Method for preparing Sb2 (S, Se) 3 film through NH4SCN-assisted hydrothermal method and solar cell

Abstract

The invention relates to the technical field of photoelectric functional materials and solar photovoltaics, in particular to a method for preparing a Sb2 (S, Se) 3 film through an NH4SCN-assisted hydrothermal method and a solar cell, a hydrothermal precursor solution containing an Sb source and an S / Se source is configured on an FTO / CdS substrate, NH4SCN is introduced through at least one of a constant bulk phase mode, a local interface mode and a delayed segmentation mode, and the Sb2 (S, Se) 3 film is prepared. According to the method for preparing the Sb2 (S, Se) 3 thin film through the NH4SCN-assisted hydrothermal method, the crystallinity of the thin film is improved, the defect density is reduced, the compactness is enhanced, the carrier transport characteristic is improved, the photoelectric conversion efficiency of the cell is remarkably improved, and the Sb2 (S, Se) 3 thin film can be applied to a light absorption layer of a solar cell through the method for preparing the Sb2 (S, Se) 3 thin film through the NH4SCN-assisted hydrothermal method. And the method is mild in process, simple and convenient to operate, low in cost, suitable for large-area preparation and good in industrialization prospect.

Description

Technical Field

[0001] This invention relates to the fields of optoelectronic functional materials and solar photovoltaic technology, specifically a method for preparing Sb2(S,Se)3 thin films and solar cells using an NH4SCN-assisted hydrothermal method. Background Technology

[0002] Sb₂(S,Se)₃ is a group IV-VI compound semiconductor material with a suitable band gap, high absorption coefficient, and excellent stability. In recent years, it has attracted widespread attention and has been applied to the light-absorbing layer of thin-film solar cells. Compared with traditional materials such as CdTe and CIGS, Sb₂(S,Se)₃ not only has advantages such as low toxicity and abundant elemental reserves, but also exhibits good environmental friendliness and potential low cost in practical applications. Currently, the main methods for preparing Sb₂(S,Se)₃ thin films include vacuum evaporation, sputtering, chemical bath deposition, and hydrothermal methods. Among these, the hydrothermal method is considered a promising low-cost preparation route due to its mild reaction conditions, low equipment cost, and controllable solution chemical environment.

[0003] However, Sb₂(S,Se)₃ thin films prepared by the traditional hydrothermal method generally suffer from insufficient crystallinity, small grain size, high defect density, and non-dense film layers. These problems severely limit the transport and separation efficiency of charge carriers, thus affecting the photoelectric conversion performance of solar cells. To improve these shortcomings, researchers have attempted to regulate the hydrothermal reaction process by introducing additives or complexing agents to optimize nucleation and crystal growth behavior. Reports have shown that appropriate additives can influence the complexation state of Sb and S / Se ions in solution, regulate precursor reaction kinetics, and thus improve the orientation of the thin film. While Sb2(S,Se)3 films have achieved high quality and density, research on how to achieve high-quality Sb2(S,Se)3 films using molecular additives remains limited. There is a lack of an effective method that can simultaneously improve film quality and optimize device performance. Therefore, it is urgent to develop new additive-assisted hydrothermal strategies to achieve high-quality, controllable growth of Sb2(S,Se)3 films and promote their application in high-efficiency, stable solar cells. Thus, in light of the above situation, it is imperative to develop an NH4SCN-assisted hydrothermal method for preparing Sb2(S,Se)3 films and solar cells to overcome the shortcomings in current practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing Sb2(S,Se)3 thin films and solar cells using an NH4SCN-assisted hydrothermal method, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing Sb2(S,Se)3 thin films via NH4SCN-assisted hydrothermal method includes the following steps: A buffer layer is formed on a conductive substrate; Prepare hydrothermal precursor solutions containing Sb and S / Se sources; NH4SCN is introduced into the hydrothermal precursor solution system during the nucleation and / or crystal growth period by at least one of the following methods: constant addition in bulk phase, local addition at the interface, and delayed segmented addition. Hydrothermal deposition was completed at the set temperature range; the deposited product was cleaned and heat-treated to obtain an Sb2(S,Se)3 thin film.

