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.