Enhancing Electron Transport Properties of Perovskite Solar Cells through V2CTx Modification of PC61BM

Abstract Phenyl-C61-butyric acid methyl ester (PC61BM) is widely used as an electron transport layer (ETL) in inverted p-i-n perovskite solar cells. However, its limited ability to passivate undercoordinated Pb2+ sites, together with incomplete film coverage, suboptimal interfacial energy-level alignment, and limited electrical conductivity, constrains the efficiency and stability of the resulting devices. In this work, two-dimensional V2CTx MXene was incorporated into PC61BM to form a modified electron transport layer (M-PC61BM). The incorporation of V2CTx regulates the carrier dynamics at the perovskite/ETL interface. The oxygen-containing −O and −OH terminations of V2CTx are proposed to serve as the principal passivation sites for undercoordinated Pb2+ sites, while the −F terminations may provide an additional contribution to the interfacial interactions. Meanwhile, the incorporation of V2CTx increases the electrical conductivity of the PC61BM ETL and improves its energy-level alignment. Together with the PL/TRPL results obtained from the perovskite/ETL bilayers, these changes collectively support improved interfacial electron transfer and reduced defect-assisted non-radiative recombination. Consequently, the M-PC61BM-based device achieved a champion power conversion efficiency of 22.2%, compared with 19.95% for the control device. In addition, the unencapsulated M-PC61BM device retained 85% of its initial efficiency after storage for 500 h in a constant-humidity chamber maintained at 25 °C and 30% relative humidity.