Preparation method of PdSe2 / Bi2O2Se Van der Waals heterojunction self-driven photoelectric detector

Abstract

The invention provides a preparation method of a PdSe2 / Bi2O2Se Van der Waals heterojunction self-driven photoelectric detector, and relates to construction of a two-dimensional material heterostructure and application of the two-dimensional material heterostructure to a photoelectric device. The method comprises the following steps; the preparation method comprises the following steps: preparing nanosheets through a chemical vapor deposition (CVD) process; respectively preparing a PdSe2 nanosheet and a Bi2O2Se nanosheet by adopting the CVD process; and preparing a heterostructure: transferring the PdSe2 nanosheet to the surface of the Bi2O2Se nanosheet in a dry transfer mode to form a Van der Waals heterojunction structure with a clean interface and tight interlayer coupling. The transfer technology keeps the lattice and morphology of the two-dimensional material complete, and reduces organic residues and solvent pollution influences. The heterojunction structure is combined with the narrow band gap of PdSe2 and the broad spectrum response characteristic of Bi2O2Se, and efficient photoelectric conversion from visible light to near-infrared light is achieved. And an electric field is built in the p-n type heterojunction, so that the device is self-driven without external bias voltage, and has the performance of low power consumption and the like. And the method is low in process thermal budget, high in compatibility and suitable for various substrates, and a technical path is provided for construction of the flexible photoelectric detector.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optoelectronic devices, and particularly relates to a preparation method of a PdSe2 / Bi2O2Se van der Waals heterojunction self-driven photodetector. BACKGROUND

[0002] With the rapid development of information technology, wearable devices, environmental monitoring, and biomedical treatment, there is an increasing demand for photodetectors with high performance, low power consumption, and wide spectral response. In recent years, two-dimensional materials with atomic thickness have become an important material system for constructing new photodetectors due to their excellent photoelectric properties, flexible heterojunction integration capability, and potential for compatibility with flexible electronic devices.

[0003] At present, photodetectors based on two-dimensional material heterostructures (such as black phosphorus / MoS2, WSe2 / MoTe2, SnS2 / MoS2, etc.) have shown advantages such as high responsivity, low dark current, and self-driving (reference: Xia, F. et al., Nat. Photonics, 2014, 8, 899-907; Roy, T. et al., Nat. Nanotechnol., 2013, 8, 826-830). Among them, two-dimensional Bi2O2Se has attracted widespread attention in recent years due to its high electron mobility, wide-band light response capability, and environmental stability, and has become a promising n-type two-dimensional semiconductor material. Previous studies have used Bi2O2Se and WSe2, SnS2, etc. to construct heterojunction photodetectors, relying on the built-in electric field generated at the heterojunction interface to achieve self-driven light response (see: Adv. Funct. Mater. 2021, 31, 2008351).

[0004] However, existing two-dimensional heterojunction photodetectors generally have the following problems: 1) the energy band matching at the heterojunction interface is not ideal, which limits the effective separation of carriers and the light response efficiency; 2) wet transfer is commonly used in the preparation process, which easily introduces interface contamination and organic residues, affecting the performance and stability of the device; 3) the response capability to near-infrared band is limited, which is difficult to meet the practical application requirements of weak light imaging and infrared detection. In addition, although there have been preliminary studies on combining PdSe2 with MoS2, WS2, etc. to construct heterostructures for photodetection in recent years, there is still no systematic report on constructing a van der Waals heterojunction of PdSe2 and Bi2O2Se and realizing a self-driven detection function. The main technical bottlenecks include the difficulty of large-area controllable growth of PdSe2, the controllable exfoliation of Bi2O2Se nanosheets, and the complexity of energy band regulation at the heterojunction interface of the two. Therefore, there is an urgent need for a preparation method of a PdSe2 / Bi2O2Se van der Waals heterojunction photodetector with high quality, low energy consumption, and simple process. SUMMARY

[0005] Technical problems solved

[0006] The present application aims to overcome the technical problems of band mismatch, interface pollution, narrow response band and complex preparation process in existing two-dimensional material heterojunction photodetectors, and proposes a preparation method of a self-driven photodetector based on a PdSe2 / Bi2O2Se van der Waals heterostructure, which has the characteristics of wide spectrum response, high sensitivity and low power consumption.