[0006] As a further aspect of the present invention: the constant addition of the bulk phase is achieved by dissolving NH4SCN in the hydrothermal precursor solution; The interface localization is achieved by treating the surface of the buffer layer with NH4SCN before hydrothermal deposition, and the hydrothermal precursor solution does not contain NH4SCN. The delayed, segmented addition refers to the introduction of NH4SCN with little or no NH4SCN during the nucleation period, and the introduction of NH4SCN during the crystal growth period through slow release or replenishment / liquid replacement.

[0007] As a further aspect of the present invention: the set temperature range is controlled in segments: the nucleation stage temperature is 100–130℃ and the temperature is maintained for a set time, and the growth stage temperature is 125–150℃ and the temperature is maintained for a set time.

[0008] As a further aspect of the present invention: the heat treatment is post-annealing in an inert atmosphere, the post-annealing temperature is 300–420℃, and the holding time is 5–30 min.

[0009] As a further aspect of the present invention: the sustained-release carrier used is a porous membrane bag or a gel block; The porous membrane bag is covered with a porous material of PTFE or PVDF, and the gel block is a PVA-based gel or a PVA-agar compound gel.

[0010] As a further aspect of the present invention: the surface of the buffer layer is treated with NH4SCN by at least one of impregnation, spin coating or spraying, and then low-temperature fixation is performed at 80–120°C.

[0011] As a further aspect of the present invention: the conductive substrate is an FTO glass substrate, and the buffer layer is a CdS buffer layer; The Sb source is potassium antimony tartrate, the S source is sodium thiosulfate pentahydrate, and the Se source is selenourea.

[0012] As a further aspect of the present invention, the obtained Sb2(S,Se)3 film, compared with the control film without the introduction of NH4SCN, satisfies at least one of the following: reduced full width at half maximum (FWHM) of the XRD main peak, increased texture factor, reduced cross-sectional porosity, and / or extended steady-state or time-resolved photometric lifetime.

[0013] As a further aspect of the present invention, NH4SCN is introduced into the hydrothermal precursor solution system in sequence or in a combination of two or three of the following methods: constant bulk addition, localized interfacial addition, and delayed segmented addition.

[0014] A solar cell includes a conductive substrate, a buffer layer, a light-absorbing layer, a hole transport layer, and an electrode stacked sequentially, wherein the light-absorbing layer is an Sb2(S,Se)3 thin film prepared by the method described in claim 1.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention introduces an appropriate amount of NH4SCN into the hydrothermal reaction system to regulate the nucleation and crystal growth behavior of Sb2(S,Se)3 thin films, thereby improving the crystallinity of the film, reducing the defect density and enhancing the film density. The prepared thin film can be directly deposited on FTO / CdS substrates and has excellent optical absorption performance and carrier transport characteristics after heat treatment. Compared to the control process without the introduction of NH4SCN, this invention improves the SCN content across three dimensions: timing, location, and concentration. - Programmable supply can significantly improve the crystallization and texture quality of thin films, specifically by reducing the full width at half maximum (FWHM) of the XRD main peak, increasing the texture factor, and significantly reducing cross-sectional pores and pinholes. Simultaneously, it can effectively suppress deep defects and interface recombination, reduce the bulk / interface recombination rate, and improve carrier lifetime and diffusion length. When this film is used to prepare the light absorption layer of solar cells, it can significantly improve the open circuit voltage (Voc) and fill factor (FF) of the cell, improve the steady-state output and EQE integral consistency, and thus significantly improve the photoelectric conversion efficiency. Furthermore, the preparation method of the present invention has mild process conditions, simple operation, wide availability of raw materials and low cost, and a wider process window and is more scalable. The slow release and interface localization scheme reduces the sensitivity to the stoichiometry and instantaneous mixing of the main solution, which is convenient for large-scale and parallel consistency control of multiple tablets. It has good environmental friendliness and industrial application prospects. Attached Figure Description

[0016] Figure 1 The images show the XRD patterns of Sb2(S,Se)3 films after treatment with untreated NH4SCN solutions of different concentrations (0.3mM, 0.4mM, 0.6mM) in the embodiments of the present invention.

[0017] Figure 2 The UV-Vis absorption spectra of Sb2(S,Se)3 films after treatment with NH4SCN solutions of different concentrations in this embodiment of the invention are shown.

