Dye-sensitized solar cells based on TiO2 hollow spheres/TiO2 nanotube array composite films

•A novel bilayer structure electrode was made with the TiO2 hollow spheres/TiO2 nanotube arrays for DSSC applications.•TiO2 nanotube arrays synthesized by an optimized process of three-step anodization are applied to DSSCs.•TiO2 hollow spheres synthesized using colloidal carbon spheres as template are applied to DSSC.•Influence of light-scattering effect of TiO2 hollow spheres on the DSSC performance is investigated.•High efficiency of 6.90% achieved in the DSSC through using TiO2 hollow spheres as light-scattering layer. In this study, a novel double-layer electrodes with TiO2 nanotube (NT) arrays as underlayer and TiO2 hollow spheres (HSs) as overlayer film have been fabricated for application in DSSCs. Both the NTs and HSs have been synthesized and the morphology and structure were characterized by XRD, SEM and TEM. Moreover, the properties of DSSCs were investigated by UV–vis reflectance spectra, IPCE and current–voltage curves, respectively. Owing to the hollow structure, the DSSC using TiO2 HSs as light-scattering layer exhibits an enhanced light harvesting efficiency, leading to a 23% increment of cell efficiency compared to that pure TiO2 NT films.