Facilitating charge transfer and band alignment in perovskite solar cells via interfacial regulation with a Nb2CTx MXene oxidized derivative

Abstract

Interface engineering to enhance carrier extraction and transfer capability, as well as controlling the morphology and defects of perovskite films, remains an imperative challenge in perovskite photovoltaics. Herein, we introduce an innovative method utilizing an oxidized derivative of Nb₂CT_x MXene to regulate the interface between the electron transport layer (ETL) and perovskite. The oxidation of Nb₂CT_x results in the formation of a hybrid structure comprising Nb₂CT_x and Nb₂O₅. This oxidized derivative (namely O–Nb₂C) provides better energy level alignment and facilitated carrier extraction, leading to optimized charge transfer and reduced electron–hole recombination. Moreover, O–Nb₂C conducts more surface functional groups associated with the enhancement of surface free energy. This enhancement is presumed to promote the homogeneous nucleation of the perovskite precursor, resulting in improved crystallization of perovskite films with less trap density. Consequently, the perovskite solar cell (PSC) with the O–Nb₂C regulation delivers a boost in power conversion efficiency (PCE) to 23.20%, surpassing the baseline PCE of 20.51% based on SnO₂, and demonstrates a minimal PCE decay of less than 15% after 1500 hours of storage. This work presents a robust method of interfacial engineering utilizing MXene derivatives for high-performance PSCs, thereby further expanding the applications of MXenes in photovoltaic devices.