Method for preparing selenium antimony sulfide thin film based on sulfur-selenium concentration gradient complementary technology and solar cell based on thin film

Abstract

The invention discloses a method for preparing a selenium antimony sulfide thin film based on a sulfur-selenium concentration gradient complementary technology and a solar cell based on the thin film. The sequential sulfur-selenium concentration gradient complementary technology is innovatively provided, the sulfur element is introduced preferentially, the Sb2 (S, Se) 3 thin film prepared in a hydrothermal mode is treated through the selenium ion solution, accordingly, the vertical concentration gradient distribution of the sulfur-selenium element in the Sb2 (S, Se) 3 thin film is accurately regulated and controlled, accurate defect passivation and anion distribution optimization are achieved, and the stability of the Sb2 (S, Se) 3 thin film is improved. And on the basis, an efficient Sb2 (S, Se) 3 solar cell with the photoelectric conversion efficiency exceeding 10.0% is prepared. The method has the advantages of simplicity and convenience in operation, low cost, small damage to the film structure in the treatment process and the like, effectively overcomes the defects of high operation difficulty, high equipment requirement, damage to the film crystal structure by high-temperature treatment and the like in the prior art, and has important application value in the fields of photoelectric materials, photovoltaic materials, devices and the like.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor optoelectronic materials and devices technology, specifically relating to a method for preparing antimony selenide thin films based on sulfur-selenium concentration gradient complementary technology and a solar cell based on the thin film. Background Technology

[0002] Antimony selenide (Sb₂(S,Se)₃) is a novel light-absorbing direct bandgap semiconductor material with a unique quasi-one-dimensional chain structure. This material possesses core advantages such as excellent structural stability, abundant resources on Earth, non-toxicity, and tunable bandgap (range 1.1–1.7 eV), making it an ideal candidate material for fabricating low-cost, high-efficiency thin-film solar cells [Nat. Energy. 5 (2020) 587; Adv. Funct. Mater. 34 (2024) 2313676]. According to the Shockley-Quyther limit theory, the theoretical photoelectric conversion efficiency of a single-junction solar cell can reach 33.7% [Angew. Chem. Int. Ed. 63 (2024) e202409609; Adv. Funct. Mater. 34 (2024) 2308021].

[0003] Currently, Sb₂(S,Se)₃ photovoltaic devices prepared by solution methods have achieved a peak photoelectric conversion efficiency exceeding 10% in less than a decade of development [Nat. Energy 2020, 5, 587-595; Adv. Mater. 2024, 36, 2410669]. However, their actual efficiency still lags significantly behind the theoretical efficiency (28%~33%) predicted by the Shockley-Quesell model, thus possessing enormous potential for performance improvement and broad development prospects [Adv. Funct. Mater. 2024, 34, 2308021]. The core reasons for this problem are mainly threefold: (1) The reactivity of sulfur and selenium sources differs significantly, and the selenium source supply is insufficient in the later stages of the hydrothermal reaction, causing a spontaneous imbalance in the sulfur-selenium atomic ratio in the vertical direction of the Sb2(S,Se)3 film, which in turn induces band mismatch and grain delamination; (2) Bulk deep-level defects (such as sulfur vacancies and antimony-sulfur antisite defects) are easily generated during the heat treatment process, and sulfur is an anion (S 2- Se 2- ) will volatilize, resulting in (Sb4(S x Se 6-X )) nThe molecular chain breaks, which eventually leads to a decrease in carrier mobility; (3) The mismatch of the interface energy level of the heterojunction will intensify the recombination of photogenerated carriers. Specifically, the mismatch of the interface energy level will aggravate the degree of band bending, form interface recombination sites, and hinder the effective injection and extraction of photogenerated carriers.

