Ga2O3 / Au / MAPbI3 flexible photoelectric detector with high external quantum efficiency and preparation method thereof

Abstract

The invention discloses a Ga2O3 / Au / MAPbI3 flexible photoelectric detector with high external quantum efficiency and a preparation method of the Ga2O3 / Au / MAPbI3 flexible photoelectric detector, and belongs to the technical field of photoelectric detectors. A fluorine crystal mica substrate with good flexibility and bending repeatability is used, firstly, an n-Ga2O3 thin film is epitaxially grown on the fluorine crystal mica substrate, then an Au interdigital electrode is deposited on the surface of the n-Ga2O3 thin film through electron beam evaporation, and finally, a p-MAPbI3 thin film is prepared on the surface of the Au interdigital electrode through one-step spin coating. And the Ga2O3 / Au / MAPbI3 flexible photoelectric detector with high external quantum efficiency is formed. The contact between the fluorine crystal mica substrate and the thin film is Van der Waals force contact, so that the influence of lattice mismatch on the quality of the thin film crystal can be effectively reduced. The external quantum efficiency of the device can be effectively improved, and the device has the advantages of being simple in preparation process, low in cost and wide in application scene.

Description

Technical Field

[0001] This invention belongs to the field of photodetector technology, specifically relating to a Ga2O3 / Au / MAPbI3 flexible photodetector with high external quantum efficiency and its fabrication method. Background Technology

[0002] With the advancement of science and technology and the development of society, the demand for ultraviolet (UV) detection in both civilian and military fields is becoming increasingly widespread. In the sun's UV spectrum, ultraviolet radiation in the UVC band (200-280 nm) is absorbed when passing through the atmosphere and is known as solar-blind UV radiation. This band of UV signals has advantages such as low susceptibility to background radiation, low false alarm rate, high sensitivity, and high signal-to-noise ratio, and has been widely used in military and civilian fields such as guidance, space security communications, ozone layer depletion monitoring, and flame detection.

[0003] Gallium oxide (Ga2O3) is an ultrawide bandgap semiconductor material with a room-temperature bandgap of approximately 4.2–4.9 eV, and its response wavelength almost covers the entire solar-blind band of the solar spectrum. Furthermore, this material exhibits excellent thermal and chemical stability, making it an ideal material for fabricating solar-blind ultraviolet detectors. However, its strong self-compensation effect has prevented effective p-type doping from being achieved.

[0004] MAPbX3 (X = Br, Cl, I) belongs to the methylamine lead-based perovskite family. The band gap can be tuned by changing the type of halogen element, thereby altering the light absorption range. MAPbI3, in particular, can achieve excellent p-type conductivity by changing the ratio of the precursor solvents MAI and PbI2. Furthermore, MAPbI3 is simple and inexpensive to prepare, and can be fabricated using spin-coating. It has been reported that n-Ga2O3 / p-MAPbI3 heterojunctions can achieve effective photodetection capabilities by adjusting the thickness and doping concentration of the n-Ga2O3 film to obtain space charge regions of varying widths within the n-Ga2O3 layer.

[0005] Fluorocrystalline mica, as a synthetic mica material, possesses excellent thermal stability and flexibility. The absence of dangling bonds on its surface allows for thin film adhesion via van der Waals forces, enabling the production of high-quality films even with significant lattice mismatch. Flexible mica substrates can greatly expand the application scenarios for detectors. Summary of the Invention

[0006] The purpose of this invention is to provide a flexible Ga2O3 / Au / MAPbI3 photodetector with high external quantum efficiency and its fabrication method by means of MOCVD and thin film spin coating process.

[0007] This invention uses a fluorinated mica substrate with good flexibility and bend repeatability. First, an n-Ga2O3 thin film is epitaxially grown on the fluorinated mica substrate using MOCVD. Then, Au interdigitated electrodes are deposited on the surface of the n-Ga2O3 thin film using electron beam evaporation. Finally, a p-MAPbI3 thin film is prepared on the surface of the interdigitated Au electrodes by one-step spin coating, thus forming the high external quantum efficiency Ga2O3 / Au / MAPbI3 flexible photodetector.

