High-quality NiOx nanoparticles synthesized via low temperature chemical precipitation method for high-performance inverted perovskite photovoltaics

Dual hole transport layers consisting of NiOx and self-assembled molecules are widely adopted in inverted perovskite solar cells, yet plagued by high impurity content, inefficient hole transport, low molecular coverage, weak interfacial binding, unstable buried interface and energy level mismatch. Herein, a low-temperature chemical precipitation strategy is developed to synthesize high-quality NiOx nanoparticles as hole transport layers. Compared with the room-temperature route, the low-temperature prepared NiOx films deliver an elevated Ni3+/Ni2+ ratio, reduced impurities, higher electrical conductivity and hole mobility. Moreover, this strategy improves molecular coverage, alleviates energy level mismatch, accelerates hole extraction and strengthens buried interface stability. The optimized cells achieve a certified power conversion efficiency of 27.1%, and the 14 cm2 minimodule reaches an efficiency of 23.18%. The devices retain 91.5% efficiency after 2100 h of continuous operation, and 91.4% efficiency after 2000 h of damp-heat aging. Liu et al. report a low temperature chemical precipitation method to synthesize high quality NiOx nanoparticles for use as the hole transport layer in inverted perovskite solar cells and modules, enabling a certified efficiency of 27.1% for small-area solar cells and 23.18% for 14 cm2 minimodules.