Enhancing the Interfacial Adhesion by a Novel Benzofuran‐Substituted Self‐Assembled Molecules for Thermal Cycle Stable Perovskite Solar Cells and Modules

ABSTRACT Inverted perovskite solar cells (PSCs) employing self‐assembled molecules (SAMs) as hole transporting layer (HTL) have achieved markedly improved performance. However, emerging evidence demonstrates that the adhesion weakness between the HTL|perovskite interface hinders the charge transfer and limits the stability of the devices. Herein, a novel SAM featuring a benzofuran substitution, (2‐(5H‐benzofuro[3,2‐c]carbazol‐5‐yl)ethyl)phosphonic acid (BFC‐2PACz) has been designed and synthesized to address this issue. Molecular characterizations demonstrate that the BFC‐2PACz exhibits strong interactions with both the perovskite and NiO x , thus not only improve the coverage of SAM, but also enhance the mechanical adhesion at the interface. By slot‐die coating the mixture of BFC‐2PACz and [4‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl)butyl]phosphonic acid (Me‐4PACz) as HTLs, we have achieved efficiencies of 21.2% and 16.8% based on a wide bandgap (1.68 eV) perovskite for small‐area solar cells and larger‐area solar modules (10.0 cm 2 ), respectively. More importantly, the devices maintain 87% of their initial efficiencies after 720 h of thermal cycling aging and 82% after 1000 h of maximum power point tracking.