Solvent and Intermediate Phase as Boosters for the Perovskite Transformation and Solar Cell Performance

High power conversion efficiency and device stabilization are two major challenges for CH 3 NH 3 PbI 3 (MAPbI 3 ) perovskite solar cells to be commercialized. Herein, we demonstrate a diffusion-engineered perovskite synthesis method using MAI/ethanol dipping, and compared it to the conventional synthesis method from MAI/iso-propanol. Diffusion of MAI/C 2 H 5 OH into the PbCl 2 film was observed to be more favorable than that of MAI/C 3 H 7 OH. Facile perovskite conversion from ethanol and highly-crystalline MAPbI 3 with minimized impurities boosted the efficiency from 5.86% to 9.51%. Additionally, we further identified the intermediates and thereby the reaction mechanisms of PbCl 2 converting into MAPbI 3 . Through straightforward engineering to enhance the surface morphology as well as the crystallinity of the perovskite with even faster conversion, an initial power conversion efficiency of 11.23% was obtained, in addition to superior stability after 30 days under an ambient condition.