Development of hole transport materials (HTMs) with comprehensive passivation effects and appropriate energy levels are urgently desirable for constructing highly efficient and stable perovskite solar cells (PSCs). Herein, we report an effective interfacial molecular doping strategy and energy level regulation approach to improve the performance of PSCs with ultrasimple carbazole-based HTMs CZ-As and CZ-Py. The pyridine-substituted HTM CZ-Py exhibits a stepped energy level with perovskite and CZ-As, effective passivation of Pb2+ defect, as well as the assistance of the formation of high-quality perovskite film and hole transport layer (HTL). By utilizing CZ-Py as interfacial doping material and CZ-As as HTM, the undesired charge carrier recombination at the perovskite/HTM interface are significantly restricted. Finally, the fabricated PSCs feature an impressive power conversion efficiency (PCE) up to 23.5% and good long-term stability. This work demonstrates a facile and highly efficient way to reduce nonradiative recombination and further improve photovoltaic performance of PSCs.

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Two novel highly efficient and low-cost phenothiazine 5,5-dioxide core building block based hole transport materials are reported, achieving a power conversion efficiency as high as 20.2%.