Dual‐Site Synergistic Regulation Enabled Interface Passivation and Strain Release Toward Efficient Perovskite Solar Cells

The continuous breakthroughs in photovoltaic conversion efficiency (PCE) of inverted perovskite solar cells (PSCs) demonstrate the enormous potential for commercial application. However, accumulating numerous defects at the buried interface and residual strain within the perovskite film severely constrain the further improvement in PCE and stability of the optoelectronic device. Herein, two benzyl phosphoric acids, brominated benzyl phosphate (4‐BrBPA) and methoxy‐substituted benzyl phosphate (4‐MeOBPA), both containing double binding sites were assembled between [4‐(3,6‐dimethyl‐9 H ‐carbazol‐9‐yl)butyl]phosphonic acid (Me‐4PACz) hole transport layers (HTLs) and perovskite as buried interface modifiers. More interestingly, the dipole orientation of 4‐BrBPA aligned with Me‐4PACz, which can promote interface energy level alignment, and facilitate carrier extraction and transport. In addition, the phosphate groups (─PO 3 H 2 ) group and Br atom in 4‐BrBPA can chelate with uncoordinated Pb 2+ and vacancy I − , which will effectively achieve perovskite interfacial defect passivation and strain release. Consequently, the PSCs based on 4‐BrBPA interface layer achieve champion efficiency of 26.62% (certified 26.22%). Moreover, this strategy is extended to wide‐bandgap (1.77 eV), large‐area (1 cm 2 ) PSCs, and mini‐module (11.3 cm 2 ), resulting in PCEs of 21.64%, 24.43%, and 21.08%, respectively. The optimized PSCs demonstrate excellent operational and storage stability. This work provides an effective strategy for interface modification and strain regulation.