the reading control line X4 are positioned on the first metal layer 30; the first voltage line X3, the reset signal line X2, and the read data line X6 are located at the second metal layer 40.

The photosensor further includes a first connecting line L1, a second connecting line L2, and a third connecting line L3, wherein the first connecting line L1, the second connecting line L2, and the third connecting line L3 are all located on the second metal layer 40. The functions of the first connecting line L1 and the second connecting line L2 are the same as those in the embodiment of fig. 5, and are not described again. Wherein the first pole of the read control transistor M3 is connected to the third connecting line L3 through a via, the first pole of the read transistor M4 is connected to the third connecting line L3 through a via, and the third connecting line L3 is connected to the read control signal read through a via, thereby achieving that the first pole of the read control transistor M3 is electrically connected to the control pole of the read control transistor M3, and the first pole of the read transistor M4 is electrically connected to the first pole of the read control transistor M3.

Fig. 15 is a schematic view of a display module according to an embodiment of the present invention, and as shown in fig. 15, the display module includes a display panel 1 and a photoelectric sensor 2 according to any embodiment of the present invention, where the photoelectric sensor 2 is attached to the back surface of the display panel 1 and overlaps with the display area of the display panel 1. The back of the display panel 1 is the back of the display screen. The display panel 1 is an organic light emitting display panel or an inorganic light emitting display panel. Photoelectric sensor 2 can be used for fingerprint identification to detect, realizes display module's fingerprint identification function.

Fig. 16 is a schematic view of another display module according to an embodiment of the present invention, and as shown in fig. 16, the display module includes a photosensor 2 according to any embodiment of the present invention, where the display module includes a stacked array layer 01 and a display layer 02, and the photosensor 2 is integrated in the array layer 01 of the display module. In the embodiment of the invention, each transistor in the light sensing circuit is a p-type transistor, so that the photoelectric sensor can be manufactured in the same process as the driving circuit in the array layer 01, and the thickness of the display module is favorably reduced.

Fig. 17 is a schematic view of a display device according to an embodiment of the present invention, and as shown in fig. 17, the display device includes a display module 100 according to any embodiment of the present invention. The display device in the embodiment of the invention can be any equipment with a display function, such as a mobile phone, a tablet computer, a notebook computer, an electronic book, a television, an intelligent watch and the like.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.