Donor–acceptor type copolymers with a carbazole side chain as hole transport materials for dopant-free perovskite solar cells

Copolymers including carbazole-substituted naphtho- and quinoxalinedithiophene blocks, along with benzothiadiazole and thiophene, have been synthesized and systematically evaluated as dopant-free hole transport materials (HTMs) for perovskite solar cells. Polymers with optimal HOMO alignment relative to the perovskite valence band, suppressed carrier recombination at polymer/perovskite interface and, crucially, those forming the most uniform films, as confirmed by AFM and s-SNOM IR microscopy demonstrated enhanced device performance. These results provide valuable insights into the relationships between molecular structure, material properties, and device efficiency, offering guidance for the design of dopant-free polymeric HTMs for high-performance perovskite solar cells.