[0018] Figure 3 The J-V characteristic curves of Sb2(S,Se)3 solar cells after untreated and treated with NH4SCN solutions of different concentrations (0.3mM, 0.4mM, 0.6mM) in the embodiments of the present invention are shown. The lower left corner of the image shows a schematic diagram of the solar cell device structure. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0021] Please see Figures 1-3 This invention provides a method for preparing Sb2(S,Se)3 thin films using an NH4SCN-assisted hydrothermal method. This method solves the problems of insufficient crystallinity, small grain size, high defect density, and non-dense film layer that exist in the traditional hydrothermal method for preparing Sb2(S,Se)3 thin films, thus affecting the photoelectric conversion performance of solar cells. The specific details are as follows: The core of this invention is to introduce NH4SCN into the hydrothermal reaction system and adopt a specific introduction strategy to regulate the nucleation and crystal growth behavior of Sb2(S,Se)3 thin films, thereby improving the crystallization quality of the thin film, reducing the defect density and enhancing the film density, and finally obtaining Sb2(S,Se)3 thin films that can be used as light absorption layers in high-efficiency solar cells.

[0022] (1) Preparation of substrate and buffer layer: A conductive substrate (preferably an FTO glass substrate) is used as the substrate, and a buffer layer (preferably a CdS buffer layer) is formed on its surface. The substrate needs to be ultrasonically cleaned to remove surface oil and impurities. The buffer layer is prepared by chemical solution deposition to provide a good interface for subsequent heterogeneous nucleation of thin films.

[0023] (2) Preparation of hydrothermal precursor solution: Potassium antimony tartrate (KSbC4H4O7・0.5H2O) as Sb source, sodium thiosulfate pentahydrate (Na2S2O3・5H2O) as S source, and selenourea (CH4N2Se) as Se source were dissolved in deionized water and stirred magnetically until the solution turned orange-yellow to ensure complete complexation of the precursor and form a homogeneous hydrothermal precursor solution.

[0024] (3) NH4SCN introduction strategy: NH4SCN is introduced into the hydrothermal system using at least one of the following methods to control the nucleation free energy, crystal plane growth rate ratio and defect states: Bulk constant addition: Dissolve NH4SCN in the main precursor solution, so that SCN... - It persists throughout the entire hydrothermal process, with the equivalent growth period concentration of NH4SCN controlled at 10–700 mM; Localized addition at the interface: Before hydrothermal deposition, the substrate / buffer layer surface is treated with NH4SCN by immersion, spin coating, or spraying (treatment solution concentration 0.05–0.5 mol·L⁻¹). -1 The processing time is 1–5 min, followed by low-temperature fixation at 80–120 °C. The main precursor solution does not contain NH4SCN. Delayed, segmented addition: No or minimal SCN introduced during the nucleation period. - During the crystal growth period, NH4SCN is gradually supplied through a slow-release carrier (porous membrane bag or gel block, the porous membrane bag is covered with PTFE or PVDF material with a pore size of 0.1–0.5 μm, and the gel carrier is PVA-based or PVA-agar composite gel) or by replenishment / replacement. The slow-release carrier needs to be placed in the convection zone away from the substrate (horizontal distance from the substrate ≥15 mm).

[0025] (4) Hydrothermal deposition: The substrate with the buffer layer is placed in a polytetrafluoroethylene-lined reactor containing a precursor solution (with or without NH4SCN, depending on the NH4SCN introduction strategy) and hydrothermal deposition is completed by segmented temperature control (nucleation period 100–130℃, holding for 10–60 min; growth period 125–150℃, holding for 60–180 min).

[0026] (5) Cleaning and post-annealing: After hydrothermal deposition, the film is rinsed with deionized water to remove residual impurities, and then annealed at 300–420°C for 5–30 min in an inert atmosphere (preferably nitrogen) to further improve the film crystal quality, reduce defect density, and optimize interface contact.

[0027] (6) Solar cell assembly: A hole transport layer (preferably Spiro-OMeTAD) is spin-coated onto the surface of the annealed Sb2(S,Se)3 thin film, and then a 50–90 nm thick gold electrode is deposited to complete the solar cell fabrication.

