Engineering the intermediate adduct phase to control the crystallization of perovskites for efficient and stable perovskite solar cells

Abstract

Perovskite solar cells (PSCs), on account of their ever-increasing power conversion efficiency (PCE), are captivating industrialists. Despite this, the performance of perovskite solar cells, especially the long life span, is the main barrier to PSCs’ commercial deployment where the inefficient perovskite layer is always convicted as the key reason behind it. In reality, the perovskite layer suffers from different intermediate transformations where dimethyl sulfoxide (DMSO), forming PbI₂·DMSO intermediates, plays an essential role in retarding the rapid crystallization of perovskite. Therefore, these intermediate phases govern the morphologies and crystallinities of the final perovskite films. In the comparison of FAPbI₃ and MAPbI₃, which are the two most studied single-cation perovskites, during intermediate phase conversions, the PbI₂·MAI·DMSO adduct provides high-quality perovskite than the PbI₂·FAI·DMSO adduct, which leads to the poor film quality of FA-based single cation and mixed cation perovskites. Herein, the intermolecular exchange of DMSO with FAI in the PbI₂·MAI·DMSO adduct is performed to get MA_xFA_1−xPbI₃ films where the grain size is dramatically enhanced, and a PCE of 20.79% is obtained with superior long term stability.