The Study On Highly Stable CsPbI_xBr_3-x Inorganic Perovskite Thin Films Doped With Alkali Metal

Organic-inorganic hybrid perovskite solar cells have become the most promising solar cell after silicon-based solar cells due to their high photoelectric conversion efficiency,low manufacturing cost and simple manufacturing process.However,its poor thermal stability severely restricts its commercialization process.Inorganic perovskite has better thermal stability,so it has quickly become a research hotspot.At present,Cs Pb I₃has a suitable band gap（1.73 e V）and is considered as a candidate material for high-efficiency perovskite solar cells.Unfortunately,the ideal cubic phase spontaneously turns into an unwanted orthogonal phase in the air.Therefore,based on improving the stability and film quality of inorganic perovskite batteries,this paper carried out the following research:（1）Preparation and properties of inorganic perovskite thin film Cs Pb I_xBr_3-x.Changing the annealing temperature and annealing time can affect the film-forming quality of the Cs Pb I_xBr_3-x inorganic perovskite thin film.When the annealing temperature is 280℃and the annealing time is 10min,the crystallinity of the Cs Pb I₂Br perovskite film is the best,the internal defects of the film are the least,and the light absorption is the highest;When the annealing temperature is 250℃and the annealing time is 10min,the crystallinity of the Cs Pb IBr₂ perovskite film is the best,the film defects are the least,and the film light absorption is the highest;The film has the least internal defects and the highest absorption.When the annealing temperature is 250℃and the annealing temperature is 10min,the Cs Pb Br₃ perovskite thin film has the best crystallinity,the largest grain size,the smoothest film surface,and the fewest defects.Among the three films of Cs Pb I₂Br,Cs Pb IBr₂ and Cs Pb Br₃,the stability of Cs Pb Br₃ film is the best,and it can be stable in the air for a long time.The stability of Cs Pb IBr₂ film is relatively good,and the phase change does not occur when placed in air at 50%humidity for one week.The stability of the Cs Pb I₂Br film is poor,and a phase change will occur when placed in air at 20%humidity for 10minutes.（2）Preparation and performance of alkali metal doped（Na I,KI）Cs Pb I₂Br and Cs Pb IBr₂ thin films.Alkali metal iodide（Na I,KI）was added to the precursor solution of Cs Pb I₂Br and Cs Pb IBr₂ to study the effect of alkali metal ion doping on the Cs Pb I₂Br and Cs Pb IBr₂ films.The research shows that the Cs Pb I₂Br perovskite thin film with the KI doping concentration of 5%has the best crystallinity,less film defects,dense film and the highest stability;when the Na I doping concentration is2.5%,the Cs Pb I₂Br perovskite thin film has a half height The smallest width,the largest grain size,and the best crystallinity;the Cs Pb IBr₂perovskite film with KI doping concentration of 5%has the best crystallinity,fewer internal defects,dense film,uniform grain size,and the highest stability;Na I doping When the impurity concentration is 5%,the half-height width of the Cs Pb I₂Br perovskite film is the smallest,the grain size is the largest,and the crystallinity is the best.At the same time,alkali metal doping can significantly improve the stability of Cs Pb I₂Br and Cs Pb IBr₂films.5%KI and 2.5%Na I-doped Cs Pb I₂Br films can not undergo a phase change in air at 20%humidity for 30 minutes.5%KI and 5%Na I The doped Cs Pb IBr₂ film does not undergo a phase change within one month in air with 50%humidity.（3）Preparation and performance of alkali metal doping on Cs Pb I₃ perovskite film added with HI.Adding HI to the Cs Pb I₃ precursor solution,first study the effect of annealing temperature and annealing time on the Cs Pb I₃ film after adding the HI solution.Secondly,the effect of doped alkali metal iodide（Na I,KI）on Cs Pb I₃ added with HI solution was studied.Experiments show that the addition of HI can reduce the annealing temperature of the Cs Pb I₃film,the optimal annealing temperature is100℃,the optimal annealing time is 10min.The 5%KI doping prepared the Cs Pb I₃perovskite film with the best crystallinity,the densest film,the fewest holes,few internal defects,and high light absorption;2.5%Na I doping can improve the crystallinity of the Cs Pb I₃ perovskite thin film with the best crystallinity,the densest film,the least holes,few internal defects and high light absorption;the stability of the Cs Pb I₃perovskite film prepared by doping 5%KI and 2.5%Na I is significantly improved.