[0007] Technical solutions

[0008] To achieve the above purpose, the present application provides a preparation method comprising the following steps:

[0009] (1) Prepare nanosheets by chemical vapor deposition (CVD) process:

[0010] PdSe2 nanosheets and Bi2O2Se nanosheets are prepared by CVD process;

[0011] (2) Heterostructure preparation:

[0012] By dry transfer technology, PdSe2 nanosheets are transferred to the surface of Bi2O2Se nanosheets to form a clean interface and tightly coupled van der Waals heterojunction structure;

[0013] (3) Device preparation:

[0014] Using ultraviolet lithography and electron beam evaporation technology, Cr / Au (5nm / 60nm) electrodes are deposited at both ends of the heterostructure to form source and drain electrodes; then the device is subjected to 150-200℃ heat treatment for 1 hour under argon atmosphere;

[0015] (4) Photodetection:

[0016] Under the condition of no external bias, the obtained device realizes self-driven photoelectric response in the wavelength range of 450-940nm.

[0017] Preferably, the preparation method of the PdSe2 nanosheets comprises the following steps:

[0018] S1. Select high-purity PdCl2 powder and Se powder as precursors;

[0019] S2. Put PdCl2 powder in the high-temperature zone of the quartz boat in the CVD device, and put Se powder in the low-temperature zone of the gas inlet;

[0020] S3. Under argon atmosphere, heat to 650-750℃, control the PdCl2 evaporation zone temperature to 500-600℃, and the Se source zone temperature to 280-320℃;

[0021] S4. After maintaining a constant temperature reaction for 30-60 minutes, naturally cool to room temperature to obtain multilayer PdSe2 nanosheets.

[0022] Preferably, the method for preparing the Bi2O2Se nanosheets comprises the following steps:

[0023] S1. Select Bi2O3 powder and Se powder as precursors;

[0024] S2. The Bi2O3 and Se powders were placed in quartz boats at different temperature zones in the low-pressure CVD system;

[0025] S3. React in a mixed gas Ar / O2 atmosphere, controlling the Bi source temperature to 520–620°C and the Se source temperature to 300–350°C;

[0026] S4. After reacting for 20-30 minutes, the mixture was cooled naturally to obtain Bi2O2Se nanosheets.

[0027] Preferably, the thickness of the PdSe2 nanosheets is controlled within the range of 4–15 nm.

[0028] Preferably, the thickness of the Bi2O2Se nanosheets is controlled within the range of 10–20 nm.

[0029] Preferably, the dry transfer process uses polyvinyl alcohol (PVA) or polydimethylsiloxane (PDMS) as an auxiliary transfer medium, and uses PVA to assist in peeling and transfer to accurately superimpose PdSe2 nanosheets on the surface of Bi2O2Se nanosheets, keeping the interface clean and achieving high-quality van der Waals heterostructure construction.

[0030] Preferably, the device has a short-circuit current of not less than 100 nA, an open-circuit voltage of not less than 0.35 V, a response time of not more than 10 ms, and a photocurrent switching ratio of not less than 10 under 520 nm laser irradiation. 3 .

[0031] (3) Beneficial effects

[0032] The present invention provides a method for preparing a PdSe2 / Bi2O2Se van der Waals heterojunction self-driven photodetector. It has the following beneficial effects:

[0033] 1. Achieve the construction of high-quality PdSe2 / Bi2O2Se heterojunctions: Through dry transfer, while maintaining the integrity of the two-dimensional material lattice, the interference of pollutants and residual solvents on the interfacial energy band is avoided, thereby improving the separation efficiency of photogenerated carriers.

[0034] 2, expand device response band and improve self-driving performance: the narrow band gap characteristics of PdSe2 and the wide band response characteristics of Bi2O2Se are used, and a stable built-in electric field is formed by constructing a p-n type van der Waals heterojunction, so as to realize wide spectrum and low power consumption photoelectric detection under the condition of no external voltage.

[0035] 3, considering process controllability and flexible integration capability: a low thermal budget and universal preparation process path is proposed, which is suitable for silicon-based, glass, flexible polyimide and other substrates, and provides process support for the application of photoelectric detectors in the fields of flexible electronics, biomedical imaging and Internet of Things. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The PdSe2 / Bi2O2Se van der Waals heterojunction structure schematic diagram of the preparation method of the PdSe2 / Bi2O2Se van der Waals heterojunction self-driven photoelectric detector proposed by the application.

[0037] Figure 2 The I-V curve diagram of the device under light and dark state of the preparation method of the PdSe2 / Bi2O2Se van der Waals heterojunction self-driven photoelectric detector proposed by the application; (a) dark state; (b) different light.

