Defect Passivation by a Sulfur‐Containing Lewis Base for Efficient Printable Mesoscopic Perovskite Solar Cells

In the rapid development of perovskite solar cells (PSCs), additive engineering has played a significant role for perovskite crystallization and passivation. The high density of defects at perovskite grain boundaries in the mesoporous scaffold leads to severe nonradiative recombination, which results in severe voltage loss. Herein, a sulfur‐containing Lewis base 2‐(methylthio)ethylamine hydrochloride (MTEACl) is applied in the perovskite precursor solution for printable mesoscopic PSCs with triple‐mesoscopic layer structure. Due to the strong electron donating ability of sulfur, the MTEACl can strongly interact with Pb2+, which can effectively passivate the defects of the perovskite. Correspondingly, the trap density of the perovskite is reduced, contributing to the improvement of power conversion efficiency from 15.18% to 17.17% and open circuit voltage to 995 mV.