Preparation method of selenium antimony sulfide thin film with adjustable selenium element concentration gradient and solar cell based on thin film

Abstract

The invention discloses a preparation method of a selenium antimony sulfide thin film with adjustable selenium element concentration gradient and a solar cell based on the thin film. According to the method, the Sb2 (S, Se) 3 thin film prepared by the hydrothermal method is treated by adopting the selenium ion solution, so that the vertical distribution of the selenium element concentration gradient in the Sb2 (S, Se) 3 thin film prepared by the hydrothermal method is adjusted, the defect state concentration is inhibited, and the Sb2 (S, Se) 3 thin film which is better in energy band structure, lower in defect state density and better in crystallinity and morphology is obtained; and a solar cell with high efficiency (more than 10%) is obtained on the basis. The method disclosed by the invention has the advantages of simplicity in operation, low equipment requirement, low cost, low toxicity of used medicines and small damage of a treatment technology to a film structure, and overcomes the defects of high operation difficulty, high equipment requirement, damage to a film crystal structure by treatment in a high-temperature environment and the like in the prior art; the method has important application value in the fields of photoelectric materials, photovoltaic materials, devices and the like.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor materials, and in particular relates to a method for preparing an antimony selenium sulfide film with an adjustable selenium element concentration gradient and a solar cell based on the film. Background Art

[0002] Antimony selenide (Sb 2 (S,Se) 3 ) is a new type of light-harvesting direct bandgap semiconductor material with unique one-dimensional characteristics, adjustable bandgap (Eg = 1.1-1.7 eV), excellent visible light absorption coefficient (greater than 10 5 cm 2 ), good electrical conductivity and outstanding structural stability, and other optoelectronic properties, and have important applications in various optoelectronic devices [Adv.Funct. Mater. 2024, 34, 2313676; Joule 2018, 2, 857-878; Adv. Sci. 2024, 11,2304963].

[0003] At present, the solution method (mainly hydrothermal method and chemical deposition method) of Sb 2 (S,Se) 3 In less than a decade, the highest efficiency of photovoltaic devices has exceeded 10% [Nat. Energy 2020, 5, 587-595; Adv. Mater. 2024, 36,2410669]. However, its efficiency is still far from the theoretical efficiency (28-33%) based on the Shockley-Queisser model, and its development prospects are very broad [Adv. Funct. Mater. 2024, 34, 2308021]. Among the various factors affecting the performance of photovoltaic devices, the concentration gradient distribution of selenium affects the Sb 2 (S,Se) 3 The band structure, trap density and number are the most important factors [Adv. Energy Mater. 2022, 12, 2103015; Angew. Chem. Int. Ed. 2024, 63, e202406512]. 2 (S,Se) 3 In the film system, due to CH 4 N 2 Se and Na 2 S 2 O 3 With C 4 H 4 KO 7 Sb-0.5H 2O has different reaction properties, and Sb 2 S 3 and Sb 2 Se 3 The solubility product constants of the prepared Sb 2 (S,Se) 3 The film has an obvious Se element concentration gradient distribution, that is, the Se element content increases along the vertical direction of Sb 2 (S,Se) 3 The direction of the film gradually decreases [Angew. Chem. Int. Ed. 2024, 63, e202409609]. This reverse selenium concentration gradient distribution will lead to an unfavorable band structure, inhibiting the transport and separation of carriers [Adv. Funct. Mater. 2023, 34,2309764]. Therefore, the Sb 2 (S,Se) 3 The band structure of the film is optimized and in-situ defect passivation is achieved to promote the efficient transport and separation of photogenerated carriers and inhibit Sb 2 (S,Se) 3 The film interior and Sb 2 (S,Se) 3 The carrier recombination at the / HTL interface is particularly important. The rapid depletion of the selenium source during the hydrothermal reaction is the cause of the Sb 2 (S,Se) 3 The concentration of selenium is high in the lower area of ​​the film, while Sb 2 (S,Se) 3 The reason why the selenium content in the upper area of ​​the film drops sharply. The current methods to improve the distribution of selenium can be roughly divided into two directions: during the hydrothermal process and after the hydrothermal process. During the hydrothermal process, Huang et al. gradually adjusted the hydrothermal deposition temperature to adjust the vertical Sb 2 (S,Se) 3 The distribution of Se / S atomic ratio in the film direction increases Sb 2 (S,Se) 3 The Se content of the film [Angew. Chem. Int. Ed. 2024, 63, e202406512]; subsequently, Chen et al. 2 (S,Se) 3 During the hydrothermal deposition of the film, an appropriate amount of thioacetamide was added to adjust the vertical Sb 2 (S,Se) 3The distribution of Se / S atomic ratio and trap density in the film direction [Angew. Chem. Int. Ed. 2024, 63, e202409609]. These methods all need to be operated during the hydrothermal process, which requires a lot of experimental staff. 2 (S,Se) 3 Increasing the selenium concentration in the upper region of the film is a simpler and more effective method. However, most of the current post-selenization processes are based on selenium powder (polyatomic cluster nanoparticles) to increase the sintered crystalline Sb at relatively high temperatures (generally 400°C). 2 (S,Se) 3 Selenium concentration in the film [ACS Appl. Mater. Interfaces 2022, 14, 31986-31997; Sol. Energy Mater. Sol. Cells 2023, 259,112464]. This method has the risk of destroying the crystallized Sb 2 (S,Se) 3 The high risk of film original morphology and structure, and the Sb 2 (S,Se) 3 The defect passivation effect of thin films is limited. Summary of the invention

