Microwave-assisted hydrothermal synthesis of TiO2 spheres with efficient photovoltaic performance for dye-sensitized solar cells

In this article, we present a microwave-assisted synthetic method to form micrometer size mesoporous TiO2 sphere for the application as photoanodes in dye-sensitized solar cells (DSCs). Thematerial properties and photovoltaic performances are compared with commercial TiO2 paste and mesoporous sphere both fabricated by traditional hydrothermal method. The mesoporous TiO2 spheres were synthesized by controlled hydrolysis and subsequently grew with microwave heating. The microwave-synthesized mesoporous TiO2 spheres with diameters in the range from 400 to 600 nm are composed of 10 nm nanocrystals as building blocks and possess anatase crystal structure and high surface area (132.49 m(2) g(-1)). The photovoltaic performances of DSCs using the photoanodes derived from hydrothermal mesoporous spheres and the microwave-synthesized mesoporous spheres yielded overall power conversion efficiencies of 5.89 and 5.43 % with the less volatile 3-methoxypropionitrile solvent electrolyte. The reaction time for crystallization process in the microwave heating was greatly shortened from 16 h to 80 min. The microwave-synthesized mesoporous spheres exhibit higher short-circuit photocurrent than commercial available hydrothermal nanocrystalline (JGC 18NRT). This is due to its superior scattering power in the entire visible and near-infrared regions, which enhanced the optical path in the photoactive medium. The incident photon to electron conversion efficiency results reflect that the better short-circuit current in the device made with microwave-synthesized mesoporous spheres electrodes is resulted from the increased light-harvesting efficiency in the red region. On the optimum condition with acetonitrile-based electrolyte, the microwave-synthesized mesoporous spheres electrode could deliver conversion efficiency of 6.19 % and higher value of 6.92 % by adding extra scattering layer of commercial paste (CCIC, HPW-400).