Efficient and Stable Inverted Perovskite Solar Cells Via a Multi-Arm Donor-Acceptor Dipole Molecular Bridge

The rapid advancement of self-assembled monolayer (SAM) engineering has substantially improved the photovoltaic performance of p-i-n perovskite solar cells (PSCs). However, interfacial defects, inefficient charge transport, and residual lattice strain at the SAM/perovskite interface still limit device efficiency and operational stability. Herein, we propose a multi-arm donor-acceptor (D-A) dipole molecular bridge strategy for buried-interface regulation. Two D-A type dipole molecules, N4IA and T4IA, were designed and synthesized to clarify the role of molecular-arm engineering. Compared with N4IA, T4IA features a multi-arm D-A framework with a larger molecular dipole, abundant triphenylamine-based hole-transport units, and multiple C═N/methoxy coordination sites. These structural features enable T4IA to optimize energy-level alignment, build efficient hole-transport pathways, accelerate charge extraction, and suppress interfacial nonradiative recombination. Meanwhile, the C═N and methoxy groups strongly interact with undercoordinated Pb²⁺ defects, reducing trap states, alleviating residual lattice strain, and improving interfacial stability. The optimized p-i-n PSCs based on T4IA interfacial regulation achieve a champion PCE of 26.79% with enhanced long-term operational and thermal cycling stability. This work provides a feasible molecular interface strategy for developing efficient and stable perovskite photovoltaic devices.