Additive and interface passivation dual synergetic strategy enables reduced voltage loss in wide-bandgap perovskite solar cells

The open-circuit voltage (VOC) loss for wide-bandgap (WBG) perovskite solar cells (PSCs) is a significant obstacle to their further development. Herein, we introduce a dual approach involving mixed potassium thiocyanate and potassium chloride (KSCN+KCl) additives combined with 2-thiophene methylamine iodine (2-ThMAI) post-passivation strategy to mitigate VOC loss in WBG PSCs. In the mixed additives, KSCN can expand the grains and reduce the grain boundary, while KCl can inhibit the migration of halogen ions, effectively preventing phase segregation in WBG perovskites under the combination of both. However, due to the substantial energy level mismatch at the perovskite/electron transport layer (ETL) interface, suppressing phase segregation alone is insufficient to reduce the VOC loss. Therefore, introducing 2-ThMAI interface passivation could uniform spatial distribution of perovskite surface potential, promote energetic alignment at perovskite/electron transport layer interface, and further reduce the VOC loss. With these optimizations, the champion WBG PSCs achieved an enhanced VOC of 1.327 V and a promising power conversion efficiency (PCE) of 19.44 %. Additionally, these modified WBG PSCs retained 94 % of their initial efficiency after 500 hours of continuous light soaking at maximum power point tracking in ambient conditions. [Display omitted] •This work introduces a novel dual synergistic strategy by combining mixed potassium additives and a 2D passivation layer to inhibit phase segregation and align the energy levels between the perovskite and electron transport layer, effectively reducing voltage loss in wide-bandgap perovskite solar cells.•In-situ PL was used to study phase segregation inhibition and identify energy level mismatch as the major cause of voltage loss, with XRD, SEM, and PLQY supporting this finding.•The optimized devices achieved a PCE of 19.44% and a VOC of 1.327 V, demonstrating significant advantages over current technologies and maintaining 94% of their initial efficiency under continuous light soaking for 500 hours.