Homologous Molecule Treatment in Perovskite Solar Cells: Synergistic Management of Holistic Defect and Charge Transfer

Abstract Perovskite solar cells (PSCs) are gaining significant attention as key players in the field of advanced photovoltaic technologies, attributed to their impressive efficiency metrics. Despite their advantages, achieving commercial viability for PSCs requires overcoming significant challenges, particularly in mitigating defects that trigger Shockley‐Read‐Hall recombination and mastering the crystallization process. Though multiple strategies tackle these issues, the complexity of molecular engineering, which often needs totally different molecules for different tasks, limits their commercial use. In this study, amidine thiourea (AT), a multifunctional compound with several strong coordination sites is introduced, which effectively passivates diverse defects within perovskite crystals and modulates the crystallization kinetics. Furthermore, a homologous molecule of AT, called 1‐phenyl‐3‐guanylthiourea (PGT) is introduced, which features an additional benzene ring, to treat surface defects and reduce interface non‐radiative recombination. The integration of AT and PGT can synergistically regulate the perovskite crystallization kinetics and address holistic defects, including both bulk and surface of perovskite. The unique electronic properties of PGT also construct an effective charge transfer channel, which significantly suppresses the interface non‐radiative combination. Based on this strategy, planar PSCs, achieving a power conversion efficiency of 26.06% is fabricated, with retention of 90% efficiency after 1400 h under continuous illumination.