A novel bilayer photoanode made of carbon nanotubes incorporated TiO2 nanorods and Mg2 + doped TiO2 nanorods for flexible dye-sensitized solar cells

TiO 2 nanorods (NRs), Mg 2   + doped TiO 2 (Mg 2   + /TiO 2 ) NRs, and carbon nanotubes incorporated TiO 2 (CNTs/TiO 2 ) NRs are fabricated from the corresponding electrospun nanofibers (NFs) by ultrasonic treatment , respectively. Then these NRs are made into various photoanodic films through electrospray deposition and hot-compression for flexible dye-sensitized solar cells (FDSSCs). The conversion efficiency of FDSSCs is improved with the CNTs incorporation or the Mg 2   + ions doping of TiO 2 . To further improve the properties of FDSSCs, various bilayer photoanodic films made of the smaller diameter NRs as under-layer and the larger diameter NRs as over-layer are prepared. Finally, a highest conversion efficiency of 3.9% is obtained using the bilayer NRs film composed of the smaller diameter CNTs/TiO 2 NRs and the larger diameter Mg 2   + /TiO 2 NRs. This efficiency is much higher than that of the single-layer NRs film based FDSSCs. This may be attributed to the increased light harvesting resulting from the scattering layer of the larger diameter NRs and the faster electron transport due to the two-level energy steps of the bilayer NRs film.