Herein we report a simple n-doping method to enhance the performance of perovskite solar cells with a planar heterojunction structure.
We report a novel fluorene-based polyelectrolyte carrying hexafluorophosphate counterions to dope into PCBM as an electron transporting layer (ETL).
The device performance is enhanced by doping a small percentage of polyethylenimine (PEI) into the PCBM.