[0004] Current methods for controlling the sulfur-selenium element distribution in Sb2(S,Se)3 thin films can be mainly divided into two major technical paths: hydrothermal process control and hydrothermal post-treatment. In the hydrothermal preparation process, Huang et al. have artificially controlled the hydrothermal deposition temperature stepwise to adjust the Se / S atomic ratio distribution in the vertical direction of the Sb2(S,Se)3 thin film, thereby increasing the selenium content in the upper part of the film [Angew. Chem. Int. Ed. 2024, 63, e202406512]; however, this method requires real-time operation during the hydrothermal process, placing high demands on the operator's technical skills. The current mainstream post-selenization process uses selenium powder as the selenium source and processes the film at relatively high temperatures (usually 400℃) to increase the selenium content of the sintered crystalline Sb2(S,Se)3 film [ACS Appl. Mater. Interfaces 2022, 14, 31986-31997; Sol. Energy Mater. Sol. Cells 2023, 259, 112464]. This process not only carries a high risk of damaging the original morphology and crystal structure of the crystalline Sb2(S,Se)3 film, but also has limited effect on the passivation of defects in the film. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a method for preparing antimony selenide thin films based on sulfur-selenium concentration gradient complementarity technology, and a solar cell based on this film. This invention, through a step-by-step strategy of "rapidly releasing sulfur ions first, then controllably replenishing and diffusing selenium ions," can effectively regulate the band structure of Sb₂(S,Se)₃ thin films, synergistically improving the inherent imbalance of the sulfur-selenium atomic ratio in the film, while simultaneously suppressing the formation of deep-level defects in the bulk phase. This method simultaneously achieves three core functions: first, through spatially selective ordered sulfur-selenium ion replenishment, it effectively reverses the harmful selenium concentration gradient distribution, achieving precise control of the film's band structure; second, through atomic-scale ordered sulfur-selenium ion release and diffusion, it efficiently passivates deep-level defects, prolongs carrier lifetime, and suppresses bulk recombination of photogenerated carriers; and third, it enhances interfacial charge transfer capabilities, promoting efficient interfacial injection and extraction of photogenerated carriers.

[0006] This invention relates to a method for preparing antimony selenide thin films based on sulfur-selenium concentration gradient complementarity technology. Firstly, during the hydrothermal preparation of the Sb₂(S,Se)₃ thin film, the sulfur concentration gradient is pre-regulated using thioacetamide. Then, a selenium ion solution is used for post-treatment of the pre-regulated film, thereby precisely controlling the vertical concentration gradient distribution of sulfur and selenium in the Sb₂(S,Se)₃ thin film and efficiently suppressing defect state concentration. Ultimately, a thin film with optimized band structure, reduced defect state density, and significantly improved crystallinity and morphology is prepared. Based on this thin film, a high-efficiency Sb₂(S,Se)₃ solar cell with a photoelectric conversion efficiency exceeding 10% is fabricated.

[0007] This invention relates to a method for preparing antimony selenide thin films based on sulfur-selenium concentration gradient complementarity technology, comprising the following steps:

[0008] Step 1: At room temperature, thioacetamide is added to a solution containing potassium antimony tartrate, sodium thiosulfate and sodium selenose to obtain a precursor solution. The solution is then transferred to a high-pressure reactor, and the substrate is immersed in the precursor solution for hydrothermal deposition to obtain an Sb2(S,Se)3 precursor film.

[0009] Step 2: Dissolve selenium powder and sodium borohydride in deionized water at 60℃ to obtain a solution containing Se. 2- An alkaline solution.

[0010] Step 3: Using the Se-containing material prepared in Step 2 2- The Sb2(S,Se)3 precursor film obtained in step 1 was subjected to selenization treatment using an alkaline solution.

[0011] Step 4: Heat-treat the Sb2(S,Se)3 precursor film after the selenization treatment in step 3 to promote film crystallization and finally obtain a Sb2(S,Se)3 film with good crystallinity.

[0012] further:

[0013] In step 1, the precursor solution contains sodium thiosulfate at a concentration of 160 mmol / L, thioacetamide at a concentration of 1 mmol / L, and potassium antimony tartrate at a concentration of 35 mmol / L.

