Indium tin oxide modified by titanium dioxide nanoparticles dispersed in poly(N-vinylpyrrolidone) for use as an electron-collecting layer in organic solar cells with an inverted structure

We report on the photovoltaic properties of polymer solar cells with an inverted structure wherein the electron-collecting electrode comprises an indium tin oxide (ITO) electrode coated with titanium dioxide (TiO2) nanoparticles dispersed into poly(N-vinylpyrrolidone) (PVP). The optimization of performance of polymer solar cells in which the TiO2 concentration in PVP was varied is presented. Pristine solar cells with the TiO2: PVP-coated ITO electrodes showed S-shape current-voltage characteristics. The S-shaped feature disappeared after the continuous exposure of the solar cells to light from an AM 1.5G solar simulator, leading to an improved device performance compared with solar cells that use an ITO or ITO/TiO2 electron-collecting electrodes.