A perovskite single crystal photodetector and its preparation method

Abstract

The present invention discloses a perovskite single crystal photodetector and a preparation method thereof, relating to the technical field of photodetectors. The preparation method of the perovskite single crystal photodetector comprises the following steps: S1. Preparation of a perovskite precursor solution; S2. Growth of a basic MAPbCl3 single crystal; S3. Growth of a heterojunction MAPbCl3-MAPbBr3 single crystal; S4. Preparation of the perovskite single crystal photodetector. The preparation method of the perovskite single crystal photodetector provided by the present invention is simple to operate, has stable technology, has no strict requirements for the preparation environment, and has easily available raw materials. The obtained perovskite single crystal photodetector has excellent effects and can work stably in an air environment, solving the technical problem that the detector can work without connecting an external voltage. The perovskite single crystal photodetector provided by the present invention has the characteristics of self-driving, high spectral responsivity and environmental stability, and can be used for the detection of long-term optical signals.

Description

Technical Field

[0001] The present invention relates to the technical field of photodetectors, and particularly to a perovskite single crystal photodetector and a preparation method thereof. Background Art

[0002] Photodetectors have the ability to convert optical signals into electrical signals and are widely used in fields such as image sensing, optical communication, and environmental monitoring. Most traditional photodetectors use inorganic semiconductor materials such as Si, SiC, InGaAs, GaN, etc. However, such semiconductor materials need to be grown in a high-vacuum environment, and the preparation process is complex. Moreover, traditional photodetectors need to be driven by an external power source to detect optical signals, which not only increases the cost but also increases the complexity of the test system.

[0003] In the past decade, due to the simple synthesis method and excellent optoelectronic properties of organic-inorganic hybrid perovskite materials, such as high absorption coefficient, long carrier diffusion length, high carrier mobility, low exciton binding energy, etc., they have been widely used in many optoelectronic device fields, including photodetectors, lasers, solar cells, light-emitting diodes, etc.

[0004] Perovskite polycrystalline thin film materials are easily degraded in an air environment due to the presence of grain boundaries and pores, and have poor stability. This problem has become a major obstacle to the practical application of perovskite materials. Compared with polycrystalline thin films, perovskite single crystals (SCs) have advantages such as low trap state density and good stability. Due to these advantages, it is crucial for the preparation of high-performance and stable photodetectors.

[0005] Self-powered detectors have advantages such as small size, light weight, and easy integration, and can meet the requirements of extreme environment testing and portable devices. Self-powered detectors can be realized through the photovoltaic effect of Schottky junctions and heterojunctions. Most of the existing perovskite-based photodetectors basically use a perovskite material and another material to form a heterojunction device structure to achieve self-powered detection.

[0006] Currently, there is no heterojunction device composed of two perovskite single crystal materials to realize a self-powered perovskite single crystal photodetector. Summary of the Invention

[0007] Aiming at the defects in the prior art, the present invention provides a perovskite single crystal photodetector and a preparation method thereof, which utilize two perovskite single crystals to form a lateral heterojunction to prepare a self-powered perovskite photodetector that is stable in an air environment.

[0008] On the one hand, the present invention provides a preparation method of a perovskite single crystal photodetector, and the steps are as follows:

[0009] S1. Preparation of perovskite precursor solution:

[0010] Weigh MACl and PbCl 2 powder, add it to a mixed solvent of dimethyl sulfoxide and dimethylformamide, and prepare a MAPbCl 3 perovskite precursor solution. Place it on a magnetic stirrer and stir overnight at 15 - 30 °C;

[0011] Weigh MABr and PbBr 2 powder, add it to a dimethylformamide solvent, and prepare a MAPbBr 3 perovskite precursor solution. Place it on a magnetic stirrer and stir overnight, and then stir overnight at 60 °C;

[0012] S2. Growth of basic MAPbCl 3 single crystal:

[0013] Filter the MAPbCl 3 perovskite precursor solution through a polytetrafluoroethylene filter into a clean bottle, dispense it into 1 - ml vials, place it on a 25 °C hot plate, raise the temperature of the hot plate for the first time and maintain it, then raise the temperature of the hot plate for the second time and maintain it to obtain MAPbCl 3 single crystal.