[0004] The present invention aims to solve the problems in the prior art and provides a method for preparing an antimony selenide sulfide film with an adjustable selenium concentration gradient and a solar cell based on the film. The present invention adopts an innovative and convenient in-situ passivation and energy band regulation strategy. 2 (S,Se) 3 The film was treated to adjust the hydrothermal prepared Sb 2 (S,Se) 3 The vertical distribution of the selenium concentration gradient in the film and the suppression of the defect state concentration have resulted in Sb with better band structure, lower defect state density, better crystallinity and morphology. 2 (S,Se) 3 Thin films were used to produce highly efficient (over 10%) solar cells.

[0005] The method for preparing an antimony selenium sulfide film with an adjustable selenium element concentration gradient of the present invention comprises the following steps:

[0006] Step 1: Dissolve selenium powder and sodium borohydride in deionized water at room temperature to obtain a Se 2- alkaline solution;

[0007] Step 2: Take the Se-containing 2-The alkaline solution has an effect on the Sb on the substrate. 2 (S,Se) 3 The precursor film is subjected to selenization treatment;

[0008] Step 3: Selenide treatment of Sb in step 2 2 (S,Se) 3 The precursor film is heat treated to obtain crystallized Sb 2 (S,Se) 3 film.

[0009] further:

[0010] In step 1, selenium powder is immersed in a small amount of anhydrous ethanol at room temperature and stirred for 10-20 seconds to disperse it; then sodium borohydride is added to the obtained solution, the molar ratio of sodium borohydride to selenium powder is 1:0.4-0.7, and the mixture is stirred at 600-800 rpm for 20-30 seconds at room temperature to obtain a mixture solution of selenium powder and sodium borohydride; then, deionized water at 40-60° C. is added to the obtained mixture solution, and the mixture is stirred at 700-900 rpm for 40-60 seconds in a water bath at 40-60° C. to obtain a clear and transparent Se-containing solution. 2- Alkaline solution, where Se 2- The concentration is 0.01-0.02 mol / L.

[0011] In step 2, Sb 2 (S,Se) 3 The precursor film is placed horizontally upward on the Se-containing 2- alkaline solution and isolate from air, and treat in a 40-60℃ water bath for 4-12 minutes; after the treatment, use deionized water to remove Sb 2 (S,Se) 3 The precursor film is rinsed clean.

