Rhenium oxide as an efficient p-dopant to overcome S-shaped current density-voltage curves in organic photovoltaics with a deep highest occupied molecular orbital level donor layer

Effect of p-dopants in a p-doped hole transport layer inserted between indium tin oxide and a donor layer of α,α′-bis(2,2-dicyanovinyl)-quinquethiophene with a deep highest occupied molecular orbital level is reported to remove the S-shape in the organic photovoltaics (OPV) cell. Among the p-dopants of ReO3, MoO3, WO3, and CuI, ReO3 possesses the largest work function and turns out to be the most efficient p-dopant to remove the S-shape of the current density-voltage curve in the OPV cells. The rest of the dopants could not get rid of the S-shape, even with a doping concentration of 25 mol. %. The difference among the dopants can be understood by the different charge generation efficiency of the dopants.