FA0. 85Cs0. 15PbI3 photoelectric detector

Abstract

The invention discloses an FA < 0.85 > Cs0. 15PbI < 3 > photoelectric detector, which comprises a transparent glass substrate, a transparent bottom electrode, an FA < 0.85 > Cs0. 15PbI < 3 > perovskite thin film, a top electrode and a bias power supply, a patterned transparent bottom electrode is arranged on the transparent glass substrate, an FA < 0.85 > Cs0. 15PbI3 perovskite thin film is arranged on the transparent glass substrate and the transparent bottom electrode, a patterned top electrode is deposited on the FA < 0.85 > Cs0. 15PbI3 perovskite thin film, and a bias power supply is arranged between the transparent bottom electrode and the top electrode. The photoelectric detector has the advantages of good absorption performance, high responsivity and stable structure; the FA0. 85Cs0. 15PbI3 perovskite thin film is prepared by a spraying method, and the perovskite thin film is post-processed by adopting an auxiliary recrystallization annealing method, so that the defects of crystal grains are reduced, the size of the crystal grains is increased, and the performance of the detector is improved.

Description

Technical Field

[0001] The present invention belongs to the field of photoelectric detection technology, and specifically relates to a FA based on auxiliary recrystallization annealing. 0.85 Cs 0.15 PbI3 high performance photodetector. Background Art

[0002] With the development of information technology, photoelectric detection has important applications in image acquisition, optical communication and other fields. Most photodetectors use the photoelectric effect of semiconductors to convert absorbed photons into photogenerated electron / hole pairs, which then form detection photocurrent. Noise and responsivity are two important performance parameters of photodetectors. In order to obtain excellent detection results, the noise of the detector is required to be as small as possible, and a sufficiently high photocurrent is also required. The performance of photodetectors is mainly determined by the photoelectric conversion material and the detector structure. The photoelectric conversion material determines the detector's ability to absorb incident photons and convert them into electron / hole pairs, while the detector structure determines the electric field and energy band distribution inside the detector, which in turn affects the transport and recombination of photogenerated carriers. Generally speaking, narrow-bandgap semiconductors such as HgCdTe, AsGa, etc. can be used to sense infrared photons; single-crystal silicon can be used to sense visible light photons; and wide-bandgap semiconductors such as diamond and GaN can be used to sense ultraviolet photons. Perovskite is a compound semiconductor that has excellent photoelectric conversion properties. It also has advantages such as long carrier diffusion distance and stable irradiation. It has important application prospects in light-emitting devices, photodetection devices, and solar cells.

[0003] In addition to the above-mentioned excellent photoelectric conversion and carrier transport properties, compared with traditional compound inorganic semiconductors, perovskites also have the advantage of being grown by cheap solution methods. In particular, the large-area growth of perovskite films by solution methods provides a new way to reduce the cost of photodetectors. There are currently a variety of methods for growing perovskite films, among which the spraying method is a method that can grow perovskite films on a large scale and at low cost. This method is a large-area thin film deposition technology that can be applied to generate uniform films on large-area substrates. However, most perovskite films grown by the spraying method have an amorphous structure, contain many holes, and have a high defect density. These defects not only affect the transport of carriers, but also cause the recombination of photogenerated electrons and holes, as well as the capture and release of carriers to form additional noise. These problems seriously affect the performance of perovskite thin film photodetectors. Therefore, new technical solutions are urgently needed to solve these problems and improve the performance of perovskite thin film photodetectors. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of poor crystal quality of the sensing layer film, high defect density, and large detection noise in the conventional spraying method for preparing perovskite photodetectors, and to propose a spraying method based on auxiliary recrystallization annealing FA 0.85 Cs 0.15 PbI3 photodetector, and use the method of auxiliary recrystallization annealing to improve the crystallinity of perovskite film, reduce holes, passivation defects, reduce photodetector noise current, and improve the photoelectric response of the detector.

