Molecular <i>Si</i>-Cyclization Enables Versatile Organic Semiconductors for Durable Perovskite Solar Cells with 24.8% Efficiency

Employing large fused-aromatic heterocycles to facilitate hole extraction and transport has been shown to significantly enhance the photovoltaic performance of perovskite solar cells (PSCs), but this approach typically results in a low intrinsic solubility and reduced device durability. In this study, we have developed two tetrathienosilole (TTS)-cored hole transporting materials (HTMs) through molecular Si-cyclization, aiming to address this common trade-off effect. The optimized atomic arrangement and enhanced planarity impart the resultant TTS-based HTMs with stronger interfacial interactions with the perovskite. Meanwhile, the perpendicular orientation of side-chains induced by the sp3-hybridized Si atom effectively improves the film morphology. By incorporating additional thiophene π-bridges, the Si-cyclized WH12 exhibits a high hole mobility and film-formation quality. Consequently, the corresponding FAPbI3-based PSCs achieved a record efficiency of 24.8% with exceptional operational durability (T80 > 1000 h). This work highlights the significant potential and versatility of the Si-cyclization strategy, opening new avenues for designing multifunctional molecular semiconductors.