Passivating Defects and Promoting Charge Transport for Efficient Wide‐Bandgap Perovskite Solar Cells Via Dipolar Conjugated Ligand Molecules π‐π Stacking

ABSTRACT Wide‐bandgap (WBG, 1.77–1.80 eV) perovskite solar cells (PSCs) are essential for constructing tandem solar cells, indoor photovoltaics, and building‐integrated applications. However, the high Br/I ratio in WBG perovskites typically leads to uncontrollable and nonuniform crystallization, thereby resulting in abundant defects, phase segregation and inefficient charge transport, finally deteriorating device power conversion efficiency (PCE) and durability. Herein, the carboxyl functionalized conjugated molecules, namely p‐phthalic acid (PTA), are leveraged to manipulate grain boundaries (GBs) of perovskite films, effectively passivating the defects, suppressing phase segregation and promoting charge transport. Furthermore, theoretical results reveal that intermolecular π‐π interactions can further reinforce the interaction of PTA with two neighboring perovskite crystal grains and promote carrier transport at GBs. Due to minimized non‐radiative recombination loss, the PTA‐modified 1.79 eV WBG PSCs fulfil a champion PCE of 20.55% accompanied by a high fill factor of 85.90%, ranking among the highest PCEs ever reported for 1.77–1.80 eV bandgap PSCs. Moreover, the PTA‐modulated WBG devices maintained over 80% of their initial PCEs after 500 h of continuous operation.