Heterojunction photoelectric material based on in-situ self-reduction surface plasma resonance effect, preparation method and application

Abstract

The invention relates to the technical field of semiconductor optoelectronic materials, in particular to a heterojunction photoelectric material based on the in-situ self-reduction surface plasma resonance effect, a preparation method and application, and the technical points are as follows: MoS2 quantum dots are deposited on a substrate, and a Cs2AgBiI6 nanosheet with a selectively exposed (100) crystal face is prepared by a low-temperature solvothermal method to obtain a Cs2AgBiI6 (100) nanosheet; cs2AgBiI6 (100) nanosheets are deposited on a MoS2QDs-substrate through a spin-coating method to prepare a Cs2AgBiI6 (100) / MoS2 QDs-substrate, a reducing agent is sprayed on the surface of the Cs2AgBiI6 (100) / MoS2 QDs-substrate, Ag elementary substances are generated through in-situ reduction, the heterojunction photoelectric material is obtained, an all-inorganic heterojunction system is constructed, the plasma resonance effect is introduced, and collaborative improvement of wide spectral response, high sensitivity, rapid response and high stability is achieved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic materials and preparation technology, specifically to a heterojunction optoelectronic material based on in-situ self-reducing surface plasmon resonance effect, its preparation method, and its application. Background Technology

[0002] Optoelectronic devices are widely used in communications, medical, military, and scientific research fields. In communications, they are used for optical signal reception in fiber optic communication systems; in medical fields, they are used for optical imaging and phototherapy; in military fields, they are used for lidar and infrared detection; and in scientific research, they are used for spectral analysis and quantum information. Developing new optoelectronic devices with higher sensitivity, faster response speeds, and wider spectral response ranges is the core driving force for industrial development.

[0003] As semiconductor technology approaches its physical limits, the development of devices based on traditional silicon-based materials faces bottlenecks. Perovskite materials, due to their advantages such as high light absorption intensity, tunable bandgap, high carrier mobility, and long carrier lifetime, as well as relatively simple fabrication processes and tunable structural properties, have attracted widespread attention in photovoltaic and optoelectronic fields such as solar cells, photodetectors, light-emitting diodes, and field-effect transistors. However, they also suffer from problems such as responding only to the visible light spectrum, low light absorption, low photoresponsivity, and low intrinsic carrier mobility. These issues prevent the fabricated optoelectronic devices from simultaneously achieving high responsivity and fast response time, and the detection range cannot reach theoretically predicted values. In recent years, researchers have addressed these problems from multiple perspectives. For example, Chinese patent CN118338746A discloses a copper-based halide-modified two-dimensional perovskite PEA2MA3Pb4I. 13 A photodetector and its fabrication method have been developed, achieving a photocurrent-to-dark-current ratio exceeding 40,000, a responsivity exceeding 0.4 A / W, and a detectivity exceeding 7.0 × 10⁻⁶. 12 Jones, with a response speed improved to 2.0 μs. Chinese patent CN118610286A discloses the preparation and application of a zero-dimensional perovskite Cs3Mo2Cl9, exhibiting good response to red light in the 650 nm, 760 nm, and 800 nm bands, as well as lower wavelength near-infrared light. Chinese patent CN 118738190A discloses a controllable growth method for a PbSe / CsPbBr3 heterojunction perovskite photodetector, effectively reducing non-radiative recombination of charge carriers and suppressing dark current. Chinese patent CN119768003A discloses a MeO-2PACz modified (FA) 0.95 MA 0.05 ) 0.95 Cs 0.05 Pb(I 0.95 Br 0.053. Perovskite photodetectors and their fabrication methods have improved the lifetime of photogenerated electrons and the crystal quality of the perovskite layer. This has enhanced the performance of perovskite optoelectronic devices to some extent, but many key technologies still need to be overcome, such as insufficient spectral response range, inadequate photoresponsivity and sensitivity, low light absorption, relatively high dark current, and easy recombination of photogenerated electrons and holes.

[0004] Current research on perovskite semiconductors mainly focuses on lead-based organic-inorganic hybrid perovskite materials. However, the toxicity of lead and the instability of organic ions in these materials do not meet the requirements for commercial applications.

[0005] Therefore, in response to the above problems, the development of novel lead-free perovskite materials with excellent optical properties is an urgent technical challenge. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a heterojunction optoelectronic material, its preparation method, and its application based on in-situ self-reducing surface plasmon resonance effect. This effectively solves the technical problems in existing technologies where perovskites, due to their lead-containing toxicity, poor stability, narrow light absorption range, low carrier transport efficiency, and high dark current, result in slow response speed, low sensitivity, and limited spectral response range in optoelectronic devices.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a heterojunction optoelectronic material based on the in-situ self-reducing surface plasmon resonance effect, comprising the following steps:

[0009] A. MoS2 quantum dots are deposited on a substrate to obtain MoS2 QDs-substrate;

[0010] B. Selectively exposed (100) crystal plane Cs2AgBiI6 nanosheets were prepared by low-temperature solvothermal method to obtain Cs2AgBiI6 (100) nanosheets.

[0011] C. The Cs2AgBiI6(100) nanosheets are deposited on the MoS2QDs-substrate obtained in step A by spin coating to obtain Cs2AgBiI6(100) / MoS2 QDs-substrate;

[0012] D. Spray a reducing agent onto the surface of the Cs2AgBiI6(100) / MoS2 QDs-substrate to reduce Ag element in situ and obtain the heterojunction optoelectronic material.

[0013] Furthermore, the substrate includes FTO, ITO, silicon wafer, silicon dioxide, or sapphire.

[0014] Furthermore, step A includes the following steps:

[0015] A1. Add 0.02~0.08 mmol of ammonium molybdate (NH4)6Mo7O 24 • Dissolve 4H2O in 2~10 mL of deionized water, and adjust the pH of the solution to 5~8 with 5%~25% ammonia water to obtain solution 1;

[0016] A2. Dissolve 0.05~0.15 mmol of thiourea CS(NH2)2 in 5~25 mL of deionized water to obtain solution 2;

[0017] A3. Add solution 1 dropwise to solution 2 and stir continuously at room temperature for 2-10 h to obtain a mixed solution;

[0018] A4. Transfer the mixed solution obtained in step A3 to a built-in 50 mL polytetrafluoroethylene stainless steel high-pressure reactor, seal it, and place it in an oven at 150~240℃ for 12~36 h. Then, allow it to cool naturally to room temperature in air to obtain the MoS2 QDs-substrate.

