Synergistic dual-additive engineering for high-performance and air-stable CsPbBr3 perovskite solar cells

In this study, a novel bifunctional additive strategy was developed to enhance the performance of fully inorganic CsPbBr 3 perovskite solar cells. Propylene glycol methyl ether (PM) was employed as a single additive, and a hybrid additive was formed by combining PM with methyl benzoate (MB). The power conversion efficiency increased from 5.77 % to 8.63 % with PM alone, and further to 9.57 % with the PM–MB hybrid. These additives reduce uncoordinated Pb 2+ ions and passivate defects. Surface electrostatic potential calculations reveal that PM and MB contain functional groups with negative electrostatic potential, enabling them to anchor to the perovskite surface without inducing damage. Binding energy calculations and X-ray photoelectron spectroscopy showed a shift of Pb peaks to lower binding energies, indicating reduced uncoordinated Pb 2+ ions and enhanced defect passivation, which promote grain growth. Additionally, the ether and ester groups in PM and MB facilitate the extraction of residual N, N- dimethylformamide (DMF). Fourier-transform infrared spectroscopy confirmed the disappearance of DMF-related peaks after treatment, indicating effective solvent removal. Grazing-incidence X-ray diffraction further demonstrated enhanced grain size and orientation, reflecting reduced solvent-induced damage and improved film quality. As a result, unencapsulated devices retained over 90 % of their initial performance after 2500 h in air.