[0014] S3. Growth of heterostructured MAPbCl 3 -MAPbBr 3 single crystal:

[0015] Clean two glass substrates successively in detergent, deionized water, acetone, and isopropanol by ultrasonic cleaning. Put the cleaned glass substrates and MAPbCl 3 single crystal into a clean glass bottle. Place the glass substrates at the bottom and top of the single crystal respectively to restrict the growth of heterostructured MAPbCl 3 -MAPbBr 3 single crystal in a specific direction. Place the glass bottle on a 60 °C hot plate, pour the MAPbBr 3 precursor solution into the glass bottle and seal it. Slowly raise the temperature and maintain it to obtain heterostructured MAPbCl 3 -MAPbBr 3 single crystal. Treat it with a MACl isopropanol solution to obtain a heterostructured MAPbCl 3 -MAPbBr 3 single crystal treated with a MACl isopropanol solution;

[0016] S4. Preparation of perovskite single - crystal photodetector:

[0017] Using a mask on the heterostructured MAPbCl 3 -MAPbBr 3A 1 mm × 1 mm Au electrode is vapor-deposited on the single-crystal center, and on the periphery of the heterojunction MAPbCl 3 -MAPbBr 3 Au electrodes are simultaneously vapor-deposited. The thickness of the electrodes is 50 nm, and the perovskite single-crystal photodetector is obtained.

[0018] Preferably, in step S1, the molar ratio of MACl to PbCl 2 powders is 1:1, the volume ratio of dimethyl sulfoxide to dimethylformamide in the dimethyl sulfoxide and dimethylformamide mixed solvent is 1:1, and the volume of the dimethyl sulfoxide and dimethylformamide mixed solvent is 5 ml; the concentration of the MAPbCl 3 perovskite precursor solution is 1 M.

[0019] Preferably, in step S1, the molar ratio of MABr to PbBr 2 powders is 1:1, the volume of the dimethylformamide solvent is 5 ml; the concentration of the MAPbBr 3 perovskite precursor solution is 1 M.

[0020] Preferably, in step S2, the pore size of the polytetrafluoroethylene filter is 0.2 μm.

[0021] Preferably, in step S2, the temperature of the hot plate is first increased and maintained at 45 °C for 5 hours.

[0022] Preferably, in step S2, the temperature of the hot plate is secondarily increased and maintained at 60 °C for 6 hours.

[0023] Preferably, in step S2, the size of the MAPbCl 3 single crystal is 3-5 mm.

[0024] Preferably, in step S3, the temperature is slowly increased and maintained at 70 °C for 1 hour.

[0025] Preferably, in step S3, treatment with a MACl isopropanol solution is adopted, and the specific steps are as follows: a 0.5 mg / ml MACl isopropanol solution is spin-coated on the surface of the heterojunction MAPbCl 3 -MAPbBr 3 single crystal for 20 seconds at a rotation speed of 4000 rpm, and then the heterojunction MAPbCl 3 -MAPbBr 3 single crystal is annealed at 60 °C for 10 minutes.

[0026] On the other hand, the present invention also protects the perovskite single-crystal photodetector prepared by the above preparation method.

[0027] The beneficial effects of the present invention are embodied in:

[0028] (1) The preparation method of the perovskite single-crystal photodetector provided by the present invention is simple in operation, stable in technology, has no strict requirements for the preparation environment, and the raw materials are easily available. The prepared perovskite single-crystal photodetector has excellent effects and can work stably in an air environment, solving the technical problem that the detector can work without connecting an external voltage.

[0029] (2) The perovskite single-crystal photodetector provided by the present invention has the characteristics of self-driving, high spectral responsivity and environmental stability, and can be used for the detection of long-term optical signals. Description of the Drawings

[0030] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts do not necessarily draw according to the actual scale.

[0031] Figure 1 (a) Partial scanning electron microscope images of the heterojunction single crystal prepared in the example; 3 MAPbCl in the heterojunction single crystal prepared in the example;

[0032] Figure 1 (b) Partial scanning electron microscope images of the heterojunction single crystal prepared in the example; 3 MAPbBr in the heterojunction single crystal prepared in the example;

[0033] Figure 2 X-ray diffraction pattern of the heterojunction single crystal prepared in the example;

[0034] Figure 3 Absorption curves of three perovskite single crystals of MAPbCl 3 single crystal, MAPbBr 3 single crystal and the heterojunction single crystal prepared in the example;

[0035] Figure 4 Absorption curves of three perovskite single crystals of MAPbCl 3 single crystal, MAPbBr 3 single crystal and the heterojunction single crystal prepared in the example, spectral responsivity curves and I-t curves under 400nm and 570nm monochromatic light illumination;

[0036] Figure 5 Stability test curve of the heterojunction single crystal prepared in this example in an air environment;

[0037] Figure 6An imaging system and a grayscale value curve using the heterojunction single-crystal photodetector prepared in this embodiment as a sensing pixel;

[0038] Figure 7 Schematic diagram of the structure of the heterojunction single-crystal photodetector prepared in this embodiment. Detailed implementation mode

[0039] The embodiments of the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, so they are only examples and cannot be used to limit the protection scope of the present invention.