[0005] The technical solution adopted by the present invention is: a FA 0.85 Cs 0.15 PbI3 photodetector, including transparent glass substrate, transparent bottom electrode, FA 0.85 Cs 0.15 PbI3 perovskite film, top electrode and bias power supply;

[0006] A patterned transparent bottom electrode is arranged on the transparent glass substrate, and a FA is arranged on the transparent glass substrate and the transparent bottom electrode. 0.85 Cs 0.15 PbI3 perovskite film, the FA 0.85 Cs 0.15 A patterned top electrode is deposited on the PbI3 perovskite film, and a bias power supply is arranged between the transparent bottom electrode and the top electrode.

[0007] When the incident light shines on the detector through the transparent glass substrate, FA 0.85 Cs 0.15 The PbI3 perovskite film absorbs incident photons and generates photogenerated electron / hole pairs through the photoelectric effect; the bias power supply forms a certain electric field distribution between the top electrode and the transparent bottom electrode; under the action of this electric field, the photogenerated electrons drift toward the top electrode and the photogenerated holes drift toward the transparent bottom electrode, forming a detection current.

[0008] Furthermore, the transparent bottom electrode is an ITO or FTO electrode.

[0009] Furthermore, the top electrode is an Au electrode.

[0010] FA prepared by conventional spraying method 0.85 Cs 0.15 The grain size of PbI3 perovskite thin film is relatively small, which has an adverse effect on the photocurrent. 0.85 Cs 0.15 The PbI3 perovskite film has a large number of voids, high film defect density and poor flatness.

[0011] Furthermore, the FA 0.85 Cs 0.15The PbI3 perovskite film was prepared by spraying, and the FA prepared by spraying was annealed by auxiliary recrystallization. 0.85 Cs 0.15 Post-processing of PbI3 perovskite film increases the grain size, reduces the film void density, and thus reduces the detector dark current and noise.

[0012] Furthermore, the FA 0.85 Cs 0.15 The PbI3 perovskite film was prepared by spraying as follows: dimethylformamide solvent (DMF) and dimethyl sulfoxide solvent (DMSO) were mixed in a volume ratio of 7:3, and then PbI2 powder, FAI powder and CsI powder were weighed in a molar ratio of 1:0.85:0.15, respectively, and the three powders were completely dissolved in the mixed solution of DMF and DMSO, and the FAI was filtered through a filter head with a pore size of 0.22 μm to obtain 0.85 Cs 0.15 PbI3 perovskite precursor liquid. Spray the precursor liquid onto the transparent glass substrate with a spray gun, then place them on a heating table and heat them to 120°C for about half a minute, then cool them naturally to room temperature to grow FA on the glass substrate. 0.85 Cs 0.15 PbI3 perovskite thin film.

[0013] Furthermore, the FA prepared by the spraying method is subjected to the auxiliary recrystallization annealing method. 0.85 Cs 0.15 The specific post-treatment of PbI3 perovskite film is as follows: spray dimethylformamide solution onto FA with a spray gun. 0.85 Cs 0.15 PbI3 perovskite film and heated to 100℃, part of FA 0.85 Cs 0.15 The PbI3 grains are dissolved by the solvent or heated to melt. Then the temperature is lowered from 100°C to room temperature, and these solutes are re-crystallized from the solution or melt. The auxiliary recrystallization annealing method dissolves and grows defective grains again, reducing the defects of the grains and improving the quality of the film.

[0014] Furthermore, a transparent bottom electrode is prepared on a transparent glass substrate by using a magnetron sputtering method through a mask.

[0015] Furthermore, the thermal evaporation method was used in FA 0.85 Cs 0.15 The top electrode was prepared on the PbI3 perovskite film.

[0016] The present invention proposes a method of assisting recrystallization annealing for FA 0.85 Cs 0.15 PbI3 film is post-treated. 0.85 Cs0.15 Spray an appropriate amount of dimethylformamide solvent on the PbI3 film and heat it. 0.85 Cs 0.15 The PbI3 grains are dissolved by the solvent or melted by heating. During the annealing process, these solutes re-crystallize from the solution or melt, dissolving and growing the defective grains again, reducing the defects of the grains, increasing the grain size, reducing the dark current density of the detector by more than an order of magnitude, and improving the detector performance.

