Modification of the TCO surface with a redox-active surface modifier is a possible approach toward enhancing OPV efficiency by providing an efficient charge-transfer pathway between either hole- or electron-harvesting contacts and the organic active layer. Two different deposition techniques were used with perylene diimide (PDI) surface modifiers in the study: adsorption from solution (SA) and spin coating (SC), to create three types of monolayer films on ITO: SA PDI–phenyl–PA, SA PDI–diphenyl–PA, and SC PDI–phenyl–PA. These thin films, designed to act as “charge-transfer mediators”, were used to study relationships between molecular structure, electron-transfer (ET) kinetics, and electronic structure.
A simple solution-based electrical doping technique could help reduce the cost of polymer solar cells and organic electronic devices, potentially expanding the applications for these technologies. By enabling production of efficient single-layer solar cells, the new process could help move organic photovoltaics into a new generation of wearable devices and enable small-scale distributed power generation.