Vertically Oriented Bisphosphonate Self‐Assembled Monolayers for Efficient and Thermocycling‐Stable Inverted Perovskite Solar Cells

ABSTRACT Inverted perovskite solar cells (PSCs) employing self‐assembled monolayers (SAMs) as hole‐selective materials have demonstrated promising device performance. However, SAMs often exhibit disordered orientation and weak interactions with both the perovskite and the transparent conductive oxide (TCO) substrate, which leads to inefficient charge extraction and significant energy losses. Herein, we proposed an integrated molecular design strategy to comprehensively restructure the SAM (MeS‐BPADCP): incorporating bisphosphonate anchoring units, aromatic linker moieties, and methylthio (MeS‐) terminal groups. This molecule promotes a nearly vertical orientation on the substrate to enhance charge extraction efficiency by employing bisphosphonate anchoring and aromatic linker, and the methylthio group can effectively passivate surface defects on the perovskite and enhance interface contact. Consequently, the MeS‐BPADCP based device achieved a remarkable power conversion efficiency (PCE) of 26.73% and exhibited excellent long‐term stability, while sustaining 94.2% of its initial efficiency after continuous operation under one‐sun illumination for 1000 h. The device also displayed outstanding thermal cycling stability, retaining 93.3% of its initial PCE after 240 cycles within a temperature range of −40°C to 85°C (ISOS‐T‐3 protocol).