[0019] Furthermore, the amount of ammonium molybdate used is 0.05 mmol, the amount of thiourea used is 0.1 mmol, the mass fraction of ammonia water is 10%, the pH value is adjusted to 6.5, the reaction temperature is 200℃, and the reaction time is 24 h.

[0020] Furthermore, step B includes the following steps:

[0021] B1. Dissolve 0.2~0.8 mmol CsI, 0.05~0.5 mmol AgI and 0.05~0.5 mmol BiI3 in 5~20 mL of the first solvent, and stir at room temperature for 2~15 h to ensure complete dissolution, to obtain precursor solution A;

[0022] B2. Take 0.2~2mL of the precursor solution A obtained in step B1 and add it dropwise to 5~20mL of the second solvent, and heat it to 40~80℃ and stir continuously for 1~5h to obtain a suspension.

[0023] B3. Centrifuge the suspension obtained in step B2 at 5000~15000 rpm / min for 3~8 min, wash with isopropanol 2~5 times, place the precipitate in a vacuum drying oven at 50~100℃ for 18~36 h, grind thoroughly to obtain Cs2AgBiI6(100) nanosheets.

[0024] Furthermore, the first solvent includes dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, dimethylacetamide, ethylene glycol, or propylene glycol;

[0025] The second solvent includes isopropanol, ethanol, ethyl acetate, n-butanol, or acetone.

[0026] Furthermore, step C includes the following steps:

[0027] The Cs2AgBiI6(100) nanosheets obtained in step B3 were spin-coated onto the MoS2 QDs-substrate obtained in step A4 using a spin-coating process of low speed (100~800 rad / min) for 5~20 s and high speed (2000~5000 rad / min) for 10~60 s, to obtain the Cs2AgBiI6(100) / MoS2 QDs-substrate.

[0028] Further, step D includes the following steps: spraying 5~30 μL of phosphorous acid onto the perovskite surface of the Cs2AgBiI6(100) / MoS2 QDs-substrate to reduce some Ag nanoparticles and obtain the heterojunction optoelectronic material.

[0029] In a second aspect, the present invention also provides a heterojunction optoelectronic material based on the in-situ self-reducing surface plasmon resonance effect, wherein the heterojunction optoelectronic material is prepared according to the preparation method described in the first aspect;

[0030] The heterojunction optoelectronic materials include: MoS2 QDs layer;

[0031] Cs2AgBiI6(100) crystal layer deposited on the MoS2 QDs layer;

[0032] Ag nanoparticles were formed on the surface of the Cs6AgBiI6(100) crystal plane by in-situ reduction method;

[0033] The heterojunction optoelectronic material responds to the spectrum in the wavelength range of 300~1000 nm.

[0034] Thirdly, the present invention provides an application of a heterojunction optoelectronic material based on the in-situ self-reducing surface plasmon resonance effect. The heterojunction optoelectronic material is prepared according to the preparation method described in the first aspect and includes applications in photodetectors, solar cells, light-emitting diodes, or image sensors.

[0035] The technical solution provided by this invention has the following advantages compared with the known prior art:

[0036] 1. This invention provides a heterojunction optoelectronic material and its preparation method based on in-situ self-reducing surface plasmon resonance effect. It realizes the efficient and controllable preparation of all-inorganic heterojunction optoelectronic materials, and comprehensively solves the contradiction between stability and performance of perovskite materials. By depositing MoS2 QDs → synthesizing Cs2AgBiI6(100) nanosheets → spin-coating to construct heterojunctions → in-situ reduction of Ag NPs, it integrates the environmental advantages of lead-free perovskite, the structural advantages of crystal plane control and the performance advantages of plasmon resonance. It fundamentally solves the problems of stability, toxicity and light absorption efficiency and carrier separation efficiency of traditional perovskite materials (especially organic-inorganic hybrid and lead-based perovskite). By constructing an all-inorganic heterojunction system and introducing plasmon resonance effect, it achieves a synergistic improvement of wide spectrum response, high sensitivity, fast response and high stability. It provides a new type of all-inorganic, lead-free perovskite material with excellent optical performance, and provides a reliable material basis for the preparation of high-performance and high-stability optoelectronic devices.

[0037] 2. This invention uses MoS2, which has a small bandgap and high conductivity, as an electron transport layer to optimize energy level matching, reduce interface recombination, reduce light reflection loss, suppress photogenerated carrier recombination, and improve the electron transport dynamics performance of optoelectronic devices. It solves the problem that traditional TiO2 electron transport layers easily adsorb impurities and form ion accumulation, leading to increased dark current. It also reduces leakage channels caused by pores and improves interface contact uniformity. MoS2 quantum dots can guide incident light and increase the transmission path of incident light in the device, thereby improving the light capture efficiency of Cs2AgBiI6.

[0038] 3. By controlling the reaction conditions, the present invention prepares Cs2AgBiI6 crystals with selectively exposed (100) crystal planes, which helps to reduce the trap state density in the material. The Cs2AgBiI6 (100) crystal plane has better surface grain boundary potential, lower carrier nonradiative recombination loss and trap state density, and higher carrier mobility.

[0039] 4. This invention reduces some Ag nanoparticles on the surface of Cs2AgBiI6(100) crystal plane by in-situ reduction method, which exhibits local surface plasmon effect and improves light absorption performance. Visible light can directly excite Ag nanoparticles to generate hot electrons. The energy of some hot electrons can be as high as crossing the Schottky barrier of the metal-semiconductor interface and entering the conduction band of the semiconductor, thereby significantly increasing the concentration of photogenerated carriers in the semiconductor.