[0014] In step 2, selenium powder is first soaked in a small amount of anhydrous ethanol at 60°C and stirred for 60 seconds to ensure uniform dispersion. Then, sodium borohydride is added to the dispersion at a molar ratio of 1:0.4 to selenium powder, and the mixture is stirred continuously at 60°C for 60 seconds to obtain a mixture of selenium powder and sodium borohydride. Next, deionized water at 60°C is added to this mixture, and the mixture is stirred at 900 rpm for 60 seconds in a 60°C water bath to finally obtain a clear and transparent solution containing Se. 2- An alkaline solution containing Se.2- Se in alkaline solution 2- The concentration is 0.01 mol / L.

[0015] In step 3, the Sb2(S,Se)3 precursor film obtained in step 1 is placed horizontally upwards on the substrate containing Se obtained in step 2. 2- The Sb2(S,Se)3 precursor film was treated in an alkaline solution in the absence of air for 1 minute in a 60°C water bath. After treatment, the film was rinsed with deionized water.

[0016] In step 4, the Sb2(S,Se)3 precursor film after selenization treatment in step 3 is vacuum dried at 50°C for 1 minute, and then transferred to a hot stage under inert gas protection and heat-treated at 370°C for 10 minutes to obtain a selenium sulfide film with sequential sulfur-selenium concentration gradient complementarity.

[0017] The substrate is an FTO / CdS substrate or a TiO2 / CdS substrate.

[0018] The inert gas is preferably nitrogen.

[0019] The present invention also provides a solar cell comprising the aforementioned sequential sulfur-selenium concentration gradient complementary antimony selenide thin film.

[0020] Specifically, the antimony selenide thin film with the sequential sulfur-selenium concentration gradient complementarity is used as the light absorption layer. After the antimony selenide thin film with the sequential sulfur-selenium concentration gradient complementarity is prepared by the above method, the hole transport layer and the electrode are prepared in sequence to obtain the solar cell.

[0021] The hole transport layer is preferably spiro-OMeTAD; the electrodes are preferably gold.

[0022] The Sb2(S,Se)3 thin film of the present invention has the characteristics of adjustable sulfur-selenium element concentration gradient, low film surface roughness, and low film defect density.

[0023] The principle of this invention is as follows:

[0024] This invention utilizes low-toxicity, safe, and low-cost compounds as raw materials to dissolve thioacetamide in a hydrothermal solution of Sb₂(S,Se)₃, thereby achieving concentration gradient control of sulfur in Sb₂(S,Se)₃ films. Highly active Se₂ is prepared by dissolving and dispersing it in a mixed system of ethanol and deionized water. 2- Solution, using the obtained Se 2-A solution was applied to the selenization treatment of Sb₂(S,Se)₃ precursor thin films on a substrate with a sulfur concentration gradient, achieving precise control of the selenium concentration distribution in the film. Subsequently, the selenized film was heat-treated to obtain a Sb₂(S,Se)₃ thin film with excellent crystallinity. Finally, a hole transport layer (HTL) and electrodes were fabricated to complete the assembly of a solar cell. The concentration distribution of selenium in the Sb₂(S,Se)₃ thin film can be controlled by adjusting the Se₂ concentration gradient. 2- The solution concentration and selenization treatment time can be precisely controlled.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. An innovative and convenient in-situ passivation and bandgap synergistic modulation strategy was proposed, successfully fabricating Sb₂(S,Se)₃ thin films with complementary sulfur-selenium elemental concentration gradients and solar cells based on these films. The prepared Sb₂(S,Se)₃ thin films possess core advantages such as optimized bandgap structure, significantly reduced defect state density, and improved crystal quality and morphology. Solar cells assembled based on these films achieve a photoelectric conversion efficiency exceeding 10%, exhibiting excellent photovoltaic performance.

[0027] 2. The raw materials selected are low-toxicity, safe, and inexpensive compounds, and the preparation process is green, environmentally friendly, and highly economical. The addition of thioacetamide as a sulfur source simplifies the operation. The selenization treatment is carried out under mild temperature conditions after the hydrothermal reaction, avoiding damage to the film structure caused by high-temperature processes. Simultaneously, through Se... 2- The orientation effect of the solution enables efficient control of the selenium concentration distribution in the Sb2(S,Se)3 precursor film, resulting in strong process controllability and high repeatability.

