Wide‐Bandgap Perovskite Solar Cell Using a Fluoride‐Assisted Surface Gradient Passivation Strategy

Wide-bandgap (1.68 eV) perovskite solar cells (PSCs) are important components of perovskite/Si tandem devices. However, the efficiency of wide bandgap PSCs has been limited by their huge open-circuit voltage (VOC) deficit due to non-radiative recombination. Deep-level acceptor defects are identified as the major killers of VOC, and they can be effectively improved by passivation with ammonium salts. Theoretical calculation predicts that increasing the distance between F and -NH3+ of fluorinated ammonium can dramatically enhance the electropositivity of -NH3+ terminals, thus providing strong adsorption onto the negatively charged IA and IPb anti-site defects. Characterizations further confirm that surface gradient passivation employing p-FPEAI demonstrates the most efficient passivation effect. Consequently, a record-efficiency of 21.63% with the smallest VOC deficit of 441 mV is achieved for 1.68 eV-bandgap inverted PSCs. Additionally, a flexible PSC and 1 cm2 opaque device also deliver the highest PCEs of 21.02% and 19.31%, respectively.