[0012] In step 3, the Sb obtained in step 2 is 2 (S,Se) 3 The precursor film is dried at 60-80° C. for 10-20 minutes in a vacuum drying oven, and then transferred to a hot stage protected by inert gas, and heat-treated at 350° C. for 10-16 minutes to obtain an antimony selenide sulfide film with an adjustable selenium concentration gradient.

[0013] The substrate can be FTO / CdS, or TiO 2 / CdS.

[0014] The inert gas is preferably nitrogen.

[0015] The present invention also provides a solar cell, comprising the antimony selenide sulfide film with adjustable selenium concentration gradient. After the antimony selenide sulfide film with adjustable selenium concentration gradient is prepared by the above method, a hole transport layer and an electrode are prepared in sequence to obtain a solar cell.

[0016] The hole transport layer is preferably spiro-OMeTAD; and the electrode is preferably gold.

[0017] The present invention Sb 2 (S,Se) 3 The film has the characteristics of adjustable selenium concentration gradient, low film surface roughness and low film defect density.

[0018] The principle of the present invention is:

[0019] The present invention uses low-toxic, safe and low-cost compounds to dissolve in ethanol and deionized water to prepare Se 2+ solution, using the obtained Se 2+ Solution to Sb on substrate 2 (S,Se) 3 The precursor film is selenized to regulate Sb 2 (S,Se) 3 The concentration distribution of selenium in the precursor film has an influence on the Sb 2 (S,Se) 3 The precursor film was heat treated to obtain crystallized Sb 2 (S,Se) 3 Thin film, finally prepare HTL and electrode to obtain solar cell. 2 (S,Se) 3 The concentration distribution of selenium in the film can be determined by Se 2+ Solution concentration and selenization treatment time control.

[0020] The beneficial effects of the present invention are:

[0021] 1. An innovative and convenient in-situ passivation and band-regulation strategy was established to prepare antimony selenide sulfide thin films and solar cells with adjustable selenium concentration gradient. 2 (S,Se) 3 The film has the characteristics of better band structure, lower defect state density, better crystallinity and morphology, and on this basis, high-efficiency (over 10%) solar cells have been obtained.

[0022] 2. The present invention uses low-toxic, safe and low-cost raw materials to prepare Se 2+ solution; after hydrothermal reaction at relatively low temperature using Se 2+ Solution for Sb 2 (S,Se) 3The precursor film is selenized to achieve the regulation of Sb 2 (S,Se) 3 The purpose of the selenium element concentration distribution in the precursor film.

[0023] 3. The work of preparing antimony selenide sulfide thin films with adjustable selenium concentration gradient in the present invention is compared with similar work by others. Others [Angew. Chem. Int. Ed. 2024, 63, e202406512; Angew. Chem. Int. Ed.2024, 63, e202409609] artificially gradually adjusted the hydrothermal deposition temperature during the hydrothermal process or added an appropriate amount of thioacetamide during the hydrothermal reaction to adjust the vertical Sb 2 (S,Se) 3 The distribution of Se / S atomic ratio in the film direction and the trap density all need to be operated during the hydrothermal process, which requires a lot of experimental personnel to operate. The present invention is a selenization treatment after the hydrothermal process, which is simpler and more stable to operate. Others [ACS Appl. Mater. Interfaces 2022,14, 31986-31997; Sol. Energy Mater. Sol. Cells 2023, 259, 112464] use selenium powder at a relatively high temperature (generally 400°C) to improve the sintered crystalline Sb 2 (S,Se) 3 Selenium concentration in the film. This method has the potential to destroy the crystallized Sb 2 (S,Se) 3 The high risk of film original morphology and structure, and the Sb 2 (S,Se) 3 The defect passivation effect of the film is limited. 2+ The solution is post-selenized at a relatively low temperature, and the preparation technology and equipment requirements are low, and there is no damage to Sb 2 (S,Se) 3 The risk of thin film and good defect passivation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The Sb 2 (S,Se) 3 -Untreated film and Sb 2 (S,Se) 3 -XRD characterization results of the film after selenization treatment for 8 min; including: (a) XRD spectrum; (b) hysteresis coefficient calculation results.