[0008] Specifically, the high external quantum efficiency Ga2O3 / Au / MAPbI3 flexible photodetector described in this invention, such as... Figure 1 As shown, it is composed of a fluorine crystal mica substrate 1, an n-Ga2O3 thin film 2 prepared on the fluorine crystal mica substrate 1, an Au interdigitated electrode 3 prepared on the n-Ga2O3 thin film 2, and a p-MAPbI3 thin film 4 prepared on the Au interdigitated electrode 3.

[0009] The fabrication method of a flexible Ga2O3 / Au / MAPbI3 photodetector with high external quantum efficiency, as described above, comprises the following steps: A. Substrate plasma treatment: First, the fluorine crystal mica substrate 1 is cleaned with acetone, ethanol and deionized water in sequence under ultrasonic conditions for 5-10 minutes, and then the substrate is dried with high-purity nitrogen gas; then the obtained fluorine crystal mica substrate 1 is placed in a plasma treatment machine and treated in an oxygen atmosphere for 3-5 minutes. B. Preparation of n-Ga₂O₃ thin film: An n-Ga₂O₃ thin film 2 is epitaxially grown on the fluorine-crystalline mica substrate 1 obtained in step A using a high-temperature MOCVD process. The thickness of the n-Ga₂O₃ thin film 2 is 270 nm to 330 nm, and the electron concentration is 1 × 10⁻⁶. 18 cm -3 ~1×10 19 cm -3 ; C. Preparation of Au interdigitated electrodes: Negative photoresist is spin-coated onto the n-Ga2O3 thin film 2 obtained in step B, and then exposed under a UV lamp in a photolithography machine using a mask for 6-8 seconds. The exposed device is then immersed in a developing solution for 40-60 seconds to obtain a cutout photoresist pattern with the same structure as the Au interdigitated electrode to be prepared. The photolithographically etched device is placed in an electron beam evaporation device to evaporate a 50-150 nm thick Au layer on it. Then, the excess photoresist and the Au layer on it are removed, retaining the interdigitated electrode pattern, thereby obtaining the Au interdigitated electrode 3 on the surface of the n-Ga2O3 thin film 2. D. Preparation of MAPbI3 precursor solution: Mix MAI and PbI2 powders in a molar ratio of 1~3:1, add to 0.2~1 mL of a mixed solution of DMF and DMSO in a volume ratio of 4:1, stir at 50~70℃ for 3~5 h until fully dissolved, to obtain 0.2~1 mL of MAPbI3 precursor solution with a concentration of 0.2~1.2 mol / L; E. Preparation of photodetector: The device with Au interdigitated electrodes on the surface obtained in step C is subjected to ultraviolet ozone treatment for 20-30 min. After treatment, the MAPbI3 precursor solution obtained in step D is spin-coated onto the surface of n-Ga2O3 film 2 and Au interdigitated electrodes 3 by one-step spin coating. During the high-speed spin coating process of one-step spin coating, 50-150 μL of antisolvent chlorobenzene is added dropwise. After spin coating, the obtained device is annealed at 90-110℃ for 15-30 min to obtain p-MAPbI3 film 4 with a thickness of 100 nm-210 nm, thereby obtaining the Ga2O3 / Au / MAPbI3 flexible photodetector.

[0010] Furthermore, in step B, the growth source is trimethylgallium and high-purity oxygen, Ar gas is used as the carrier gas for trimethylgallium, the n-type dopant is silane gas, the growth temperature is 750°~850°C, the growth time is 25~35 min, the flow rates of trimethylgallium and high-purity oxygen are 10~40 sccm and 400~800 sccm, respectively, the flow rate of silane (SiH4) is 0.004~0.015 μmol / min, and the growth pressure is 10~40 mbar; In step C, the finger width of the interdigitated electrode is 8~12μm, the finger spacing is 8~12μm, the finger length is 300~500μm, and the number of finger pairs is 8~12 pairs; In step E, the low-speed spin coating speed is 500~800 r / min and the spin coating time is 8~15 s, while the high-speed spin coating speed is 3000~3500 r / min and the spin coating time is 25~35 s.