[0017] Beneficial effects:

[0018] 1. The basic molecular structure of perovskite is ABX3, where the A position is a monovalent cation, the B position is a divalent metal cation, and the X position is usually occupied by a halogen anion. Selecting different A, B, and X elements can form a rich perovskite structure. The present invention proposes to use FA 0.85 Cs 0.15 PbI3 photodetector. First, FA 0.85 Cs 0.15 PbI3 has a relatively large bandgap modulation range and can absorb photons well from near infrared to ultraviolet. 0.85 Cs 0.15 The effective atomic number and mass density of PbI3 are superior to other perovskites, so it also has good absorption of high-energy photons such as X-rays / γ-rays and can be used in X-ray / γ-ray detectors; third, FA 0.85 Cs 0.15 PbI3 has a higher carrier mobility, which is beneficial to improve the detector's responsiveness; Fourth, compared with other types of perovskites, FA 0.85 Cs 0.15 The ion migration of PbI3 is relatively weak, so based on FA 0.85 Cs 0.15 PbI3 photodetectors are relatively stable.

[0019] 2. The present invention proposes an auxiliary recrystallization annealing method to spray-grown FA 0.85 Cs 0.15 A certain amount of solvent is deposited on the surface of the PbI3 perovskite film, and then it is naturally annealed. During the recrystallization process, the sprayed solvent dissolves or melts the grains, and then re-crystallizes from the solution or melt. The auxiliary recrystallization annealing method dissolves and grows defective grains again, reduces the defects of the grains, and improves the surface uniformity of the film;

[0020] 3. Compared with the traditional thermal annealing method and the atmosphere annealing method, the auxiliary recrystallization annealing method proposed in the present invention can significantly reduce crystal defects, thereby reducing dark current and noise current;

[0021] 4. Compared with the traditional thermal annealing method and atmosphere annealing method, the auxiliary recrystallization annealing method proposed in the present invention can improve FA 0.85 Cs 0.15 The carrier mobility of PbI3 perovskite film can be increased, thereby increasing the responsiveness of the detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 FA of the present invention 0.85 Cs 0.15 Schematic diagram of PbI3 photodetector;

[0023] Figure 2 FA of the present invention 0.85 Cs 0.15 Schematic diagram of the PbI3 film growth apparatus;

[0024] Figure 3 This is a schematic diagram of the auxiliary recrystallization annealing device of the present invention;

[0025] Figure 4 This is an electron microscope image of the natural thermal annealed perovskite film;

[0026] Figure 5 This is an electron microscope image of the perovskite film annealed in a solvent atmosphere;

[0027] Figure 6 This is an electron microscope image of the annealed perovskite film after auxiliary recrystallization;

[0028] Figure 7 Schematic diagram of the comparison of XRD patterns of perovskite films with different annealing methods;

[0029] Figure 8 Schematic diagram for comparison of dark current density of perovskite film photodetectors with different annealing methods;

[0030] In the figure: 1. Transparent glass substrate; 2. Transparent bottom electrode; 3. FA 0.85 Cs 0.15 PbI3 perovskite film; 4. Top electrode; 5. Bias power supply; 6. Spray gun; 7. Precursor solution; 8. Heating platform; 9. Dimethylformamide solution. DETAILED DESCRIPTION

[0031] In order to better understand the purpose, detector structure and function of the present invention, the following is a FA based on recrystallization of the present invention in conjunction with the accompanying drawings. 0.85 Cs 0.15 The PbI3 high performance photodetector is described in further detail.

[0032] like Figure 1 As shown, a FA 0.85 Cs 0.15PbI3 photodetector, comprising a transparent glass substrate 1, a transparent bottom electrode 2, and a FA 0.85 Cs 0.15 PbI3 perovskite film 3, top electrode 4 and bias power supply 5;

[0033] The transparent glass substrate 1 is provided with a patterned transparent bottom electrode 2, and the transparent glass substrate 1 and the transparent bottom electrode 2 are provided with FA 0.85 Cs 0.15 PbI3 perovskite film 3, the FA 0.85 Cs 0.15 A patterned top electrode 4 is deposited on the PbI3 perovskite film 3 , and a bias power supply 5 is arranged between the transparent bottom electrode 2 and the top electrode 4 .

