Conventional polymer solar cells with power conversion efficiencies increased to >9% by a combination of methanol treatment and an anionic conjugated polyelectrolyte interface layer

The power conversion efficiency of PTB7:PC₇₁BM polymer solar cells was improved to 9.1% by treatment with methanol followed by a water- and alcohol-soluble conjugated polyelectrolyte cathode interface layer. This improvement in efficiency is a result of a combination of an enriched PC₇₁BM ratio on the top surface in the active layer and the presence of the preferred dipole at the cathode interface.