Investigation of a Solution-Processable, Nonspecific Surface Modifier for Low Cost, High Work Function Electrodes.

We demonstrate the ability of the highly fluorinated, chemically inert copolymer poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) to significantly increase the work function of a variety of common electrode materials. The work function change is hypothesized to occur via physisorption of the polymer layer and formation of a surface dipole at the polymer/conductor interface. When incorporated into organic solar cells, an interlayer of PVDF-HFP at an Ag anode increases the open circuit voltage by 0.4 eV and improves device power conversion efficiency by approximately an order of magnitude relative to Ag alone. Solution-processable in air, PVDF-HFP thin films provide one possible route toward achieving low cost, nonreactive, high work function electrodes.