Research On Composition Optimization And Photoelectric Properties Of APbI₃ Perovskite Materials

Organic-inorganic hybrid perovskite solar cells have been developed rapidly in recent years,and the photoelectric conversion efficiency has exceeded 23%.In addition,the perovskite film could be prepared by solution method,which could reduce production cost and simplify operation,showing a very great potential for application.Methylamine lead iodine（MAPbI₃）has become the most commonly used ligh-absorbing material due to its excellent photoelectric properties.However,when prepared by one-step solution method,the quality of MAPbI₃ thin film is difficult to control,because small grain size,holes and other defects are easy to appear.In addition,the instability of MAPbI₃ material in the air environment and high temperature cannot be ignored.Therefore,it is necessary to improve the quality and stability of perovskite thin films.As we all know,the composition of ions in perovskite directly affects the photoelectric properties and stability.Based on this consideration,in this work the influence of doping A-position cation of traditional MAPbI₃ on the photoelectric properties and stability of the perovskites was studied.Mixed-cation perovskite（GABA）_xMA_1-xPbI₃ was prepared by using 4-aminobutyric acid ion（GABA⁺）containing bifunctional groups as mixed cation in the precursor solution.As a result,high quality film has been synthesized and showed better pore-filling and higher crystallinity,improving the power conversion efficiency to 18.31%,which is 21.4%higher than that of the controlled MAPbI₃ solar cells（15.08%）,and is more stable in air.In order to broaden the absorption range and improve thermal stability,the formamidine ion（FA⁺）with smaller band gap and better thermal stability was further doped to prepare FA_y(GABA_0.1MA_0.9)_1-yPbI₃perovskite.As expected,the absorption range red-shifted,resulting to the device efficiency reaching to 20.03%,and the thermal stability was greatly improved.Based on the fact that FAPbI₃ has excellent photoelectric properties,but at room temperature,perovskite phase（α-phase）was instability in the atmosphere,GABA⁺was firstly doped in FAPbI₃ to obtain（GABA）_xFA_1-xPbI₃ with better film quality.Furthermore,Cs⁺ions with small radius were further doped to prepare Cs_y(GABA_xFA_1-x)_1-yPbI₃,which can maintain a stable perovskite phase at room temperature.Importantly,the efficiency was comparable to that of FA_0.2(GABA_0.1MA_0.9)_0.8PbI₃ with better thermal stability.This study provides a reliable idea for further optimizing perovskite photoelectric properties and improving its stability.