[0038] Figure 3 The light response diagram under different wavelength light of the preparation method of the PdSe2 / Bi2O2Se van der Waals heterojunction self-driven photoelectric detector proposed by the application. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the application will be described below in conjunction with the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, not all. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0040] Embodiment one:

[0041] The embodiment of the application provides a preparation method of a PdSe2 / Bi2O2Se van der Waals heterojunction self-driven photoelectric detector, which comprises the following steps:

[0042] (I) prepare nanosheets by chemical vapor deposition (CVD) process:

[0043] PdSe2 nanosheets and Bi2O2Se nanosheets are prepared by CVD process;

[0044] (II) heterostructure preparation:

[0045] PdSe2 nanosheets were transferred to the surface of Bi2O2Se nanosheets through dry transfer technology, forming a van der Waals heterojunction structure with a clean interface and tight interlayer coupling.

[0046] (3) Device preparation:

[0047] Cr / Au (5nm / 60nm) electrodes were deposited at both ends of the heterostructure using UV lithography and electron beam evaporation techniques to form source and drain electrodes. The device was then thermally annealed at 150°C for 1 hour in an argon atmosphere.

[0048] (4) Photoelectric detection:

[0049] Under no external bias conditions, the obtained device achieves self-driven photoelectric response in the 450nm band.

[0050] The dry transfer technology used in step (2) mainly includes polyvinyl alcohol (PVA) or polydimethylsiloxane (PDMS) assisted transfer, which precisely superimposes Bi2O2Se nanosheets on PdSe2 to construct a clean, pollution-free vertical van der Waals heterostructure; align the boundaries under a microscope and slowly release PVA or PDMS to ensure close contact between the crystals and no bubbles or wrinkles on the interface.

[0051] The device construction in step (iii) mainly involves electrode construction and device integration. The electrode pattern is defined by a standard UV lithography process; Cr / Au (5nm / 60nm) is deposited as the source and drain electrode metal by electron beam evaporation; and finally, thermal annealing or vacuum annealing (150°C, 30min) is used to improve the electrode contact quality and interface stability.

[0052] The preparation method of PdSe2 nanosheets includes the following steps:

[0053] S1. Select high-purity PdCl2 powder and Se powder as precursors;

[0054] S2. The PdCl2 powder is placed in a quartz boat in the high temperature zone of the CVD apparatus, and the Se powder is placed in the low temperature zone at the inlet end;

[0055] S3. Under an argon atmosphere, the temperature was raised to 750°C, the PdCl2 evaporation zone temperature was controlled at 500°C, and the Se source zone temperature was 280°C;

[0056] S4. After maintaining the constant temperature for 30 minutes, the mixture was naturally cooled to room temperature to obtain multilayer PdSe2 nanosheets.

[0057] During the preparation process of PdSe2 nanosheets, a fresh sapphire or SiO2 / Si substrate is placed downstream and the system pressure is controlled at 50Pa; after 30 minutes of reaction and cooling, large-sized PdSe2 flakes with layered structure and good crystal orientation are obtained.

[0058] The preparation method of Bi2O2Se nanosheets includes the following steps:

[0059] S1. Select Bi2O2 powder and Se powder as precursors;

[0060] S2. The Bi2O3 and Se powders were placed in quartz boats at different temperature zones in the low-pressure CVD system;

[0061] S3. The reaction was carried out in a mixed gas Ar / O2 atmosphere, controlling the Bi source temperature to 620°C and the Se source temperature to 350°C;

[0062] S4. After reacting for 30 minutes, the mixture was naturally cooled to obtain Bi2O2Se nanosheets.

[0063] During the preparation of Bi2O2Se nanosheets, fresh mica or SiO2 / Si substrate is placed downstream, and Bi2O2Se layered crystals with controllable thickness can be obtained after cooling.

[0064] The thickness of the PdSe2 nanosheets is controlled within the range of 4 nm.

[0065] The thickness of Bi2O2Se nanosheets is controlled within the range of 10 nm.

[0066] The dry transfer process uses polyvinyl alcohol (PVA) or polydimethylsiloxane (PDMS) as an auxiliary transfer medium. PVA is used to assist in peeling and transfer, and PdSe2 nanosheets are precisely superimposed on the surface of Bi2O2Se nanosheets, keeping the interface clean and achieving high-quality van der Waals heterostructure construction.