[0040] It should be noted that unless otherwise specified, the technical terms or scientific terms used in this application should be the ordinary meanings understood by those skilled in the art to which the present invention belongs.

[0041] This embodiment provides a preparation method for a perovskite single-crystal photodetector, and the steps are as follows:

[0042] S1. Preparation of perovskite precursor solution:

[0043] a. Weigh MACl and PbCl 2 powders with a molar ratio of 1:1, mix the two and add them to a 5 ml mixed solvent of dimethyl sulfoxide and dimethylformamide with a volume ratio of 1:1 to prepare a 1 M MAPbCl 3 perovskite precursor solution, and place it on a magnetic stirrer and stir overnight at room temperature.

[0044] b. Weigh MABr and PbBr 2 powders with a molar ratio of 1:1, mix the two and add them to 5 ml of dimethylformamide solvent to prepare a 1 M MAPbBr 3 perovskite precursor solution, and place it on a magnetic stirrer and stir overnight at 60°.

[0045] S2. Growth of basic MAPbCl 3 single crystal: Filter the MAPbCl 3 precursor solution through a 0.2 μm pore size polytetrafluoroethylene (PTFE) filter into a clean bottle. In order to grow MAPbCl 3 single crystal, divide the filtered precursor solution into small vials (1 ml each), place them on a hot plate at 25 °C, raise the temperature of the hot plate to 45 °C and keep it for 5 hours, and continue heating to raise the temperature of the hot plate to 60 °C and keep it for 6 hours. Then MAPbCl3 single crystals with a size of 3-5 mm are obtained.

[0046] S3. Heterogeneous MAPbCl 3 -MAPbBr 3Growth of single crystal (heterojunction single crystal): The heterojunction single crystal is grown by the space confinement method and the inverse temperature crystallization method. Two glass substrates are successively ultrasonically cleaned in detergent, deionized water, acetone and isopropanol. The cleaned glass substrates and MAPbCl 3 single crystal are placed in a clean glass bottle, and the glass substrates are placed at the bottom and top of the single crystal to restrict the growth of the heterojunction single crystal in a specific direction. The glass bottle is placed on a hot plate at 60 °C. Then, MAPbBr 3 precursor solution is poured into the glass bottle and sealed. The temperature is slowly raised to 70 °C and maintained for 1 hour. Then the heterojunction single crystal is obtained. The obtained heterojunction single crystal is treated with MACl isopropanol solution. The MACl isopropanol solution (0.5 mg / ml) is spin-coated on the surface of the heterojunction single crystal (4000 rpm, 20 s), and then the heterojunction single crystal is annealed at 60 °C for 10 minutes.

[0047] S4. Preparation of perovskite single crystal photodetector: A 1 mm × 1 mm Au electrode is evaporated in the center of the heterojunction single crystal using a mask, and Au electrodes are simultaneously evaporated around the heterojunction single crystal. The thickness of the electrode is 50 nm, and the perovskite single crystal photodetector is obtained.

[0048] Test example

[0049] Inspect the surface morphology and properties of the heterojunction MAPbCl 3 -MAPbBr 3 single crystal (heterojunction single crystal)

[0050] 1. Scanning electron microscopy analysis

[0051] The heterojunction single crystal is analyzed by scanning electron microscopy. As Figure 1 shown, Figure 1 it can be clearly observed that the surface of the heterojunction single crystal prepared in the example has no defects and has a very high growth quality.

[0052] 2. XRD analysis

[0053] The heterojunction single crystal is analyzed by XRD. As Figure 2 shown, Figure 2 the diffraction peaks reflected by the curves in it match the crystal planes highly, and there are no extra diffraction peaks after growing the heterojunction single crystal, indicating that the perovskite single crystal synthesized in the example has a high quality.

[0054] 3. Spectral absorption analysis

[0055] The heterojunction single crystal is analyzed by spectral absorption. As Figure 3 shown, Figure 3 it can be seen from the absorption curve that the light absorption positions of the heterojunction single crystal prepared in the example correspond to MAPbCl 3Single crystal and MAPbBr 3 The light absorption position of the single crystal indicates that the two single crystals are successfully synthesized together by the method provided in the examples.