[0040] 5. This invention selects MoS2 with energy level matching as the electron transport layer (ETL) of the Cs2AgBiI6(100) system to ensure that the LUMO energy level of the ETL matches the conduction band energy level of the perovskite (the energy level offset is controlled within 0.2-0.5 eV), avoids charge injection barriers, improves separation efficiency, and utilizes the bipolar transport characteristics of the perovskite itself to provide a simplified structure of "perovskite / ETL / electrode". Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0042] Figure 1 This is a technical roadmap for the fabrication of Ag NPs / Cs2AgBiI6(100) / MoS2 QDs heterojunction optoelectronic materials;

[0043] Figure 2 XRD patterns of Ag NPs / Cs2AgBiI6(100) / MoS2 QDs;

[0044] Figure 3 The scanning electron microscope image and selected area electron diffraction pattern of Cs2AgBiI6(100) are shown.

[0045] Figure 4 Scanning electron microscope (SEM) image, transmission electron microscope (TEM) image, and selected area electron diffraction (SED) pattern of MoS2 QDs;

[0046] Figure 5 XPS spectra of Ag NPs / Cs2AgBiI6(100) / MoS2 QDs;

[0047] Figure 6 Here is a structural model diagram of Cs2AgBiI6;

[0048] Figure 7 The band structure of Cs2AgBiI6 obtained from DFT theoretical calculations;

[0049] Figure 8 The density of states spectrum of Cs2AgBiI6 obtained by DFT theory calculation;

[0050] Figure 9 The UV-Vis absorption spectra of Cs2AgBiI6, Cs2AgBiI6(100) / MoS2 QDs and Ag NPs / Cs2AgBiI6(100) / MoS2 QDs were obtained by testing.

[0051] Figure 10 The fluorescence spectra of Cs2AgBiI6, Cs2AgBiI6(100) / MoS2 QDs and Ag NPs / Cs2AgBiI6(100) / MoS2 QDs obtained by testing are shown. Detailed Implementation

[0052] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0053] This invention provides a method for preparing heterojunction optoelectronic materials based on in-situ self-reducing surface plasmon resonance effect. Figure 1 This paper presents a technical roadmap for the fabrication of Ag NPs / Cs2AgBiI6(100) / MoS2 QDs heterojunction optoelectronic materials and devices, including the following steps:

[0054] A. MoS2 quantum dots are deposited on a substrate to obtain MoS2 QDs-substrate;

[0055] B. Selectively exposed (100) crystal plane Cs2AgBiI6 nanosheets were prepared by low-temperature solvothermal method to obtain Cs2AgBiI6 (100) nanosheets.

[0056] C. Cs2AgBiI6(100) nanosheets were deposited on the MoS2QDs-substrate obtained in step A by spin coating to obtain Cs2AgBiI6(100) / MoS2QDs-substrate;

[0057] D. Spray a reducing agent onto the surface of a Cs2AgBiI6(100) / MoS2 QDs- substrate to generate Ag element in situ, thus obtaining a heterojunction optoelectronic material.

[0058] The substrate in this invention includes FTO, ITO, silicon wafer, silicon dioxide, or sapphire.

[0059] To address the limited efficiency of traditional pn junction charge separation mechanisms in perovskites, this invention develops an all-inorganic perovskite and replaces the traditional low-mobility, high-defect transport layer TiO2 with a high-electron-mobility electron transport layer MoS2. This reduces electron transport hysteresis and improves interface stability and electron extraction efficiency. The transport layer energy levels are controlled to ensure that the LUMO energy level of the electron transport layer matches the perovskite conduction band energy level (energy level shift controlled within 0.2-0.5 eV), avoiding charge injection barriers and improving separation efficiency. A simplified "perovskite / ETL / electrode" structure is implemented by utilizing the perovskite's inherent "bipolar transport characteristics" (simultaneous transport of electrons and holes).

[0060] To improve the photogenerated carrier transport performance, this invention uses MoS2, which has a small bandgap and high conductivity, as the electron transport layer (ETL). This optimizes energy level matching, reduces interface recombination, minimizes light reflection loss, suppresses photogenerated carrier recombination, and improves the electron transport dynamics performance of optoelectronic devices. Furthermore, MoS2 quantum dots can guide incident light, increasing the propagation path of incident light within the device, thereby improving the light capture efficiency of Cs2AgBiI6.

[0061] To address the issue of easy recombination of photogenerated electrons and holes, MoS2 quantum dots (MoS2-QDs) are loaded onto the surface of Cs2AgBiI6(100) to form a heterojunction. Interface band matching improves charge separation efficiency and provides an electron transport path. The energy level difference between different semiconductors in the heterojunction provides a driving force for the migration of photogenerated carriers along specific directions, causing holes and electrons to move towards the electrodes along directional paths, thereby improving the separation efficiency of photogenerated electrons and holes.

[0062] Step A includes the following steps:

[0063] A1. Add 0.02~0.08 mmol of ammonium molybdate (NH4)6Mo7O 24 Dissolve 4H2O in 2~10 mL of deionized water, and adjust the pH of the solution to 5~8 with 5%~25% ammonia water to obtain solution 1;

[0064] A2. Dissolve 0.05~0.15 mmol of thiourea CS(NH2)2 in 5~25 mL of deionized water to obtain solution 2;

[0065] A3. Add solution 1 dropwise to solution 2 and stir continuously at room temperature for 2-10 hours to obtain a mixed solution;

[0066] A4. Transfer the mixed solution obtained in step A3 to a built-in 50 mL polytetrafluoroethylene stainless steel high-pressure reactor, seal it, and place it in an oven at 150~240℃ for 12~36 h. Then, allow it to cool naturally to room temperature in air to obtain the MoS2 QDs-substrate.

[0067] In some embodiments, the preferred implementation is as follows: the amount of ammonium molybdate is 0.05 mmol, the amount of thiourea is 0.1 mmol, the mass fraction of ammonia is 10%, the pH value is adjusted to 6.5, the reaction temperature is 200℃, and the reaction time is 24 h.

[0068] To address the problem of easy defect formation, this invention introduces a crystallization regulator by controlling reaction conditions to induce directional crystal growth. It then uses a low-temperature solvothermal method to prepare cubic crystals with regular shapes and high crystallinity, thereby reducing defects and lowering the density of grain boundaries and traps in the crystals.