[0028] 3. This invention compares the preparation of antimony selenide thin films with sequential sulfur-selenium concentration gradient complementarity with similar work by others. Others [Angew. Chem. Int. Ed. 2024, 63, e202406512] artificially controlled the hydrothermal deposition temperature in steps to adjust the Se / S atomic ratio distribution in the vertical direction of the Sb2(S,Se)3 film, thereby increasing the selenium content in the upper part of the film; however, this method requires real-time operation during the hydrothermal process, placing high demands on the operator's technical skills. Others [ACS Appl. Mater. Interfaces 2022, 14, 31986-31997; Sol. Energy Mater. Sol. Cells 2023, 259,112464] used selenium powder as the selenium source in a post-selenization process, treating it at a relatively high temperature (usually 400℃) to increase the selenium content of the sintered crystalline Sb2(S,Se)3 film. This process not only carries a high risk of damaging the original morphology and crystal structure of the crystalline Sb2(S,Se)3 film, but also has limited passivation effect on film defects. In contrast, this invention uses thioacetamide for pretreatment, a simple and easy-to-implement process that requires no complex dynamic control; subsequent utilization of Se... 2- The solution undergoes post-selenization treatment under mild temperature conditions. The preparation process has low equipment requirements, no risk of damaging the original structure of the film, and can achieve efficient passivation of film defects through atomic-scale ion gradient control, while simultaneously improving the uniformity of film composition and crystal quality, ultimately achieving a comprehensive improvement in photovoltaic performance. Attached Figure Description

[0029] Figure 1 The XRD characterization results are those of the Sb2(S,Se)3-untreated thin film and the Sb2(S,Se)3-sulfur-selenium complementary thin film described in this invention; wherein: (a) XRD pattern; (b) hysteresis coefficient calculation results.

[0030] Figure 2 These are the SEM characterization results of the Sb2(S,Se)3-untreated thin film and the Sb2(S,Se)3-sulfur-selenium complementary thin film described in this invention; wherein: (a) surface image of the Sb2(S,Se)3-untreated thin film; (b) surface image of the Sb2(S,Se)3-sulfur-selenium complementary thin film; (c) cross-sectional image of the Sb2(S,Se)3-untreated thin film; (d) cross-sectional image of the Sb2(S,Se)3-sulfur-selenium complementary thin film.

[0031] Figure 3The results are HRTEM characterizations of the Sb2(S,Se)3-untreated thin film and the Sb2(S,Se)3-sulfur-selenium complementary thin film described in this invention; wherein: (a) cross-sectional image of the Sb2(S,Se)3-sulfur-selenium complementary thin film and corresponding element mapping; (b) cross-sectional image of the Sb2(S,Se)3-untreated thin film and corresponding element mapping; (c) comparison of the Se / Sb atomic ratio distribution in the longitudinal direction of the Sb2(S,Se)3-sulfur-selenium complementary thin film and the Sb2(S,Se)3-unselenized thin film.

[0032] Figure 4 These are the current density-voltage characteristic curves of the Sb2(S,Se)3-untreated solar cell and the Sb2(S,Se)3-sulfur-selenium complementary solar cell described in this invention.

[0033] Figure 5 These are the external quantum efficiency and integral current density curves of the Sb2(S,Se)3-untreated solar cell and the Sb2(S,Se)3-sulfur-selenium complementary-1min solar cell described in this invention.

[0034] Figure 6 The results are SEM characterization of the Sb2(S,Se)3-sulfur-selenium complementary 2 min thin film described in this invention; where: (a) surface image; (b) cross-sectional image.

[0035] Figure 7 This is the current density-voltage characteristic curve of the Sb2(S,Se)3-sulfur-selenium complementary 2-min solar cell described in this invention.

[0036] Figure 8 The curves show the external quantum efficiency and integral current density of the Sb2(S,Se)3-sulfur-selenium complementary 2-min solar cell described in this invention. Detailed Implementation

[0037] The technical solution of the present invention will be further analyzed and explained through specific embodiments below.

