阅读说明：本技术 异质结太阳能电池的制备方法 (Preparation method of heterojunction solar cell ) 是由 龚道仁 辛科 周肃 徐晓华 王文静 梅志纲 程尚之 李晨 于 2021-07-09 设计创作，主要内容包括：本发明提供一种异质结太阳能电池的制备方法,包括：提供半导体衬底层；在所述半导体衬底层的两侧均分别形成掺杂半导体层；对所述半导体衬底层至少一侧的所述掺杂半导体层进行等离子体处理,以钝化所述掺杂半导体层的晶界缺陷。本发明通过对半导体衬底层至少一侧的掺杂半导体层进行等离子体处理,钝化掺杂半导体层的晶界缺陷,用以改善膜层的界面态密度,掺杂半导体层晶界缺陷较少、结晶率高,异质结电池的光电转换效率提高。(The invention provides a preparation method of a heterojunction solar cell, which comprises the following steps: providing a semiconductor substrate layer; forming doped semiconductor layers on two sides of the semiconductor substrate layer respectively; and carrying out plasma treatment on the doped semiconductor layer on at least one side of the semiconductor substrate layer so as to passivate the grain boundary defects of the doped semiconductor layer. According to the invention, the doped semiconductor layer on at least one side of the semiconductor substrate layer is subjected to plasma treatment to passivate the crystal boundary defects of the doped semiconductor layer, so that the interface state density of the film layer is improved, the crystal boundary defects of the doped semiconductor layer are less, the crystallization rate is high, and the photoelectric conversion efficiency of the heterojunction battery is improved.)

1. A method for manufacturing a heterojunction solar cell comprises the steps of providing a semiconductor substrate layer, and is characterized by further comprising the following steps:

forming doped semiconductor layers on two sides of the semiconductor substrate layer respectively;

and carrying out plasma treatment on the doped semiconductor layer on at least one side of the semiconductor substrate layer so as to passivate the grain boundary defects of the doped semiconductor layer.

2. The method of manufacturing a heterojunction solar cell of claim 1,

the step of forming said doped semiconductor layer on either side of a semiconductor substrate layer comprises: sequentially forming a plurality of laminated sub-doping layers on one side of the semiconductor substrate layer;

the step of plasma treating the doped semiconductor layer comprises: after each sub-doping layer is formed, carrying out plasma treatment on the sub-doping layers;

preferably, the doped semiconductor layer is nanocrystalline or microcrystalline.

3. The method of manufacturing a heterojunction solar cell of claim 1,

the step of forming a doped semiconductor layer comprises: forming a first doped semiconductor layer on one side of the semiconductor substrate layer; forming a second doped semiconductor layer on the other side of the semiconductor substrate layer;

the step of plasma treating the doped semiconductor layer comprises: carrying out first plasma treatment on the side, away from the semiconductor substrate layer, of the first doped semiconductor layer, and/or carrying out second plasma treatment on the side, away from the semiconductor substrate layer, of the second doped semiconductor layer;

preferably, when the second doped semiconductor layer is located on the back side of the semiconductor substrate layer, the valence band difference between the second doped semiconductor layer and the semiconductor substrate layer is 0.35eV-0.55 eV.

4. The method of manufacturing a heterojunction solar cell of claim 3,

the step of forming the first doped semiconductor layer includes: sequentially forming a plurality of stacked first sub-doping layers on one side of the semiconductor substrate layer;

after each first sub-doping layer is formed, performing first plasma treatment on the first sub-doping layers;

the step of forming the second doped semiconductor layer includes: sequentially forming a plurality of stacked second sub-doping layers on the other side of the semiconductor substrate layer;

after each second sub-doping layer is formed, second plasma treatment is performed on the second sub-doping layer.

5. The method of manufacturing a heterojunction solar cell of claim 3, wherein said first doped semiconductor layer is located on the front side of said semiconductor substrate layer and said second doped semiconductor layer is located on the back side of said semiconductor substrate layer;

preferably, the material of the first doped semiconductor layer is SiO doped with N-type conductive ions_x1Or SiC_y1(ii) a When the material of the first doped semiconductor layer is SiO of N-type conductive ions_x1In the first plasma treatment, the gas used comprises a hydrogen-containing gas and/or an oxygen-containing gas; when the material of the first doped semiconductor layer is SiC of N-type conductive ions_y1Wherein the gas used for the first plasma treatment comprises a hydrogen-containing gas; preferably, x1 is an integer of 1-2; y1 is an integer of 0 to 1;

preferably, the material of the second doped semiconductor layer is SiO doped with P-type conductive ions_x2Or SiC_y2(ii) a When the material of the second doped semiconductor layer is SiO doped with P-type conductive ions_x2In the second plasma treatment, the gas used comprises a hydrogen-containing gas and/or an oxygen-containing gas; when the material of the second doped semiconductor layer is SiC doped with P-type conductive ions_y2The gas used for the second plasma treatment comprises a hydrogen-containing gas; preferably, x2 is an integer of 1-2, and y2 is an integer of 0-1;

preferably, the parameters of the first plasma treatment include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter; preferably, the parameters of the second plasma treatment include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the plasma rate density is 500 watts per square meter-900 watts per square meter.

