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 t(80) (the time required to reach 80% of the initial PCE) of 300 h under high-humidity conditions. This significantly surpasses the control devices, whose t(80) 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.