[0034] First, the transparent glass substrate 1 is placed in deionized water, acetone solution and anhydrous ethanol solution for ultrasonic cleaning for 20 minutes, and then taken out and placed in a UV ozone cleaning machine for UV ozone treatment for 30 minutes. The patterned transparent bottom electrode 2 is deposited through a mask by magnetron sputtering. In order for the incident light to penetrate the electrode and enter the sensing layer, the transparent bottom electrode 2 needs to be light-transmissive. Typical transparent electrodes are ITO electrodes and FTO electrodes.

[0035] In the second step, FA is grown on the transparent glass substrate 1 and the transparent bottom electrode 2 by spraying. 0.85 Cs 0.15 PbI3 perovskite film 3, such as Figure 2 As shown. The precursor solution 7 of perovskite is loaded into the spray gun 6. The preparation method of the precursor solution 7 is as follows: the materials required for preparation include lead iodide powder (PbI2), formamidine hydroiodide powder (FAI), cesium iodide powder (CsI), dimethylformamide solvent (DMF) and dimethyl sulfoxide solvent (DMSO). Dimethylformamide solvent (DMF) and dimethyl sulfoxide solvent (DMSO) are mixed in a volume ratio of 7:3, and then PbI2 powder, FAI powder and CsI powder are weighed respectively in a molar ratio of 1:0.85:0.15, and the three powders are completely dissolved in the mixed solution of DMF and DMSO successively. After the solute is completely dissolved, filter with a filter head with a pore size of 0.22μm to obtain FA 0.85 Cs 0.15 Precursor solution 7 of PbI3 perovskite. Spray the precursor solution 7 onto the transparent glass substrate 1 and the transparent bottom electrode 2, and then place them on a heating platform 8, the temperature of which is 120°C. The heating time is about half a minute, and then naturally cool to room temperature to grow FA on the transparent glass substrate 1. 0.85 Cs 0.15 PbI3 film.

[0036] In the third step, the FA grown on the transparent glass substrate 1 0.85Cs 0.15 PbI3 film is annealed to improve film quality. There are generally two annealing methods:

[0037] Natural thermal annealing method: After the precursor solution is heated to 120°C on the heating stage 8, it is naturally cooled to room temperature to form FA 0.85 Cs 0.15 PbI3 polycrystalline film. Figure 4 FA obtained by natural thermal annealing 0.85 Cs 0.15 SEM image of PbI3 polycrystalline thin film, from which we can see that FA 0.85 Cs 0.15 The particle size of PbI3 is less than 5 μm, and there are a large number of voids in the film.

[0038] Solvent atmosphere annealing method. In addition to the natural thermal annealing method, people have also reported the solvent atmosphere annealing method. The sprayed transparent glass substrate 1 and the glass dish containing 10 ml of dimethylformamide solution (DMF) are covered with a sealed glass cover and placed on a heating table at 100°C. After the dimethylformamide solution (DMF) in the glass dish is completely evaporated, the glass substrate is naturally cooled to room temperature. Figure 5 FA obtained by solvent atmosphere annealing 0.85 Cs 0.15 SEM image of PbI3 polycrystalline thin film, from which we can see that FA 0.85 Cs 0.15 The PbI3 grain size increases to more than 5μm, some grains exceed 10μm, and the number of voids in the film is significantly reduced.

