A selenium-bismuth-oxide / molybdenum ditelluride heterojunction phototransistor with gate voltage regulation of photoelectric conversion efficiency and a preparation method and application thereof

Abstract

The application belongs to the field of two-dimensional photoelectric transistors, and discloses a Bi2O2Se / MoTe2 heterojunction photoelectric transistor with gate voltage regulated photoelectric conversion efficiency and a preparation method and application thereof. The photoelectric transistor comprises a SiO2 / Si substrate, a Bi2O2Se / MoTe2 heterojunction and an electrode. First, Bi2O2Se nanosheets are transferred to the SiO2 / Si substrate, and then MoTe2 nanosheets are vertically stacked on the Bi2O2Se nanosheets, and the overlapping part forms the Bi2O2Se / MoTe2 heterojunction. A metal adhesion layer / Au electrode is prepared outside the heterojunction area. The photoelectric transistor has a gate regulated photoelectric conversion efficiency of 1-8%, and has excellent self-driven photoelectric performance in a wide spectrum band range of 405-1310 nm, and can be used in the fields of solar cells, ultraviolet-visible light-near infrared imaging and low-power optoelectronic devices.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of two-dimensional optoelectronic transistors, and more specifically relates to a selenium-bismuth-oxygen (Bi2O2Se) / molybdenum ditelluride (MoTe2) heterojunction phototransistor with gate voltage regulation of photoelectric conversion efficiency and a preparation method and application thereof. BACKGROUND

[0002] With the progress of technology and the development of the times, the optoelectronic transistor has become one of the components of many modern devices and is widely used in military, space exploration, medical devices and people's daily life, and has been highly concerned and researched by the academic circle. The optoelectronic transistor prepared by traditional materials is limited in application scenarios due to process and technical limits, production capacity and energy consumption problems, at which time the optoelectronic transistor based on two-dimensional semiconductor materials is a new choice for the development of the industry. Common two-dimensional materials include graphene, hexagonal boron nitride (h-BN), black phosphorus (BP), etc. The band gap of the material is from 0eV to several eV, which can realize wide-spectrum absorption from ultraviolet, visible light, near-infrared to far-infrared wavelengths, and has strong light-matter interaction ability and excellent carrier transport ability, which is a candidate material for constructing an optoelectronic transistor with high sensitivity, large photoresponsivity and fast response speed.

[0003] Bi2O2Se has ultra-high mobility, outstanding stability, tunable band gap and excellent mechanical properties, and shows significant application prospects in the field of electronics and optoelectronics. Since 2017, Peng Hailin et al. of Peking University successfully synthesized two-dimensional Bi2O2Se composed of (Bi2O2) 2n+ and (Se) 2n- which are combined layer by layer by electrostatic force. Compared with the mechanical exfoliation method, the CVD method can obtain large-area, high-quality, atomic-layer-thickness Bi2O2Se nanosheets. In addition, Bi2O2Se can exist stably in air, has a narrow band gap of 0.8eV, a Hall mobility of up to 20000cm 2 V -1 s -1 at a temperature of 2K, a wide-band spectral response of 360-1600nm, and an extremely high on-off ratio of more than 10 6 . Recently, Peng et al. observed that selenium-poor Bi2O2Se has SdH oscillation greater than 500% and linear magnetoresistance.

[0004] However, due to high carrier concentration (10 18 -10 20 cm -3 ) and intrinsic radiation effects, most Bi2O2Se-based phototransistors will exhibit an on-off ratio greater than 10 -6Bi2O2Se nanosheets exhibit several drawbacks, including dark current, a small optical on / off ratio (less than 10), relatively slow or unstable response speed, and persistent photoconductive behavior. While these can be mitigated through precise and controllable synthesis processes and top-gate modulation, they hinder their potential applications in large-scale manufacturing and high-speed imaging. In recent years, with the rapid development of polymer transfer technology, high-quality Bi2O2Se nanosheets can be completely isolated from mica, improving the performance of Bi2O2Se devices and promoting the exploration of novel functional devices such as memristors, THz detectors, phototransistors, resistive switches, photonic integrated circuits, and thermoelectric converters. For Bi2O2Se / 3D van der Waals heterojunctions, Jiang et al. transferred Bi2O2Se onto silicon waveguides for communication applications, achieving a high degree of stability and performance in V0... ds A small dark current of 72.9 nA and a power output of 3.5 A·W were obtained under a voltage of 2V. -1 High light responsivity, 22 / 78ns response time, and 15.1pW·Hz -0.5 Low noise equivalent power.

