Enhanced stability of perovskite solar cells using hydrophobic organic fluoropolymer

Hydrophobic organic fluoropolymers (HOFPs) with excellent hydrophobic, heat-resistant, and sunlight-transparent properties were synthesized by emulsion polymerization. The HOFP layer was inserted between a (FAMA)Pb(IBr)3 active layer and a hole transport layer in perovskite solar cells (PSCs). The performance of the resulting PSC devices depends highly on the thickness of the HOFP layer. Under optimized HOFP thickness, a moderate steady power conversion efficiency (PCE) of 16.9% was achieved. Remarkably, the optimized PSCs without any encapsulation exhibit outstanding shelf stability under ambient conditions, and the PCE could maintain 80% of its initial value after 2400 h (100 days), which was among the ever reported best stability whereas, the reference device without HOFP shows rapid severe degradation after only a few days. The significantly improved stability of PSCs was mainly ascribed to the impermeable barrier properties of the HOFP layer, which protect the perovskite active layer against moisture and oxygen from the ambient atmosphere.