6. The method for manufacturing a heterojunction solar cell according to claim 3, wherein after the step of performing the first plasma treatment on the side of the first doped semiconductor layer facing away from the semiconductor substrate layer, the method further comprises: forming a third doped semiconductor layer on the surface of one side, away from the semiconductor substrate layer, of the first doped semiconductor layer; performing third plasma treatment on the third doped semiconductor layer to passivate crystal boundary defects of the third doped semiconductor layer;

preferably, the third doped semiconductor layer is in a nanocrystalline state or a microcrystalline state;

preferably, the doping concentration of the conductive ions in the third doped semiconductor layer is greater than the doping concentration of the conductive ions in the first doped semiconductor layer;

preferably, the material of the third doped semiconductor layer is SiO doped with N-type conductive ions_x3Or SiC_y3(ii) a When the material of the third doped semiconductor layer is SiO doped with N-type conductive ions_x3In the third plasma treatment, the gas used comprises a hydrogen-containing gas and/or an oxygen-containing gas; when the material of the third doped semiconductor layer is SiC doped with N-type conductive ions_y3In this case, the gas used for the third plasma treatment includes a hydrogen-containing gas; preferably, x3 is an integer of 1-2; y3 is an integer of 0 to 1;

preferably, the conductivity type of the third doped semiconductor layer is the same as the conductivity type of the first doped semiconductor layer; the optical band gap width of the third doped semiconductor layer is larger than that of the first doped semiconductor layer;

preferably, the refractive index of the first doped semiconductor layer is smaller than that of the semiconductor substrate layer, and the refractive index of the third doped semiconductor layer is smaller than that of the first doped semiconductor layer;

preferably, the step of forming the third doped semiconductor layer includes: sequentially forming a plurality of stacked third sub-doping layers on one side of the first doped semiconductor layer, which is far away from the semiconductor substrate layer; after each layer of the third sub-doping layer is formed, third plasma treatment is carried out on the third sub-doping layer;

preferably, the parameters of the third plasma treatment include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

7. The method of manufacturing a heterojunction solar cell of claim 3,

after the second plasma processing step is carried out on the side of the second doped semiconductor layer, which faces away from the semiconductor substrate layer, the method further comprises the following steps: forming a fourth doped semiconductor layer on the surface of one side, away from the semiconductor substrate layer, of the second doped semiconductor layer; performing fourth plasma treatment on the fourth doped semiconductor layer to passivate grain boundary defects of the fourth doped semiconductor layer;

preferably, the fourth doped semiconductor layer is in a nanocrystalline state or a microcrystalline state;

preferably, when the fourth doped layer is located on the back side of the semiconductor substrate layer, the doping concentration of the conductive ions in the fourth doped semiconductor layer is greater than the doping concentration of the conductive ions in the second doped semiconductor layer; preferably, the volume percentage doping concentration range of the conductive ions in the fourth doped semiconductor layer is 0.5% -2%;

preferably, the material of the fourth doped semiconductor layer is SiO doped with P-type conductive ions_x4Or SiC_y4(ii) a When the fourth doped semiconductor layer is made of SiO doped with P-type conductive ions_x4When said fourth is equal toThe gas used for the plasma treatment comprises hydrogen-containing gas and/or oxygen-containing gas; when the material of the fourth doped semiconductor layer is SiC doped with P-type conductive ions_y4In this case, the gas used for the fourth plasma treatment includes a hydrogen-containing gas; preferably, x4 is an integer of 1-2, and y4 is an integer of 0-1;

preferably, the step of forming the fourth doped semiconductor layer includes: sequentially forming a plurality of stacked fourth sub-doping layers on one side of the second doped semiconductor layer, which is far away from the semiconductor substrate layer; after each fourth sub-doping layer is formed, fourth plasma treatment is carried out on the fourth sub-doping layers;

preferably, the parameters of the fourth plasma treatment include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

8. The method of fabricating a heterojunction solar cell of any of claims 3 to 7, further comprising, prior to forming said first doped semiconductor layer: forming a first intrinsic semiconductor layer on one side of the semiconductor substrate layer; carrying out sixth plasma treatment on the first intrinsic semiconductor layer to passivate defects on the surface of the first intrinsic semiconductor layer;

after forming the first doped semiconductor layer, the first intrinsic semiconductor layer is located between the semiconductor substrate layer and the first doped semiconductor layer;

preferably, before forming the second doped semiconductor layer, the method further includes: forming a second intrinsic semiconductor layer on the other side of the semiconductor substrate layer; carrying out seventh plasma treatment on the second intrinsic semiconductor layer to passivate defects on the surface of the second intrinsic semiconductor layer;

after forming the second doped semiconductor layer, the second intrinsic semiconductor layer is located between the semiconductor substrate layer and the second doped semiconductor layer.

9. The method of fabricating a heterojunction solar cell of claim 8, further comprising, prior to forming the first and second intrinsic semiconductor layers: performing fifth plasma treatment on the surface of the semiconductor substrate layer to passivate defects on the surface of the semiconductor substrate layer;

preferably, the gas used for the fifth plasma treatment includes a hydrogen-containing gas;

preferably, the parameters of the fifth plasma treatment include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

10. The method of claim 8, wherein the gas used for the sixth plasma treatment comprises a hydrogen-containing gas; the gas used for the seventh plasma treatment comprises a hydrogen-containing gas;

preferably, the parameters of the sixth plasma process include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter;

preferably, the parameters of the seventh plasma process include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

Technical Field

The invention relates to the technical field of heterojunction cells, in particular to a preparation method of a heterojunction solar cell.

Background

The heterojunction solar cell is a novel solar cell, and has wide market prospect due to simple structure, few process steps, wide raw material source, low production cost and convenience for large-scale production. In the prior art, an amorphous silicon thin film is one of the core raw materials of a solar cell.

In the existing preparation technology, the semiconductor layer obtained by the heterojunction solar cell has more crystal boundary defects, relatively thicker layer thickness and poorer crystallization rate, so that more parasitic absorption can be brought, and the short-circuit current of the cell is reduced. Furthermore, the crystallization rate of the prepared semiconductor layer is poor, so that the film layer has low conductivity, the series internal resistance of the cell can be increased, and the poor crystallization rate can cause more tunneling current recombination, so that the photoelectric conversion efficiency of the cell is reduced.