[0005] For Bi₂O₂Se / 2D van der Waals heterostructures, integrating two-dimensional materials with bipolar conductivity, such as WSe₂ and BP, with Bi₂O₂Se can suppress dark current, broaden the response spectrum, and improve the response speed. In 2021, Liu et al. studied a broadband phototransistor based on a Bi₂O₂Se / BP van der Waals type I heterojunction, achieving a responsivity of 4.3 A·W at a wavelength of 1310 nm. -1 The response time is 9 ms. However, the relatively low rectification ratio (20) and the instability of BP in air limit its further application. In contrast, Peng et al. developed a type II Bi2O2Se / WSe2 van der Waals heterojunction, which has a wide spectral detection capability of 365-2000 nm due to its efficient charge separation and strong interlayer coupling. However, the photoresponsivity of the device is only 284 mA·W at a wavelength of 532 nm. -1 However, this approach has not gained industry acceptance. 2H-MoTe2 is a bipolar semiconductor material stable in air, with a bandgap of 0.80–1.15 eV and thickness-dependent conductivity, possessing the advantage of transitioning from p-type to bipolar to n-type. However, theoretical bandgap matching calculations, characterization, electrical, and optoelectronic properties of Bi2O2Se / MoTe2 heterojunctions have not been reported. Therefore, research on this structure could enrich the Bi2O2Se-based device family and is expected to promote the development of Bi2O2Se van der Waals heterojunction systems. Summary of the Invention

[0006] In order to overcome the shortcomings and disadvantages of the existing technology, the present invention aims to provide a Bi2O2Se / MoTe2 heterojunction phototransistor with gate voltage-controlled photoelectric conversion efficiency.

[0007] Another object of the present application is to provide a preparation method of the above-mentioned phototransistor with a Bi2O2Se / MoTe2 heterojunction having a gate voltage regulated photoelectric conversion efficiency.

[0008] Still another object of the present application is to provide an application of the above-mentioned phototransistor with a Bi2O2Se / MoTe2 heterojunction having a gate voltage regulated photoelectric conversion efficiency.

[0009] To achieve the above-mentioned objects, the present application uses the following technical solutions:

[0010] A phototransistor with a Bi2O2Se / MoTe2 heterojunction having a gate voltage regulated photoelectric conversion efficiency, the phototransistor with a Bi2O2Se / MoTe2 heterojunction comprises a SiO2 / Si substrate, a vertical Bi2O2Se / MoTe2 heterojunction and an electrode; the phototransistor is prepared by transferring Bi2O2Se nanosheet material on the SiO2 / Si substrate with the aid of polystyrene, then stacking MoTe2 nanosheet on the Bi2O2Se nanosheet by dry method, the overlapping part of the Bi2O2Se nanosheet and the MoTe2 nanosheet forms the vertical Bi2O2Se / MoTe2 heterojunction, then performing photoetching development and evaporating metal adhesion layer / Au electrode on the Bi2O2Se nanosheet and the MoTe2 nanosheet outside the heterojunction region, respectively.

[0011] Preferably, the thickness of the Bi2O2Se nanosheet is 0.8-200 nm, and the lateral size is 2-200 μm; the thickness of the MoTe2 nanosheet is 0.7-100 nm, and the lateral size is 10-100 μm.

[0012] Preferably, the Bi2O2Se nanosheet is grown on a mica substrate by a chemical vapor deposition method, and the MoTe2 nanosheet is prepared by chemical vapor deposition synthesis or mechanical peeling of a tape to a SiO2 / Si substrate.

[0013] Preferably, the metal adhesion layer is Cr or Ti, and the thickness is 3-15 nm, and the thickness of the Au is 20-200 nm.

