Rigid molecules anchoring on NiO_x enable >26% efficiency perovskite solar cells

The surface defects of nickel oxide (NiO_x) and its interfacial redox reactions with perovskites often impede the efficiency improvement of inverted perovskite solar cells (PSCs). To address these issues, we designed ((9H-fluoren-9-ylidene)methyl) cyanophosphonic acid (FY-CPA) with a rigid backbone as an optimal multi-dentate anchoring (MDA) molecule to enhance the anchorage with bottom NiO_x by forming tetradentate binding and parallel orientation. Dense and uniform coverage of FY-CPA at the NiO_x/perovskite interface was achieved through in situ deposition, which can minimize interfacial redox reactions and suppress non-radiative recombination. The champion device demonstrated a power conversion efficiency (PCE) of 26.21% with a certified value of 25.99%. In addition, the larger area device (1.02 cm²) also showed a PCE of 25.31% with a certified value of 24.90%, which is among the highest PCEs reported so far for greater than 1 cm² sized PSCs. Moreover, the as-prepared device exhibited enhanced thermal and operational stability during long-term storage.