Phenethylammonium Iodide Passivation Layers for Flexible Planar Perovskite Solar Cells

Flexible perovskite solar cells (PSC) represent a viable technology for applications requiring high power-to-weight ratios, seamless integration onto a variety of shapes, and low embedded energy. Strategies to boost the performance of flexible PSC, which still lag behind their rigid counterparts, include passivation of the perovskite surface with ammonium salts. Here, we report the optimization of low temperature solution processed phenethylammonium iodide (PEAI) layers to passivate triple cation perovskite films as an effective strategy for flexible planar PSCs. The best PEAI-passivated cell delivers a maximum power conversion efficiency (PCE) of 15.2% in forward scan, which is 22% higher in relative terms compared to non-passivated devices, due to a major improvement in both VOC and FF. Optoelectrical characterization highlights that PEAI films effectively reduce trap-mediated charge recombination, without hindering charge transport across the perovskite/hole transport layer interface. Light soaking stability of non-encapsulated cells with PEAI layers is also greatly enhanced, retaining 80% of the initial PCE for twice as long as the reference devices, therefore proving the potential of this material for the development of efficient and durable flexible PSCs.