Charge-Transfer Enhancement by PEI/MXene Buffer Layer for Boosting Performance of Inverted Perovskite Solar Cells

devices. A set of complementary electrical and spectroscopic techniques confirmed that MXenes optimize PCBM/PEI/MX/Ag interfaces. The improved interfacial features result in suppressed recombination losses, increased charge carrier lifetime, and enhanced extraction of photogenerated charges. These improvements are reflected in the enhanced photovoltaic parameters, particularly the open-circuit voltage and fill factor. Notably, PEI/MX based PSCs show enhanced PCE achieving 22.0 ± 0.8% (23.1% for champion PSC device) when compared to the pure PEI based device (18.9 ± 0.6%). Hence, the results presented in this work indicate that solution-processable PEI/MX is a promising candidate to substitute conventional cathode buffer layer materials.