Nanotextured 2D/3D Perovskite Heterojunctions With Built‐in Field Engineered by Halide Composition for 25.5% Efficiency Solar Cells

ABSTRACT Two‐dimensional/three‐dimensional (2D/3D) perovskite (PVK), combining the excellent photovoltaic performance of 3D and stability of 2D PVK, holds the potential to address the efficiency‐stability trade‐off. However, retarded carrier transport kinetics at the 2D/3D heterointerface limit further performance improvement of 2D/3D PVK solar cells (PSCs). Herein, we propose a band energy and morphology synergy regulation strategy, fabricating 2D/3D PSCs with nanotextured (NT) surfaces via halide composition engineering and solvent‐induced surface reconstruction. Halide modulation in the 2D layer strengthens the built‐in electric field, promoting charge separation and suppressing non‐radiative recombination; the NT structure extends the optical pathlength, boosting light‐harvesting efficiency. The champion 2D/3D‐NT PSCs achieves a 25.55% power conversion efficiency ( PCE ), outperforming the conventional device (22.77%) with a 7% higher short‐circuit current density. It retains 94% of its initial PCE after 1200 h of ambient storage at 30°C and a relative humidity of 40% ± 10%, demonstrating excellent long‐term ambient storage stability. This work provides novel insights for resolving the efficiency‐stability dilemma through optoelectronic co‐optimization.