Disclosure of Invention

Therefore, the technical problem to be solved by the present invention is to overcome the disadvantage of low photoelectric conversion efficiency of the existing heterojunction cell, thereby providing a method for manufacturing a heterojunction solar cell.

The invention provides a preparation method of a heterojunction solar cell, which comprises the following steps: providing a semiconductor substrate layer; forming doped semiconductor layers on two sides of the semiconductor substrate layer respectively; and carrying out plasma treatment on the doped semiconductor layer on at least one side of the semiconductor substrate layer so as to passivate the grain boundary defects of the doped semiconductor layer.

Optionally, the step of forming the doped semiconductor layer on either side of the semiconductor substrate layer includes: sequentially forming a plurality of laminated sub-doping layers on one side of the semiconductor substrate layer;

the step of plasma treating the doped semiconductor layer comprises: after each sub-doping layer is formed, plasma treatment is performed on the sub-doping layers.

Optionally, the doped semiconductor layer is in a nanocrystalline state or a microcrystalline state.

Optionally, the step of forming a doped semiconductor layer includes: forming a first doped semiconductor layer on one side of the semiconductor substrate layer; forming a second doped semiconductor layer on the other side of the semiconductor substrate layer;

the step of plasma treating the doped semiconductor layer comprises: and carrying out first plasma treatment on the side of the first doped semiconductor layer, which is far away from the semiconductor substrate layer, and/or carrying out second plasma treatment on the side of the second doped semiconductor layer, which is far away from the semiconductor substrate layer.

Optionally, when the second doped semiconductor layer is located on the back side of the semiconductor substrate layer, the valence band difference between the second doped semiconductor layer and the semiconductor substrate layer is 0.35eV-0.55 eV.

Optionally, the step of forming the first doped semiconductor layer includes: sequentially forming a plurality of stacked first sub-doping layers on one side of the semiconductor substrate layer; after each first sub-doping layer is formed, performing first plasma treatment on the first sub-doping layers; the step of forming the second doped semiconductor layer includes: sequentially forming a plurality of stacked second sub-doping layers on the other side of the semiconductor substrate layer; after each second sub-doping layer is formed, second plasma treatment is performed on the second sub-doping layer.

Optionally, the first doped semiconductor layer is located on the front side of the semiconductor substrate layer, and the second doped semiconductor layer is located on the back side of the semiconductor substrate layer.

Optionally, the first doped semiconductor layer is made of SiO doped with N-type conductive ions_x1Or SiC_y1(ii) a When the material of the first doped semiconductor layer is SiO of N-type conductive ions_x1In the first plasma treatment, the gas used comprises a hydrogen-containing gas and/or an oxygen-containing gas; when the first doped semiconductor isThe material of the body layer is SiC of N-type conductive ions_y1Wherein the gas used for the first plasma treatment comprises a hydrogen-containing gas; preferably, x1 is an integer of 1-2; y1 is an integer of 0 to 1.

Optionally, the second doped semiconductor layer is made of P-type conductive ion doped SiO_x2Or SiC_y2(ii) a When the material of the second doped semiconductor layer is SiO doped with P-type conductive ions_x2In the second plasma treatment, the gas used comprises a hydrogen-containing gas and/or an oxygen-containing gas; when the material of the second doped semiconductor layer is SiC doped with P-type conductive ions_y2The gas used for the second plasma treatment comprises a hydrogen-containing gas; preferably, x2 is an integer of 1 to 2, and y2 is an integer of 0 to 1.

Optionally, the parameters of the first plasma processing include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

Optionally, the parameters of the second plasma processing include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the plasma rate density is 500 watts per square meter-900 watts per square meter.

Optionally, after the step of performing the first plasma treatment on the side of the first doped semiconductor layer away from the semiconductor substrate layer, the method further includes: forming a third doped semiconductor layer on the surface of one side, away from the semiconductor substrate layer, of the first doped semiconductor layer; and carrying out third plasma treatment on the third doped semiconductor layer to passivate the grain boundary defects of the third doped semiconductor layer.

Optionally, the third doped semiconductor layer is in a nanocrystalline state or a microcrystalline state.

Optionally, the doping concentration of the conductive ions in the third doped semiconductor layer is greater than the doping concentration of the conductive ions in the first doped semiconductor layer.

Optionally, the third doped semiconductor layerThe material is SiO doped with N-type conductive ions_x3Or SiC_y3(ii) a When the material of the third doped semiconductor layer is SiO doped with N-type conductive ions_x3In the third plasma treatment, the gas used comprises a hydrogen-containing gas and/or an oxygen-containing gas; when the material of the third doped semiconductor layer is SiC doped with N-type conductive ions_y3In this case, the gas used for the third plasma treatment includes a hydrogen-containing gas; preferably, x3 is an integer of 1-2; y3 is an integer of 0 to 1.

Optionally, the conductivity type of the third doped semiconductor layer is the same as the conductivity type of the first doped semiconductor layer; the third doped semiconductor layer has an optical band gap width greater than that of the first doped semiconductor layer.

Optionally, the refractive index of the first doped semiconductor layer is smaller than the refractive index of the semiconductor substrate layer, and the refractive index of the third doped semiconductor layer is smaller than the refractive index of the first doped semiconductor layer.

Optionally, the step of forming the third doped semiconductor layer includes: sequentially forming a plurality of stacked third sub-doping layers on one side of the first doped semiconductor layer, which is far away from the semiconductor substrate layer; after each layer of the third sub-doping layer is formed, third plasma treatment is performed on the third sub-doping layer.

