Orthogonal small-molecule zinc porphyrin derivative as efficient hole transport material for high-performance inverted perovskite solar cells

Hole transport materials (HTMs) are crucial components for achieving efficient and stable perovskite solar cells (PSCs). Inverted p-i-n structured devices offer advantages such as low-temperature film formation and flexible manufacturing. In this study, we designed and synthesized a star-shaped small-molecule zinc porphyrin derivative with an orthogonal spatial configuration, ZnP-4ThDPP, as the HTM layer, and further optimized the PSCs using LiTFSI as a dopant. The unique spatial configuration and excellent low-temperature film formation properties of ZnP-4ThDPP improve the efficiency of hole extraction while reducing manufacturing costs. The PSCs also exhibit good reproducibility and long-term stability. The LiTFSI dopant, which induces p-type doping, enhances the conductivity of the hole transport layer, improves the crystallization quality of the upper perovskite film, and reduces the defect state density. These combined effects collectively boost the device efficiency to 20.25%, representing the highest reported value for inverted PSCs using small-molecule zinc porphyrin-based HTMs.