Preparation And Photovoltaic Performance Study Of High Stability Cs-rich Cs_1-xA_xPbI₂Br（A:FA/DMA）

In recent years,there have been continuous advancements in perovskite solar cells due to their suitable bandgap,high carrier diffusion length,strong absorption of visible and near-infrared light,high efficiency,and low processing costs.Currently,the highest efficiency of a single perovskite solar cell has reached 25.7%,but its poor stability has always been a bottleneck for large scale application of this material.Hence,this study attempts to use FA⁺and DMA⁺with larger organic ion radius to substitute Cs⁺in Cs PbI₂Br,aiming to simultaneously improve its moisture stability and maintain good photo-thermal stability.The specific results are as follows:（1）Cs_1-xFA_xPbI₂Br（0≤x≤0.4）thin films with low FA substitution doping were successfully prepared by a substrate preheating method,and the problem of phase separation at the Cs content higher than 40%can be solved.With the FA content increasing,the bandgap of Cs_1-xFA_xPbI₂Br（0≤x≤0.4）decreased and could be tuned between 1.9 e V and 1.79 e V.When the FA doping content reached 30%,the highest efficiency of the corresponding solar cell was12.3%.Compared with Cs PbI₂Br,not only the moisture stability of Cs_0.7FA_0.3PbI₂Br has been significantly improved,but also its its good thermal and optical stability were still maintained.（2）Based on the synthesis of DMAPbI₃ powder,DMA⁺were introduced into Cs PbI₂Br.The effects of Cs_1-xDMA_xPbI₂Br film preparation process parameters such as annealing temperature,intermediate phase type,annealing method,and annealing conditions on the its crystal phase,morphology,and bandgap were investigated.Ultimately,α-phase Cs_1-xDMA_xPbI₂Br（0≤x≤0.4）pure phase thin films were successfully synthesized.As the DMA content increased,the bandgap of this film first decreased and then increased and adjustable between 1.9 e V and 1.82 e V.When the DMA doping content reached 20%,Cs_0.8DMA_0.2PbI₂Br has the best moisture stability,and its efficiency of the corresponding device was 6.01%compared to Cs PbI₂Br.Moreover,Cs_0.8DMA_0.2PbI₂Br still maintained good optical stability.