Yixin Zhao1 Taiyang Zhang1 Ge Li1 Feng Xu1 Yong Wang1

1, Shanghai Jiao Tong University, Shanghai, , China

The high quality phase pure organic-inorganic perovskite such as MA1-xFAxPbI3 or FAPbI3 planar films with extended absorption and enhanced thermal stability were difficult to deposit by regular simple solution chemistry approaches due to the crystallization competition between the easy-to-crystallize but unwanted δ-FAPbI3/MAPbI3 and FAxMA1-xPbI3 or FAPbI3 requiring rigid crystallization condition. A faclile 2D-3D conversion was developed to transform compact 2D mixed composition HMA1-xFAxPbI3Cl perovskite precursor films into 3D MA1-xFAxPbI3 (x=0.1-0.9) perovskites.The high quality phase pure MA1-xFAxPbI3 (x=0.1-0.9) and FAPbI33 perovskite films via 2D-3D conversion achieve a >20% efficiency with higher thermal stability. The all-inorganic α-CsPbI3 perovskite with the most suitable band gap for tandem solar cell application faces an issue of phase instability under ambient conditions. We discovered that a small amount of 2D EDAPbI4 perovskite containing ethylene diamine (EDA) cation stabilizes the α-CsPbI3 to avoid the undesirable formation of the non-perovskite delta phase, achieveing a record efficiency of 11.8%.In all, the 2D-3D conversion and 2D/3D hybridzation would be a promising strategy for fabricating and stabilizing lead halide perovskite solar cells.