Suppression of light-induced phase segregation in all-inorganic wide-bandgap perovskite solar cells via molecular interaction design

Wide-bandgap mixed-halide perovskites, particularly CsPbIBr₂, hold great promise for multi-junction solar cells due to their well-matched bandgap and all-inorganic material system. However, their inherent susceptibility to light-induced phase segregation (LIPS) limits efficiency and stability. In this work, we investigate the effect of three organic additives—4-cyclopentene-1,3-dione (CPD), maleimide (HPD), and 3,4-dibromo-1H-pyrrole-2,5(2H,5H)-dione (BrPD)—on LIPS in wide-bandgap CsPbIBr₂ perovskite films. The additives form various chemical interactions, including coordination bonds, hydrogen bonds, and ionic bonds, with I⁻ and undercoordinated Pb²⁺ ions, among which BrPD has the strongest interaction. This interaction regulates crystallization and improves film morphology. The BrPD-modified films have the largest grain size and the highest light stability, suppressing LIPS, enhancing carrier transfer, and improving device performance. BrPD-modified CsPbIBr₂-based solar cells achieve a power conversion efficiency (PCE) of 11.34%, outperforming the control (8.96%) and other additives. Moreover, BrPD-modified devices show excellent stability, retaining 94% of their initial PCE after 60 min of continuous light exposure. This work highlights the potential of strategically selected organic additives to enhance the stability and performance of perovskite solar cells, offering valuable insights for the design of high-efficiency and long-lasting perovskite-based optoelectronic devices.