Optionally, the parameters of the third plasma treatment include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

Optionally, after the step of performing second plasma processing on a side of the second doped semiconductor layer away from the semiconductor substrate layer, the method further includes: forming a fourth doped semiconductor layer on the surface of one side, away from the semiconductor substrate layer, of the second doped semiconductor layer; and performing fourth plasma treatment on the fourth doped semiconductor layer to passivate the grain boundary defects of the fourth doped semiconductor layer.

Optionally, when the fourth doped layer is located on the back side of the semiconductor substrate layer, the doping concentration of the conductive ions in the fourth doped semiconductor layer is greater than the doping concentration of the conductive ions in the second doped semiconductor layer; preferably, the volume percentage doping concentration of the conductive ions in the fourth doped semiconductor layer ranges from 0.5% to 2%.

Optionally, the fourth doped semiconductor layer is in a nanocrystalline state or a microcrystalline state.

Optionally, the fourth doped semiconductor layer is made of P-type conductive ion doped SiO_x4Or SiC_y4(ii) a When the fourth doped semiconductor layer is made of SiO doped with P-type conductive ions_x4In the above case, the gas used in the fourth plasma treatment includes a hydrogen-containing gas and/or an oxygen-containing gas; when the material of the fourth doped semiconductor layer is SiC doped with P-type conductive ions_y4In this case, the gas used for the fourth plasma treatment includes a hydrogen-containing gas; preferably, x4 is an integer of 1 to 2, and y4 is an integer of 0 to 1.

Optionally, the step of forming the fourth doped semiconductor layer includes: sequentially forming a plurality of stacked fourth sub-doping layers on one side of the second doped semiconductor layer, which is far away from the semiconductor substrate layer; after each layer of the fourth sub-doping layer is formed, fourth plasma treatment is performed on the fourth sub-doping layer.

Optionally, the parameters of the fourth plasma processing include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

Optionally, before forming the first doped semiconductor layer, the method further includes: forming a first intrinsic semiconductor layer on one side of the semiconductor substrate layer; carrying out sixth plasma treatment on the first intrinsic semiconductor layer to passivate defects on the surface of the first intrinsic semiconductor layer; after forming the first doped semiconductor layer, the first intrinsic semiconductor layer is located between the semiconductor substrate layer and the first doped semiconductor layer.

Optionally, before forming the second doped semiconductor layer, the method further includes: forming a second intrinsic semiconductor layer on the other side of the semiconductor substrate layer; carrying out seventh plasma treatment on the second intrinsic semiconductor layer to passivate defects on the surface of the second intrinsic semiconductor layer; after forming the second doped semiconductor layer, the second intrinsic semiconductor layer is located between the semiconductor substrate layer and the second doped semiconductor layer.

Optionally, before forming the first intrinsic semiconductor layer and the second intrinsic semiconductor layer, the method further includes: and performing fifth plasma treatment on the surface of the semiconductor substrate layer to passivate defects on the surface of the semiconductor substrate layer.

Optionally, the gas used for the fifth plasma treatment includes a hydrogen-containing gas.

Optionally, the parameters of the fifth plasma processing include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

Optionally, the gas used for the sixth plasma treatment comprises a hydrogen-containing gas; the gas used for the seventh plasma treatment includes a hydrogen-containing gas.

Optionally, the parameters of the sixth plasma process include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

Optionally, the parameters of the seventh plasma process include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

The technical scheme of the invention has the following advantages:

firstly, carrying out plasma treatment on a doped semiconductor layer on at least one side of a semiconductor substrate layer to passivate crystal boundary defects of the doped semiconductor layer, so as to improve interface state density of a film layer, improve quality of the film layer and improve photoelectric conversion efficiency of a heterojunction battery.

And secondly, carrying out plasma treatment on the intrinsic semiconductor layer to passivate defects on the surface of the intrinsic semiconductor layer. The method can improve the interface state density of the surface of the intrinsic semiconductor layer, improve the quality of the film layer, and is beneficial to nucleation and crystallization of the doped semiconductor layer, so that the thickness of the doped semiconductor layer is reduced, the absorption of a long-wave optical wave band can be reduced, and the short-circuit current of the cell is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a flow chart of a fabrication method using the heterojunction solar cell provided in the embodiment of the present invention;

fig. 2 to fig. 18 are schematic structural diagrams of a heterojunction solar cell manufactured by the method for manufacturing a heterojunction solar cell according to an embodiment of the present invention.

Description of the labeling:

a semiconductor substrate layer 101; a first doped semiconductor layer 103; a third doped semiconductor layer 104;

a first intrinsic semiconductor layer 102; a second intrinsic semiconductor layer 105; a second doped semiconductor layer 106;

a fourth doped semiconductor layer 107; a first transparent electrode layer 108; a second transparent electrode layer 109;

a first gate line 110; a second gate line 111.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood 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.

In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

As shown in fig. 1, the present invention provides a method for manufacturing a heterojunction solar cell, comprising:

and S1, providing a semiconductor substrate layer.

And S2, forming doped semiconductor layers on two sides of the semiconductor substrate layer respectively.

And S3, carrying out plasma treatment on the doped semiconductor layer on at least one side to passivate the grain boundary defects of the doped semiconductor layer.

The invention provides a preparation method of a heterojunction solar cell, which is characterized in that plasma treatment is carried out on a doped semiconductor layer on at least one side of a semiconductor substrate layer so as to improve the interface state density of a film layer, improve the quality of the film layer and finally passivate the crystal boundary defect of the doped semiconductor layer; and the subsequent nucleation and crystallization on the surface of the doped semiconductor layer are facilitated, the crystallization rate of the doped layer arranged on one side, away from the semiconductor layer, of the doped semiconductor layer is improved, meanwhile, the thickness of the doped layer is reduced, the light transmittance and the conductivity of the doped layer are improved, and finally, the conversion efficiency of the heterojunction battery is improved.