[0067] When the device is irradiated with 520nm laser, its short-circuit current is not less than 100nA, its open-circuit voltage is not less than 0.35V, its response time is not more than 10ms, and its photocurrent switching ratio is not less than 10. 3 .

[0068] Example 2:

[0069] The embodiment of the present invention provides a method for preparing a PdSe2 / Bi2O2Se van der Waals heterojunction self-driven photodetector, comprising the following steps:

[0070] (1) Preparation of nanosheets by chemical vapor deposition (CVD) process:

[0071] PdSe2 nanosheets and Bi2O2Se nanosheets were prepared by CVD process;

[0072] (2) Preparation of heterogeneous structures:

[0073] PdSe2 nanosheets were transferred to the surface of Bi2O2Se nanosheets through dry transfer technology, forming a van der Waals heterojunction structure with a clean interface and tight interlayer coupling.

[0074] (3) Device preparation:

[0075] Cr / Au (5nm / 60nm) electrodes were deposited at both ends of the heterostructure using UV lithography and electron beam evaporation techniques to form source and drain electrodes. The device was then thermally annealed at 180°C for 3 hours in an argon atmosphere.

[0076] (4) Photoelectric detection:

[0077] Under no external bias conditions, the obtained device achieves self-driven photoelectric response in the 940nm band.

[0078] The preparation method of PdSe2 nanosheets includes the following steps:

[0079] S1. Select high-purity PdCl2 powder and Se powder as precursors;

[0080] S2. The PdCl2 powder is placed in a quartz boat in the high temperature zone of the CVD apparatus, and the Se powder is placed in the low temperature zone at the inlet end;

[0081] S3. Under an argon atmosphere, the temperature was raised to 650°C, the PdCl2 evaporation zone temperature was controlled at 550°C, and the Se source zone temperature was 300°C;

[0082] S4. After maintaining a constant temperature for 60 minutes, the mixture was naturally cooled to room temperature to obtain multilayer PdSe2 nanosheets.

[0083] The preparation method of Bi2O2Se nanosheets includes the following steps:

[0084] S1. Select Bi2O2 powder and Se powder as precursors;

[0085] S2. The Bi2O3 and Se powders were placed in quartz boats at different temperature zones in the low-pressure CVD system;

[0086] S3 reaction in a mixed gas Ar / O2 atmosphere, controlling the Bi source temperature to 580 ℃, the Se source temperature to 320 ℃;

[0087] S4. After reacting for 20-30 minutes, the mixture was cooled naturally to obtain Bi2O2Se nanosheets.

[0088] The thickness of the PdSe2 nanosheets is controlled within the range of 15 nm.

[0089] The thickness of Bi2O2Se nanosheets is controlled within the range of 20 nm.

[0090] The dry transfer process uses polyvinyl alcohol (PVA) or polydimethylsiloxane (PDMS) as an auxiliary transfer medium. PVA is used to assist in peeling and transfer, and PdSe2 nanosheets are precisely superimposed on the surface of Bi2O2Se nanosheets, keeping the interface clean and achieving high-quality van der Waals heterostructure construction.

[0091] When the device is irradiated with 520nm laser, its short-circuit current is not less than 100nA, its open-circuit voltage is not less than 0.35V, its response time is not more than 10ms, and its photocurrent switching ratio is not less than 10. 3 .

[0092] By optimizing material selection, heterostructure design, and device integration, we have achieved multiple technological breakthroughs and superior device performance, primarily as follows:

[0093] 1. Achieving self-driven photodetection with wide spectral response

[0094] The constructed PdSe2 / Bi2O2Se heterojunction is based on a pn band docking mechanism, forming a significant built-in electric field. Without the need for an external bias, the built-in electric field effectively separates photogenerated carriers, resulting in a stable photocurrent output and excellent self-driven performance. This structure is capable of responding to laser irradiation from the visible to near-infrared band (450-940nm), exhibiting a broad spectrum of response, making it suitable for a variety of optoelectronic applications, including environmental monitoring, bioimaging, and smart wearables.

[0095] 2. Low power consumption, green and energy-saving

[0096] Because the device requires no external bias voltage during operation, it consumes extremely low energy, making it particularly suitable for power-sensitive applications such as edge computing and smart sensor networks. This "zero-power standby" feature is difficult to achieve with traditional active photodetectors and has significant engineering application value and widespread adoption.