[0025] Figure 2 The Sb2 (S,Se) 3 -Untreated film and Sb 2 (S,Se) 3 -SEM characterization results of the film treated with selenization for 8 min; (a) Sb 2 (S,Se) 3 -Untreated film surface image; (b) Sb 2 (S,Se) 3 -Selenization treatment -8 min film surface image; (c) Sb 2 (S,Se) 3 - Untreated film cross-section image; (d) Sb 2 (S,Se) 3 -Selenization treatment-8 min film cross-section image.

[0026] Figure 3 The Sb 2 (S,Se) 3 -Untreated film and Sb 2 (S,Se) 3 -HRTEM characterization results of the film treated with selenization for 8 min; where: (a) Sb 2 (S,Se) 3 -Selenization treatment - 8 min film cross-sectional image and corresponding position element mapping; (b) Sb 2 (S,Se) 3 - Unprocessed film cross-section image and corresponding position element mapping; (c) Sb 2 (S,Se) 3 -Selenization treatment - 8 min film and Sb 2 (S,Se) 3 -Comparison of the Se / Sb atomic ratio distribution of the non-selenized film in the longitudinal direction of the film.

[0027] Figure 4 The Sb 2 (S,Se) 3 -Untreated solar cells and Sb 2 (S,Se) 3 -Current density-voltage characteristic curve of the solar cell after selenization treatment for 8 min.

[0028] Figure 5 The Sb 2 (S,Se) 3 -Untreated solar cells and Sb 2 (S,Se) 3 -External quantum efficiency and integrated current density curves of solar cells treated with selenization for 8 min.

[0029] Figure 6 The Sb 2 (S,Se) 3 -SEM characterization results of the film after selenization treatment for 12 min; including: (a) surface image; (b) cross-sectional image.

[0030] Figure 7 The Sb 2 (S,Se) 3 -Current density-voltage characteristic curve of the solar cell after selenization treatment for 12 min.

[0031] Figure 8 The Sb 2 (S,Se) 3 -External quantum efficiency and integrated current density curves of solar cells treated with selenization for 12 min.

[0032] Fig. 9 The Sb 2 (S,Se) 3 -Current density-voltage characteristic curve of the solar cell after selenization treatment for 4 min.

[0033] Fig.10 The Sb 2 (S,Se) 3 -External quantum efficiency and integrated current density curves of solar cells treated with selenization for 4 min. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further analyzed and explained below through specific embodiments.

[0035] Example 1: Preparation of antimony selenide sulfide film with adjustable selenium concentration gradient and solar cell

[0036] (1-1) Preparation of FTO / CdS substrate

[0037] The FTO conductive glass was ultrasonically cleaned with acetone, isopropanol, and ultrapure water for 20 minutes in sequence to obtain a clean FTO conductive glass substrate, which was then dried and used to prepare a CdS film by chemical bath deposition. Specifically, 0.8467 g of CdSO 4 Dissolve in 172 ml of deionized water, then add 28 ml of ammonia water (concentration 28%) and stir in a water bath at 65 °C. Then, place the FTO substrate that has been treated with UV for 15 minutes vertically into the CdSO 4The solution was added with 1.256 g of thiourea to start film deposition, and the deposition process lasted for 15 minutes. After the deposition was completed, the CdS precursor film was quickly rinsed with deionized water and dried. Finally, a methanol solution of cadmium chloride with a concentration of 20 mg / ml was spin-coated on the surface of the CdS precursor film (spin coating speed 2500 rpm, spin coating time 30 seconds), and the spin-coated CdS precursor film was kept on a 400°C hot stage for 10 minutes, and the FTO / CdS substrate was obtained after cooling.

