阅读说明：本技术 基于钙钛矿材料的x射线探测器及其制备方法 (Perovskite material-based X-ray detector and preparation method thereof ) 是由 刘生忠 张云霞 刘渝城 于 2019-10-10 设计创作，主要内容包括：本发明一种基于钙钛矿材料的X射线探测器及其制备方法,所述方法包括：步骤1,按照摩尔比为3：2称取AI和BI<Sub>3</Sub>原料,溶于有机溶剂中,得到混合前驱体液；其中,AI为CsI,CH<Sub>3</Sub>NH<Sub>3</Sub>I或RbI；BI<Sub>3</Sub>为BiI<Sub>3</Sub>或SbI<Sub>3</Sub>；步骤2,将混合前驱体液密封,加热到60-100℃,保持2～48小时,使其达到充分的溶解平衡后取上清液,得到前驱体的完全饱和溶液；步骤3,将前驱体的完全饱和溶液置于比步骤2中加热终止温度低的环境温度下,以小于5℃/day的速度逐渐升温,直至晶体析出,温度继续增加最多10℃后停止升温,得到A<Sub>3</Sub>B<Sub>2</Sub>I<Sub>9</Sub>钙钛矿单晶；步骤4,将单晶晶体取出并烘干；步骤5,在单晶晶体表面蒸镀叉指金属电极。(The invention relates to an X-ray detector based on perovskite materials and a preparation method thereof, wherein the method comprises the following steps: step 1, preparing a mixture of a raw material and a solvent according to a molar ratio of 3:2 weighing AI and BI 3 Dissolving raw materials in an organic solvent to obtain a mixed precursor liquid; wherein AI is CsI, CH 3 NH 3 I or RbI; BI (BI) 3 Is BiI 3 Or Sbi 3 (ii) a Step 2, sealing the mixed precursor liquid, heating to 60-100 ℃, keeping for 2-48 hours to ensure that the mixed precursor liquid is fully dissolved and balanced, and taking supernate to obtain a fully saturated solution of the precursor; step 3, placing the fully saturated solution of the precursor at an ambient temperature lower than the heating termination temperature in the step 2, gradually heating at a speed of less than 5 ℃/day until crystals are precipitated, and stopping heating after the temperature is continuously increased by at most 10 ℃ to obtain A 3 B 2 I 9 A perovskite single crystal; step 4, taking out and drying the single crystal; and 5, evaporating an interdigital metal electrode on the surface of the single crystal.)

1. An X-ray detector based on perovskite material, characterized in that it comprises A as light-absorbing layer₃B₂I₉A perovskite-type material and an electrode provided on one surface thereof.

2. The perovskite material-based X-ray detector of claim 1, wherein a is₃B₂I₉In the perovskite-type material, A is CH₃NH₃ ⁺，Cs⁺Or Rb⁺(ii) a B is Bi³⁺Or Sb³⁺。

3. The perovskite material-based X-ray detector of claim 1, wherein a is₃B₂I₉The perovskite material is A₃B₂I₉A type of single crystal material.

4. The perovskite material-based X-ray detector of claim 1, wherein the electrodes are metal interdigitated electrodes.

5. The perovskite material-based X-ray detector of claim 4, wherein the electrode is a gold electrode or a copper electrode.

6. The preparation method of the X-ray detector based on the perovskite material is characterized by comprising the following steps:

step 1, preparing a mixture of a raw material and a solvent according to a molar ratio of 3:2 weighing AI and BI₃Dissolving raw materials in an organic solvent to obtain a mixed precursor liquid; wherein AI is CsI, CH₃NH₃I or RbI; BI (BI)₃Is BiI₃Or Sbi₃；

Step 2, sealing the mixed precursor liquid, heating to 60-100 ℃, keeping for 2-48 hours to ensure that the mixed precursor liquid is fully dissolved and balanced, and taking supernate to obtain a fully saturated solution of the precursor;

step 3, placing the fully saturated solution of the precursor at an ambient temperature lower than the heating termination temperature in the step 2, gradually heating at a speed of less than 5 ℃/day until crystals are precipitated, continuously increasing the temperature by at most 10 ℃, and stopping heating to obtain A₃B₂I₉A perovskite single crystal;

step 4, taking out and drying the single crystal;

and 5, evaporating an interdigital metal electrode on the surface of the single crystal to obtain the semiconductor X-ray detector.