[0056] 4. Spectral responsivity analysis

[0057] From Figure 4 It can be seen from the test curve of (a) that the spectral response range at 0 V is from 250 nm to 570 nm. The two cut-off wavelengths are located at ≈430 nm and ≈570 nm respectively. The spectral responsivity above 570 nm drops sharply, and this result is consistent with the absorption spectrum. The two peak responsivities are 26.8 mA / W at 400 nm and 0.21 mA / W at 570 nm respectively.

[0058] Figure 4 (b) shows the spectral responsivity curves of three single crystal devices under a 1 V bias. It can be seen from the curve that by laterally growing MAPbBr 3 single crystal around the MAPbCl 3 single crystal, the response in the ultraviolet region is enhanced. Compared with the MAPbCl 3 single crystal device, the overall responsivity of the heterojunction single crystal device in the ultraviolet region is increased by nearly 470%. Due to the introduction of MAPbBr 3 single crystal, the heterojunction single crystal device still has spectral response in the range of 440 nm - 570 nm, but the responsivity is lower than that of the MAPbBr 3 single crystal device. This is because the carrier concentration provided by the MAPbBr 3 single crystal part in the heterojunction single crystal device is lower than that provided by the pure MAPbBr 3 single crystal device.

[0059] The I-t curves of the three single crystal devices under 1 V bias under light irradiation at wavelengths of 400 nm and 570 nm are as shown in Figure 4 (c) and Figure 4 (d). When 400 nm monochromatic light is applied and removed, all three photodetectors can generate periodically varying currents, indicating that the device has significant reproducibility and stability. Among them, Figure 4 the I light / I dark change of the heterojunction single crystal device in (c) is the largest. When tested with 570 nm monochromatic light, the MAPbCl 3 single crystal device does not have periodic changes because 570 nm is not within the applicable range of this device. Figure 4 (d) shows that the photocurrent generated by the MAPbBr 3 single crystal device is greater than that generated by the heterojunction device. This is due to the pure MAPbBr 3The photo-generated carrier concentration generated by the single crystal is greater than that of the MAPbBr of the heterojunction single crystal 3 The photo-generated carrier concentration of the partial generation. This phenomenon is consistent with Figure 4 (b) Responsivity spectrum. In addition, the spectral response of the heterojunction single crystal photodetector can be tested without any external power supply, demonstrating the possibility of the present invention.

[0060] 5. Stability test of heterojunction single crystal in air environment

[0061] The change of the spectral responsivity of the heterojunction single crystal within 120 days was tested. It can be seen from the Figure 5 curve that the spectral responsivity hardly changes in the atmospheric environment with a humidity of 40%, proving that the heterojunction single crystal photodetector prepared in the embodiment of the present invention has high air stability and can be used for long-term optical signal detection.

[0062] 6. Imaging ability of heterojunction single crystal electro-optical detector at 0V

[0063] To test the imaging ability of the heterojunction single crystal self-powered photodetector at 0V, an imaging system using the heterojunction single crystal photodetector prepared in this embodiment as a sensing pixel was constructed as follows Figure 6 (a) shown.

[0064] Use a laser cutter to make an object with a hollowed-out pattern (the school emblem of Harbin Normal University) on a steel plate as the target object of the imaging system. The object is installed on a computer-controlled X-Y direction translation stage and can move continuously in the horizontal and vertical directions. Use a 405nm laser (5mW) as the test light source. As the translation stage moves, the photocurrent generated by the photodetector is extracted and recorded by a lock-in amplifier and a computer, and is recorded simultaneously with the position coordinates of the object. Then, an image is obtained by combining the current intensity and the position coordinates, as Figure 6 (b) shown. It can be observed from the imaging diagram that the boundary of the test image is clear and highly consistent with the shape of the target object. Use MATLAB to extract the gray values along the Figure 6 dotted line marked in (b), as Figure 6 (c) shown. The gray value changes from high to low, corresponding to the image boundary. It shows that using the heterojunction single crystal photodetector as a sensing pixel, the imaging system has high-fidelity characteristics. These results show that the heterojunction single crystal photodetector provided by the present invention can meet the requirements of the imaging system without any external power supply.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention, and they should all be covered by the scope of the claims and the specification of the present invention.