[0039] Although solvent atmosphere annealing improves FA 0.85 Cs 0.15 The quality of PbI3 polycrystalline film, but from Figure 4 In order to further improve the film quality and reduce the density of voids, the present invention proposes auxiliary recrystallization annealing, and the annealing device is as follows: Figure 3 shown. Figure 3 The auxiliary recrystallization annealing device shown is Figure 2 FA shown 0.85 Cs 0.15 The PbI3 film growth device is similar, but it is sprayed with dimethylformamide solution 9. Spray dimethylformamide solution 9 onto the FA 0.85 Cs 0.15 PbI3 film is heated to 100℃, and some FA 0.85 Cs 0.15The PbI3 grains are dissolved by the solvent or heated and melted. When the temperature drops from 100°C to room temperature, these solutes re-crystallize from the solution or melt. The auxiliary recrystallization annealing method re-dissolves and grows the defective grains, reduces the defects of the grains, and improves the quality of the film. Figure 6 FA obtained by assisted recrystallization annealing 0.85 Cs 0.15 SEM image of PbI3 polycrystalline thin film, from which we can see that FA 0.85 Cs 0.15 The PbI3 grain size increases, and no obvious void defects are observed in the film. Figure 7 and Figure 8 The FA obtained by different annealing methods were compared. 0.85 Cs 0.15 The X-ray diffraction spectrum (XRD) and dark current density curve of PbI3 polycrystalline film show that the FA 0.85 Cs 0.15 The crystalline quality of PbI3 film is improved, and the dark current density is reduced by 1 order of magnitude.

[0040] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A FA 0.85 Cs 0.15 PbI3 photodetector, characterized by: Including transparent glass substrate, transparent bottom electrode, FA 0.85 Cs 0.15 PbI3 perovskite film, top electrode and bias power supply; A patterned transparent bottom electrode is arranged on the transparent glass substrate, and a FA is arranged on the transparent glass substrate and the transparent bottom electrode. 0.85 Cs 0.15 PbI3 perovskite film, the FA 0.85 Cs 0.15 A patterned top electrode is deposited on the PbI3 perovskite film, and a bias power supply is arranged between the transparent bottom electrode and the top electrode.

2. A FA according to claim 1 0.85 Cs 0.15 PbI3 photodetector, characterized by: The transparent bottom electrode is an ITO or FTO electrode.

3. A FA according to claim 1 0.85 Cs 0.15 PbI3 photodetector, characterized by: The top electrode is an Au electrode.

4. A FA according to claim 1 0.85 Cs 0.15 PbI3 photodetector, characterized by: The FA 0.85 Cs 0.15 The PbI3 perovskite film was prepared by spraying, and the FA prepared by spraying was annealed by auxiliary recrystallization. 0.85 Cs 0.15 Post-treatment of PbI3 perovskite films.

5. A FA according to claim 4 0.85 Cs 0.15 PbI3 photodetector, characterized by: The FA 0.85 Cs 0.15 The PbI3 perovskite film was prepared by spraying as follows: dimethylformamide solvent and dimethyl sulfoxide solvent were mixed in a volume ratio of 7:3, and then PbI2 powder, FAI powder and CsI powder were weighed in a molar ratio of 1:0.85:0.15, respectively, and the three powders were completely dissolved in the mixed solution of dimethylformamide solvent and dimethyl sulfoxide solvent successively, and the FAI was filtered through a filter head with a pore size of 0.22 μm to obtain the FAI powder. 0.85 Cs 0.15 PbI3 perovskite precursor liquid is sprayed onto a transparent glass substrate with a spray gun, and then placed on a heating table and heated to 120°C for about half a minute, and then naturally cooled to room temperature to grow FA on the glass substrate. 0.85 Cs 0.15 PbI3 perovskite thin film.

6. A FA according to claim 5 0.85 Cs 0.15 PbI3 photodetector, characterized by: The method of using auxiliary recrystallization annealing to treat FA prepared by spraying 0.85 Cs 0.15 The specific post-treatment of PbI3 perovskite film is as follows: spray dimethylformamide solution onto FA with a spray gun. 0.85 Cs 0.15 PbI3 perovskite film and heated to 100℃, part of FA 0.85 Cs 0.15 The PbI3 grains are dissolved by the solvent or heated to melt; then the temperature is lowered from 100°C to room temperature, and the solutes crystallize again from the solution or melt.

7. A FA according to claim 6 0.85 Cs 0.15 PbI3 photodetector, characterized by: A transparent bottom electrode is prepared on a transparent glass substrate through a magnetron sputtering method.

8. A FA according to claim 6 0.85 Cs 0.15 PbI3 photodetector, characterized by: Thermal evaporation method in FA 0.85 Cs 0.15 The top electrode was prepared on the PbI3 perovskite film.

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