Moisture-inhibited deprotonation at the buried interface enables efficient perovskite solar cells with a high fill factor of over 86%

Abstract

SnO₂ is one of the best electron-transport materials for perovskite solar cells (PSCs). However, the limited interfacial contact and the reaction occurring at the buried interface between the perovskite and SnO₂ reduce their performance. Herein, we revealed a strong deprotonation reaction of formamidinium cation that occurred at the buried interface during perovskite growth under a nitrogen atmosphere. In contrast, this reaction was considerably inhibited by moisture when the perovskite was grown under an ambient atmosphere (Amb-perovskite). Thus, defects at the buried interface of the Amb-perovskite were reduced, considerably suppressing the non-radiative recombination. Amb-PSC resulted in an efficiency of 25.69%, with an ultra-high fill factor of 86.21% and enhanced operational stability without decay after more than 1000 h under continuous 1-sun illumination. This work provides an efficient strategy for perovskite film annealing under an ambient atmosphere to minimise the buried interface loss. Its scaling-up potential and easy-processibility make it a promising strategy for low-cost large-scale manufacturing of PSCs.