[0028] The Sb₂(S,Se)₃ thin films prepared using the above-described technical solution exhibit, compared to the control film without NH₄SCN, a reduced XRD peak full width at half maximum (FWHM), an increased texture factor, fewer cross-sectional voids, and a longer steady-state or time-resolved photoluminescence (PL) lifetime. When used as a light-absorbing layer in solar cells, it can reduce carrier recombination rate, increase carrier lifetime and diffusion length, improve open-circuit voltage (Voc) and fill factor (FF), enhance steady-state output and EQE integral consistency, and significantly improve photoelectric conversion efficiency. Furthermore, this technical solution offers mild process conditions, simple operation, widely available raw materials, low cost, a wide process window, and scale-up friendliness, making it suitable for the large-scale fabrication and industrial application of Sb₂(S,Se)₃ thin-film solar cells.

[0029] The above technical solution will be described in detail below through specific embodiments. Each embodiment corresponds to a different NH4SCN introduction strategy. Process parameters not explicitly stated shall follow the limitations of the overall technical solution described above.

[0030] Example 1: Preparation of Sb2(S,Se)3 thin film and solar cell by adding NH4SCN to the bulk phase at constant volume This embodiment employs a constant addition of NH4SCN in the bulk phase, ensuring the continuous presence of SCN⁻ throughout the hydrothermal process, thereby achieving full control over film nucleation and crystal growth. The specific steps are as follows: Substrate and buffer layer preparation: The FTO glass substrate was sequentially immersed in ordinary detergent, isopropanol, acetone, ethanol, and deionized water for ultrasonic cleaning to remove surface oil and impurities and ensure substrate cleanliness. Subsequently, a 70-100 nm thick CdS buffer layer was grown on the cleaned FTO substrate surface using chemical solution deposition to provide a good interface for the heterogeneous nucleation of Sb2(S,Se)3 thin films.

[0031] Precursor solution preparation: Potassium antimony tartrate (KSbC4H4O7・0.5H2O) was used as the Sb source, sodium thiosulfate pentahydrate (Na2S2O3・5H2O) as the S source, and selenourea (CH4N2Se) as the Se source. Accurately weigh 1.0684 g of KSbC4H4O7・0.5H2O, 3.1764 g of Na2S2O3・5H2O, and 0.0920 g of CH4N2Se, and dissolve them in 140 mL of deionized water. Mix thoroughly with magnetic stirring until the solution color changes from colorless to orange-yellow, ensuring complete precursor complexation and providing a uniform ionic environment for film growth.

[0032] Bulk introduction of NH4SCN: The mixed precursor solution prepared above was dispensed into polytetrafluoroethylene-lined reactors, with 35 mL of solution injected into each reactor, and 5 mL of a 0.25–0.5 mol·L⁻¹ solution was added simultaneously.-1 The NH4SCN solution was prepared to keep the equivalent growth-phase concentration of NH4SCN within the process window of 10–700 mM. The addition of NH4SCN can regulate the reducing power and complexation state distribution of the Sb–Se composite system, thereby adjusting the nucleation free energy, crystal plane growth rate ratio, and defect states, laying the foundation for obtaining high-quality thin films.

[0033] Hydrothermal deposition: An FTO substrate with a CdS buffer layer was placed in the aforementioned reactor with the CdS buffer layer side facing down. The reactor was then transferred to a constant-temperature furnace, set to 135°C, and held for 2 hours to complete the hydrothermal deposition. Mild hydrothermal conditions combined with SCN... - Continuous regulation can prevent abnormal grain growth during thin film growth and reduce defect generation.

[0034] Cleaning and post-annealing: After hydrothermal deposition, the substrate was removed from the reactor and rinsed with deionized water to remove any residual solution adhering to the surface, removing unreacted precursors and impurities. The film was then placed in an inert atmosphere under nitrogen protection and annealed at 360-390℃ for 10 min. This post-annealing further improved the film's crystallinity, reduced defect density, enhanced film density, and optimized the interfacial contact performance between the film and the buffer layer, thereby improving carrier transport efficiency. Compared to the control sample without NH4SCN, this treatment resulted in a lower full width at half maximum (FWHM) of the XRD main peak, an increased texture factor, and a significant reduction in cross-sectional porosity.

