Controlled synthesis of ZnO spindles and fabrication of composite photoanodes at low temperature for quasi-solid state dye-sensitized solar cells

In this paper, by altering reactants concentration, ZnO spindles with different sizes were controllably prepared through a fast precipitation process in aqueous solution. Some important characteristics such as specific area, macropore structure, light scattering and electron transport properties of the photoanodes were systematically investigated. The results showed that photoanodes composed of small-sized ZnO spindles had a larger specific area for dye-loading, while the large-sized ZnO spindles had more efficient light scattering and electron transport properties. Furthermore, to combine the advantages of different sized ZnO particles, composite photoanodes were fabricated by mixing together ZnO spindles of different sizes. Compared with the dye sensitized solar cells (DSCs) using photoanodes with single-sized ZnO spindles, the devices based on composite photoanodes showed a higher short-circuit photocurrent density without obvious decrease in open-circuit voltage and fill factor. As a result, photovoltaic performances of the DSCs were improved remarkably.