Going Beyond Surface Physics: Interface Engineering of PTAA for Efficient p‐i‐n Perovskite Photovoltaics

Poor wettability of poly(triarylamine) (PTAA) surfaces and insufficient control over residual PbI 2 clusters remain critical bottlenecks limiting the performance of PTAA‐based p‐i‐n perovskite solar cells (PSCs). Herein, we introduce an effective interface engineering strategy through the incorporation of the ionic liquid 1‐butyl‐3‐methylimidazolium acetate (BMIMAc). Owing to its strong affinity for the perovskite precursor solvent (N,N‐dimethylformamide, DMF), BMIMAc significantly enhances PTAA wettability, promoting the formation of uniform and defect‐passivated perovskite films. In addition, BMIMAc modulates the energy level alignment of PTAA, facilitating more efficient hole extraction and transport across the interface. More importantly, BMIMAc interacts with PbI 2 to decelerate perovskite crystallization kinetics, enabling a more complete conversion of PbI 2 into the perovskite phase. This synergistic regulation yields perovskite films with enlarged grain sizes, reduced trap densities, and suppressed nonradiative recombination losses. Benefiting from these advances, the optimized PTAA‐based p‐i‐n PSCs achieve a record‐high power conversion efficiency of 25.10% with significantly enhanced operational stability.