[0097] 3. High on / off ratio and low dark current

[0098] The band structure of the heterojunction has a significant barrier control effect, which inhibits the flow of carriers in the dark state, thereby significantly reducing the dark current of the device (~nA level). Under light conditions, the built-in electric field can quickly drive the separation of carriers, forming a large photocurrent, and the device exhibits a high photoelectric switching ratio (I on / I off >10 3), which improves the signal-to-noise ratio and ensures the accuracy and stability of the detection signal.

[0099] 4. Good stability and strong environmental adaptability

[0100] Both PdSe2 and Bi2O2Se are stable two-dimensional materials with layered structures. They are stable in air and not easily oxidized. Moreover, there is no lattice mismatch at the van der Waals interface between the two and no chemical bond connection is required, which makes the overall heterostructure have excellent structural stability and anti-interference ability, which is conducive to long-term service and adaptation to complex environments.

[0101] In summary, the PdSe2 / Bi2O2Se heterojunction self-driven photodetector proposed in the present invention has high performance, low power consumption, wide spectral response and manufacturing compatibility. It overcomes the defects of existing photodetectors such as the need for external bias, high dark current, and high energy consumption. It has significant technological progress and practical value, and provides an effective solution and theoretical basis for the development of a new generation of low-energy optoelectronic devices.

[0102] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a PdSe2 / Bi2O2Se van der Waals heterojunction self-driven photodetector, characterized by: The following steps are involved: (1) Preparation of nanosheets by chemical vapor deposition (CVD) process: PdSe2 nanosheets and Bi2O2Se nanosheets were prepared by CVD process; (2) Preparation of heterogeneous structures: PdSe2 nanosheets were transferred to the surface of Bi2O2Se nanosheets through dry transfer technology, forming a van der Waals heterojunction structure with a clean interface and tight interlayer coupling. (3) Device preparation: Cr / Au (5nm / 60nm) electrodes were deposited at both ends of the heterostructure using UV lithography and electron beam evaporation technology to form source and drain electrodes; The device is then subjected to a thermal annealing treatment at 150-200° C. for 1-5 hours in an argon atmosphere; (4) Photoelectric detection: Under no external bias conditions, the obtained device achieves self-driven photoelectric response in the 450–940 nm band.

2. The preparation method according to claim 1, wherein: The preparation method of the PdSe2 nanosheets comprises the following steps: S1. Select high-purity PdCl2 powder and Se powder as precursors; S2. The PdCl2 powder is placed in a quartz boat in the high temperature zone of the CVD apparatus, and the Se powder is placed in the low temperature zone at the inlet end; S3. Under an argon atmosphere, the temperature was raised to 650-750°C, the PdCl2 evaporation zone temperature was controlled at 500-600°C, and the Se source temperature was 280-320°C; S4. After maintaining a constant temperature reaction for 30-60 minutes, naturally cool to room temperature to obtain multilayer PdSe2 nanosheets.

3. The preparation method according to claim 1, wherein: The preparation method of the Bi2O2Se nanosheets comprises the following steps: S1. Select Bi2O2 powder and Se powder as precursors; S2. The Bi2O3 and Se powders were placed in quartz boats at different temperature zones in the low-pressure CVD system; S3. React in a mixed gas Ar / O2 atmosphere, controlling the Bi source temperature to 520–620°C and the Se source temperature to 300–350°C; S4. After reacting for 20-30 minutes, the mixture was cooled naturally to obtain Bi2O2Se nanosheets.

4. The preparation method according to claim 2, wherein: The thickness of the PdSe2 nanosheets is controlled within the range of 4–15 nm.

5. The preparation method according to claim 1, wherein: The thickness of the Bi2O2Se nanosheets is controlled within the range of 10-20 nm.

6. The method for preparing a PdSe2 / Bi2O2Se van der Waals heterojunction self-driven photodetector according to claim 1, characterized in that: The dry transfer process uses polyvinyl alcohol (PVA) or polydimethylsiloxane (PDMS) as an auxiliary transfer medium, and uses PVA to assist in peeling and transfer, accurately superimposing PdSe2 nanosheets on the surface of Bi2O2Se nanosheets, keeping the interface clean and achieving high-quality van der Waals heterostructure construction.

7. The preparation method according to claim 1, wherein: The device has a short-circuit current of not less than 100nA, an open-circuit voltage of not less than 0.35V, a response time of not more than 10ms, and a photocurrent switching ratio of not less than 10 under 520nm laser irradiation. 3 .

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