Multifunctional Interface Modifier Enables High‐Performance Wide‐Bandgap Perovskite Solar Cells

Wide‐bandgap (WBG, ≥1.68 eV) perovskite solar cells (PSCs) represent promising top‐cell candidates for monolithic perovskite tandem photovoltaics. However, fast crystallization kinetics of perovskite precursors and incomplete surface coverage of hole‐transporting self‐assembled monolayers (SAMs) commonly degrade perovskite film quality and introduce detrimental defects at the buried interface. Herein, we report a buried‐interface engineering strategy using a rationally designed dioxaboranaphthoanthracene‐based modifier, which exhibits preferential accumulation at the perovskite buried interface. The results support additional interfacial coverage associated with DOBNA‐3PA enrichment, while modulation of perovskite crystallization kinetics enlarges grain size and reduces residual strain, contributing to improved interfacial charge transport. Consequently, the inverted 1.68 eV PSC delivers a champion power conversion efficiency of 24.55% with an open‐circuit voltage of 1.281 V and a fill factor of 85.39%, alongside a negligible hysteresis index of 1.37%. The device retains 94% of its initial efficiency after 1800 h of storage in ambient air (40–45% relative humidity) under ISOS‐D‐1 testing protocols. Notably, this strategy exhibits outstanding generalizability across different perovskite bandgaps, enabling PCEs of 26.44% and 21.04% for 1.54 and 1.78 eV PSCs. This work establishes a dual‐function modifier strategy for improving both perovskite bulk crystallization and buried interface modification, offering a generalizable pathway toward highly efficient and stable WBG PSCs.