PCBM doped with fluorene-based polyelectrolytes as electron transporting layers for improving the performance of planar heterojunction perovskite solar cells.

We report a novel fluorene-based polyelectrolyte carrying hexafluorophosphate counterions to dope into PCBM as an electron transporting layer (ETL). Inverted planar heterojunction perovskite solar cells showed improved photovoltaic performance, including short-circuit current density, the fill factor, and power conversion efficiency, compared with the one using pure PCBM as an ETL.