[0011] Effects and benefits of the present invention: (1) The fluorine-crystal mica substrate used in this invention has a van der Waals contact with the thin film, which can effectively reduce the influence of lattice mismatch on the crystal quality of the thin film; (2) The p-MAPbI3 thin film has a high hole concentration and good p-type conductivity; (3) The Schottky barrier and built-in electric field of the Ga2O3 / Au / MAPbI3 structure can effectively reduce the dark current of the photodetector and significantly improve the photo-dark current ratio and external quantum efficiency of the device; (4) The fluorine-crystal mica substrate can withstand high temperatures above 1000℃ and can be bent more than 120°. The good flexibility of the substrate allows the device to work normally under multiple bending conditions, greatly enriching the working scenarios of the device. Therefore, this invention can not only effectively improve the external quantum efficiency of the device, but also has the advantages of simple preparation process, low cost and wide application scenarios. Attached Figure Description

[0012] Figure 1 : A schematic diagram of the structure of the device fabricated according to the present invention; Figure 2 XRD patterns of the n-Ga2O3 and p-MAPbI3 films in Example 1 and the (-201) bicrystalline rocking curve of the n-Ga2O3 film. Figure 3 The photoresponse of the device under different light intensities in Example 1 IV Curve (a) and the optical response of the device in Example 1 in the flat state, the initial bending state, and after 100 bending cycles. IV Curve (b). Detailed Implementation

[0013] Example 1 A flexible Ga2O3 / Au / MAPbI3 photodetector with high external quantum efficiency has the following structure: Figure 1 As shown, it consists of a fluorine crystal mica substrate 1, an n-Ga2O3 thin film 2 on the fluorine crystal mica substrate 1, an Au interdigitated electrode 3 on the n-Ga2O3 thin film 2, and a p-MAPbI3 thin film 4 on the Au interdigitated electrode 3.

[0014] The specific steps of the fabrication method for the high external quantum efficiency Ga2O3 / Au / MAPbI3 flexible photodetector described above are as follows: A. The fluorine crystal mica substrate 1 used for epitaxy was prepared by the molten salt method and had a thickness of 200 μm. First, the fluorine crystal mica substrate 1 was cleaned with acetone, ethanol and deionized water for 8 minutes in sequence under ultrasonic conditions. Then, the substrate was dried with high-purity nitrogen. The obtained fluorine crystal mica substrate 1 was then placed in a plasma treatment machine and treated in an oxygen atmosphere for 4 minutes. B. The n-Ga₂O₃ thin film 2 was obtained by MOCVD epitaxy. The reaction source was trimethylgallium and high-purity oxygen, and silane was used as the n-type dopant. During the growth process, the electron concentration of the thin film was controlled by adjusting the silane flow rate. The flow rates of trimethylgallium and high-purity oxygen were 10 sccm and 800 sccm, respectively, the silane flow rate was 0.015 μmol / min, the growth pressure was 40 mbar, and the growth time was 30 min, thus obtaining the n-Ga₂O₃ thin film 2 on the fluorine mica substrate 1. The thickness of the n-Ga₂O₃ thin film was 310 nm, and the electron concentration was 1 × 10⁻⁶. 19 cm -3 ; C. Spin-coat a layer of AZ2020 negative photoresist onto the n-Ga2O3 thin film 2 obtained in step B, and then expose it under a UV lamp in a lithography machine for 7 seconds. The structure of the mask is the same as the structure of the interdigitated electrode to be prepared. Then, immerse the exposed device in a developing solution for 50 seconds to remove the unexposed photoresist, obtaining a cutout photoresist pattern with the same structure as the Au interdigitated electrode to be prepared. Place the photolithographically lithographic device into an electron beam evaporation device to evaporate a 100nm thick Au layer on it. Then, remove the excess photoresist and the Au layer on it, retaining the interdigitated electrode pattern, thereby obtaining the Au interdigitated electrode 3 on the surface of the n-Ga2O3 thin film 2. The interdigitated electrode has a finger width of 10μm, a finger spacing of 10μm, a finger length of 400μm, and 10 finger pairs. D. After the electrode is fabricated, mix MAI and PbI2 powders in a molar ratio of 3:1, add them to 1 mL of a mixed solution of DMF and DMSO in a volume ratio of 4:1, and stir in a stirrer at 60℃ for 4 h until fully dissolved to obtain 1 mL of 0.2 mol / L MAPbI3 precursor solution. E. The device with Au interdigitated electrodes obtained in step C is subjected to ultraviolet ozone treatment for 25 min. Then, the MAPbI3 precursor solution obtained in step D is spin-coated onto the ozone-treated Au interdigitated electrode surface using a one-step spin-coating method. The low-speed spin-coating speed is 500 r / min and the spin-coating time is 10 s, while the high-speed spin-coating speed is 3000 r / min and the spin-coating time is 25 s. During the high-speed spin-coating process, 100 μL of chlorobenzene is added as an anti-solvent. After spin-coating, the obtained device is annealed on a hot plate at 100 °C for 20 min to obtain a p-MAPbI3 thin film 4 with a thickness of 110 nm, thereby obtaining a Ga2O3 / Au / MAPbI3 flexible photodetector with high external quantum efficiency.

