Preparation And Optimization Of Lead-free Double Perovskite Cs₂AgBiBr₆ Solar Cell

In recent years,lead-based halogen perovskite materials(APb X₃,A=Cs,FA,MA;X=halogen)have received widespread attention due to their excellent optical and electrical properties such as large absorption coefficient and long carrier diffusion distance.At present,the optimal energy conversion efficiency of solar cells using this type of perovskite material is25.5%,which has reached the level of commercialization.However,due to lead toxicity and environmental instability,its commercial application development is limited.The lead-free double perovskite Cs₂AgBiBr₆ has become the most promising material for commercial applications in solar cells due to its stable environment,green,non-toxic,and good optical and electrical properties.However,their power conversion efficiency(PCE)is still far lower than that of lead halide perovskites,which is mainly associated with their poor quality films.Therefore,it is of great significance to optimize the Cs₂AgBiBr₆ perovskite film and solar cell devices.This paper aims to optimize the photoelectric conversion efficiency of Cs₂AgBiBr₆perovskite solar cells,and explores the optimization of inverted and upright device structures by studying the preparation of the transmission layer.Finally,based on the upright structure,GBL,DMF and DMAc are used as additives to form a co-solvent with DMSO solvent.The effect of the ratio and composition of the additives on the morphology,microstructure and device performance of the film is studied,and on this basis,the preheating temperature of the substrate was further optimized.Finally,a Lewis base adduct,Bi Br₃(DMSO)₂ was developed as a precursor,and the morphology,crystal structure of the Cs₂AgBiBr₆ perovskite film prepared by this method was systematically explored,and the optical and electrical properties of devices were further optimized.The main findings are as follows:The electron transport layer prepared by the C₆₀ doped PCBM one-step solution method optimizes the photoelectric conversion efficiency(PCE)of the Cs₂AgBiBr₆ perovskite inverted solar cell device,and when the PCBM:C₆₀ ratio is 8:2,the device performance is better.Based on the investigation of the dispersion concentration of Sn O₂ and the oxidation time of Spiro-OMe TAD,the PCE of the upright device is optimized,and the performance is better than that of the inverted device.The co-solvent method of butyrolactone(GBL)and dimethylacetamide(DMAc)effectively improved the quality of the Cs₂AgBiBr₆ perovskite film.The thickness of the Cs₂AgBiBr₆ perovskite film prepared by the butyrolactone(GBL)co-solvent method is reduced,which does not suitable for preparing perovskite solar cells.When using DMAc co-solvent method,as the proportion of DMAc in the co-solvent decreases,the quality of the film increases,and the photoelectric conversion efficiency of the device increases.Finally,Preheating treatment before annealing on the basis of DMAc co-solvent method further improves the performance of the device.Based on Bi Br3(DMSO)2 adduct solution to produce high-coverage and smooth Cs2Ag Bi Br6 films with large grains.Accordingly,the as-constructed planar solar cells deliver a champion PCE of 0.73%,which is 40%higher with enhanced open circuit voltages and fill factors in comparison to those without the use of Bi Br3(DMSO)2 adduct solution.