Molecular Engineering in Donor–Acceptor-Conjugated Hole-Transporting Materials for High-Performance Perovskite Solar Cells

Hole mobility and film formation capability of hole-transporting materials (HTMs) play crucial roles in enhancing both the power conversion efficiency and operational durability of perovskite solar cells (PSCs). However, the molecular structural demands of these properties are fundamentally competing, constituting a primary challenge in the molecular design of high-performance hole-transporting materials. Herein, a donor–acceptor-conjugated hole-transporting material termed CS-101 is designed through molecular engineering, containing a planar benzothiadiazole acceptor core and 3,6-dimethoxydiphenylamine-substituted carbazole donor groups. CS-101 features a diphenylamine peripheral group that exhibits a relatively compact structure, improves the planarity, and strengthens intermolecular π–π stacking, significantly increasing the hole mobility and film formation. As a result, incorporating doped CS-101 as the hole-transporting material in PSCs results in a photoelectric conversion efficiency of 23.18%, while the doped reference HTM exhibits a low efficiency of merely 14.95%. The CS-101-based PSCs also deliver improved long-term stability, maintaining over 93% of their initial efficiency after more than 1000 h of exposure to 35 ± 5% humidity at 25 °C. This work provides meaningful insight and a generalizable strategy for designing high-performance HTM molecules for perovskite solar cells.