The step of forming said doped semiconductor layer on either side of a semiconductor substrate layer comprises: sequentially forming a plurality of laminated sub-doping layers on one side of the semiconductor substrate layer; after each sub-doping layer is formed, plasma treatment is performed on the sub-doping layers.

Preferably, the doped semiconductor layer is nanocrystalline or microcrystalline. The doped semiconductor layer is in a nano crystalline state or a microcrystalline state, which greatly contributes to the improvement of the photoelectric conversion efficiency.

The step of forming doped semiconductor layers on both sides of the semiconductor substrate layer respectively comprises: forming a first doped semiconductor layer on one side of the semiconductor substrate layer; forming a second doped semiconductor layer on the other side of the semiconductor substrate layer; the step of performing plasma treatment on the doped semiconductor layer on at least one side of the semiconductor substrate layer comprises the following steps: and carrying out first plasma treatment on the side of the first doped semiconductor layer, which is far away from the semiconductor substrate layer, and/or carrying out second plasma treatment on the side of the second doped semiconductor layer, which is far away from the semiconductor substrate layer.

The following description will take as an example the first plasma treatment of the side of the first doped semiconductor layer facing away from the semiconductor substrate layer and the second plasma treatment of the side of the second doped semiconductor layer facing away from the semiconductor substrate layer.

The method of fabricating the heterojunction solar cell of the present invention is specifically explained below with reference to fig. 1 to 18. The first doped semiconductor layer 103 and the third doped semiconductor layer 104 are located on the front side of the semiconductor substrate layer 101.

As shown in fig. 2, a semiconductor substrate layer 101 is provided. The material of the semiconductor substrate layer 101 comprises N-type crystalline silicon.

In the present embodiment, as shown in fig. 3, the preparation method further includes performing a fifth Plasma treatment (Plasma) on the surface of the semiconductor substrate layer 101. The interface state density of the surface of the semiconductor substrate layer 101 can be improved through the fifth plasma treatment, the interface quality is improved, and nucleation and crystallization of the first intrinsic semiconductor layer 102 and the second intrinsic semiconductor layer 105 are facilitated.

The gas used for the fifth plasma treatment includes a hydrogen-containing gas; the parameters of the fifth plasma process include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

As shown in fig. 4, a first intrinsic semiconductor layer 102 is formed on one side of the semiconductor substrate layer 101; a second intrinsic semiconductor layer 105 is formed on the side of the semiconductor substrate layer 101 facing away from the first intrinsic semiconductor layer 102. The material of the first intrinsic semiconductor layer 102 and the second intrinsic semiconductor layer 105 includes hydrogenated amorphous silicon (a-Si: H), which may be a multi-layered stacked structure. After the fifth plasma treatment is performed, the first intrinsic semiconductor layer 102 and the second intrinsic semiconductor layer 105 are formed.

As shown in fig. 5, a sixth plasma treatment is performed on the first intrinsic semiconductor layer 102 to passivate defects on the surface of the first intrinsic semiconductor layer 102. The sixth plasma treatment can improve the interface state density of the surface of the first intrinsic semiconductor layer 102, improve the interface quality, and facilitate the nucleation and crystallization of the first doped semiconductor layer.

Preferably, the gas used for the sixth plasma treatment includes a hydrogen-containing gas; the parameters of the sixth plasma process include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

As shown in fig. 6, a first doped semiconductor layer 103 is formed on a side of the first intrinsic semiconductor layer 102 facing away from the semiconductor substrate layer 101.

Preferably, the first doped semiconductor layer 103 is in a nanocrystalline state or a microcrystalline state.

The first doped semiconductor layer is made of SiO doped with N-type conductive ions_x1Or SiC_y1。

As shown in fig. 7, a first plasma process is performed on the first doped semiconductor layer 103. The first plasma treatment may passivate grain boundary defects of the first doped semiconductor layer 103.

The interface state density of the first doped semiconductor layer 103 is improved, the interface quality is improved, the subsequent nucleation and crystallization of the third doped semiconductor layer are facilitated, the crystallization rate of the third doped semiconductor layer can be improved, the thickness of the third doped semiconductor layer is reduced, the light transmittance and the conductivity of the layer are improved, and the conversion efficiency of the heterojunction solar cell is improved.

In an embodiment, the step of forming the first doped semiconductor layer 103 includes: sequentially forming a plurality of stacked first sub-doping layers on one side of the semiconductor substrate layer 101; after each first sub-doping layer is formed, first plasma treatment is performed on the first sub-doping layer.

The parameters of the first plasma process include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

When the material of the first doped semiconductor layer is SiO of N-type conductive ions_x1In the first plasma treatment, the gas used comprises a hydrogen-containing gas and/or an oxygen-containing gas; when the material of the first doped semiconductor layer is SiC of N-type conductive ions_y1Wherein the gas used for the first plasma treatment comprises a hydrogen-containing gas; preferably, x1 is an integer of 1-2; y1 is an integer of 0 to 1. When y1 is 0, the material of the first doped semiconductor layer is Si doped with N-type conductivity ions.

As shown in fig. 8, a third doped semiconductor layer 104 is formed on a surface of the first doped semiconductor layer 103 facing away from the semiconductor substrate layer 101.

Preferably, the third doped semiconductor layer 104 is in a nanocrystalline state or a microcrystalline state.

The material of the third doped semiconductor layer 104 is SiO doped with N-type conductive ions_x3Or SiC_y3. Preferably, x3 is an integer of 1-2; y3 is an integer of 0 to 1. When y3 is 0, the material of the third doped semiconductor layer 104 is Si doped with N-type conductivity ions.