[0069] Regarding crystal plane control: Through calculation, this invention found that the growth mode of Cs2AgBiI6(100) crystal plane helps to reduce the density of trapped states in the material, resulting in better surface grain boundary potential, lower carrier nonradiative recombination loss and trapped state density, and higher carrier mobility. This invention prepares Cs2AgBiI6 crystals with selectively exposed (100) crystal planes by controlling the reaction conditions.

[0070] To address the issue of high dark current, this invention employs coordinating molecules (such as dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), ethylene glycol (EG), propylene glycol (PG), etc.) to slow down the perovskite crystallization rate, induce directional growth, reduce film porosity and defect density, improve perovskite crystal compactness, and reduce ion vacancies and migration channels. Simultaneously, MoS2, a semiconductor material with good conductivity, is selected as the electron transport layer to reduce energy level mismatch, defect states, or ion accumulation at the electrode interface, suppressing Schottky tunneling and the formation of interface leakage current. The LUMO energy level of the electron transport layer is ensured to be lower than the perovskite conduction band energy level, preventing carriers from being injected back into the perovskite from the transport layer.

[0071] Step B includes the following steps:

[0072] B1. Dissolve 0.2~0.8 mmol CsI, 0.05~0.5 mmol AgI and 0.05~0.5 mmol BiI3 in 5~20 mL of the first solvent, and stir at room temperature for 2~15 h to ensure complete dissolution, to obtain precursor solution A;

[0073] B2. Take 0.2~2mL of the precursor solution A obtained in step B1 and add it dropwise to 5~20mL of the second solvent, and heat it to 40~80℃ and stir continuously for 1~5h to obtain a suspension.

[0074] B3. Centrifuge the suspension obtained in step B2 at 5000~15000 rpm / min for 3~8 min, wash with isopropanol 2~5 times, place the precipitate in a vacuum drying oven at 50~100℃ for 18~36 h, grind thoroughly to obtain Cs2AgBiI6(100) nanosheets.

[0075] The first solvent includes dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, dimethylacetamide, ethylene glycol, or propylene glycol;

[0076] The second solvent may include isopropanol, ethanol, ethyl acetate, n-butanol, or acetone.

[0077] Through the above preparation process, a cubic crystal system Cs2AgBiI6 with good crystallinity was synthesized. The use of all-inorganic perovskite material to replace organic-inorganic hybrid perovskite resulted in stronger structural stability, lower ion mobility, and the formation of a more stable pn-like junction interface. Combined with an inorganic electron transport layer, an all-inorganic device was constructed, reducing the interfacial compatibility problem of organic materials and improving long-term stability and charge separation efficiency.

[0078] Step C includes the following steps:

[0079] The Cs2AgBiI6(100) nanosheets obtained in step B3 were spin-coated onto the MoS2 QDs-substrate obtained in step A4 using a spin-coating process of low speed (100~800 rad / min) for 5~20 s and high speed (2000~5000 rad / min) for 10~60 s, to obtain the Cs2AgBiI6(100) / MoS2 QDs-substrate.

[0080] To improve light absorption performance, this invention uses an in-situ reduction method to reduce some Ag nanoparticles on the surface of Cs2AgBiI6(100) crystal plane to enhance light absorption.

[0081] Step D includes the following steps: spraying 5~30 μL of phosphorous acid onto the perovskite surface of the Cs2AgBiI6(100) / MoS2 QDs-substrate to reduce some Ag nanoparticles and obtain heterojunction optoelectronic materials.

[0082] Noble metal Ag nanoparticles exhibit a redshift in their absorption spectrum due to localized surface plasmon resonance (LSPR), enabling visible light absorption and significantly increasing the concentration of photogenerated carriers in semiconductors. They can also effectively trap photogenerated electrons, separating electrons from holes. Visible light directly excites Ag nanoparticles to generate hot electrons, some of which can reach energies high enough to overcome the Schottky barrier at the metal-semiconductor interface and enter the semiconductor's conduction band.

[0083] This invention also provides a heterojunction optoelectronic material based on in-situ self-reducing surface plasmon resonance effect. The heterojunction optoelectronic material is prepared according to the above preparation method. The heterojunction optoelectronic material includes: a MoS2 QDs layer; a Cs2AgBiI6(100) crystal plane layer deposited on the MoS2 QDs layer; Ag nanoparticles formed on the surface of the Cs6AgBiI6(100) crystal plane by in-situ reduction method; and the heterojunction optoelectronic material responds to the spectrum in the wavelength range of 300~1000 nm.

[0084] Among them, the MoS2 QDs layer serves as the electron transport layer, and the Cs2AgBiI6(100) crystal plane layer serves as the light absorption layer; Ag nanoparticles have a surface plasmon resonance effect, which causes the absorption spectrum to redshift and achieve visible light absorption.

[0085] The Cs2AgBiI6(100) crystal plane is a cubic crystal with selectively exposed (100) crystal planes. The band gap is 1.63 eV, the conduction band potential is -3.98 eV, and the valence band potential is -5.55 eV.

[0086] Among them, Ag NPs are Ag nanoparticles, MoS2QDs are MoS2 quantum dots, and the FTO substrate is fluorine-doped tin oxide transparent conductive glass.