[0035] Solar cell assembly: A hole transport layer Spiro-OMeTAD is spin-coated onto the surface of an annealed Sb2(S,Se)3 thin film, followed by the deposition of a 50-90 nm thick gold electrode via vapor deposition to complete the fabrication of the solar cell. Due to the excellent crystal quality and low defect density of the Sb2(S,Se)3 thin film, the carrier recombination rate of the cell decreases, the open-circuit voltage (Voc) and fill factor (FF) are effectively improved, the consistency between steady-state output and EQE integral is enhanced, and the photoelectric conversion efficiency is significantly improved.

[0036] Example 2: Preparation of Sb2(S,Se)3 thin film and solar cell by localized addition of NH4SCN at the interface This embodiment employs a method of locally incorporating NH4SCN at the interface, introducing SCN only at the substrate / buffer layer interface. - The specific steps for inducing preferred orientation and dense heterogeneous nucleation of thin films are as follows: Substrate and buffer layer pretreatment: The FTO substrate was ultrasonically cleaned and the CdS buffer layer was grown according to the method in step 1 of Example 1. Subsequently, the FTO / CdS composite substrate underwent NH4SCN interface treatment. One of the following two methods can be used: 1) Immersing the composite substrate in 0.10–0.30 mol·L⁻¹ water. -1The first step is to spin-coat a layer of 0.2 mol·L⁻¹ NH₄SCN aqueous solution for 2–5 min; the second step is to spin-coat a layer of 0.2 mol·L⁻¹ NH₄SCN aqueous solution at a rotation speed of 2000 rpm for 30 s. -1 An NH4SCN solution was used. SCN was introduced onto the surface of the CdS buffer layer through interfacial treatment. - Coordination / polarity sites provide directional induction for subsequent thin film nucleation.

[0037] Low-temperature fixation: The FTO / CdS composite substrate treated with NH4SCN was dried and fixed. First, nitrogen blowing was performed at room temperature for 30 seconds to remove most of the free water on the surface. Then, it was placed on a hot plate at 80–100°C for 3–5 minutes to further remove residual moisture and allow a small amount of SCN to adhere. - Stable retention on the CdS surface / interface, preventing SCN from being absorbed during subsequent hydrothermal processes. - Rapid churn rate, ensuring effective user interface persuasion.

[0038] Precursor solution preparation: Following the formulation and method in step 2 of Example 1, a hydrothermal precursor solution containing Sb, S, and Se sources was prepared. Unlike Example 1, the main precursor solution in this example does not contain NH4SCN; SCN is introduced only through interface pretreatment. - Avoid body phase SCN - Interference with the nucleation process.

[0039] Hydrothermal deposition: The FTO / CdS composite substrate, after low-temperature fixation, is placed in the precursor solution with the CdS buffer layer side facing down. The reactor is then transferred to a constant-temperature furnace and held at 130–140°C for 1.5–3.0 h to complete the hydrothermal deposition. SCN remains at the interface. - Under induction, Sb2(S,Se)3 films nucleate and grow along a preferred direction, significantly improving film density and effectively reducing pinhole and pore defects.

[0040] Cleaning and post-annealing: Following the method in step 5 of Example 1, the hydrothermally deposited film was rinsed with deionized water and annealed under nitrogen protection at a temperature of 360-380℃ for 10 minutes. Post-annealing further optimized the film's crystal structure, improved the texture factor, and extended the carrier lifetime and diffusion length. The steady-state or time-resolved pulse lifetime of the film was significantly extended compared to the control sample.

[0041] Solar cell assembly: Following the method in step 6 of Example 1, the hole transport layer Spiro-OMeTAD was spin-coated and a gold electrode was deposited to complete the solar cell fabrication. Due to the preferred orientation and low defect density of the thin film, the carrier transport and separation efficiency of the cell is improved, the photoelectric conversion performance is effectively optimized, and this strategy reduces the sensitivity to the stoichiometry and instantaneous mixing of the main solution, resulting in stronger process stability.

[0042] Example 3: Preparation of Sb2(S,Se)3 thin film and solar cell by delayed segmented addition of NH4SCN (slow-release method) This embodiment uses a slow-release carrier to achieve delayed, segmented addition of NH4SCN, introducing minimal (≤10mM) or no SCN during the nucleation period. - SCN is gradually supplied during the crystal growth period. - This allows for segmented and precise control of the nucleation and growth processes. The specific steps are as follows: Substrate and buffer layer preparation: Following the method in step 1 of Example 1, ultrasonic cleaning of the FTO substrate and growth of a 70-100 nm thick CdS buffer layer were completed to ensure the cleanliness and integrity of the substrate and buffer layer.