[0038] (1-2) Sb 2 (S,Se) 3 Preparation of precursor films

[0039] The hydrothermal method was used to prepare Sb 2 (S,Se) 3 Precursor film. First, 0.2671 g C 4 H 4 KO 7 Sb-0.5H 2 O and 0.7942 g Na 2 S 2 O 3 -5H 2 O was dissolved in 40 ml of deionized water and stirred at 750 rpm for 4 min. Then 25 mg of selenourea was added to the solution and stirred at the same speed for 8 min until the solution turned light yellow to obtain Sb 2 (S,Se) 3 Then, the FTO / CdS substrate was suspended horizontally in a polytetrafluoroethylene reactor and Sb 2 (S,Se) 3 The precursor solution was prepared and the reaction vessel was sealed and the film was deposited in an oven at 135°C for 120 minutes. 2 (S,Se) 3 The precursor film was rinsed with deionized water, blown dry with a nitrogen gun and dried for use.

[0040] (1-3) Se 2+ Se with a concentration of 0.0125 mol / L 2+ Solution preparation

[0041] Selenium powder was immersed in a small amount of anhydrous ethanol at room temperature and stirred for 15 seconds to disperse it; sodium borohydride was then added to the resulting solution, the molar ratio of sodium borohydride to selenium powder was 1:0.5, and the mixture was stirred at 750 rpm for 25 seconds at room temperature to obtain a mixture solution of selenium powder and sodium borohydride; finally, deionized water at 50°C was added to the mixture solution, and the mixture was stirred at 750 rpm for 50 seconds in a 50°C water bath to obtain a clear and transparent Se 2- Solution, where Se2- The concentration is 0.0125 mol / L. 2- The solution is colorless, homogeneous and transparent.

[0042] (1-4) Selenization treatment for 8 min to regulate Sb 2 (S,Se) 3 Selenium concentration gradient in the film

[0043] The Sb prepared by hydrothermal method 2 (S,Se) 3 The precursor film was placed horizontally with its face upwards in a Se solution with a concentration of 0.0125 mol / L. 2+ The solution was isolated from air and treated in a 50°C water bath for 8 minutes. After the treatment, Sb 2 (S,Se) 3 The reaction precursor film is rinsed clean (this process is referred to as selenization treatment). Then, the selenized Sb 2 (S,Se) 3 The precursor film was dried in a vacuum oven at 70 °C for 15 min. 2 (S,Se) 3 Precursor film and selenized Sb 2 (S,Se) 3 The precursor film was moved to a hot stage protected by inert gas and heat treated at 350 °C for 14 minutes to obtain unregulated Sb 2 (S,Se) 3 Thin film (abbreviated as Sb 2 (S,Se) 3 -untreated film) and Sb controlled by selenium concentration gradient 2 (S,Se) 3 Thin film (abbreviated as Sb 2 (S,Se) 3 -Selenization treatment-8 min film).

[0044] (1-5) Sb 2 (S,Se) 3 Preparation of solar cells

[0045] First, Spiro-OMeTAD was completely dissolved in chlorobenzene (concentration 36.6 mg / ml), and then 14.5 μl of TBP and 9.5 μl of Li-TFSI in acetonitrile (concentration 520 mg / ml) were added. After stirring for 2 hours, the Spiro-OMeTAD precursor solution was obtained. Then, the Spiro-OMeTAD precursor solution was spin-coated onto Sb 2 (S,Se) 3-Untreated film and Sb 2 (S,Se) 3 -Selenization treatment-8 min film (spin coating speed 3000 rpm, spin coating time 30 seconds) to obtain a hole transport layer. Finally, a 70 nm gold film was prepared by thermal evaporation on the hole transport layer as a counter electrode to obtain a Sb-based 2 (S,Se) 3 -Untreated thin film solar cells (abbreviated as Sb 2 (S,Se) 3 -untreated solar cells) and Sb-based 2 (S,Se) 3 -Selenization treatment-8 min thin film solar cell (abbreviated as Sb 2 (S,Se) 3 -Selenization treatment -8 min solar cells).

