Preparation And Research Of High-efficiency Planar Perovskite Solar Cells Without Hysteresis Effect

At present,the photovoltaic performance of organic-inorganic hybrid perovskite solar cells(PSCs)certified by third-party agencies has continuously exceeded new highs.Relying on the advantages of adjustable band gap,long carrier diffusion length,and low-cost large-area preparation,perovskite is considered one of the most promising materials in the field of photovoltaic materials.However,during the PSCs performance testing process,the forward voltage scanning J-V curves do not usually coincide with the reverse one.The hysteresis effect greatly affects the repeatability and accuracy of the J-V test.Recent studies have shown that the combination of charge capture and release processes at the interface and ion migration at the perovskite grain boundaries are the main causes of the hysteresis effect.Based on this,this article first uses interface engineering(PMMA:C60)to passivate the defect states at the interface,and grain boundary engineering(PTABr)to post-treated the perovskite film.With Cs0.15FA0.85PbI3 as the starting point,it gradually extends to perovskite of other components.Besides,additive engineering(CsCI)is used to replace the original CsI precursor materials to prepare high-quality large-grain size perovskite films.We explore the effects of interface,grain boundary and additive engineering on the photoelectric performance and hysteresis of planar PSCs,The specific details are as follows:(1)We have developed a universal strategy combining interface engineering(PMMA:C60)and grain boundary engineering(PTABr)for the preparation of planar PSCs with high efficiency and negligible hysteresis effect.A series of tests such as DFT and photoelectrochemistry show that the carbonyl groups in PMMA can passivate under-coordinated Pb ion to reduce non-radiative recombination caused by defect states at the interface between the electron transport layer and perovskite.Post-treatment of PTABr induced Ostwald reaction can increase the grain size of perovskite films and reduce the density of grain boundary.Hence the dual treatments lead to negligible hysteresis and high performance PSCs based on various compositional perovskites including MAPbl3,Cs0.15FA0.85PbI3 and Cs0.15FA0.75MA0.1PbI3,with power conversion efficiency(PCE)of 18.99%,19.82%,21.41%and extra-low hysteresis index of 0.011,0.007,0.005,respectively(2)We develop a simple and effective one-step solution method for the preparation of high-quality CsxFA1-xPbI3 perovskite films upon the addition of CsCl to the pure FAPbI3 precursor solution.A series characterizations such as XRD,Uv-vis,SEM and AFM show that the Cs cation replaces partial FA cation,and into the perovskite lattice to inhibit the formation of yellow-phases perovskite(δ-FAPbI3)and PbI2,thus effectively increase the black-phases perovskite(α-FAPbI3)crystallinity.Simultaneously,the FACl generated by Cl ions and FA ions gradually sublimates with high temperature,which increases the size of perovskite grains to the micron level and reduces the surface roughness of perovskite.PL and electrochemical tests show that CsCl additive can effectively reduce carrier recombination and enhance charge transport capabilities.With an optimal 15 mol%CsCl additive,the average PCE increases from 14.53±0.51%to 18.96±0.35%with a champion PCE of 19.63%from reverse scan.In addition,the hysteresis index reduces from 0.06 to 0.02.