7. The method for preparing an X-ray detector based on perovskite material according to claim 6, wherein the concentration of the mixed precursor liquid is 0.2-1.5 mol/L.

8. The method for preparing an X-ray detector based on perovskite material as claimed in claim 6, wherein the organic solvent is at least one of γ -butyrolactone, N-dimethylformamide, dimethyl sulfoxide and N-methyl-2-pyrrolidone.

9. The method for preparing an X-ray detector based on perovskite material as claimed in claim 6, wherein in step 3, the fully saturated solution of the precursor is placed at an ambient temperature 2-5 ℃ lower than the termination temperature of heating in step 2.

10. The method for preparing an X-ray detector based on perovskite material as claimed in claim 6, wherein in step 3, the temperature is kept constant or the temperature is increased continuously by at most 10 ℃ until crystals are precipitated, and then the temperature is stopped.

Technical Field

The invention relates to the field of semiconductor X-ray detectors, in particular to an X-ray detector based on perovskite materials and a preparation method thereof.

Background

The semiconductor radiation detector has been widely applied to industries such as national defense and military, medical health, public safety, high-end industry, scientific research and the like by virtue of the advantages of high energy resolution, high detection efficiency, large stopping power and the like. The semiconductor detector for detecting radioactive rays directly converts absorbed ray energy into electron-hole pairs, and the electron-hole pairs drift under the action of an external electric field to output signals. In practical application, different semiconductors are selected as light absorption layer materials of the detector according to different applications. Currently in the medical field, digital medical imaging has become an important part of current medical diagnostic treatment. In recent years, X-ray Flat Panel Detectors (FPDs) have received much attention and research due to their excellent imaging performance. The X-ray flat panel detector is divided into a direct type and an indirect type, and compared with the direct type flat panel detector, the direct type flat panel detector has better spatial resolution and simpler system device. Direct X-ray flat panel detectors using α -Se, Si and CdZnTe as light absorbing layers have been commercially used. However, these materials still have problems such as complicated preparation process, high price, low sensitivity due to small atomic number of the material, and insufficient detection dose. Therefore, the development of new semiconductor materials with higher sensitivity and lower detection limit for X-rays is very urgent and necessary.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides an X-ray detector based on perovskite material and a preparation method thereof, and the X-ray detector based on perovskite material A₃B₂I₉The perovskite type single crystal has the advantages of simple preparation method, no toxicity, no pollution and low cost, and the obtained semiconductor X-ray detector has high detection sensitivity, low detection limit and high stability.

The invention is realized by the following technical scheme:

x-ray detector based on perovskite material, comprising A as light-absorbing layer₃B₂I₉A perovskite-type material and an electrode provided on one surface thereof.

Preferably, A is₃B₂I₉In the perovskite-type material, A is CH₃NH₃ ⁺，Cs⁺Or Rb⁺(ii) a B is Bi³⁺Or Sb³⁺。

Preferably, A is₃B₂I₉The perovskite material is A₃B₂I₉A type of single crystal material.

Preferably, the electrodes are metal interdigital electrodes.

Further, the electrode is a gold electrode or a copper electrode.

The preparation method of the X-ray detector based on the perovskite material comprises the following steps:

step 1, preparing a mixture of a raw material and a solvent according to a molar ratio of 3:2 weighing AI and BI₃Dissolving raw materials in an organic solvent to obtain a mixed precursor liquid; wherein AI is CsI, CH₃NH₃I or RbI; BI (BI)₃Is BiI₃Or Sbi₃；

Step 2, sealing the mixed precursor liquid, heating to 60-100 ℃, keeping for 2-48 hours to ensure that the mixed precursor liquid is fully dissolved and balanced, and taking supernate to obtain a fully saturated solution of the precursor;

step 3, placing the fully saturated solution of the precursor at an ambient temperature lower than the heating termination temperature in the step 2, gradually heating at a speed of less than 5 ℃/day until crystals are precipitated, continuously increasing the temperature by at most 10 ℃, and stopping heating to obtain A₃B₂I₉A perovskite single crystal;

step 4, taking out and drying the single crystal;

and 5, evaporating an interdigital metal electrode on the surface of the single crystal to obtain the semiconductor X-ray detector.

