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

Abstract

AbstractWide‐band gap (1.68 eV) perovskite solar cells (PSCs) are important components of perovskite/Si tandem devices. However, the efficiency of wide band gap 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‐band gap inverted PSCs. Additionally, a flexible PSC and 1 cm2 opaque device also deliver the highest PCEs of 21.02 % and 19.31 %, respectively.