One-step air-processed FAPbI3 n-i-p perovskite solar cells with the efficiency of over 20 %

The fabrication of perovskite solar cells (PSCs) in an ambient atmosphere is highly desirable for commercial manufacturing. Recently, the power conversion efficiency (PCE) of air-processed PSCs has surpassed 25 %, approaching that of those fabricated in a glove box. However, the highly efficient air-processed PSCs are predominantly achieved via the two-step method, while one-step fabrication struggles to exceed 20 % efficiency. In this study, we present a facile strategy to achieve high-efficiency PSCs via one-step fabrication at 70 % relative humidity, without the use of an air knife or substrate heating. By incorporating a volatile solvent and trifluoroacetic acid (TFA) into the perovskite precursor, we achieve a pinhole-free, tensile stress-relieved perovskite layer. The carboxyl group of TFA interacts with dangling lead ions, effectively passivating interfacial defects, while its fluoromethyl group protects perovskite grains from moisture ingress. These dual functions enable the formation of high-quality perovskite under high-humidity conditions. The resulting passivation leads to a low trap-state density, high charge recombination resistance, extended charge carrier lifetime, well-matched energy levels, and enhanced long-term stability. Consequently, the PSCs achieve a PCE of 20.78 %, surpassing many previously reported values for one-step air-processed PSCs under high-humidity conditions. • Achieved 20.78 % efficiency in one-step air-processed PSCs at 70 % RH. • Introduced TFA to passivate defects and enhance moisture resistance. • Pinhole-free perovskite layer through ACE and TFA incorporation. • Fabrication process do need air knives or substrate heating. • TFA incorporation improves long-tern stability.