Preferably, the concentration of the mixed precursor liquid is 0.2 to 1.5 mol/L.

Preferably, the organic solvent is at least one of γ -butyrolactone, N-dimethylformamide, dimethyl sulfoxide and N-methyl-2-pyrrolidone.

Preferably, in step 3, the fully saturated solution of the precursor is placed at an ambient temperature 2-5 ℃ lower than the termination temperature of heating in step 2.

Preferably, in step 3, the temperature is maintained or increased by a further maximum of 10 ℃ until crystals precipitate, and then the temperature is stopped.

Compared with the prior art, the invention has the following beneficial technical effects:

the invention adopts A₃B₂I₉Perovskite single crystal is taken as light absorption layer to prepare X-ray detector, and is taken as A of light absorption layer₃B₂I₉The perovskite single crystal has large atomic number, high absorption coefficient to rays, high carrier mobility and long service life, and is beneficial to realizing higher ray sensitivity; the relatively large resistivity is beneficial to realizing lower detection limit; the heat stability and the humidity stability are good; the interdigital electrode arranged on one side face is matched, so that the X-ray detection interdigital electrode is simple in structure, short in preparation process flow and low in cost, direct and rapid derivation of electrons and holes is realized, and extremely high X-ray detection performance is realized.

The invention can obtain the fully saturated solution of the precursor and simultaneously fully remove impurities and precipitated mixed crystals in the solution by sealing, heating and maintaining the mixed precursor solution. Meanwhile, the initial temperature of crystal growth is lower than the holding temperature of sealing and heating, so that the continuous and stable rate can be kept when the single crystal is separated out, and the forming quality of the crystal is ensured. After the crystal is precipitated, the temperature is continuously raised at a certain rate or kept for a period of time, so as to fully utilize solute in the precursor solution and grow and obtain crystals with larger size.

Drawings

Fig. 1 is a schematic structural diagram of an X-ray detector based on perovskite material according to an embodiment of the present invention. In the figure, first and second interdigital electrodes 1 and 2 and a light absorption layer 3 are shown.

Fig. 2 is a graph of attenuation efficiency versus thickness for 40KeV energy radiation for the different materials described in the examples of the present invention.

FIG. 3 is an I-t plot of 40KeV energy lines measured by the X-ray detector in an example of the present invention.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

The X-ray detector based on the perovskite material comprises A as an absorption layer of the device₃B₂I₉A perovskite-type single crystal and an interdigital electrode arranged on the surface of the absorption layer. The method is that the growth A is controlled in the solution₃B₂I₉The perovskite single crystal is used as a ray absorption layer, and then an interdigital electrode is evaporated on the surface of the perovskite single crystal to collect electrons and holes, so that the device assembly is directly completed in one step. The semiconductor X-ray detector has the advantages of simple method and process, high response sensitivity, low detection limit, environmental friendliness, long service life and the like, and has wide application prospect.

Specifically, the perovskite material-based X-ray detector comprises: a. the₃B₂I₉Perovskite type single crystal and interdigital electrode prepared on the surface of the single crystal. Wherein A is₃B₂I₉The perovskite single crystal is used as the light absorption layer material of the X-ray detector, A is CH₃NH₃ ⁺，Cs⁺，Rb⁺(ii) a B is Bi³⁺，Sb³⁺. The interdigital electrode is a metal electrode, gold (Au) or copper (Cu).

The invention relates to a preparation method of an X-ray detector based on a perovskite material, which specifically comprises the following steps:

step 1, preparing a mixture of a raw material and a solvent according to a molar ratio of 3:2 weighing AI and BI₃Dissolving raw materials in an organic solvent to obtain a mixed precursor liquid with the concentration of 0.2-1.5 mol/L; wherein AI is CsI, CH₃NH₃I，RbI；BI₃Is BiI₃，SbI₃(ii) a The organic solvent is at least one of gamma-butyrolactone, N-dimethylformamide, dimethyl sulfoxide and N-methyl-2-pyrrolidone;

step 2, putting the mixed precursor liquid into a crystallizing dish, sealing, heating to 60-100 ℃, keeping for 2-48 hours to ensure that the mixed precursor liquid is fully dissolved and balanced, and taking supernate to obtain a fully saturated solution of the precursor;