[0038] Example 1: Fabrication of antimony selenide thin films and solar cells using sequential sulfur-selenium concentration gradient complementary technology.

[0039] (1-1) Fabrication of FTO / CdS substrate

[0040] The FTO conductive glass substrate was ultrasonically cleaned for 30 minutes sequentially with acetone, isopropanol, and ultrapure water to obtain a clean FTO conductive glass substrate. After drying, it was used to prepare CdS films via chemical bath deposition. Specifically, 86.59 mg of cadmium sulfate (CdSO4) was added to 187.5 mL of deionized water, and the mixture was continuously stirred and heated until a clear solution was formed. This solution was preheated and maintained at a constant temperature of 65°C. Then, 30 mL of ammonia water (concentration 25-28%) was added, and the mixture was stirred for 2 minutes. Next, 11.25 mL of 1.5 mol / L thiourea solution was added, and the reaction was carried out with continuous stirring at 65°C for 15 minutes. After deposition, the CdS precursor film was quickly rinsed with deionized water and dried. The surface of the deposited CdS layer was spin-coated with a 20 mg / mL cadmium chloride methanol solution (spin-coating speed 3000 rpm, spin-coating time 30 seconds), and finally annealed in air at 400°C for 10 minutes. The prepared FTO / CdS substrate was placed in a drying oven for later use.

[0041] (1-2) Preparation of Sb2(S,Se)3 precursor thin film

[0042] 0.3158 g of selenium powder and 2.0166 g of sodium sulfate (Na2SO3) were added to 80 mL of deionized water and reacted at 120℃ for 8 hours to prepare sodium selenosulfate (Na2SeSO3) solution for later use.

[0043] 1.41 × 10 -3 6.41 × 10⁻⁶ mol of potassium antimony tartrate trihydrate (C₄H₄KO₇Sb⁻³H₂O) -3 mol sodium thiosulfate pentahydrate (Na₂S₂O₃⁻⁵H₂O), 4 × 10⁻⁶ -5 1 mol of thioacetamide (TA) and 5.5 mL of a pre-prepared 50 mmol / L sodium selenose sulfate solution were dissolved together in 40 mL of deionized water. After stirring at room temperature for 1 minute, the solution was transferred to a Teflon-lined high-pressure reactor. The CdS side of the pre-prepared FTO / CdS substrate was immersed in the precursor solution, and hydrothermal deposition was performed at 135 °C for 120 minutes. After naturally cooling to room temperature, the film was carefully removed, thoroughly rinsed with deionized water, and dried with nitrogen to obtain the deposited Sb2(S,Se)3 film.

[0044] (1-3)Se 2- Se with a concentration of 0.01 mol / L 2- Solution preparation

[0045] At 60°C, selenium powder was first soaked in a small amount of anhydrous ethanol and stirred for 60 seconds to ensure uniform dispersion. Then, sodium borohydride was added to the dispersion at a molar ratio of 1:0.4 to selenium powder, and the mixture was stirred continuously at 750 rpm for 60 seconds at 60°C to obtain a mixture of selenium powder and sodium borohydride. Next, deionized water at 60°C was added to the mixture, and the mixture was stirred at 900 rpm for 60 seconds in a 60°C water bath to finally obtain a clear and transparent solution containing Se. 2- An alkaline selenized solution containing Se. 2- Se in alkaline solution 2- The concentration was 0.01 mol / L. This Se... 2- The solution is colorless, uniform, and transparent.

[0046] (1-4) Selenization treatment for 1 min to regulate the selenium concentration gradient in Sb2(S,Se)3 thin film.

