Dithieno[3,2‐b:2′,3′‐d]pyrrole Cored p‐Type Semiconductors Enabling 20 % Efficiency Dopant‐Free Perovskite Solar Cells

Organic p‐type semiconductors with tunable structures offer great opportunities for hybrid perovskite solar cells (PVSCs). We report herein two dithieno[3,2‐b:2′,3′‐d]pyrrole (DTP) cored molecular semiconductors prepared through π‐conjugation extension and an N‐alkylation strategy. The as‐prepared conjugated molecules exhibit a highest occupied molecular orbital (HOMO) level of −4.82 eV and a hole mobility up to 2.16×10−4 cm2 V−1 s−1. Together with excellent film‐forming and over 99 % photoluminescence quenching efficiency on perovskite, the DTP based semiconductors work efficiently as hole‐transporting materials (HTMs) for n‐i‐p structured PVSCs. Their dopant‐free MA0.7FA0.3PbI2.85Br0.15 devices exhibit a power conversion efficiency over 20 %, representing one of the highest values for un‐doped molecular HTMs based PVSCs. This work demonstrates the great potential of using a DTP core in designing efficient semiconductors for dopant‐free PVSCs. Cores and effect: Dithieno[3,2‐b:2′,3′‐d]pyrrole cored p‐type semiconductors are developed as dopant‐free hole‐transport materials for perovskite solar cells with an efficiency surpassing 20 %. The modification via π‐conjugation extension and N‐alkylation fine‐tunes the HOMO energy levels, hole mobility, solubility, and film‐forming characteristics.