In Situ Interface Engineering with a Spiro‐OMeTAD/CoO Hierarchical Structure via One‐Step Spin‐Coating for Efficient and Stable Perovskite Solar Cells

Abstract Interface engineering plays crucial role for fabricating high efficiency perovskite solar cells (PSCs) because the trap defects, especially those existing at the interfaces, will become recombination centers during the generation and transport of photo‐generated charges and seriously influence photovoltaic performance. Commonly, interface engineering with semiconductor nanomaterials usually use ex situ method, which brings about more tedious fabricating steps. Here, a hierarchical structure is successfully fabricated with CoO nanoplates underneath and (N,N‐di‐p‐methoxyphenylamine)‐9,9′‐Spirobifluorene (Spiro‐OMeTAD) on top by one‐step spin‐coating the hybrid. This in situ formed CoO thin passivation layer shows functions for realizing better charge transport kinetics and effectively inhibiting dark recombination in the corresponding device. These benefits are propitious to achieving better photovoltaic performance and long‐term stability than those of the control one. Therefore, it is an easy and feasible way for interface engineering in the PSCs.