[0087] Reference Figures 2 to 10 ,in, Figure 2 The XRD patterns of Ag NPs / Cs2AgBiI6(100) / MoS2 QDs are shown, indicating that Ag, Cs2AgBiI6(100) and MoS2 components were successfully synthesized and a composite heterojunction structure was formed. Figure 3 The scanning electron microscope (SEM) image and selected area electron diffraction (SAED) pattern of Cs2AgBiI6(100) are shown. It can be seen that the Cs2AgBiI6(100) prepared by the low-temperature solvothermal method in this invention has a cubic nanocrystalline structure and is a cubic crystal system with a relatively uniform size distribution. The selected area electron diffraction pattern shows regular and single diffraction spots, indicating that the crystallinity is high. Figure 4 The scanning electron microscope (SEM), transmission electron microscope (TEM), and selected area electron diffraction (SAED) images of MoS2 QDs are shown. MoS2 has a hexagonal quantum dot structure and a small size. Figure 5 XPS spectra of Ag NPs / Cs2AgBiI6(100) / MoS2 QDs are shown, indicating the presence of elements such as Ag, Cs, Bi, I, Mo, and S. Figure 6 The structural model of Cs2AgBiI6 is shown, which is a cubic crystal system belonging to the p-6m2 space group. Figure 7The band structure of Cs2AgBiI6 obtained by DFT calculation is shown. The spin-up and spin-down bands of Cs2AgBiI6 do not coincide, indicating that it is an indirect bandgap semiconductor. The specific values ​​of bandgap, conduction band level, and valence band level are shown in Table 1. The bandgap is 1.63 eV, the conduction band potential is -3.98 eV, and the valence band potential is -5.55 eV. Figure 8 The density of states spectrum of Cs2AgBiI6 obtained by DFT theoretical calculation is shown. It can be seen from the figure that the CBM and VBM of Cs2AgBiI6 mainly come from the Cs, Bi and I atomic orbitals. Figure 9 The UV-Vis absorption spectra of Cs2AgBiI6, Cs2AgBiI6(100) / MoS2 QDs and Ag NPs / Cs2AgBiI6(100) / MoS2 QDs obtained by testing are shown. It can be seen that the light absorption intensity of Ag NPs / Cs2AgBiI6(100) / MoS2 QDs is significantly improved in the 300-1000 nm range, and the light absorption range is broadened to 1000 nm. There is also a significant absorption peak at a wavelength of 425 nm, which corresponds to the LSPR absorption peak of Ag nanoparticles. Figure 10 The fluorescence spectra of Cs2AgBiI6, Cs2AgBiI6(100) / MoS2 QDs and AgNPs / Cs2AgBiI6(100) / MoS2 QDs obtained by testing are shown. As can be seen from the figure, the fluorescence intensity of AgNPs / Cs2AgBiI6(100) / MoS2 QDs is significantly lower than that of Cs2AgBiI6, indicating that the photogenerated electron-hole recombination is suppressed in the surface plasmon effect heterojunction system. The characteristic peak is blue-shifted, indicating that the band gap is reduced and the spectral range that can respond is broadened.

[0088] Table 1. Band structure of Cs2AgBiI6(100): band gap, conduction band level, valence band level

[0089]

[0090] Applications of a heterojunction optoelectronic material based on in-situ self-reducing surface plasmon resonance effect, including applications in photodetectors, solar cells, light-emitting diodes, or image sensors.

[0091] In some embodiments, the prepared heterojunction optoelectronic material is transferred to a high-vacuum evaporation coating machine, and a metal electrode is deposited on the surface of the optoelectronic material to form an optoelectronic device as a source / drain electrode. The metal electrode material may be Au, Cu, or Pt.

[0092] The present invention also provides an application of heterojunction optoelectronic materials based on in-situ self-reducing surface plasmon resonance effect, including applications in photodetectors, solar cells, light-emitting diodes or image sensors.

[0093] Example 1:

[0094] This embodiment provides one implementation of a method for preparing heterojunction optoelectronic materials based on in-situ self-reducing surface plasmon resonance effect, comprising the following steps:

[0095] 1. Add 0.02 mmol of ammonium molybdate (NH4)6Mo7O 24 • Dissolve 4H2O in 2 mL of deionized water, and adjust the pH of the solution to 5 with 5% ammonia water to obtain solution 1;

[0096] 2. Dissolve 0.05 mmol of thiourea CS(NH2)2 in 5 mL of deionized water to obtain solution 2;

[0097] 3. Add solution 1 dropwise to solution 2 and stir continuously at room temperature for 2 hours to obtain a mixed solution;

[0098] 4. Transfer the mixed solution obtained in step 3 to a 50 mL polytetrafluoroethylene stainless steel high-pressure reactor with an internal FTO glass plate, seal it, and place it in a 150℃ oven for 12 h. Then, allow it to cool naturally to room temperature in air.

[0099] 5. Blow the FTO substrate with MoS2 quantum dots deposited in step 4 with nitrogen plasma gas for 2 min to remove organic matter and moisture from the surface, thus obtaining MoS2 QDs-FTO.

[0100] 6. Dissolve 0.2 mmol CsI, 0.05 mmol AgI and 0.05 mmol BiI3 in 5 mL of dimethyl sulfoxide (DMSO) and stir at room temperature for 2 h to ensure complete dissolution, to obtain solution A;

[0101] 7. Take 0.2 mL of the precursor solution A obtained in step 6 and add it dropwise to 5 mL of isopropanol, and heat it to 30°C and stir continuously for 1 h to obtain a suspension;

[0102] 8. Centrifuge the suspension obtained in step 7 at 5000 rpm / min for 3 min, wash once with isopropanol, place the precipitate in a vacuum drying oven at 50℃ for 18 h, grind thoroughly to obtain Cs2AgBiI6(100) nanosheets.

[0103] 9. The Cs2AgBiI6(100) obtained in step 8 is spin-coated at a low speed of 100 rad / min for 5 s and at a high speed of 2000 rad / min for 10 s onto the MoS2 QDs-FTO obtained in step 5 to obtain Cs2AgBiI6(100) / MoS2 QDs-FTO, wherein the perovskite Cs2AgBiI6(100) is the light absorption layer, MoS2 QDs is the electron transport layer, and FTO is the substrate;

[0104] 10. Spray 5 μL of phosphorous acid onto the perovskite surface of the Cs2AgBiI6(100) / MoS2 QDs-FTO obtained in step 9 to reduce some Ag single atoms, thus obtaining Ag NPs / Cs2AgBiI6(100) / MoS2 QDs-FTO.

