Additive with Multinary Interactions to Perovskite Precursor Species for Catalyzed Crystallization of Antisolvent‐Free α‐FAPbI 3 Solar Cells

Abstract Antisolvent‐free processes exhibit numerous advantages for fabricating perovskite solar cells (PSCs) while requiring exquisite control of nucleation and crystallization of perovskite film. Without the addition of Cs and Br species, more obstacles are faced for the preferred α‐phase pure formamidinium lead triiodide (α‐FAPbI 3 ) to achieve high power conversion efficiency (PCE) and stability. In this work, a novel additive, parecoxib (Pr), is proposed, which catalyzes the direct crystallization of α‐FAPbI 3 through multinary interactions with the solvate perovskite precursor. Detailed molecular interactions and in situ analysis reveal that Pr provides nucleation sites, reduces the grain growth rate, suppresses the formation of δ‐FAPbI 3 , and ultimately enhances the quality of the perovskite film. Furthermore, Pr can in situ passivate the grain boundaries, reduce nonradiative recombination, and enhance open‐circuit voltage ( V oc ) up to 1.195 V. As a result, high‐performance antisolvent‐free α‐FAPbI 3 PSCs are achieved with the PCE reaching 25.38% and 19.64% for mini‐modules (93 cm 2 ). The unencapsulated device maintains 91.08% of the initial PCE for 1000 h at 85 °C, and 90.62% after 1000 h of maximum power point tracking.