[0043] Precursor solution preparation: Prepare a hydrothermal precursor solution containing Sb source, S source and Se source according to the formula and method in step 2 of Example 1, ensuring that the precursor is completely complexed and dissolved to form a uniform and stable orange-yellow solution.

[0044] Preparation and arrangement of the sustained-release carrier: Weigh 0.60 g of solid NH4SCN and place it into a porous membrane bag covered with a PTFE porous membrane (pore size 0.1–0.5 μm). After venting, heat-seal the bag to prepare the NH4SCN sustained-release carrier. Suspend the sustained-release carrier above the PTFE liner using a PTFE cable, ensuring a horizontal distance ≥15 mm from the substrate surface and a distance ≥5 mm from the liquid surface. This arrangement avoids initial localized high concentrations of SCN. - Flushing the substrate ensures SCN - Smooth dissolution.

[0045] Hydrothermal deposition and segmented temperature control: The prepared precursor solution was injected into the liners containing the sustained-release carrier, 35 mL of solution per liner. Then, the FTO / CdS composite substrate was placed inside the liners with the CdS buffer layer facing down, and the sustained-release carrier suspended on the side away from the substrate and immersed in the solution. After the liners were placed in the reactor, they were transferred to a constant-temperature furnace, where segmented temperature control was employed. Nucleation stage: Heat to 120℃ and hold for 35 minutes. During this stage, SCN... - The low dissolution rate is beneficial for dense heterogeneous nucleation on the CdS surface.

[0046] Growth period: Continue to raise the temperature to 135℃ and hold for 100–110 minutes. After enhanced convection, SCN... - It dissolves gradually, and its dissolution rate depends on the pore size, charge amount, and convection intensity.

[0047] Cleaning and post-annealing: Following the method in step 5 of Example 1, the film was rinsed with deionized water and annealed under nitrogen protection at a temperature of 360-390℃ for 10 minutes. After treatment, the film exhibited high crystallinity, low defect density, dense film layer, and a significantly reduced bulk / interface recombination rate.

[0048] Solar cell assembly: Following the method in step 6 of Example 1, the hole transport layer and gold electrode are fabricated to obtain a solar cell. This strategy utilizes a programmable SCN supply... - This technology enables segmented control of the nucleation and growth processes, improving the photoelectric conversion efficiency, stability, and consistency of the battery. It also provides a wider process window, making it more suitable for large-scale and parallel fabrication of multiple cells.

[0049] This invention can also combine the three NH4SCN introduction strategies—constant bulk addition, localized interface addition, and delayed segmented addition—in sequence or in parallel. For example, the CdS buffer layer can be first treated with localized interface treatment, and then an appropriate amount of NH4SCN can be added to the main precursor solution along with a slow-release carrier. Through multi-dimensional regulation, the film quality and device performance can be further optimized. The process parameters of the combined strategy (such as NH4SCN concentration, processing time, temperature range, slow-release carrier parameters, etc.) all follow the relevant limitations in the above embodiments. The core is to achieve high-quality and controllable growth of Sb2(S,Se)3 films through the synergistic regulation of the three dimensions of timing, location, and concentration.

[0050] The apparatus corresponding to the method described in this invention includes a hydrothermal reactor with an inert liner and a sustained-release component (porous membrane bag, gel block, or equivalent structure) for delayed supply of NH4SCN. The materials (PTFE, PVDF, PVA-based gel, etc.), structural parameters (pore size, loading amount, encapsulation method, etc.), and arrangement of the sustained-release component are all designed to support the aforementioned method flow. Specifically, equivalent configurations and reasonable selections can be made according to the chosen introduction strategy (e.g., a delayed, segmented addition strategy requires matching a corresponding sustained-release carrier). All aspects related to process steps, parameter settings, and operating conditions are subject to the descriptions in the above embodiments.