[0014] The preparation method of the phototransistor with a Bi2O2Se / MoTe2 heterojunction having a gate voltage regulated photoelectric conversion efficiency comprises the following specific steps:

[0015] S1. Growing Bi2O2Se nanosheets on mica substrates by a method of chemical vapor deposition, and selecting Bi2O2Se nanosheets using an optical metallographic microscope; then transferring the Bi2O2Se nanosheets onto a cleaned SiO2 / Si substrate without damage by using a polystyrene assisted transfer, and then immersing them in toluene and acetone respectively to remove the polystyrene residues and other organic molecules on the surface of the samples;

[0016] S2. Selecting MoTe2 nanosheets prepared by chemical vapor deposition or mechanical exfoliation by an optical metallographic microscope, and stacking the MoTe2 nanosheets onto the Bi2O2Se nanosheets on a three-dimensional micro-region transfer platform by a dry transfer process to prepare a vertical Bi2O2Se / MoTe2 heterojunction;

[0017] S3. Using an ultraviolet lithography system to lithograph and develop an electrode pattern on the vertical Bi2O2Se / MoTe2 heterojunction, and evaporating a metal adhesive layer / Au electrode on the Bi2O2Se nanosheet and the MoTe2 nanosheet respectively by electron beam and thermal evaporation to prepare a phototransistor of the Bi2O2Se / MoTe2 heterojunction.

[0018] The application of the phototransistor of the selenium-oxygen-bismuth / molybdenum ditelluride heterojunction with gate voltage regulating photoelectric conversion efficiency in the fields of solar cells, ultraviolet-visible light-near infrared imaging or low-power photoelectronic devices.

[0019] Compared with the prior art, the application has the following beneficial effects:

[0020] 1. The phototransistor of the Bi2O2Se / MoTe2 van der Waals heterojunction with gate voltage regulating photoelectric conversion efficiency has a direct tunneling electrical transport mechanism, and the phototransistor can achieve a high rectification ratio of 1.3×10 ds 2 at a bias voltage V

[0021] 2. The phototransistor of the Bi2O2Se / MoTe2 van der Waals heterojunction realizes high photoelectric conversion efficiency and a fill factor, and has a significant gate regulating characteristic. Under the condition of a gate voltage of 0V to -60V, the fill factor of the phototransistor of the Bi2O2Se / MoTe2 van der Waals heterojunction increases from 0.37 to 0.52, and the photoelectric conversion efficiency increases from 2.7% to 8%, and the high fill factor and high photoelectric conversion efficiency enable the phototransistor of the Bi2O2Se / MoTe2 van der Waals heterojunction to be applied in solar cells and logic photoelectric devices.​

[0022] 3. The photo-transistor of the Bi2O2Se / MoTe2 van der Waals heterojunction of the present application has excellent wide-spectrum response (405-1310 nm) and self-driven photoelectric performance, when V ds = 0 V, V g = 0 V, the maximum photo-response of the photo-transistor reaches 1.24 A·W -1 , and the maximum specific detectivity reaches 1.5 x 10 12 Jones; when V g = -60 V, the maximum photo-response reaches 4.96 A·W -1 , and the maximum specific detectivity reaches 4.37 x 10 12 Jones, which is at the upstream level in photo-transistors.

[0023] 4. The photo-transistor of the Bi2O2Se / MoTe2 van der Waals heterojunction of the present application has good ohmic contact, ultra-high light switch ratio (more than 10 4 ), excellent working stability (stable photo-response after 300 cycles), and ultra-fast response speed (rise time and fall time are 16 ms and 21.2 ms, respectively), and compared with the same kind of Bi2O2Se photoelectric detector, the dark current of the present application can be reduced by 10 3 orders of magnitude (0.52 pA), which can be used in the field of low-power and high-sensitivity photoelectric detection, so that the present application has broad application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic diagram of the photo-transistor of the Bi2O2Se / MoTe2 van der Waals heterojunction of the present application.

[0025] Figure 2 is an optical microscope photo of the photo-transistor of the Bi2O2Se / MoTe2 van der Waals heterojunction prepared in Example 1.

[0026] Figure 3 is the KPFM test result of the Bi2O2Se / MoTe2 heterojunction of Example 1.

[0027] Figure 4 is the voltage-current curve of the photo-transistor of the Bi2O2Se / MoTe2 van der Waals heterojunction of Example 1 under dark conditions.