[0046] (1-6) Sample characterization and device performance testing

[0047] Sb 2 (S,Se) 3 -Selenization treatment-8 min film characterization results are shown in Figure 1-3 , Sb 2 (S,Se) 3 -Selenization treatment-8min solar cell test results see Figure 4-5 .

[0048] XRD patterns show that Sb 2 (S,Se) 3 In the film, except for the normalized signal peak of the FTO substrate, there are no other impurity peaks. 2 (S,Se) 3 The precursor film undergoes a chemical reaction during the heat treatment and crystallizes into Sb 2 (S,Se) 3 Thin films, crystallized films have high purity and crystallinity. In addition, Sb 2 (S,Se) 3 -Selenization treatment-8 min film characteristic peak 2θ value is less than Sb 2 (S,Se) 3 - Untreated film, which means that during the selenization and heat treatment, Se atoms were inserted into Sb 2 (S,Se) 3 The results of hysteresis coefficient show that the hysteresis coefficients of the two films are not much different, indicating that the selenization process will hardly change the orientation of the crystal. SEM results show that the prepared Sb 2 (S,Se) 3-Selenization treatment-8 min The film surface is smoother, denser and has larger grain size. The element mapping and Se / Sb atomic ratio distribution in the HRTEM results show that Sb 2 (S,Se) 3 -Selenization treatment-8 min The selenium concentration in the upper part of the film is higher and the selenium concentration gradient decreases more slowly. The selenization treatment achieves the regulation of the selenium concentration gradient. The current density-voltage characteristic curve (JV characteristic curve) shows that Sb 2 (S,Se) 3 -Selenization treatment-8 min The open circuit voltage of the solar cell is 0.706 V and the short circuit current is 23.46 mA / cm 2 , fill factor is 62.00%, efficiency is 10.27%, and Sb 2 (S,Se) 3 -The voltage of the untreated solar cell is 0.628 V and the short-circuit current is 21.21 mA / cm 2 , fill factor is 61.14%, efficiency is 8.14%, Sb 2 (S,Se) 3 -Selenization treatment-8 min The open circuit voltage and efficiency of the solar cell are significantly improved. The external quantum efficiency curve shows that the prepared device has good absorption and conversion capabilities for 400-800 nanometers of light, and Sb 2 (S,Se) 3 -Selenization treatment-8 min solar cells are better. The integral current curve shows that the obtained integral current is basically consistent with the short-circuit current density in the JV characteristic curve.

[0049] Example 2: Preparation of antimony selenide sulfide film with adjustable selenium concentration gradient and solar cell

[0050] (2-1) Preparation of FTO / CdS substrate: same as in Example 1.

[0051] (2-2) Sb 2 (S,Se) 3 Preparation of precursor film: same as in Example 1.

[0052] (2-3) Se 2+ Se with a concentration of 0.0125 mol / L 2+ Preparation of solution: same as in Example 1.

[0053] (2-4) Selenization treatment for 12 min to regulate Sb 2 (S,Se) 3 Selenium concentration gradient in the film

[0054] The Sb prepared by hydrothermal method 2(S,Se) 3 The precursor film was placed horizontally with its face upwards in a Se solution with a concentration of 0.0125 mol / L. 2+ The solution was isolated from air and treated in a 50°C water bath for 12 minutes. After the treatment, Sb 2 (S,Se) 3 The reaction precursor film is rinsed clean (this process is referred to as selenization treatment). Then, the obtained Sb 2 (S,Se) 3 The precursor film was dried in a vacuum oven at 70 °C for 15 min. 2 (S,Se) 3 The precursor film was moved to a hot stage protected by inert gas and heat treated at 350°C for 14 minutes to obtain Sb 2 (S,Se) 3 Thin film (abbreviated as Sb 2 (S,Se) 3 -Selenization treatment-12 min film).