The conductivity type of the third doped semiconductor layer 104 is the same as the conductivity type of the first doped semiconductor layer 103.

Preferably, the doping concentration of the conductive ions in the third doped semiconductor layer 104 is greater than the doping concentration of the conductive ions in the first doped semiconductor layer 103.

The optical band gap width of the third doped semiconductor layer 104 is larger than that of the first doped semiconductor layer 103. The refractive index of the first doped semiconductor layer 103 is smaller than that of the semiconductor substrate layer 101, and the refractive index of the third doped semiconductor layer 104 is smaller than that of the first doped semiconductor layer 103. Because the n side is the incident light surface of sunlight, a relatively high optical band gap is needed, so that the minimum optical absorption loss is ensured; in addition, the refractive index of the third doped semiconductor layer 104 and the first doped semiconductor layer 103 is required to be between that of the transparent electrode layer (refractive index of about 2.1) and that of the semiconductor substrate layer 101 (refractive index of about 3.8) on the front surface, so that the effect of reducing the reflection of incident light rays can be achieved.

As shown in fig. 9, the third doped semiconductor layer 104 is subjected to a third plasma treatment to passivate grain boundary defects of the third doped semiconductor layer 104, so as to improve the quality of the film layer, and the crystallization rate can be increased, so that the conductivity of the film layer is increased, and the series internal resistance of the battery is reduced. Since the third doped semiconductor layer 104 is processed by the third plasma, the crystallization rate of the third doped semiconductor layer 104 is increased, the thickness of the third doped semiconductor layer 104 is reduced, absorption of incident light is reduced, and the short-circuit current of the battery is increased.

The parameters of the third plasma process include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the plasma rate density is 500 watts per square meter-900 watts per square meter.

When the material of the third doped semiconductor layer is SiO doped with N-type conductive ions_x3In the third plasma treatment, the gas used comprises a hydrogen-containing gas and/or an oxygen-containing gas; when the material of the third doped semiconductor layer is SiC doped with N-type conductive ions_y3In this case, the gas used for the third plasma treatment may include a hydrogen-containing gas.

In one embodiment, when the material of the first doped semiconductor layer 103 is SiO doped with N-type conductivity ions_x1The material of the third doped semiconductor layer 104 is SiC doped with N-type conductive ions_y3。

In another embodiment, when the material of the first doped semiconductor layer 103 is SiC doped with N-type conductivity ions_y1The material of the third doped semiconductor layer 104 is SiO doped with N-type conductive ions_x3。

In other embodiments, the material of the first doped semiconductor layer 103 is SiO doped with N-type conductivity ions_x1The material of the third doped semiconductor layer 104 is SiO doped with N-type conductive ions_x3(ii) a In other embodiments, the material of the first doped semiconductor layer 103 is SiC doped with N-type conductivity ions_y1The material of the third doped semiconductor layer 104 is SiC doped with N-type conductivity ions_y3。

Role of oxygen (O) plasma in the interface treatment in the present invention: 1, O plasma can diffuse into SiO doped with N-type conductive ions_xPassivating oxygen vacancies in the semiconductor layer; 2, Si and the gap O can be rearranged in an atomic level on the microstructure under the action of simultaneous heating, so that the SiO doped with N-type conductive ions can be obtained_xRe-crystallization of the semiconductor layer to increase the crystallization rate; 3, the Si dangling bonds on the surface can be passivated by the O plasma, and the current is reducedSurface recombination of (2); 4, and most importantly: the O plasma can be physically adsorbed by the surface and bonded with B or P on the surface, so that the density of heterogeneous nucleation on the surface is improved, and the better crystallinity of the following nanocrystalline and microcrystalline silicon film layers is facilitated.

In this embodiment, the step of forming the third doped semiconductor layer 104 includes: sequentially forming a plurality of stacked third sub-doping layers on the side, away from the semiconductor substrate layer 101, of the first doped semiconductor layer 103; after each layer of the third sub-doping layer is formed, third plasma treatment is performed on the third sub-doping layer.

The first doped semiconductor layer 103 and the third doped semiconductor layer 104 of the present invention may be a multi-layered stack structure, which has the following advantages: the refractive index of the multilayer laminated structure is continuously adjustable, and the adjustment range is 1.5-2.6. The adjustment of the refractive index of the first doped semiconductor layer 103 to 2.6 can be achieved by changing the preparation parameters of the first doped semiconductor layer 103; the refractive index of the third doped semiconductor layer 104 is adjusted by 2.2 by changing the preparation parameters of the third doped semiconductor layer 104, so that a process of gradually changing the refractive index exists from the upper transparent electrode layer (refractive index 2.0) to the third doped semiconductor layer 104 (refractive index 2.2) to the first doped semiconductor layer 103 (refractive index 2.6) to the semiconductor substrate layer 101 (refractive index 3.8), and the reflection can be reduced and the light transmission can be increased. Since the optical band gap width of the third doped semiconductor layer 104 is greater than the optical band gap width of the first doped semiconductor layer 103, the multi-film laminated layer structure of the first doped semiconductor layer 103 and the third doped semiconductor layer 104 can reduce the parasitic absorption of light to the maximum extent and increase the transmittance of light.

In other embodiments, the third doped semiconductor layer 104 may also have a single-layer structure, and the first doped semiconductor layer 103 may also have a single-layer structure.

The conductivity type of the first doped semiconductor layer 103 and the third doped semiconductor layer 104 is the same as the conductivity type of the semiconductor substrate layer.

