24.64%‐Efficiency MA‐Free Perovskite Solar Cell with Voc of 1.19 V Enabled by a Hinge‐Type Fluorine‐Rich Complex

Abstract

AbstractHigh density of defects at interface severely affects the performance of perovskite solar cells (PSCs). Herein, cobalt (II) hexafluoro‐2,4‐pentanedionat (CoFAc), a hinge‐type fluorine‐rich complex, is introduced onto the surface of formamidinium cesium lead iodide (FACsPbI3) film to address the issues of perovskite/Spiro‐OMeTAD interface. The existence of CoFAc passivates both organic cation and halide anion vacancies by establishing powerful hydrogen bonds with HC(NH2)2+ (FA+) and strong ionic bonds with Pb2+ in perovskite films. In addition, CoFAc serves as a connecting link to enhance interfacial hole‐transport kinetics via interacting with Spiro‐OMeTAD. Consequently, FACsPbI3 PSCs with CoFAc modification display a champion power conversion efficiency (PCE) of 24.64% with a charming open‐circuit voltage (VOC) of 1.191 V, which is the record VOC among all the reported organic‐inorganic hybrid PSCs with TiO2 as electron transport layer. Furthermore, CoFAc‐modified devices exhibit an outstanding long‐term stability, which can maintain 95% of their initial PCEs after exposure to ambient atmosphere for 1500 h without any encapsulation.