Cross-linkable fullerene interfacial contacts for enhancing humidity stability of inverted perovskite solar cells

In situ cross-linking encapsulation has been demonstrated to be an efficient strategy for enhancing the humidity stability of perovskite solar cells (PSCs). In this study, a novel cross-linkable fullerene derivative, namely 1-(p-benzoate-(p-methylvinylbenzene)-indolino[2,3][60] fullerene (FPPS), was readily synthesized from commercially available building blocks in two steps. This FPPS was employed as an interfacial modifier on perovskite surfaces in inverted planar p–i–n PSCs. Owing to the fast interfacial charge extraction and efficient trap passivation, PSCs based on the cross-linked FPPS (C-FPPS) exhibited excellent performance. The PSCs had a top-performing power conversion efficiency (PCE) of 17.82% with negligible hysteresis, compared to the control devices without C-PFFS (16.99%). Moreover, the strong water resistance of the C-FPPS interfacial layer distinctly enhances the ambient stability of PSC devices, exhibiting a t80 (the time required to reach 80% of the initial PCE) of 300 h under high-humidity conditions. This significantly surpasses the control devices, whose t80 was only 130 h. These results demonstrate that cross-linkable fullerene derivatives can be promising interfacial materials for designing high-efficiency, hysteresis-free, air-stable PSCs.