Double light-scattering layer film based on TiO2 hollow spheres and TiO2 nanosheets: Improved efficiency in dye-sensitized solar cells

Highlights: ► A novel TiO2 double-layer composite film is successfully fabricated. ► The TiO2-hollow spheres overlayer exhibited intense scattering ability. ► The TiO2-nanosheets underlayer can enlarge the contact area and increase the contact points between TiO2 photoelectrode and FTO glass. ► TiO2-double light-scattering layer film cells have the maximum conversion efficiency. -- Abstract: A novel TiO2 double light-scattering layer (TiO2-DLL) film consisting of TiO2 hollow spheres (TiO2-HS) as overlayer and TiO2 nanosheets (TiO2-NS) as underlayer was designed as the photoelectrode of dye-sensitized solar cells (DSSCs). The photoelectric conversion performances of DSSCs based on TiO2-HS film, TiO2-NS film, and TiO2-DLL film were investigated. It was found that the TiO2-DLL film cell achieved the highest conversion efficiency and reached up to a maximum value of 5.08%, which is 23.3% higher than that of TiO2-HS film cell (η = 3.62%) and 8.3% higher than that of TiO2-NS film cell (η = 4.31%) under identical film thickness at a constant irradiation of 100 mW cm−2. The enhanced efficiency of TiO2-DLL film can be attributed to its relatively high specific surface area and enhanced light-scattering capability. Furthermore, the TiO2-NS underlayer ensures good electronic contact between TiO2 film and the F-doped tin oxide (FTO) conducting glass