Enhancement of the power conversion efficiency of P3HT:PCBM based solar cells by an interfacial effect between P3HT and PEDOT

We report a process that enhances the power conversion efficiency (PCE) of organic solar cells based on poly(3-hexythiophene) and [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM). In this process, the active material is maintained in the liquid state for a prolonged period of time to promote interfacial contact with the poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) buffer layer. It is observed that through this process, the PCE of the device provided a further 19% enhancement on top of the enhancement obtained by the familiar solvent annealing process. This process depends critically on the presence of the PEDOT:PSS buffer layer, and it is hypothesized that the action of this enhancement process involves interfacial interactions between P3HT and PEDOT polymers.