Highly efficient charge collection in dye-sensitized solar cells based on nanocomposite photoanode filled with indium-tin oxide interlayer

Owing to the electron scattering at the surface, the grain boundaries, and the defects of titanium dioxide (TiO2) nanoparticles (NPs), the electron diffusion length in the mesoporous TiO2 layer is shorter than that of TiO2 bulk single crystal, leading to a significantly increased charge recombination in dye-sensitized solar cells (DSSCs), herein TiO2 photoanode sandwiching a layer of high-mobility indium-tin-oxide (ITO) granular film to form a TiO2/ITO/TiO2 (TIT) photoanode. A large number of ITO NPs would penetrate deep into the mesoporous TiO2 bottom layer to form the interconnected network, which can be served as high-speed electron transport channels, thereby enhancing the electron transfer and collection abilities. Compared with the reference device assembled with TiO2/TiO2 (TT) photoanode, an increase of 14.78% in power conversion efficiency (PCE) was obtained for the optimized TIT device (8.23 vs 7.17%), which can be ascribed to the synergistic effects of faster electron transport and less charge recombination. Moreover, the electron transfer ability of TIT layer was also superior to TiO2-ITO composite photoanode, in which ITO NPs were uniformly dispersed in the TiO2 mesoporous layer. Overall, this method paves a facile and effective way to improve the photovoltaic performance for highly efficient DSSCs of practical significance.