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

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 MAPbI₃ perovskite solar cells has revealed that the MAPbI₃ perovskite exhibits a fracture resistance of only ∼0.5 J/m², while solar cells containing fullerene electron transport layers fracture at even lower values, below ∼0.25 J/m². To address this weakness, a novel styrene-functionalized fullerene derivative, MPMIC₆₀, has been developed as a replacement for the fragile PC₆₁BM and C₆₀ transport layers. MPMIC₆₀ can be transformed into a solvent-resistant material through curing at 250 °C. As-deposited films of MPMIC₆₀ exhibit a marked 10-fold enhancement in fracture resistance over PC₆₁BM and a 14-fold enhancement over C₆₀. Conventional-geometry perovskite solar cells utilizing cured films of MPMIC₆₀ 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 C₆₀ control, enabling larger V_OC and J_SC values. Inverted cells fabricated with MPMIC₆₀ exhibited a 438% improvement in fracture resistance with only a 6% reduction in PCE (12.3% vs 13.1%) in comparison to those utilizing PC₆₁BM, again producing a higher J_SC.