[0015] To investigate the crystal quality of n-Ga2O3 and p-MAPbI3 films and their impact on device performance, we used an Ultima IV X-ray diffractometer to test the crystal quality of the n-Ga2O3 and p-MAPbI3 films in this embodiment and performed photoresponse testing on the device. The results are as follows: 1. Crystal quality analysis of the sample in the example Figure 2 The XRD 2Theta patterns of the Ga2O3 and MAPbI3 films in Example 1 are shown in the inset, with the bicrystalline rocking curve of the Ga2O3 film in the (-201) crystal orientation shown. The figure reveals that the Ga2O3 film is a single crystal, and the full width at half maximum (FWHM) of the (-201) crystal orientation rocking curve is 1.6°, indicating that the Ga2O3 film possesses high crystal quality. Since the substrate and film are in van der Waals force contact, this effectively reduces the quality degradation caused by lattice mismatch between the substrate and the film.

[0016] 2. Photoresponse Analysis of the Device in the Example Example Figure 3 The photoresponse of the device in Example 1 under different light intensities IV Curve (a) and the light response of the device in Example 1 in the flat state, the initial bending state, and after 100 bending cycles. IV Curve (b). As shown in Figure (a), the photocurrent increases significantly with increasing optical power, indicating that the device has strong sensitivity to ultraviolet light. Calculations show that the device has a responsivity of 35 A / W, an external quantum efficiency of 6536%, and a detectivity greater than 10⁻⁶ under flat conditions. 14 Jones. As shown in Figure (b), the device maintains a high photocurrent-to-dark current ratio and external quantum efficiency even after bending, even after 100 bends, and still exhibits strong ultraviolet detection performance. In summary, the Ga2O3 / Au / MAPbI3 flexible photodetector prepared by this method has high external quantum efficiency and wide application scenarios. Experimental results prove the feasibility of this process.

Claims

1. A flexible photodetector with high external quantum efficiency, characterized in that: From bottom to top, it consists of a fluorinated mica substrate (1), an n-Ga2O3 thin film (2) prepared on the fluorinated mica substrate (1), an Au interdigitated electrode (3) prepared on the n-Ga2O3 thin film (2), and a p-MAPbI3 thin film (4) prepared on the Au interdigitated electrode (3).