[0047] The Sb2(S,Se)3 precursor film prepared in (1-2) was placed horizontally upwards in a 0.01 mol / L Se solution. 2- The Sb2(S,Se)3 precursor film was treated in a solution without air for 1 minute in a 60°C water bath. After treatment, the film was rinsed with deionized water (this process is referred to as selenization treatment). Then, the selenized Sb2(S,Se)3 precursor film was dried in a vacuum drying oven at 50°C for 1 minute. Finally, the Sb2(S,Se)3 precursor film without TA addition and without selenization treatment, and the Sb2(S,Se)3 precursor film treated with sequential sulfur-selenium concentration gradient complementarity technology, were transferred to an inert gas-protected hot stage and heat-treated at 370°C for 10 minutes to obtain uncontrolled Sb2(S,Se)3 film (referred to as Sb2(S,Se)3-untreated film) and sequential sulfur-selenium concentration gradient complementarity Sb2(S,Se)3 film (referred to as Sb2(S,Se)3-sulfur-selenium complementary film), respectively.

[0048] (1-5) Fabrication of Sb2(S,Se)3 solar cells

[0049] First, Spiro-OMeTAD was completely dissolved in chlorobenzene (concentration 36.6 mg / ml), then 14.5 mL of TBP and 9.5 mL of an acetonitrile solution of Li-TFSI (concentration 520 mg / ml) were added, and the mixture was stirred for 2 hours to obtain the Spiro-OMeTAD precursor solution. Then, the Spiro-OMeTAD precursor solution was spin-coated in air onto untreated Sb2(S,Se)3-films and Sb2(S,Se)3-sulfur-selenium complementary films (spin-coating speed 3000 rpm, spin-coating time 30 seconds) to obtain hole transport layers. Finally, a 60 nm gold thin film was thermally evaporated on the hole transport layer to serve as the counter electrode, resulting in a solar cell based on the untreated Sb2(S,Se)3 thin film (referred to as the Sb2(S,Se)3 untreated solar cell) and a solar cell based on the Sb2(S,Se)3 sulfur-selenium complementary thin film (referred to as the Sb2(S,Se)3 sulfur-selenium complementary solar cell).

[0050] (1-6) Characterization of samples and performance testing of devices

[0051] The characterization results of the Sb2(S,Se)3-sulfur-selenium complementary thin film are shown in the figure. Figures 1-3 The test results for Sb2(S,Se)3-sulfur-selenium complementary solar cells are shown in [the table below]. Figures 4-5 .

[0052] X-ray diffraction (XRD) was used to characterize the crystal structure, grain size, and orientation of the Sb₂(S,Se)₃ thin film. XRD patterns showed that, apart from the normalized signal peak of the FTO substrate, no other impurity peaks were present in the Sb₂(S,Se)₃ thin film. The Sb₂(S,Se)₃ precursor film on the substrate underwent a chemical reaction and crystallized into the Sb₂(S,Se)₃ thin film during heat treatment, exhibiting high purity and crystallinity. Furthermore, the characteristic peak 2θ value of the Sb₂(S,Se)₃ sulfur-selenium complementary film was smaller than that of the untreated Sb₂(S,Se)₃ film, indicating that Se atoms were inserted into the Sb₂(S,Se)₃ lattice during selenization and heat treatment. Texture coefficient (TC) analysis showed a stronger preferred orientation along the [hkl, l≠0] direction, confirming that sequential sulfur-selenium ion gradient modulation technology can effectively control the orientation of the Sb₂(S,Se)₃ thin film. This optimized Sb2(S,Se)3 orientation is beneficial for the efficient transport and separation of photogenerated carriers to the collecting electrode (FTO / Au).

[0053] Cross-sectional scanning electron microscopy (SEM) images indicated that post-selenization treatment did not significantly alter the average thickness of the Sb₂(S,Se)₃ film. Although the average thicknesses of the two films were similar (approximately 310 nm), the Sb₂(S,Se)₃ sulfur-selenium complementary film exhibited narrower thickness fluctuations and significantly better surface uniformity than the untreated Sb₂(S,Se)₃ film. Obvious pores were observed at the CdS / Sb₂(S,Se)₃ interface in both heterostructures, with a significantly reduced porosity in the Sb₂(S,Se)₃ sulfur-selenium complementary film.