[0105] Example 2:

[0106] This embodiment provides one implementation of a method for preparing heterojunction optoelectronic materials based on in-situ self-reducing surface plasmon resonance effect, comprising the following steps:

[0107] 1. Add 0.05 mmol of ammonium molybdate (NH4)6Mo7O 24 • Dissolve 4H2O in 2 mL of deionized water, and adjust the pH of the solution to 5 with 10% ammonia water to obtain solution 1;

[0108] 2. Dissolve 0.1 mmol of thiourea CS(NH2)2 in 15 mL of deionized water to obtain solution 2;

[0109] 3. Add solution 1 dropwise to solution 2 and stir continuously at room temperature for 5 hours to obtain a mixed solution;

[0110] 4. Transfer the mixed solution obtained in step 3 to a 50 mL polytetrafluoroethylene stainless steel high-pressure reactor with an internal FTO glass plate, seal it, and place it in a 150℃ oven for 36 h. Then, allow it to cool naturally to room temperature in air.

[0111] 5. Blow the FTO substrate with MoS2 quantum dots deposited in step 4 with nitrogen plasma gas for 20 min to remove organic matter and moisture from the surface, thus obtaining MoS2 QDs-FTO.

[0112] 6. Dissolve 0.2 mmol CsI, 0.1 mmol AgI and 0.1 mmol BiI3 in 10 mL dimethyl sulfoxide (DMSO) and stir at room temperature for 15 h to ensure complete dissolution, to obtain solution A;

[0113] 7. Take 5 mL of the precursor solution A obtained in step 6 and add it dropwise to 20 mL of isopropanol, and heat it to 50 °C and stir continuously for 5 h to obtain a suspension.

[0114] 8. Centrifuge the suspension obtained in step 7 at 10,000 rpm / min for 8 min, wash twice with isopropanol, place the precipitate in a vacuum drying oven at 50℃ for 36 h, and grind thoroughly to obtain Cs2AgBiI6(100) nanosheets.

[0115] 9. The Cs2AgBiI6(100) obtained in step 8 is spin-coated at a low speed of 800 rad / min for 10 s and at a high speed of 3000 rad / min for 20 s onto the MoS2 QDs-FTO obtained in step 5 to obtain Cs2AgBiI6(100) / MoS2 QDs-FTO, wherein the perovskite Cs2AgBiI6(100) is the light absorption layer, the MoS2 QDs is the electron transport layer, and the FTO is the substrate;

[0116] 10. Spray 10 μL of phosphorous acid onto the perovskite surface of the Cs2AgBiI6(100) / MoS2 QDs-FTO obtained in step 9 to reduce some Ag single atoms, thus obtaining Ag NPs / Cs2AgBiI6(100) / MoS2 QDs-FTO.

[0117] Example 3:

[0118] This embodiment provides one implementation of a method for preparing heterojunction optoelectronic materials based on in-situ self-reducing surface plasmon resonance effect, comprising the following steps:

[0119] 1. Add 0.05 mmol of ammonium molybdate (NH4)6Mo7O 24 • Dissolve 4H2O in 5 mL of deionized water, and adjust the pH of the solution to 6.5 with 10% ammonia water to obtain solution 1;

[0120] 2. Dissolve 0.1 mmol of thiourea CS(NH2)2 in 10 mL of deionized water to obtain solution 2;

[0121] 3. Add solution 1 dropwise to solution 2 and stir continuously at room temperature for 5 hours to obtain a mixed solution;

[0122] 4. Transfer the mixed solution obtained in step 3 to a 50 mL polytetrafluoroethylene stainless steel high-pressure reactor with an internal FTO glass plate, seal it, and place it in a 200℃ oven for 24 h. Then, allow it to cool naturally to room temperature in air.

[0123] 5. Blow the FTO substrate with MoS2 quantum dots deposited in step 4 with nitrogen plasma gas for 10 min to remove organic matter and moisture from the surface, thus obtaining MoS2 QDs-FTO.

[0124] 6. Dissolve 0.4 mmol CsI, 0.2 mmol AgI and 0.2 mmol BiI3 in 10 mL dimethyl sulfoxide (DMSO) and stir at room temperature for 5 h to ensure complete dissolution, to obtain solution A;

[0125] 7. Take 1 mL of the precursor solution A obtained in step 6 and add it dropwise to 10 mL of isopropanol, and heat to 50 °C and stir continuously for 2 h to obtain a suspension.

[0126] 8. Centrifuge the suspension obtained in step 7 at 8000 rpm / min for 5 min, wash it three times with isopropanol, place the precipitate in a vacuum drying oven at 80℃ for 24 h, and grind it thoroughly to obtain Cs2AgBiI6(100) nanosheets.

[0127] 9. The Cs2AgBiI6(100) obtained in step 8 was spin-coated at a low speed of 500 rad / min for 10 s and at a high speed of 3000 rad / min for 30 s onto the MoS2 QDs-FTO obtained in step 5 to obtain Cs2AgBiI6(100) / MoS2 QDs-FTO, wherein the perovskite Cs2AgBiI6(100) is the light absorption layer, MoS2 QDs is the electron transport layer, and FTO is the substrate;

[0128] 10. Spray 15 μL of phosphorous acid onto the perovskite surface of the Cs2AgBiI6(100) / MoS2 QDs-FTO obtained in step 9 to reduce some Ag single atoms, thus obtaining Ag NPs / Cs2AgBiI6(100) / MoS2 QDs-FTO.

[0129] Example 4:

[0130] This embodiment provides one implementation of a method for preparing heterojunction optoelectronic materials based on in-situ self-reducing surface plasmon resonance effect, comprising the following steps:

[0131] 1. Add 0.05 mmol of ammonium molybdate (NH4)6Mo7O 24 • Dissolve 4H2O in 5 mL of deionized water, and adjust the pH of the solution to 8 with 10% ammonia water to obtain solution 1;

[0132] 2. Dissolve 0.15 mmol of thiourea CS(NH2)2 in 10 mL of deionized water to obtain solution 2;

[0133] 3. Add solution 1 dropwise to solution 2 and stir continuously at room temperature for 5 hours to obtain a mixed solution;

[0134] 4. Transfer the mixed solution obtained in step 3 to a 50 mL polytetrafluoroethylene stainless steel high-pressure reactor with an internal FTO glass plate, seal it, and place it in a 200℃ oven for 24 h. Then, allow it to cool naturally to room temperature in air.