[0028] Figure 5 is the transfer curve of the photo-transistor of the Bi2O2Se / MoTe2 van der Waals heterojunction of Example 1 under the condition of V ds = 1 V, 2 V and 3 V.

[0029] Figure 6 Time response curve of the phototransistor of Bi2O2Se / MoTe2 van der Waals heterojunction of Example 1 under self-driven condition at Vg=0V with 405nm, 635nm, 808nm, 1310nm laser irradiation. ds Time response curve of the phototransistor of Bi2O2Se / MoTe2 van der Waals heterojunction of Example 1 under self-driven condition at Vg=0V with 405nm, 635nm, 808nm, 1310nm laser irradiation.

[0030] Figure 7 Responsivity, specific detectivity and light power density curve of the phototransistor of Bi2O2Se / MoTe2 van der Waals heterojunction of Example 1 at Vg=0V, -60V with 405nm laser.

[0031] Figure 8 Dynamic response speed curve of the phototransistor of Bi2O2Se / MoTe2 van der Waals heterojunction of Example 1 at Vg=0V, -60V with 405nm laser.

[0032] Figure 9 Time response curve of the phototransistor of Bi2O2Se / MoTe2 van der Waals heterojunction of Example 1 under self-driven condition at Vg=-60V with 405nm laser for more than 160 cycles.

[0033] Figure 10 Fill factor and light conversion efficiency vs. light power density curve of the phototransistor of Bi2O2Se / MoTe2 van der Waals heterojunction of Example 1 at Vg=0V, -60V with 405nm incident light.

[0034] Figure 11 Optical microscope photo of the phototransistor of Bi2O2Se / MoTe2 van der Waals heterojunction prepared in Example 2.

[0035] Figure 12 Time response curve of the phototransistor of Bi2O2Se / MoTe2 van der Waals heterojunction prepared in Example 2 at different light power density with 405nm laser.

[0036] Figure 13 Optical microscope photo of the phototransistor of Bi2O2Se / MoTe2 van der Waals heterojunction prepared in Example 3.

[0037] Figure 14 Time response curve of the phototransistor of Bi2O2Se / MoTe2 van der Waals heterojunction prepared in Example 3 at different light power density with 405nm laser. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings, but should not be construed as limiting the present invention. Based on the embodiments of the present invention, the experimental methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials described are all available from publicly available commercial sources unless otherwise specified. The present invention will now be described in further detail.

[0039] Example 1

[0040] 1. Sonicate the mica and SiO2 / Si substrate with acetone, isopropanol and deionized water for 10 min each, then dry them with a nitrogen gun for later use.

[0041] 2. Bi2O2Se nanosheets were grown on a mica substrate using chemical vapor deposition. The lateral dimensions of the nanosheets were 2–200 μm and the thickness was controlled between 0.8 and 200 nm.

[0042] 3. Using an optical metallurgical microscope, select Bi2O2Se nanosheets of appropriate thickness (12nm) and shape on the mica substrate in step 2. Transfer the Bi2O2Se nanosheets to the cleaned SiO2 / Si substrate using a polystyrene film-assisted transfer method. Finally, use toluene and acetone liquid to clean away the polystyrene film and residual contaminants, exposing the clean surface of the Bi2O2Se nanosheets.

[0043] 4. MoTe2 nanosheets were exfoliated from the cleaned SiO2 / Si substrate using a mechanical exfoliation method. MoTe2 nanosheets with a lateral size of 10-100 μm and a thickness of 14 nm were then selected using an optical metallographic microscope.

[0044] 5. Using a dry transfer method on a three-dimensional micro-region transfer platform, the MoTe2 nanosheets selected in step 4 are transferred to the Bi2O2Se nanosheets selected in step 3, causing partial overlap between the two. Then, the nanosheets are immersed in dimethyl sulfoxide to remove residual reagents used in the transfer process, thus preparing a vertical Bi2O2Se / MoTe2 heterojunction.