Claims

1. A preparation method of a perovskite single crystal photodetector, characterized in that: The preparation method is as follows: S1. Preparation of perovskite precursor solution: Weigh MACl and PbCl 2 powder, add it to a mixed solvent of dimethyl sulfoxide and dimethylformamide, and prepare a MAPbCl 3 perovskite precursor solution. Place it on a magnetic stirrer and stir overnight at 15 - 30 °C; Weigh MABr and PbBr 2 powder, add it to the dimethylformamide solvent, and prepare a MAPbBr 3 perovskite precursor solution, place it on a magnetic stirrer and stir overnight, and stir overnight at 60 °C; S2. Basic MAPbCl 3 Growth of single crystal: Filter the MAPbCl 3 perovskite precursor solution through a polytetrafluoroethylene filter into a clean bottle, dispense it into 1-ml vials, place them on a 25 °C hot plate, raise the temperature of the hot plate for the first time and maintain it, then raise the temperature of the hot plate for the second time and maintain it to obtain MAPbCl 3 single crystals; S3. Heterogeneous MAPbCl 3 -MAPbBr 3 Growth of single crystals: Two glass substrates were successively ultrasonically cleaned in detergent, deionized water, acetone, and isopropyl alcohol. The cleaned glass substrates and MAPbCl 3 single crystals were placed in a clean glass bottle. The glass substrates were respectively placed at the bottom and top of the single crystals to confine the hetero MAPbCl 3 -MAPbBr 3 single crystal growth in a specific direction. The glass bottle was placed on a 60 °C hot plate, and the MAPbBr 3 precursor solution was poured into the glass bottle and sealed. The temperature was slowly raised and maintained, and MAPbBr grew laterally around the MAPbCl 3 single crystal. The hetero MAPbCl 3 -MAPbBr 3 single crystal was prepared. It was treated with a MACl isopropyl alcohol solution to obtain the hetero MAPbCl 3 -MAPbBr 3 single crystal after treatment with the MACl isopropyl alcohol solution; 3 ​ S4. Preparation of perovskite single crystal photodetector: Using a mask on the heterojunction MAPbCl after treatment with an isopropanol solution of MACl 3 -MAPbBr 3 Evaporating Au electrodes with a size of 1 mm × 1 mm on the center of the single crystal and simultaneously evaporating Au electrodes around the periphery of the heterojunction MAPbCl 3 -MAPbBr 3 single crystal. The thickness of the electrodes is 50 nm to obtain the perovskite single crystal photodetector described above.

2. The preparation method of the perovskite single crystal photodetector according to claim 1, characterized in that: In step S1, the molar ratio of MACl to PbCl 2 powder is 1:1, the volume ratio of dimethyl sulfoxide to dimethylformamide in the mixed solvent of dimethyl sulfoxide and dimethylformamide is 1:1, and the volume of the mixed solvent of dimethyl sulfoxide and dimethylformamide is 5 ml; the concentration of the MAPbCl 3 perovskite precursor solution is 1 M.

3. The preparation method of the perovskite single crystal photodetector according to claim 1, characterized in that: In step S1, the molar ratio of the MABr to the PbBr 2 powder is 1:1, and the volume of the dimethylformamide solvent is 5 ml; the concentration of the MAPbBr 3 perovskite precursor solution is 1 M.

4. The preparation method of the perovskite single crystal photodetector according to claim 1, characterized in that: In step S2, the pore size of the polytetrafluoroethylene filter is 0.2 μm.

5. The preparation method of the perovskite single crystal photodetector according to claim 1, characterized in that: In step S2, the first increase in the temperature of the hot plate and maintaining is to increase the temperature to 45 °C and hold for 5 hours.

6. The preparation method of the perovskite single crystal photodetector according to claim 1, characterized in that: In step S2, the second increase in the temperature of the hot plate and maintaining is to increase the temperature to 60 °C and hold for 6 hours.

7. The preparation method of the perovskite single crystal photodetector according to claim 1, characterized in that: In step S2, the MAPbCl 3 single crystal has a size of 3-5 mm.

8. The preparation method of the perovskite single crystal photodetector according to claim 1, characterized in that: In step S3, the slow heating and maintaining is to increase the temperature to 70 °C and hold for 1 hour.

9. The preparation method of the perovskite single crystal photodetector according to claim 1, characterized in that: In step S3, the treatment with the MACl isopropanol solution is carried out as follows: The 0.5 mg / ml MACl isopropanol solution is spin-coated on the heterojunction MAPbCl 3 -MAPbBr 3 single crystal surface for 20 seconds at a rotation speed of 4000 rpm, and then the heterojunction MAPbCl 3 -MAPbBr 3 single crystal is annealed at 60 °C for 10 minutes.

10. A perovskite single crystal photodetector prepared by the preparation method according to any one of claims 1-9.

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