Holistic Defect Passivation by a Dual-Additive Strategy Enables Efficient and Stable Wide Bandgap Perovskite Solar Cells and Perovskite/CZTSSe Tandem Solar Cells

Wide bandgap (1.65–1.7 eV) inverted perovskite solar cells (WBG PSCs) are crucial top subcells of perovskite-based tandem solar cells (TSCs) to achieve next-generation superhigh-efficiency photovoltaic devices. The challenges in WBG PSCs include phase instability and nonradiative recombination in the bulk and at interfaces. To address these issues, a dual-additive strategy was developed utilizing functional molecules such as (aminomethyl)phosphonic acid (AMP) and 4-chlorobenzenesulfonate (4Cl-BZS) to synergistically improve the crystal quality and passivate interface defects of WBG PSCs. Specifically, AMP mainly settles at the bottom interface of the perovskite, leading to reduced hole-trap density and improved band alignment of the hole transporting layer/perovskite. In contrast, 4Cl-BZS is prone to distribute on the surface of perovskite films, reducing the electron-trap density at the perovskite/C 60 interface by passivating undercoordinated Pb 2+ ions. Consequently, the holistic defect passivation in the bulk and interfaces enables WBG PSCs with a champion power conversion efficiency (PCE) of 23.05%. The devices can retain 80% of their initial efficiency for 800 h after maximum power point tracking under continuous one sun illumination and 1300 h after annealing at 85 °C in N 2, respectively. Moreover, based on this dual-additive strategy, four-terminal (4-T) perovskite/CZTSSe TSCs achieved a record PCE of 24.43%. This study offers crucial insights into the dual-additive strategy for the holistic defect passivation and the development of efficient and stable WBG PSCs and perovskite-based TSCs.