Enhancing the Interfacial Adhesion by a Novel Benzofuran-Substituted Self-Assembled Molecules for Thermal Cycle...

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 cm²), 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.