[0055] (2-5) Sb 2 (S,Se) 3 Preparation of solar cells

[0056] First, Spiro-OMeTAD was completely dissolved in chlorobenzene (concentration 36.6 mg / ml), and then 14.5 μl of TBP and 9.5 μl of Li-TFSI in acetonitrile (concentration 520 mg / ml) were added. After stirring for 2 hours, the Spiro-OMeTAD precursor solution was obtained. Then, the Spiro-OMeTAD precursor solution was spin-coated onto the Sb 2 (S,Se) 3 -Selenization treatment-12 min film (spin coating speed 3000 rpm, spin coating time 30 seconds) to obtain a hole transport layer. Finally, a 70 nm gold film was prepared by thermal evaporation on the hole transport layer as a counter electrode to obtain a Sb-based 2 (S,Se) 3 -Selenization treatment-12 min thin film solar cell (abbreviated as Sb 2 (S,Se) 3 -Selenization treatment -12 min solar cells).

[0057] (2-6) Sample characterization and device performance testing

[0058] Sb 2 (S,Se) 3 -Selenization treatment-12 min film characterization results are shown in Figure 6 , Sb2 (S,Se) 3 -Selenization treatment-12min solar cell test results see Figure 7-8 The SEM results show that the 12-minute selenization treatment has some damage to the surface morphology of the film and some reduction in the film thickness. The current density-voltage characteristic curve (JV characteristic curve) shows that the open circuit voltage of the obtained solar cell is 0.61 V and the short circuit current is 22.01 mA / cm 2 , fill factor is 58.03%, efficiency is 7.86%, the reduction of various parameters is related to the destruction of film surface morphology and the reduction of film thickness. The external quantum efficiency curve shows that the prepared device has good absorption and conversion capabilities mainly for 400-800 nanometers of light. The integral current curve shows that the obtained integral current is basically consistent with the short-circuit current density in the JV characteristic curve.

[0059] Example 3: Preparation of antimony selenide sulfide film with adjustable selenium concentration gradient and solar cell

[0060] (3-1) Preparation of FTO / CdS substrate: same as in Example 1.

[0061] (3-2) Sb 2 (S,Se) 3 Preparation of precursor film: same as in Example 1.

[0062] (3-3) Se 2+ Se with a concentration of 0.0125 mol / L 2+ Preparation of solution: same as in Example 1.

[0063] (3-4) Selenization treatment for 4 min to regulate Sb 2 (S,Se) 3 Selenium concentration gradient in the film

[0064] The hydrothermally prepared Sb 2 (S,Se) 3 The precursor film was placed horizontally with its face upwards in a Se solution with a concentration of 0.0125 mol / L. 2+ The solution was isolated from air and treated in a 50°C water bath for 4 minutes. After the treatment, Sb 2 (S,Se) 3 The reaction precursor film is rinsed clean (this process is referred to as selenization treatment). Then, the obtained Sb 2 (S,Se) 3 The precursor film was dried in a vacuum oven at 70 °C for 15 min. 2 (S,Se) 3The precursor film was moved to a hot stage protected by inert gas and heat treated at 350°C for 14 minutes to obtain Sb 2 (S,Se) 3 Thin film (abbreviated as Sb 2 (S,Se) 3 -Selenization treatment -4 min film).

[0065] (3-5) Sb 2 (S,Se) 3 Preparation of solar cells

[0066] First, Spiro-OMeTAD was completely dissolved in chlorobenzene (concentration 36.6 mg / ml), and then 14.5 μl of TBP and 9.5 μl of Li-TFSI in acetonitrile (concentration 520 mg / ml) were added. After stirring for 2 hours, the Spiro-OMeTAD precursor solution was obtained. Then, the Spiro-OMeTAD precursor solution was spin-coated onto the Sb 2 (S,Se) 3 -Selenization treatment-4 min film (spin coating speed 3000 rpm, spin coating time 30 seconds) to obtain a hole transport layer. Finally, a 70 nm gold film was prepared by thermal evaporation on the hole transport layer as a counter electrode to obtain a Sb-based 2 (S,Se) 3 -Selenization treatment-4 min thin film solar cell (abbreviated as Sb 2 (S,Se) 3 -Selenization treatment -4 min solar cells).

