Self‐Induced Bi‐interfacial Modification via Fluoropyridinic Acid For High‐Performance Inverted Perovskite Solar Cells

The 5-fluoropyridinic acid (FPA) self-induced bifacial passivation strategy not only effectively passivates the uncoordinated Pb/Pb²⁺ at the upper and lower interfaces of the perovskite films, but also improves the quality of the films. Furthermore, due to the matching of the energy levels, the extraction rate of the carriers at the bifacial interface is simultaneously improved.

Abstract

The uncontrolled crystallization of perovskite generates a significant number of internal and interfacial defects, posing a major challenge to the performance of perovskite solar cells (PSCs). In this paper, a novel bi-interfacial modification strategy utilizing 5-fluoropyridinic acid (FPA) is proposed to modulate crystal growth and provide defect passivation. It is demonstrated that FPA is self-deposited at both the top and bottom interfaces of perovskite films during thermal annealing. The CO and N functional groups in FPA serve as chelating agents, binding closely to uncoordinated Pb²⁺/Pb clusters, thereby passivating defects and reducing charge recombination at the interfaces. The strong chemical interactions between FPA and Pb further stabilize the Pb-I framework, promoting the formation of high-quality perovskite films, as confirmed by in situ photoluminescence measurements. Consequently, the modified inverted PSCs achieved an exceptional power conversion efficiency (PCE) of 25.37%. Moreover, the devices retained over 93.17% of initial efficiency after 3000 h of continuous illumination under one-sun equivalent conditions in a nitrogen atmosphere. This paper presents a promising pathway for enhancing the performance and stability of inverted PSCs through a self-induced bi-interfacial modification approach.