“…The PMMA and PMMA:MX solutions containing different concentrations of MXenes were spin-coated on top of the perovskite layer at 4000 rpm for 60 s and then thermally annealed at 100 1C for 10 min. For the ETL layer, a [6,6]phenyl-C61-butyric acid methyl ester (PCBM, NanoC) solution in CB (20 mg mL À1 ) was spin-coated at 1000 rpm for 20 s. Lastly, a 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline Bathocuproine (BCP, TCI Chemicals) solution (4 mg mL À1 ) in isopropanol was spin-coated at 4000 rpm for 60 s, with a thermally evaporated Ag layer (80 nm) as the top electrode.…”