Double-layer composite film based on hollow TiO2 boxes and P25 as photoanode for enhanced efficiency in dye-sensitized solar cells

• A novel TiO2 double-layer composite film is successfully fabricated.
• The TiO2-HB overlayer exhibited intense scattering ability.
• The P25 particles underlayer can enlarge the contact area and increase the contact points between TiO2-HB and FTO glass.
• TiO2-DLL film cells have the maximum conversion efficiency.

A TiO2 double-layer composite film consisting of hollow TiO2 boxes (HB-TiO2) as overlayer and commercial-grade TiO2 nanoparticles (P25) as underlayer is designed as the photoelectrode of dye-sensitized solar cells (DSSCs). The hollow TiO2 box has been employed as light-scattering part to increase the optical length in the film and enhance light-harvesting. It was found that the double-layer film cell with lower absorbed dye achieved the highest conversion efficiency and reach up to a maximum value of 6.4%, which is 226% higher than that of pure HB-TiO2 film cell (η = 1.96%) and 57.2% higher than that of pure P25 particles film cell under identical film thickness at a constant irradiation of 100 mW cm−2. The enhanced efficiency of double-layer film can be attributed to its light-scattering capability.

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