In one embodiment, the first doped semiconductor layer 103 is a single-layer structure, and the third doped semiconductor layer 104 includes a three-layer stackAnd (5) structure. The specific preparation process flow comprises the following steps: 1, forming a first sub-doping layer, carrying out plasma treatment on a hydrogen-containing gas on the first sub-doping layer, wherein the power adopted in the process of carrying out the plasma treatment on the first sub-doping layer is high, the air pressure is low, the hydrogen-containing gas comprises hydrogen, the volume flow of the hydrogen-containing gas is 2000sccm-5000sccm, the pressure is 0.8mBa-1.2mBar, the temperature is 180-240 ℃, and the plasma power density is 750-900 watts per square meter; 2, forming a first third sub-doping layer, carrying out plasma treatment on the first third sub-doping layer by using oxygen-containing gas, wherein the plasma treatment on the first third sub-doping layer is low in power and high in gas pressure, and the oxygen-containing gas comprises CO₂，CO₂The volume flow of the plasma is 5000sccm-8000sccm, the pressure is 1.2mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the plasma power density is 500 watts per square meter-750 watts per square meter; 3, forming a second third sub-doping layer, carrying out oxygen-containing gas plasma treatment on the second third sub-doping layer, wherein the plasma treatment on the second third sub-doping layer has low power and high pressure, and the oxygen-containing gas comprises CO₂，CO₂The volume flow of the plasma generator is 5000sccm-8000sccm, the pressure cavity is 1.2-1.5 mBar, the temperature is 180-240 ℃, and the plasma power density is 500 watts per square meter-750 watts per square meter; 4, forming a third sub-doping layer, carrying out plasma treatment on the third sub-doping layer by oxygen-containing gas, wherein the plasma treatment on the third sub-doping layer has high power and low pressure, and the oxygen-containing gas comprises CO₂，CO₂The volume flow of the plasma is 2000sccm-5000sccm, the pressure is 0.8mBar-1.2mBar, the temperature is 180 ℃ -240 ℃, and the plasma power density is 750 watts per square meter-900 watts per square meter.

Note that, in other embodiments, the step of forming the third doped semiconductor layer 104 and the step of performing the third plasma treatment may not be performed.

As shown in fig. 10, the second intrinsic semiconductor layer 105 is subjected to a seventh plasma treatment to passivate defects on the surface of the second intrinsic semiconductor layer 105 and to increase the crystallization rate of the second doped semiconductor layer, so that the thickness of the second doped semiconductor layer can be reduced, which can reduce absorption in a long wavelength optical band and increase a short circuit current of the cell.

The gas used for the seventh plasma treatment comprises a hydrogen-containing gas; the parameters of the seventh plasma process include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

As shown in fig. 11, a second doped semiconductor layer 106 is formed on a side of the second intrinsic semiconductor layer 105 facing away from the semiconductor substrate layer 101.

Preferably, the second doped semiconductor layer 106 is in a nanocrystalline state or a microcrystalline state.

In this embodiment, the second doped semiconductor layer 106 is located on the back surface side of the semiconductor substrate layer 101.

When the second doped semiconductor layer 106 is located on the back side of the semiconductor substrate layer 101, the valence band difference between the second doped semiconductor layer 106 and the semiconductor substrate layer 101 is 0.35eV-0.55 eV. Since the wide optical bandgap of the second doped semiconductor layer 106 at the p-side of the heterojunction cell also provides a high valence band difference with the N-type semiconductor substrate layer 101, the high valence band difference enables a good open circuit voltage to be obtained.

The material of the second doped semiconductor layer 106 is SiO doped with P-type conductive ions_x2Or SiC_y2Preferably, x2 is an integer of 1 to 2, and y2 is an integer of 0 to 1. When y2 is 0, the material of the second doped semiconductor layer 106 is Si doped with P-type conductivity ions.

As shown in fig. 12, performing a second plasma treatment on the second doped semiconductor layer 106; specifically, the surface of the second doped semiconductor layer 106, which is away from the semiconductor substrate layer, is subjected to second plasma treatment to passivate grain boundary defects of the second doped semiconductor layer 106, so that the crystallization rate of the second doped semiconductor layer is improved, and the higher crystallization rate can reduce tunneling current recombination and improve the efficiency of the cell.

Specifically, the second plasma treatment may also improve the film quality of the second doped semiconductor layer 106; meanwhile, the subsequent film nucleation crystallization is facilitated, the crystallization rate of the subsequent fourth doped semiconductor layer can be improved, the thickness of the fourth doped semiconductor layer is reduced, the light transmittance and the electric conductivity of the layer are improved, and the conversion efficiency of the heterojunction solar cell is improved.

The step of forming the second doped semiconductor layer 106 includes: sequentially forming a plurality of stacked second sub-doping layers on the other side of the semiconductor substrate layer 101; after each second sub-doping layer is formed, second plasma treatment is performed on the second sub-doping layer.

When the material of the second doped semiconductor layer is SiO doped with P-type conductive ions_x2In the second plasma treatment, the gas used comprises a hydrogen-containing gas and/or an oxygen-containing gas; when the material of the second doped semiconductor layer is SiC doped with P-type conductive ions_y2In this case, the gas used for the second plasma treatment includes a hydrogen-containing gas.

The parameters of the second plasma process include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

As shown in fig. 13, a fourth doped semiconductor layer 107 is formed on a surface of the second doped semiconductor layer 106 facing away from the semiconductor substrate layer 101.

The fourth doped semiconductor layer is positioned on the back side of the semiconductor substrate layer 101; when the fourth doped semiconductor layer is located on the back side of the semiconductor substrate layer 101, the doping concentration of the conductive ions in the fourth doped semiconductor layer 107 is greater than the doping concentration of the conductive ions in the second doped semiconductor layer 106. Preferably, the volume percentage doping concentration range of the conductive ions in the fourth doped semiconductor layer is 0.5% -2%; preferably, the fourth doped semiconductor layer 107 is in a nanocrystalline state or a microcrystalline state.

