Dry plasma reduction to synthesize supported platinum nanoparticles for flexible dye-sensitized solar cells

A dye-sensitized solar cell (DSC) can be a promising device as a ubiquitous power source, if it is flexible. Since the annealing step of TiO2 nanoparticles (NPs) is a major obstacle to using a thermoplastic film as a transparent photoanode (PA), a transparent counter electrode (CE) using a thermoplastic film as a photo illumination window can be a reasonable alternative for developing a flexible DSC together with a non-transparent PA using a flexible metal foil coated with TiO2 NPs. To achieve this purpose together with improving photo conversion efficiency, it is necessary to deposit highly active supported platinum (Pt) NPs with homogeneous size dispersity on the surface of a transparent conducting oxide (TCO). Various methods developed so far, however, have critical process restrictions such as high temperature, low pressure, liquid environment, and chemical toxicity, which render them difficult to develop into an economic continuous process. Here we report an excellent method of directly depositing Pt-NPs on the surface of a TCO using dry plasma reduction (DPR) under atmospheric pressure without using any toxic chemicals while keeping the temperature below 70 degrees C. After determining an optimum concentration of Pt precursor solution to maximize the photovoltaic performance of DSCs, we successfully demonstrate a new flexible DSC which is composed of a non-transparent PA using thin Ti foil coated with TiO2 NPs and a transparent CE, as a photo illumination window, using Pt-NPs supported on a PET/ITO film.