Polyvinylpyrrolidone-modified indium tin oxide as an electron-collecting electrode for inverted polymer solar cells

We report on the photovoltaic properties of inverted polymer solar cells that use a polyvinylpyrrolidone (PVP) modified indium tin oxide (ITO) layer as the electron-collecting electrode. An ultrathin PVP layer, prepared by spin-coating, on top of ITO, was used to induce a reduction of its work function, allowing it to act as an electron-collecting electrode. Devices made on pristine ITO showed s-shape current-voltage characteristics, which were removed after exposure to ultraviolet radiation due to a reduction of the work function of ITO. Inverted solar cells with ITO/PVP electrodes yield efficiencies comparable to devices with ITO/ZnO electron-selective electrodes. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4745772]