[0135] 5. Blow the FTO substrate with MoS2 quantum dots deposited in step 4 with nitrogen plasma gas for 10 min to remove organic matter and moisture from the surface, thus obtaining MoS2 QDs-FTO.

[0136] 6. Dissolve 0.4 mmol CsI, 0.2 mmol AgI and 0.2 mmol BiI3 in 20 mL dimethyl sulfoxide (DMSO) and stir at room temperature for 5 h to ensure complete dissolution, to obtain solution A;

[0137] 7. Take 1 mL of the precursor solution A obtained in step 6 and add it dropwise to 20 mL of isopropanol, and heat it to 50 °C and stir continuously for 2 h to obtain a suspension.

[0138] 8. Centrifuge the suspension obtained in step 7 at 8000 rpm / min for 8 min, wash it three times with isopropanol, place the precipitate in a vacuum drying oven at 80℃ for 24 h, and grind it thoroughly to obtain Cs2AgBiI6(100) nanosheets.

[0139] 9. The Cs2AgBiI6(100) obtained in step 8 was spin-coated at a low speed of 500 rad / min for 10 s and at a high speed of 3000 rad / min for 30 s onto the MoS2 QDs-FTO obtained in step 5 to obtain Cs2AgBiI6(100) / MoS2 QDs-FTO, wherein the perovskite Cs2AgBiI6(100) is the light absorption layer, MoS2 QDs is the electron transport layer, and FTO is the substrate;

[0140] 10. Spray 5 μL of phosphorous acid onto the perovskite surface of the Cs2AgBiI6(100) / MoS2 QDs-FTO obtained in step 9 to reduce some Ag single atoms, thus obtaining Ag NPs / Cs2AgBiI6(100) / MoS2 QDs-FTO.

[0141] Example 5:

[0142] This embodiment provides one implementation of a method for preparing heterojunction optoelectronic materials based on in-situ self-reducing surface plasmon resonance effect, comprising the following steps:

[0143] 1. Add 0.08 mmol of ammonium molybdate (NH4)6Mo7O 24 • Dissolve 4H2O in 10 mL of deionized water, and adjust the pH of the solution to 8 with 25% ammonia water to obtain solution 1;

[0144] 2. Dissolve 0.15 mmol of thiourea CS(NH2)2 in 25 mL of deionized water to obtain solution 2;

[0145] 3. Add solution 1 dropwise to solution 2 and stir continuously at room temperature for 10 hours to obtain a mixed solution;

[0146] 4. Transfer the mixed solution obtained in step 3 to a 50 mL polytetrafluoroethylene stainless steel high-pressure reactor with an internal FTO glass plate, seal it, and place it in a 240℃ oven for 36 h. Then, allow it to cool naturally to room temperature in air.

[0147] 5. Blow the FTO substrate with MoS2 quantum dots deposited in step 4 with nitrogen plasma gas for 20 min to remove organic matter and moisture from the surface, thus obtaining MoS2 QDs-FTO.

[0148] 6. Dissolve 0.8 mmol CsI, 0.5 mmol AgI and 0.5 mmol BiI3 in 20 mL dimethyl sulfoxide (DMSO) and stir at room temperature for 15 h to ensure complete dissolution, to obtain solution A;

[0149] 7. Take 5 mL of the precursor solution A obtained in step 6 and add it dropwise to 20 mL of isopropanol, and heat to 80 °C and stir continuously for 5 h to obtain a suspension.

[0150] 8. Centrifuge the suspension obtained in step 7 at 15000 rpm / min for 8 min, wash with isopropanol 5 times, place the precipitate in a vacuum drying oven at 100℃ for 36 h, grind thoroughly to obtain Cs2AgBiI6(100) nanosheets.

[0151] 9. The Cs2AgBiI6(100) obtained in step 8 was spin-coated at a low speed of 800 rad / min for 20 s and at a high speed of 5000 rad / min for 60 s onto the MoS2 QDs-FTO obtained in step 5 to obtain Cs2AgBiI6(100) / MoS2 QDs-FTO, wherein the perovskite Cs2AgBiI6(100) is the light absorption layer, MoS2 QDs is the electron transport layer, and FTO is the substrate;

[0152] 10. Spray 20 μL of phosphorous acid onto the perovskite surface of the Cs2AgBiI6(100) / MoS2 QDs-FTO obtained in step 9 to reduce some Ag single atoms, thus obtaining Ag NPs / Cs2AgBiI6(100) / MoS2 QDs-FTO.

[0153] Performance testing:

[0154] 1. Characterization of Ag NPs / Cs2AgBiI6(100) / MoS2 QDs optoelectronic materials

[0155] The surface morphology of the samples was characterized using a Dimension ICON atomic force microscope (AFM). X-ray diffraction (XRD) was performed using a D8 Advance-Bruker diffractometer (Cu Ka X-ray, λ=1.5418 Å). Raman spectroscopy was collected in air using an HR-800 micro Raman system excited by a 532 nm laser. The absorption spectra of different materials were measured using a Shimadzu UV-3600i Plus UV-Vis-NIR spectrophotometer. The fluorescence spectra and carrier lifetimes of the materials were measured using a HORIBA FluoroMax-4 fluorescence spectrometer.

[0156] 2. Light response test

[0157] The performance parameters of the Ag NPs / Cs2AgBiI6(100) / MoS2 QDs-FTO photodetector were obtained using a B1500A semiconductor tester. The LEDs used for testing included three wavelengths: 425 nm, 550 nm, and 715 nm. The spot diameter was 3 mm, much larger than the length and width of the device channel. The fabricated Ag / Cs2AgBiI6(100) / MoS2 QDs heterojunction, used in the photodetector, can respond to a spectrum in the range of 300 nm to 1000 nm and can be driven by ultra-low bias voltages of 0.1 mV and 0.1 V. The photoresponsivity and specific detectivity reached 1.8 × 10⁻⁶, respectively. 4 A / W and 9.2x1013 Jones (@550 nm) has 98 A / W and 5.2 x 10⁻⁶ at 1000 nm. 11 Jones. At an input power of 3.52 mW·cm -2 Irradiation with a 550 nm laser showed a value of 1.2 x 10⁻⁶. -8 The photodetector exhibits an ultra-low dark current and a response time of 249 ns, which is superior to existing perovskite-based photodetectors. The photocurrent rises rapidly under laser irradiation and then decays sharply when the laser is turned off, indicating improved photogenerated carrier mobility in this heterojunction. The photodetector demonstrates fast response and short response time at different laser wavelengths (450, 550, and 1000 nm), indicating its effectively broadened spectral response characteristics. The photoelectric properties of samples obtained from different embodiments are shown in Table 2.

