Cross-Linkable, Solvent-Resistant Fullerene Contacts for Robust and Efficient Perovskite Solar Cells with Increased J and V.

The active layers of perovskite solar cells are also structural layers and are central to ensuring that the structural integrity of the device is maintained over its operational lifetime. Our work evaluating the fracture energies of conventional and inverted solution-processed MAPbI perovskite solar cells has revealed that the MAPbI perovskite exhibits a fracture resistance of only ∼0.5 J/m, while solar cells containing fullerene electron transport layers fracture at even lower values, below ∼0.25 J/m. To address this weakness, a novel styrene-functionalized fullerene derivative, MPMIC, has been developed as a replacement for the fragile PCBM and C transport layers. MPMIC can be transformed into a solvent-resistant material through curing at 250 °C. As-deposited films of MPMIC exhibit a marked 10-fold enhancement in fracture resistance over PCBM and a 14-fold enhancement over C. Conventional-geometry perovskite solar cells utilizing cured films of MPMIC showed a significant, 205% improvement in fracture resistance while exhibiting only a 7% drop in PCE (13.8% vs 14.8% PCE) in comparison to the C control, enabling larger V and J values. Inverted cells fabricated with MPMIC exhibited a 438% improvement in fracture resistance with only a 6% reduction in PCE (12.3% vs 13.1%) in comparison to those utilizing PCBM, again producing a higher J.