Controlled synthesis of symbiotic structured TiO2 microspheres to improve the performance of dye-sensitized solar cells

Abstract

Due to the excellent light scattering and dye loading ability, mesoporous TiO2 microspheres are vastly utilized in dye-sensitized solar cells (DSSCs) to serve as photoanode. Despite of the good electron transport properties due to the unique geometry of mesoporous TiO2 microspheres, the existence of large holes between adjacent microspheres limits the formation of necking and deteriorates the device performance. In this work, we report a simple 2-step process to synthesize symbiotic structured TiO2 microspheres treated with different ammonia concentrations. Meanwhile, the nitrogen doping of TiO2 microspheres is also introduced while ammonia treatment is performed and as a result, the charge transport property is greatly improved. By using the symbiotic structured TiO2 to substitute pure TiO2 microspheres photo anode, the photovoltaic performance of DSSCs was greatly improved from 8.77% to 9.58%. It is demonstrated that the improvement is mainly due to the improved charge transportation property of symbiotic structured TiO2 photoanodes and the effective suppression of carrier recombination. The results give us a comprehensive understanding of electron transport and recombination mechanism in mesoporous TiO2 microspheres, which will provide significant information for the optimization of TiO2 structures for DSSC and other optoelectrical applications.