[0045] 6. Photoresist was spin-coated onto a SiO2 / Si substrate with a vertical Bi2O2Se / MoTe2 heterojunction. Electrode patterns were then developed on Bi2O2Se nanosheets and MoTe2 nanosheets outside the vertical Bi2O2Se / MoTe2 heterojunction using a UV lithography system. Finally, 10nm Cr / 50nm Au electrodes were fabricated on the Bi2O2Se nanosheets and MoTe2 nanosheets outside the Bi2O2Se / MoTe2 van der Waals heterojunction region using an evaporation process, thus obtaining a Bi2O2Se / MoTe2 heterojunction photodiode.

[0046] Figure 1Schematic diagram of the phototransistor of Bi2O2Se / MoTe2 van der Waals heterojunction. Wherein, the black line marked is Bi2O2Se nanosheet and MoTe2 nanosheet, 1 and 2, 3 and 4 are two pairs of electrodes evaporated on Bi2O2Se and MoTe2 materials respectively.

[0047] Figure 2 Optical microscope photo of the Bi2O2Se / MoTe2 heterojunction photodiode prepared in Example 1, wherein the MoTe2 nanosheet and Bi2O2Se nanosheet surrounded by the dotted line are respectively. The photo was taken by the optical microscope of the Leica DM2700P. Figure 2 It can be seen that the Bi2O2Se / MoTe2 heterojunction-based phototransistor is to transfer the Bi2O2Se nanosheet onto the SiO2 / Si substrate, and then use the dry transfer method to partially stack the MoTe2 nanosheet on the Bi2O2Se nanosheet, and the overlapping part forms a vertical Bi2O2Se / MoTe2 van der Waals heterojunction, and then two pairs of Ti / Au electrodes are evaporated on the Bi2O2Se nanosheet and MoTe2 nanosheet outside the Bi2O2Se / MoTe2 heterojunction region respectively.

[0048] Figure 3 KPFM image of the overlapping edge position of the phototransistor of the Bi2O2Se / MoTe2 van der Waals heterojunction of Example 1, the results show that there is a clear contact potential difference on the contact surface of the Bi2O2Se nanosheet and the MoTe2 nanosheet, a built-in electric field is formed in the heterojunction region, and there is a 1 μm length of depletion region. The built-in electric field near the heterojunction region is the main factor that the Bi2O2Se / MoTe2 van der Waals heterojunction phototransistor can carry out self-driven photodetection.

[0049] Figure 4 IV curve of the phototransistor of the Bi2O2Se / MoTe2 van der Waals heterojunction of Example 1 under dark condition. From Figure 4 It can be seen that the electrical transport characteristics of the heterojunction are direct tunneling, and the rectification ratio of the device is greater than 10 2 at V ds =-1 V / 1 V, which has good rectification characteristics.

[0050] Figure 5 Transfer curve of the phototransistor of the Bi2O2Se / MoTe2 van der Waals heterojunction of Example 1 under dark condition at V ds =1 V, 2 V and 3 V. From Figure 5 It can be seen that the gate has a strong control ability on the current of the phototransistor, and the phototransistor has obvious bipolarity.

[0051] Figure 6 Transfer curve of the phototransistor of the Bi2O2Se / MoTe2 van der Waals heterojunction of Example 1 at Vds The self-driven time response curves at 0V under laser irradiation conditions of 405nm, 635nm, 808nm, and 1310nm. Under laser irradiation of four wavelengths, the Bi2O2Se / MoTe2 van der Waals heterojunction phototransistor can generate significant photocurrents, indicating that the photoelectric response range of this phototransistor is 405–1310nm, making it an excellent broadband photodetector.

[0052] Figure 7 The graph shows the responsivity, specific detectivity, and optical power density of the Bi2O2Se / MoTe2 van der Waals heterojunction phototransistor of Example 1 at 405nm laser gate voltages of 0V and -60V. Figure 8 The image shows the dynamic response speed curves of the Bi2O2Se / MoTe2 van der Waals heterojunction phototransistor of Example 1 at 405nm laser gate voltages of 0V and -60V. From... Figure 7 and 8 It can be seen that the phototransistor of the Bi2O2Se / MoTe2 heterojunction is in V g At 0V, the maximum photoresponsivity reaches 1.24 A·W. -1 The maximum specific detectivity is 1.5 × 10⁻⁶. 12 Jones, rise / fall time is 42.3 / 32.1ms; when V g At -60V, the maximum photoresponsivity of this phototransistor reaches 4.96 A·W. -1 The maximum specific detectivity reached 4.37 × 10⁻⁶. 12 Jones values ​​show rise / fall times of 16.1 / 21.2 ms, indicating that applying a gate voltage can effectively improve the photoelectric signal detection capabilities of the Bi2O2Se / MoTe2 van der Waals phototransistor, including responsivity, specific detectivity, and response speed. This demonstrates the modulating effect of the gate voltage on the photoelectric detection capability of the Bi2O2Se / MoTe2 heterojunction.