[0054] The elemental mapping and Se / Sb atomic ratio distribution diagrams in the HRTEM results show that the sulfur concentration is higher in the lower part of the Sb2(S,Se)3 sulfur-selenium complementary film, and the sulfur concentration gradient increases more slowly, indicating that TA treatment has achieved regulation of the sulfur concentration gradient; the selenium concentration is higher in the upper part, and the selenium concentration gradient decreases more slowly, indicating that selenization treatment has achieved regulation of the selenium concentration gradient.

[0055] The current density-voltage characteristic curve (JV characteristic curve) shows that the open-circuit voltage of the Sb2(S,Se)3-sulfur-selenium complementary solar cell is 0.584V and the short-circuit current is 28.83 mA / cm². 2 The fill factor is 64.42%, the efficiency is 10.84%, while the voltage of the untreated Sb2(S,Se)3- solar cell is 0.545 V and the short-circuit current is 27.19 mA / cm². 2 With a fill factor of 58.10% and an efficiency of 8.62%, the open-circuit voltage and efficiency of the Sb2(S,Se)3-sulfur-selenium complementary solar cell have been significantly improved.

[0056] The external quantum efficiency curves show that the fabricated devices have good absorption and conversion capabilities for light in the 600-900 nm range, with the Sb2(S,Se)3-sulfur-selenium complementary solar cell being even better. The integral current curves show that the obtained integral current is basically consistent with the short-circuit current density in the JV characteristic curve.

[0057] Example 2: Fabrication of antimony selenide thin films and solar cells using sequential sulfur-selenium concentration gradient complementary technology.

[0058] (2-1) Preparation of FTO / CdS substrate: Same as in Example 1.

[0059] (2-2) Preparation of Sb2(S,Se)3 precursor film: Same as in Example 1.

[0060] (2-3)Se 2- Se at a concentration of 0.01 mol / L 2- Solution preparation: Same as in Example 1.

[0061] (2-4) Selenization treatment for 2 min to regulate the selenium concentration gradient in Sb2(S,Se)3 thin film.

[0062] The Sb2(S,Se)3 precursor film prepared by hydrothermal method was placed horizontally upwards in a 0.01 mol / L Se solution. 2- The Sb2(S,Se)3 precursor film was treated in a solution, isolated from air, at 60°C for 2 minutes. After treatment, the film was rinsed with deionized water. Then, the resulting Sb2(S,Se)3 precursor film was dried in a vacuum drying oven at 50°C for 1 minute. Finally, the dried Sb2(S,Se)3 precursor film was transferred to a hot plate under inert gas protection and heat-treated at 370°C for 10 minutes to obtain a sulfur-selenium concentration gradient complementary Sb2(S,Se)3 film (abbreviated as Sb2(S,Se)3-sulfur-selenium complementary film).

[0063] (2-5) Preparation of Sb2(S,Se)3 solar cells

[0064] First, Spiro-OMeTAD was completely dissolved in chlorobenzene (concentration 36.6 mg / ml), then 14.5 mL of TBP and 9.5 mL of an acetonitrile solution of Li-TFSI (concentration 520 mg / ml) were added, and the mixture was stirred for 2 hours to obtain a Spiro-OMeTAD precursor solution. Next, the Spiro-OMeTAD precursor solution was spin-coated onto a Sb₂(S,Se)₃ sulfur-selenium complementary thin film in air (spin-coating speed 3000 rpm, spin-coating time 30 seconds) to obtain a hole transport layer. Finally, a 60 nm gold film was thermally evaporated onto the hole transport layer to prepare a counter electrode, resulting in a solar cell based on the Sb₂(S,Se)₃ sulfur-selenium complementary thin film (referred to as an Sb₂(S,Se)₃ sulfur-selenium complementary solar cell).

[0065] (2-6) Characterization of samples and performance testing of devices

[0066] The characterization results of the Sb2(S,Se)3-sulfur-selenium complementary thin film are shown in the figure. Figure 6 The test results for Sb2(S,Se)3-sulfur-selenium complementary solar cells are shown in [link to test results]. Figures 7-8 .

