An n-type naphthalene diimide ionene polymer as cathode interlayer for organic solar cells

Polymer solar cells (PSCs) based on non-fullerene acceptors have the advantages of synthetic versatility, strong absorption ability, and high thermal stability. These characteristics result in impressive power conversion efficiency values, but to further push both the performance and the stability of PSCs, the insertion of appropriate interlayers in the device structure remains mandatory. Herein, a naphthalene diimide-based cathode interlayer (NDI-OH) is synthesized with a facile three-step reaction and used as a cathode interlayer for fullerene and non-fullerene PSCs. This cationic polyelectrolyte exhibited good solubility in alcohol solvents, transparency in the visible range, self-doping behavior, and good film forming ability. All these characteristics allowed the increase in the devices' power conversion efficiencies (PCE) both for fullerene and non-fullerene-based PSCs. The successful results make NDI-OH a promising cathode interlayer to apply in PSCs.