Blade‐Coating (100)‐Oriented α‐FAPbI3 Perovskite Films via Crystal Surface Energy Regulation for Efficient and Stable Inverted Perovskite Photovoltaics

Abstract Photoactive black‐phase formamidinium lead triiodide (α‐FAPbI 3 ) perovskite has dominated the prevailing high‐performance perovskite solar cells (PSCs), normally for those spin‐coated, conventional n‐i‐p structured devices. Unfortunately, α‐FAPbI 3 has not been made full use of its advantages in inverted p‐i‐n structured PSCs fabricated via blade‐coating techniques owing to uncontrollable crystallization kinetics and complicated phase evolution of FAPbI 3 perovskites during film formation. Herein, a customized crystal surface energy regulation strategy has been innovatively developed by incorporating 0.5 mol % of N‐aminoethylpiperazine hydroiodide (NAPI) additive into α‐FAPbI 3 crystal‐derived perovskite ink, which enabled the formation of highly‐oriented α‐FAPbI 3 films. We deciphered the phase transformation mechanisms and crystallization kinetics of blade‐coated α‐FAPbI 3 perovskite films via combining a series of in‐situ characterizations and theoretical calculations. Interestingly, the strong chemical interactions between the NAPI and inorganic Pb−I framework help to reduce the surface energy of (100) crystal plane by 42 %, retard the crystallization rate and lower the formation energy of α‐FAPbI 3 . Benefited from multifaceted advantages of promoted charge extraction and suppressed non‐radiative recombination, the resultant blade‐coated inverted PSCs based on (100)‐oriented α‐FAPbI 3 perovskite films realized promising efficiencies up to 24.16 % (~26.5 % higher than that of the randomly‐oriented counterparts), accompanied by improved operational stability. This result represented one of the best performances reported to date for FAPbI 3 ‐based inverted PSCs fabricated via scalable deposition methods.