[0067] SEM results show that the 2-minute selenization treatment causes some damage to the surface morphology of the thin film and reduces the film thickness. The current density-voltage characteristic curve (JV characteristic curve) indicates that the obtained solar cell has an open-circuit voltage of 0.561V and a short-circuit current of 28.40 mA / cm². 2The fill factor was 58.12% and the efficiency was 9.27%. The decrease in these parameters is related to the damage to the film surface morphology and the reduction in film thickness. The external quantum efficiency curve shows that the fabricated device mainly exhibits good absorption and conversion capabilities for light in the 600-900 nm range. The integral current curve shows that the obtained integral current is basically consistent with the short-circuit current density in the JV characteristic curve.

Claims

1. A method for preparing antimony selenide thin films based on sulfur-selenium concentration gradient complementary technology, characterized in that: A sulfur-replenishing pretreatment was performed on the Sb2(S,Se)3 precursor film prepared by the hydrothermal method using a dual sulfur source. Then, a selenization treatment was performed on the antimony selenide film prepared by the dual sulfur source hydrothermal method using a selenium ion solution to precisely control the vertical concentration gradient distribution of sulfur and selenium elements in the film, while suppressing the concentration of defect states in the film. Finally, an Sb2(S,Se)3 film with optimized band structure, reduced defect state density, and improved crystallinity and morphology was obtained.

2. The method according to claim 1, characterized in that... Includes the following steps: Step 1: At room temperature, thioacetamide is added to a solution containing potassium antimony tartrate, sodium thiosulfate and sodium selenose sulfate to obtain a precursor solution, which is then transferred to a high-pressure reactor. The substrate is immersed in the precursor solution and hydrothermally deposited to obtain an Sb2(S,Se)3 precursor film. Step 2: Dissolve selenium powder and sodium borohydride in deionized water at 60℃ to obtain a solution containing Se. 2- Alkaline solutions; Step 3: Using the Se-containing material prepared in Step 2 2- The Sb2(S,Se)3 precursor film obtained in step 1 was subjected to selenization treatment using an alkaline solution. Step 4: Heat-treat the Sb2(S,Se)3 precursor film after the selenization treatment in step 3 to promote film crystallization and finally obtain a Sb2(S,Se)3 film with good crystallinity.

3. The method according to claim 2, characterized in that: In step 1, the concentration of thioacetamide in the precursor solution is 1 mmol / L.

4. The method according to claim 2, characterized in that: In step 1, the substrate is an FTO / CdS substrate or a TiO2 / CdS substrate.

5. The method according to claim 2, characterized in that: In step 2, selenium powder is first soaked in a small amount of anhydrous ethanol at 60°C and stirred for 60 seconds to ensure uniform dispersion. Then, sodium borohydride is added to the dispersion at a molar ratio of 1:0.4 to selenium powder, and the mixture is stirred continuously at 60°C for 60 seconds to obtain a mixture of selenium powder and sodium borohydride. Next, deionized water at 60°C is added to this mixture, and the mixture is stirred in a 60°C water bath to obtain a clear and transparent solution containing Se. 2- An alkaline solution.

6. The method according to claim 5, characterized in that: The containing Se 2- Se in alkaline solution 2- The concentration is 0.01 mol / L.

7. The method according to claim 2, characterized in that: In step 3, the Sb2(S,Se)3 precursor film obtained in step 1 is placed horizontally upwards on the substrate containing Se obtained in step 2. 2- The Sb2(S,Se)3 precursor film was treated in an alkaline solution in the absence of air for 1 minute in a 60°C water bath. After treatment, the film was rinsed with deionized water.

8. The method according to claim 2, characterized in that: In step 4, the Sb2(S,Se)3 precursor film after selenization treatment in step 3 is vacuum dried at 50°C for 1 minute, and then transferred to a hot stage under inert gas protection and heat-treated at 370°C for 10 minutes to obtain a selenium sulfide film with sequential sulfur-selenium concentration gradient complementarity.

9. A solar cell comprising a thin film of antimony selenide sulfide prepared by any one of the preparation methods of claims 1-8.

10. The solar cell according to claim 9, characterized in that: Solar cells are assembled using antimony selenide thin films with complementary sulfur-selenium concentration gradients as light-absorbing layers.

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