PEDOTs-PCnBMs polymer-fullerene BHJ solar cells: Quantum mechanical calculations of photovoltaic and photophysical properties

► The performance of polymer-fullerene solar cell is optimized by reducing energy gaps. ► Trifluoro PEDOT/C70 fullerene is the best, out of 24 blends, for PCE. ► HOMOs are localized on the donor subunits, and LUMOs on the bridges between them. ► Functionalizing donor subunits enhances the charge transfer to an acceptor. ► PCE increases with increasing βxxx, μx, and chemical shifts.