[0053] Figure 9 The graph shows the self-driven response time of the Bi2O2Se / MoTe2 van der Waals heterojunction phototransistor of Example 1 after more than 160 cycles with a 405nm laser gate voltage of -60V. Under self-driven operating conditions, the photoresponse current did not significantly decrease after hundreds of cycles, and the dark current remained at an extremely low level. This indicates that the Bi2O2Se / MoTe2 van der Waals heterojunction phototransistor can remain stable during high-performance photodetection, demonstrating that the phototransistor in Example 1 has strong anti-aging capabilities.

[0054] Figure 10The fill factor, photoconversion efficiency, light and light power density relationship curve of the Bi2O2Se / MoTe2 van der Waals heterojunction phototransistor of Example 1 under 405 nm incident light and gate voltage of 0 V, -60 V. From Figure 10 It can be seen that when V g = 0 V, the maximum fill factor and photoelectric conversion efficiency of the phototransistor are 0.37 and 2.7%, respectively, which has obvious characteristics of a photocell. And the gate voltage has a strong control effect on the photoconversion efficiency and fill factor of the phototransistor, V g = -60 V can make the fill factor rise to 0.52, and the photoelectric conversion efficiency increases to 8%, which shows excellent photoelectric conversion ability and photocell performance.

[0055] Example 2

[0056] The difference from Example 1 is that the thickness of Bi2O2Se is about 8.1 nm, and the thickness of MoTe2 is 11.2 nm. Figure 11 The optical microscope photo of the Bi2O2Se / MoTe2 van der Waals heterojunction phototransistor prepared in Example 2. Figure 12 The time response curve of the Bi2O2Se / MoTe2 van der Waals heterojunction phototransistor prepared in Example 2 under different light power densities of 405 nm laser, from Figure 11 and 12 It can be seen that the phototransistor can generate a photocurrent of 0.2-2 nA under the conditions of different power of 405 nm laser irradiation, V ds = 0 V, V gs = -60 V. It shows that the phototransistor can also generate a strong self-driven photocurrent under light conditions.

[0057] Example 3

[0058] The difference from Example 1 is that the thickness of Bi2O2Se is about 7.8 nm, and the thickness of MoTe2 is 10.8 nm. Figure 13 The optical microscope photo of the Bi2O2Se / MoTe2 van der Waals heterojunction phototransistor prepared in Example 3. Figure 14 The time response curve of the Bi2O2Se / MoTe2 van der Waals heterojunction phototransistor prepared in Example 3 under different light power densities of 405 nm laser, from Figure 13 and 14 It can be seen that the phototransistor can generate a photocurrent of 0.2-2.5 nA under the conditions of different power of 405 nm laser irradiation, V ds = 0 V, V gs = -60 V. It shows that the phototransistor can also generate a strong self-driven photocurrent under light conditions.

[0059] In summary, the photoelectric transistor of the Bi2O2Se / MoTe2 van der Waals heterojunction with the gate voltage regulating the photoelectric conversion efficiency has a direct tunneling electrical transport mechanism, and the photoelectric transistor can achieve a high rectification ratio of 1.3x10 ds 2 under the bias voltage V 4 =1 / -1V. The photoelectric transistor has a gate-regulated photoelectric conversion efficiency of 1-8%, and excellent self-driven photoelectric performance in a wide spectral band range of 405-1310 nm, and can be used in the fields of solar cells, ultraviolet-visible-near infrared imaging and low-power optoelectronic devices. The photoelectric transistor of the Bi2O2Se / MoTe2 van der Waals heterojunction of the present application realizes high photoelectric conversion efficiency and fill factor, and has significant gate-regulated characteristics. In addition, it also has excellent wide-spectrum response (405-1310 nm) and self-driven photoelectric performance, good ohmic contact, ultra-high optical switching ratio (more than 10 4 3 ), excellent working stability (can maintain stable photoresponse after 300 cycles), and ultra-fast response speed (rise time and fall time are 16 ms and 21.2 ms, respectively), and compared with the same kind of Bi2O2Se photoelectric detector, the dark current of the present application can be reduced by 10 3 orders of magnitude (0.52 pA), which can be used in the field of low-power and high-sensitivity photoelectric detection, so that the present application can have broad application prospects.