2. The method for fabricating a flexible Ga2O3 / Au / MAPbI3 photodetector with high external quantum efficiency as described in claim 1, comprising the following steps: A. Plasma treatment of substrate: First, the fluorine crystal mica substrate (1) is cleaned with acetone, ethanol and deionized water in the ultrasonic state for 5-10 minutes respectively, and then the substrate is dried with high-purity nitrogen; then the obtained fluorine crystal mica substrate (1) is placed in a plasma treatment machine and treated in an oxygen atmosphere for 3-5 minutes. B. Preparation of n-Ga2O3 thin film: n-Ga2O3 thin film (2) is epitaxially grown on the fluorine crystal mica substrate (1) obtained in step A using a high-temperature MOCVD process. The thickness of the n-Ga2O3 thin film (2) is 270nm~330nm and the electron concentration is 1×10⁻⁶. 18 cm -3 ~1×10 19 cm -3 ; C. Preparation of Au interdigitated electrodes: Spin-coat negative photoresist onto the n-Ga2O3 thin film (2) obtained in step B, then expose it under the ultraviolet lamp of the photolithography machine using a mask for 6-8s, and then immerse the exposed device in the developer for 40-60s to obtain a hollow photoresist pattern with the same structure as the Au interdigitated electrode to be prepared; place the photolithographically etched device into an electron beam evaporation device to evaporate a 50-150nm thick Au layer on it; then remove the excess photoresist and the Au layer on it, retaining the interdigitated electrode pattern, thereby obtaining the Au interdigitated electrode (3) on the surface of the n-Ga2O3 thin film (2). D. Preparation of MAPbI3 precursor solution: Mix MAI and PbI2 powders in a molar ratio of 1~3:1, add to 0.2~1 mL of a mixed solution of DMF and DMSO in a volume ratio of 4:1, stir at 50~70℃ for 3~5 h until fully dissolved, to obtain 0.2~1 mL of MAPbI3 precursor solution with a concentration of 0.2~1.2 mol / L; E. Preparation of photodetector: The device with Au interdigitated electrodes on the surface obtained in step C is subjected to ultraviolet ozone treatment for 20-30 min. After treatment, the MAPbI3 precursor solution obtained in step D is spin-coated onto the surface of n-Ga2O3 film (2) and Au interdigitated electrodes (3) by one-step spin coating. During the high-speed spin coating process of one-step spin coating, 50-150 μL of antisolvent chlorobenzene is added dropwise. After spin coating is completed, the obtained device is annealed at 90-110℃ for 15-30 min to obtain p-MAPbI3 film (4). The thickness of p-MAPbI3 film (4) is 100 nm-210 nm, thereby obtaining the Ga2O3 / Au / MAPbI3 flexible photodetector.

3. The method for fabricating a flexible Ga2O3 / Au / MAPbI3 photodetector with high external quantum efficiency as described in claim 2, characterized in that: In step B, the growth source is trimethylgallium and high-purity oxygen, Ar gas is used as the carrier gas for trimethylgallium, silane gas is used as the n-type dopant, the growth temperature is 750°~850°C, the growth time is 25~35 min, the flow rates of trimethylgallium and high-purity oxygen are 10~40 sccm and 400~800 sccm respectively, the flow rate of silane is 0.004~0.015 sccm, and the growth pressure is 10~40 mbar.

4. The method for fabricating a flexible Ga2O3 / Au / MAPbI3 photodetector with high external quantum efficiency as described in claim 2, characterized in that: In step C, the finger width of the interdigitated electrode is 8~12μm, the finger spacing is 8~12μm, the finger length is 300~500μm, and the number of finger pairs is 8~12 pairs.

5. The method for fabricating a flexible Ga2O3 / Au / MAPbI3 photodetector with high external quantum efficiency as described in claim 2, characterized in that: In step E, the low-speed spin coating speed is 500~800 r / min and the spin coating time is 8~15 s, while the high-speed spin coating speed is 3000~3500 r / min and the spin coating time is 25~35 s.

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