The fourth doped semiconductor layer 107 is made of SiO doped with P-type conductive ions_x4Or SiC_y4. Preference is given toWherein x4 is an integer of 1 to 2, and y4 is an integer of 0 to 1.

Since light which can reach the P side of the cell is little after being absorbed and generated by the N-type semiconductor substrate layer 101, mainly a small part of long-wave light which is difficult to absorb, the fourth doped semiconductor layer 107 adopts microcrystalline or nanocrystalline silicon which has better doping and mobility, so that a strong P/N junction built-in electric field can be achieved; on the other hand, the contact barrier with the transparent electrode layer on the back surface can be reduced through heavy doping, and the hole carrier transmission on the p side is increased.

As shown in fig. 14, performing a fourth plasma treatment on the fourth doped semiconductor layer 107 to passivate grain boundary defects of the fourth doped semiconductor layer 107, so as to increase the crystallization rate of the fourth doped semiconductor layer 107, where a higher crystallization rate results in better conductivity of the fourth doped semiconductor layer 107, and reduces the series internal resistance of the battery; meanwhile, the contact barrier when the fourth doped semiconductor layer 107 with a higher crystallization rate is combined with the second transparent electrode is lowered, and the series resistance of the cell is also reduced.

When the fourth doped semiconductor layer is made of SiO doped with P-type conductive ions_x4In the above case, the gas used in the fourth plasma treatment includes a hydrogen-containing gas and/or an oxygen-containing gas; when the material of the fourth doped semiconductor layer is SiC doped with P-type conductive ions_y4i, the gas used for the fourth plasma treatment comprises a hydrogen-containing gas.

The parameters of the fourth plasma process include: the total flow of the adopted gas is 2000sccm-8000sccm, the pressure of the chamber is 0.8mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the power density of the plasma is 500 watts per square meter-900 watts per square meter.

The step of forming the fourth doped semiconductor layer 107 includes: sequentially forming a plurality of stacked fourth sub-doping layers on the side, away from the semiconductor substrate layer 101, of the second doped semiconductor layer 106; after each layer of the fourth sub-doping layer is formed, fourth plasma treatment is performed on the fourth sub-doping layer.

The second doped semiconductor layer 106 and the fourth doped semiconductor layer 107 prepared by the invention are of a multilayer laminated structure, and the advantages are as follows: the purpose of the second doped semiconductor layer 106 stack is to increase the accumulation of holes, increasing the open circuit voltage of the cell; the function of the fourth doped semiconductor layer 107 stack is: the stack can realize heavy doping, increase the built-in electric field with the semiconductor substrate layer 101(P/N junction), and improve the carrier collection capability. In other embodiments, the fourth doped semiconductor layer 107 may also have a single-layer structure, and the second doped semiconductor layer 106 may also have a single-layer structure.

In an embodiment, the second doped semiconductor layer 106 includes a three-layer stacked structure, and the fourth doped semiconductor layer 107 is a single-layer structure. The specific preparation process flow comprises the following steps: 1, forming a first and a second sub-doping layers, and performing a plasma treatment process of oxygen-containing gas on the first and the second sub-doping layers, wherein the plasma treatment process is high-power and low-pressure CO₂The volume flow of the plasma is 2000sccm-5000sccm, the pressure is 0.8mBar-1.2mBar, the temperature is 180 ℃ -240 ℃, and the plasma power density is 750 watts per square meter-900 watts per square meter; 2, forming a second sub-doping layer, and performing oxygen-containing gas plasma treatment on the second sub-doping layer to obtain CO with low power and high pressure₂The volume flow of the plasma is 5000sccm-8000sccm, the pressure is 1.2mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the plasma power density is 500 watts per square meter-750 watts per square meter; 3, forming a third second sub-doping layer, and carrying out plasma treatment process of oxygen-containing gas on the third second sub-doping layer, wherein the plasma treatment process is low in power and high in pressure, and CO is adopted₂The volume flow of the plasma is 5000sccm-8000sccm, the pressure is 1.2mBar-1.5mBar, the temperature is 180 ℃ -240 ℃, and the plasma power density is 500 watts per square meter-750 watts per square meter; and 4, forming a fourth sub-doping layer, and carrying out plasma treatment process of hydrogen-containing gas on the fourth sub-doping layer, wherein the plasma treatment process comprises the following steps: the volume flow rate of the hydrogen-containing gas is 2000sccm-5000sccm, the pressure is 0.8mBar-1.2mBar, the temperature is 180 ℃ -240 ℃, and the plasma power density is 750 watts per square meter-900 watts per square meter.

Note that, in other embodiments, the step of forming the fourth doped semiconductor layer 107 and the step of the fourth plasma treatment may not be performed.

As shown in fig. 15, a first transparent electrode layer 108 is formed on a surface of the third doped semiconductor layer 104 facing away from the first doped semiconductor layer 103.

The material of the first transparent electrode layer 108 is indium tin oxide.

And when the third doped semiconductor layer is not formed, forming a first transparent electrode layer on the surface of the first doped semiconductor layer on the side departing from the first doped semiconductor layer.

As shown in fig. 16, a second transparent electrode layer 109 made of ito is formed on a surface of the fourth doped semiconductor layer 107 facing away from the second doped semiconductor layer 106.

And when the fourth doped semiconductor layer is not formed, forming a second transparent electrode layer on the surface of the second doped semiconductor layer on the side departing from the second doped semiconductor layer.

As shown in fig. 17, a first gate line 110 is formed on a surface of the first transparent electrode layer 108 facing away from the third doped semiconductor layer 104.

As shown in fig. 18, a second gate line 111 is formed on a surface of the second transparent electrode layer 109 on a side away from the fourth doped semiconductor layer 107.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.