[0158] Table 2. Photoelectric properties of samples obtained from different embodiments

[0159]

[0160] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing heterojunction optoelectronic materials based on in-situ self-reducing surface plasmon resonance effect, characterized in that, Includes the following steps: A. MoS2 quantum dots are deposited on a substrate to obtain MoS2 QDs-substrate; B. Selectively exposed (100) crystal plane Cs2AgBiI6 nanosheets were prepared by low-temperature solvothermal method to obtain Cs2AgBiI6 (100) nanosheets. C. The Cs2AgBiI6(100) nanosheets are deposited on the MoS2QDs-substrate obtained in step A by spin coating to obtain Cs2AgBiI6(100) / MoS2 QDs-substrate; D. Spray a reducing agent onto the surface of the Cs2AgBiI6(100) / MoS2 QDs- substrate to reduce Ag element in situ and obtain the heterojunction optoelectronic material.

2. The method for preparing a heterojunction optoelectronic material based on in-situ self-reducing surface plasmon resonance effect according to claim 1, characterized in that, The substrate includes FTO, ITO, silicon wafer, silicon dioxide, or sapphire.

3. The method for preparing a heterojunction optoelectronic material based on in-situ self-reducing surface plasmon resonance effect according to claim 1, characterized in that, Step A includes the following steps: A1. Add 0.02~0.08 mmol of ammonium molybdate (NH4)6Mo7O 24 Dissolve 4H2O in 2~10 mL of deionized water, and adjust the pH of the solution to 5~8 with 5%~25% ammonia water to obtain solution 1; A2. Dissolve 0.05~0.15 mmol of thiourea CS(NH2)2 in 5~25 mL of deionized water to obtain solution 2; A3. Add solution 1 dropwise to solution 2 and stir continuously at room temperature for 2-10 h to obtain a mixed solution; A4. Transfer the mixed solution obtained in step A3 to a built-in 50 mL polytetrafluoroethylene stainless steel high-pressure reactor, seal it, and place it in an oven at 150~240℃ for 12~36 h. Then, allow it to cool naturally to room temperature in air to obtain the MoS2 QDs-substrate.

4. The method for preparing a heterojunction optoelectronic material based on in-situ self-reducing surface plasmon resonance effect according to claim 3, characterized in that, The amount of ammonium molybdate used is 0.05 mmol, the amount of thiourea used is 0.1 mmol, the mass fraction of ammonia water is 10%, the pH value is adjusted to 6.5, the reaction temperature is 200℃, and the reaction time is 24 h.

5. The method for preparing a heterojunction optoelectronic material based on in-situ self-reducing surface plasmon resonance effect according to claim 1, characterized in that, Step B includes the following steps: B1. Dissolve 0.2~0.8 mmol CsI, 0.05~0.5 mmol AgI and 0.05~0.5 mmol BiI3 in 5~20 mL of the first solvent, and stir at room temperature for 2~15 h to ensure complete dissolution, to obtain precursor solution A; B2. Take 0.2~2mL of the precursor solution A obtained in step B1 and add it dropwise to 5~20mL of the second solvent, and heat it to 40~80℃ and stir continuously for 1~5h to obtain a suspension. B3. Centrifuge the suspension obtained in step B2 at 5000~15000 rpm / min for 3~8 min, wash with isopropanol 2~5 times, place the precipitate in a vacuum drying oven at 50~100℃ for 18~36 h, grind thoroughly to obtain Cs2AgBiI6(100) nanosheets.

6. The method for preparing a heterojunction optoelectronic material based on in-situ self-reducing surface plasmon resonance effect according to claim 5, characterized in that, The first solvent includes dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, dimethylacetamide, ethylene glycol, or propylene glycol; The second solvent includes isopropanol, ethanol, ethyl acetate, n-butanol, or acetone.

7. The method for preparing a heterojunction optoelectronic material based on in-situ self-reducing surface plasmon resonance effect according to claim 1, characterized in that, Step C includes the following steps: The Cs2AgBiI6(100) nanosheets obtained in step B3 were spin-coated onto the MoS2 QDs-substrate obtained in step A4 using a spin-coating process of low speed (100~800 rad / min) for 5~20 s and high speed (2000~5000 rad / min) for 10~60 s, to obtain the Cs2AgBiI6(100) / MoS2 QDs-substrate.

8. The method for preparing a heterojunction optoelectronic material based on in-situ self-reducing surface plasmon resonance effect according to claim 1, characterized in that, Step D includes the following steps: spraying 5~30 μL of phosphorous acid onto the perovskite surface of the Cs2AgBiI6(100) / MoS2 QDs-substrate to reduce some Ag nanoparticles and obtain the heterojunction optoelectronic material.

9. A heterojunction optoelectronic material based on in-situ self-reducing surface plasmon resonance effect, characterized in that, The heterojunction optoelectronic material is prepared by the preparation method according to any one of claims 1 to 8; The heterojunction optoelectronic materials include: MoS2 QDs layer; Cs2AgBiI6(100) crystal layer deposited on the MoS2 QDs layer; Ag nanoparticles were formed on the surface of the Cs6AgBiI6(100) crystal plane by in-situ reduction method; The heterojunction optoelectronic material responds to the spectrum in the wavelength range of 300~1000 nm.

10. An application of a heterojunction optoelectronic material based on in-situ self-reducing surface plasmon resonance effect, characterized in that, The heterojunction optoelectronic material is prepared by the preparation method according to any one of claims 1 to 7, and is used in photodetectors, solar cells, light-emitting diodes or image sensors.

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