[0060] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A selenium-bismuth-oxide / molybdenum ditelluride heterojunction phototransistor with gate voltage regulated photoelectric conversion efficiency, characterized in that, The formula of the selenium bismuth oxide / molybdenum ditelluride heterojunction is Bi2O2Se / MoTe2, and the phototransistor of the heterojunction comprises a SiO2 / Si substrate, a vertical Bi2O2Se / MoTe2 heterojunction and electrodes; the phototransistor is prepared by transferring Bi2O2Se nanosheet material on a SiO2 / Si substrate with the aid of polystyrene, then stacking MoTe2 nanosheet on the Bi2O2Se nanosheet by dry method, and forming a vertical Bi2O2Se / MoTe2 heterojunction in the overlapping part of the Bi2O2Se nanosheet and the MoTe2 nanosheet, then performing photoetching and developing and evaporating a metal adhesion layer / Au electrode on the Bi2O2Se nanosheet and the MoTe2 nanosheet outside the heterojunction region, respectively. 2.The BiOS / MoTe2 heterojunction phototransistor with gate voltage modulated photoelectric conversion efficiency of claim 1, wherein, The thickness of the Bi2O2Se nanosheet is 0.8-200 nm, and the lateral size is 2-200 μm; the thickness of the MoTe2 nanosheet is 0.7-100 nm, and the lateral size is 10-100 μm. 3.The BiOS / MoTe2 heterojunction phototransistor with gate voltage modulated photoelectric conversion efficiency of claim 1, wherein, The Bi2O2Se nanosheet is grown on a mica substrate by a chemical vapor deposition method, and the MoTe2 nanosheet is prepared by synthesizing or mechanically peeling off from a SiO2 / Si substrate by a chemical vapor deposition method. 4.The BiOS / MoTe2 heterojunction phototransistor with gate voltage modulated photoelectric conversion efficiency of claim 1, wherein, The metal adhesion layer is Cr or Ti, and the thickness is 3-15 nm; the thickness of the Au is 20-200 nm.

5. The method of claim 1-4, wherein the method further comprises the step of: The method comprises the following specific steps: ​ S1. growing Bi2O2Se nanosheet on a mica substrate by a chemical vapor deposition method, and selecting the Bi2O2Se nanosheet by an optical metallographic microscope; then transferring the Bi2O2Se nanosheet to a cleaned SiO2 / Si substrate without damage by transferring with the aid of polystyrene, and then immersing the sample in toluene and acetone to remove the residual polystyrene and other organic molecules on the surface of the sample; S2. selecting MoTe2 nanosheet prepared by a chemical vapor deposition method or mechanically peeled off by an optical metallographic microscope, and stacking the MoTe2 nanosheet on the Bi2O2Se nanosheet on a three-dimensional micro area transfer platform by a dry transfer process to prepare a vertical Bi2O2Se / MoTe2 heterojunction; S3. using an ultraviolet photoetching system to photoetch and develop an electrode pattern on the vertical Bi2O2Se / MoTe2 heterojunction, and evaporating a metal adhesion layer / Au electrode on the Bi2O2Se nanosheet and the MoTe2 nanosheet by electron beam and thermal evaporation, respectively, to prepare a Bi2O2Se / MoTe2 heterojunction phototransistor.

6. Application of the selenium bismuth oxide / molybdenum ditelluride heterojunction phototransistor with gate voltage regulated photoelectric conversion efficiency in the fields of solar cells, ultraviolet-visible light-near infrared imaging or low-power photoelectron devices according to any one of claims 1-4.

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