Halides‐Enhanced Buried Interfaces for Stable and Extremely Low‐Voltage‐Deficit Perovskite Solar Cells

Abstract The perovskite buried interfaces have demonstrated pivotal roles in determining both the efficiency and stability of perovskite solar cells (PSCs); however, challenges remain in understanding and managing the interfaces due to their non‐exposed feature. Here, we proposed a versatile strategy of pre‐grafted halides to strengthen the SnO 2 –perovskite buried interface by precisely manipulating perovskite defects and carrier dynamics through alteration of halide electronegativity ( χ ), thereby resulting in both favorable perovskite crystallization and minimized interfacial carrier losses. Specifically, the implementation of fluoride with the highest χ induces the strongest binding affinity to uncoordinated SnO 2 defects and perovskite cations, leading to retarded perovskite crystallization and high‐quality perovskite films with reduced residual stress. These improved properties enable champion efficiencies of 24.2% (the control: 20.5%) and 22.1% (the control: 18.7%) in rigid and flexible devices with extremely low voltage deficit down to 386 mV, all of which are among the highest reported values for PSCs with a similar device architecture. In addition, the resulting devices exhibit marked improvements in the device longevity under various stressors of humidity (>5000 h), light (1000 h), heat (180 h), and bending test (10 000 times). This method provides an effective way to improve the quality of buried interfaces toward high‐performance PSCs.