step 3, putting the fully saturated solution of the precursor at the environment temperature which is 2-5 ℃ lower than the heating termination temperature in the step 2, and keeping the temperature at less than 5 ℃/daGradually raising the temperature at the speed of y until crystals are precipitated, continuing to increase the temperature by at most 10 ℃, and stopping raising the temperature to obtain A₃B₂I₉A perovskite single crystal;

step 4, taking out and drying the single crystal;

and 5, evaporating an interdigital metal electrode on the surface of the single crystal to obtain the semiconductor X-ray detector. The metal interdigital electrode is an Au electrode or a Cu electrode.

A obtained in the preferred embodiment₃B₂I₉Perovskite Single Crystal X-ray Detector, as shown in FIG. 1, A₃B₂I₉The perovskite single crystal is used as a light absorption layer 3, and a pair of first and second interdigital electrodes 1, 2 are oppositely arranged above the light absorption layer. A. the₃B₂I₉The perovskite is a defective perovskite material, the material is extremely easy to nucleate in a large amount by the existing solution growth method, crystal growth is mainly controlled by nucleation, so that polycrystal or twin crystal is formed, and large-size block single crystal with high quality and low defect is difficult to obtain. Therefore, the invention controls the nucleation quantity by reducing the nucleation sites, so that the dominant crystal nucleus preferentially grows, and good single crystal crystals are obtained. In the steps 2 and 3, the mixed precursor liquid is put into a crystallizing dish for sealing, heated to 60-100 ℃, and kept for 2-48 hours, so that a large number of active sites which are easy to nucleate are eliminated, and meanwhile, the solution is ensured to reach the optimal saturated state, so that the solution is fully dissolved and balanced; taking supernatant in a crystallizing dish, placing the supernatant in a 60-100 ℃ oven, gradually heating at a speed of less than 5 ℃/day, and after a large number of nucleation sites are eliminated, controlling crystal precipitation by temperature regulation, thereby growing to obtain high-quality A₃B₂I₉A perovskite single crystal.

Compared with the traditional up-down structure, the planar structure X-ray detector prepared by the arranged interdigital electrodes has the advantages of simple preparation process, low cost and easy integration. Most importantly, the X-ray detector with the planar structure prepared by the interdigital electrode has lower detection limit and higher response speed, which is beneficial to reducing the dosage of the X-ray detector and shortening the radiation time, thereby greatly reducing the radiation injury to patients in medical use.

As shown in FIG. 2, A of the present invention₃B₂I₉Perovskite single crystal as absorption layer, and other Si, C, Cs₂AgBiBr₆，MAPbI₃Compared with the prior art, the method has the obvious advantage that the attenuation efficiency of rays is higher under the same thickness. Compared with the material prepared by the X-ray detector used for commercial use at present, the X-ray detector based on the perovskite material has larger average relative atomic number because of containing heavy atoms of Cs, Bi and I. (the larger the atomic number, the stronger the attenuation of X-rays), so A₃B₂I₉Perovskite type is a very good X-ray absorbing material; in addition, experiments have demonstrated that this material is comparable to previous perovskites (MAPbI)₃，MAPbBr₃，Cs2AgBiBr₆) Has better properties, such as low dark current, small ion migration and excellent stability. The low dark current of the semiconductor photoelectric material has the advantages that the intrinsic carrier concentration of the material is low, the noise current generated as a device is low, and particularly for X-rays, the detection limit can be effectively reduced; since the X-ray detector generally needs to work under a large electric field, ion migration is easily caused, and the ion migration may cause structural damage of the material, resulting in rapid decomposition. In addition, the ion migration can affect the working stability of the device, shorten the service life, and also cause the problems of unstable detection signals, poor imaging quality, reduced resolution ratio and the like. Since perovskite is a soft lattice material, the ion migration problem is very common, so that the problem of ion migration can be effectively solved by growing the perovskite crystal, and the stability of the perovskite crystal is ensured.

As shown in FIG. 3, the I-t curve of the X-ray detector based on perovskite material under the irradiation of 40KeV ray under the condition of applying an electric field of 1.5V/mum is shown in FIG. 3, when the ray is switched and circulated, the X-ray detector has high on-off current ratio and good detection performance.