Ethyl Thioglycolate Assisted Multifunctional Surface Modulation for Efficient and Stable Inverted Perovskite Solar Cells

Abstract As the core component of sandwich‐like perovskite solar cells (PSCs), the quality of perovskite layer is a challenge for further progress in PSCs due to the unfavorable defects and uncontrollable crystallization. Here, a surface post‐treatment strategy employing ethyl thioglycolate (ET) as ligand molecule is developed for property manipulation of perovskite films. ET can lower surface energy of perovskite facets and induces secondary growth of grains, giving films with higher crystallinity and lower defect density. Meanwhile, both carbonyl and sulfhydryl in ET can bind to the Pb²⁺, thus forming bidentate anchoring on the surface for defect passivation. Besides, the perovskite/ET/C₆₀ interface presents improved charge transfer owing to the well‐aligned energy levels. Consequently, the power‐conversion‐efficiency (PCE) is boosted to 22.42% and 23.56% (certified 23.29%) for the FA_0.85Cs_0.15Pb(I_0.95Br_0.05)₃ and FA_0.9MA_0.05Cs_0.05Pb(I_0.95Br_0.05)₃ PSCs, respectively, and the FA_0.85Cs_0.15Pb(I_0.95Br_0.05)₃‐based PSC with a larger area (1.03 cm²) delivers a PCE of 20.01%. Importantly, ET demonstrates effective management of I₂ and PbI₂, thereby preventing accelerated degradation and lead leakage of devices. Thanks to the multiple effects of ET, the resulting devices exhibit significantly enhanced ambient stability over a course of 800 h, and a thermal stability of over 1500 h while maintaining 80.4% of its original efficiency.