[0051] The Sb₂(S,Se)₃ thin films prepared by the above embodiments of the present invention all possess excellent crystallinity, low defect density, dense film layers, and distinct preferred orientation. When used as light-absorbing layers in solar cells, they can significantly improve the photoelectric conversion efficiency of the devices. Furthermore, the preparation method of the present invention features mild process conditions, simple operation, widely available raw materials, low cost, a wide process window, and scale-up friendliness, making it suitable for the large-scale preparation and industrial application of Sb₂(S,Se)₃ thin-film solar cells.

[0052] It should be noted that, in this invention, although the specification describes the embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing Sb2(S,Se)3 thin films via NH4SCN-assisted hydrothermal method, characterized in that, Includes the following steps: A buffer layer is formed on a conductive substrate; Prepare hydrothermal precursor solutions containing Sb and S / Se sources; NH4SCN is introduced into the hydrothermal precursor solution system during the nucleation and / or crystal growth period by at least one of the following methods: constant addition in bulk phase, local addition at the interface, and delayed segmented addition. Hydrothermal deposition was completed at the set temperature range; the deposited product was cleaned and heat-treated to obtain an Sb2(S,Se)3 thin film.

2. The method for preparing Sb₂(S,Se)₃ thin films by NH₄SCN-assisted hydrothermal method according to claim 1, characterized in that, The constant addition of the bulk phase involves dissolving NH4SCN in the hydrothermal precursor solution; The interface localization involves treating the surface of the buffer layer with NH4SCN before hydrothermal deposition, and the hydrothermal precursor solution does not contain NH4SCN. The delayed, segmented addition refers to the introduction of NH4SCN with little or no NH4SCN during the nucleation period, and the introduction of NH4SCN during the crystal growth period through slow release or replenishment / liquid replacement.

3. The method for preparing Sb₂(S,Se)₃ thin films by NH₄SCN-assisted hydrothermal method according to claim 1, characterized in that, The set temperature range is controlled in segments: the nucleation stage temperature is 100–130℃ with a set holding time, and the growth stage temperature is 125–150℃ with a set holding time.

4. The method for preparing Sb₂(S,Se)₃ thin films by NH₄SCN-assisted hydrothermal method according to claim 1, characterized in that, The heat treatment is a post-annealing process performed in an inert atmosphere at a temperature of 300–420°C for 5–30 minutes.

5. The method for preparing Sb₂(S,Se)₃ thin films by NH₄SCN-assisted hydrothermal method according to claim 2, characterized in that, The sustained-release carrier used is a porous membrane bag or a gel block; The porous membrane bag is covered with a porous material of PTFE or PVDF, and the gel block is a PVA-based gel or a PVA-agar compound gel.

6. The method for preparing Sb₂(S,Se)₃ thin films by NH₄SCN-assisted hydrothermal method according to claim 2, characterized in that, The surface of the buffer layer is treated with NH4SCN by at least one of immersion, spin coating or spraying, and then low-temperature curing is performed at 80–120°C.

7. The method for preparing Sb₂(S,Se)₃ thin films by NH₄SCN-assisted hydrothermal method according to claim 1, characterized in that, The conductive substrate is an FTO glass substrate, and the buffer layer is a CdS buffer layer; The Sb source is potassium antimony tartrate, the S source is sodium thiosulfate pentahydrate, and the Se source is selenourea.

8. The method for preparing Sb₂(S,Se)₃ thin films by NH₄SCN-assisted hydrothermal method according to claim 1, characterized in that, The resulting Sb2(S,Se)3 film, compared to the control film without NH4SCN, satisfies at least one of the following: reduced full width at half maximum (FWHM) of the XRD main peak, increased texture factor, reduced cross-sectional porosity, and / or extended steady-state or time-resolved photoperiod lifetime.

9. The method for preparing Sb₂(S,Se)₃ thin films by NH₄SCN-assisted hydrothermal method according to claim 1 or 2, characterized in that, NH4SCN is introduced into the hydrothermal precursor solution system in sequence or in a combination of two or three of the following methods: constant bulk addition, local interfacial addition, and delayed segmented addition.

10. A solar cell, characterized in that, It includes a conductive substrate, a buffer layer, a light absorption layer, a hole transport layer and an electrode stacked in sequence, wherein the light absorption layer is an Sb2(S,Se)3 thin film prepared by the method described in claim 1.

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