Crystallization Control of Methylammonium‐Free Perovskite in Two‐Step Deposited Printable Triple‐Mesoscopic Solar Cells

Abstract

The evolution from the original methylammonium (MA)‐ to formamidinium (FA)‐dominated perovskite makes a crucial contribution to improve the photoelectric performance of perovskite solar cells (PSCs) in a decade. However, to obtain α‐FAPbI 3 , annealing temperature above 100 °C is essential. In addition, it is still challenging to deposit a uniform and high‐quality FA‐based perovskite absorber in printable triple‐mesoscopic PSC due to the complicated mesoscopic structure. Herein, a low‐temperature, two‐step sequential deposition method is used for pure FAPbI 3 perovskite in printable triple‐mesoscopic PSC. By using different lead sources, the crystallization and morphology of lead iodide (PbI 2 ) are finely controlled, which modulates the crystallization and pore filling of perovskite in mesoscopic structure. The improved interface contact promotes the transfer of charge carrier from perovskite to TiO 2 . With the further introduction of cesium bromide (CsBr) into lead precursor, a power conversion efficiency of 16.24% is achieved. This study provides a deeper understanding of the pore filling and crystallization for both PbI 2 and perovskite, and helps explore and optimize the deposition process of perovskite in mesoscopic structure.