Enhanced Efficiency and Moisture Stability of Dopant-Free P3HT Perovskite Solar Cells via a Tricarboxytriphenylamine Molecular Lock

Dopant-free poly(3-hexylthiophene) (P3HT) has attracted increasing interest as a stable and solution-processable hole-transporting layer (HTL) for perovskite solar cells (PSCs), yet its relatively weak interfacial contact and limited hole-extraction capability remain major constraints on device efficiency. Here, we demonstrate an effective interfacial engineering strategy using two π-conjugated molecules, triphenylamine (TPA) and 4,4′,4″-tricarboxytriphenylamine (TCTA), to simultaneously regulate the perovskite/P3HT interface and suppress interfacial defects. The benzene-ring frameworks of TPA and TCTA enable strong π–π stacking interactions with the thiophene units of P3HT, improving molecular ordering and facilitating more efficient hole transport. Meanwhile, the carboxyl groups in TCTA provide robust coordination with undercoordinated Pb2+, leading to superior defect passivation and more favorable energy-level alignment at the interface. As a result, TCTA-treated devices exhibit significantly enhanced charge extraction, reduced nonradiative recombination, and improved operational stability. Benefiting from these synergistic effects, the power conversion efficiency of dopant-free P3HT-based PSCs is boosted from 12.66% to 17.17% and 19.68% for TPA- and TCTA-modified devices, accompanied by markedly improved moisture stability and long-term durability. This work provides a promising molecular design principle for constructing high-performance and stable dopant-free P3HT-HTL–based PSCs.