[0067] (3-6) Sample characterization and device performance testing

[0068] Sb 2 (S,Se) 3 -Selenization treatment-4 min solar cell test results see Figure 9-10 The current density-voltage characteristic curve (JV characteristic curve) shows that the open circuit voltage of the obtained solar cell is 0.66 V and the short circuit current is 21.85 mA / cm 2 , fill factor is 60.09%, efficiency is 8.74%, among which, open circuit voltage and short circuit current are lower than those of Sb 2 (S,Se) 3 - The untreated solar cells have been improved to a certain extent. The external quantum efficiency curve shows that the prepared device has good absorption and conversion capabilities mainly for 400-800 nanometers of light. 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 an antimony selenium sulfide film with an adjustable selenium concentration gradient, characterized in that: The Sb2(S,Se)3 precursor film prepared by the hydrothermal method was selenized using a selenium ion solution, thereby adjusting the vertical distribution of the selenium element concentration gradient in the Sb2(S,Se)3 film prepared by the hydrothermal method and suppressing the defect state concentration, thereby obtaining a Sb2(S,Se)3 film with a better band structure, lower defect state density, better crystallinity and morphology.

2. The preparation method according to claim 1, characterized in that The steps include: Step 1: Dissolve selenium powder and sodium borohydride in deionized water at room temperature to obtain a Se 2- alkaline solution; Step 2: Take the Se-containing 2- The Sb2(S,Se)3 precursor film on the substrate is selenized with an alkaline solution; Step 3: Heat treat the Sb2(S,Se)3 precursor film after the selenization treatment in step 2 to obtain a crystalline Sb2(S,Se)3 film.

3. The preparation method according to claim 2, characterized in that: In step 1, the selenium powder is immersed in a small amount of anhydrous ethanol at room temperature and stirred for 10-20 seconds to disperse it; Then, sodium borohydride was added to the obtained solution, and the mixture was stirred at room temperature for 20-30 seconds to obtain a mixture solution of selenium powder and sodium borohydride; then, deionized water at 40-60°C was added to the obtained mixture solution, and the mixture was stirred in a water bath at 40-60°C for 40-60 seconds to obtain a clear and transparent mixture containing Se. 2- of alkaline solution.

4. The preparation method according to claim 3, characterized in that: The molar ratio of sodium borohydride to selenium powder is 1:0.4-0.

7.

5. The preparation method according to claim 3, characterized in that: The Se 2- Se in alkaline solution 2- The concentration is 0.01-0.02 mol / L.

6. The preparation method according to claim 2, characterized in that: In step 2, the Sb2(S,Se)3 precursor film is placed horizontally upward on the Se-containing 2- The precursor film is placed in an alkaline solution and isolated from air, and treated in a water bath at 40-60°C for 4-12 minutes; after the treatment, the Sb2(S,Se)3 precursor film is rinsed with deionized water.

7. The preparation method according to claim 2, characterized in that: In step 3, the Sb2(S,Se)3 precursor film obtained in step 2 is vacuum dried at 60-80°C for 10-20 minutes, then transferred to a hot plate protected by inert gas and heat treated at 350°C for 10-16 minutes to obtain an antimony selenide sulfide film with an adjustable selenium concentration gradient.

8. An antimony selenide sulfide film with an adjustable selenium concentration gradient, prepared according to any one of the preparation methods of claims 1-7.

9. A solar cell assembled using the antimony selenium sulfide film with adjustable selenium concentration gradient as claimed in claim 8 as a light absorption layer.

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