Fabrication of TiO 2 hollow microspheres assembly from nanosheets (TiO 2 -HMSs-NSs) with enhanced photoelectric conversion efficiency in DSSCs and photocatalytic activity

Abstract Fabrication of TiO 2 hollow microspheres (TiO 2 -HMSs) with complex structure is of great importance but remains a great challenge. In this paper, hierarchical TiO 2 hollow microspheres assembly from nanosheets (TiO 2 -HMSs-NSs) were prepared by hydrothermal treatment of TiO 2 -HMSs precursor in NaOH solution and followed by acid wash and calcination. The effect of hydrothermal reaction time on the structure and photoelectric conversion performances of TiO 2 -HMSs-NSs film solar cells was systematically studied. It was found that both the BET surface area and photocatalytic activity of TiO 2 -HMSs-NSs, in photocatalytic degradation of Brilliant Red X-3B dye, are positively related to the hydrothermal reaction time (from 0 to 3 h). The BET specific area of TiO 2 -HMSs-NSs steady increase from 21 m 2  g −1 of TiO 2 -HMSs precursor (H0) to 184 m 2  g −1 (H3), improved by a factor of 8.76, while the photocatalytic activity of H3 increased 7.50 times when compared with that of H0 sample. The highest photoelectric conversion efficiency (5.97%) of TiO 2 -HMSs-NSs film solar cell was obtained for H2 sample, exceeding that of TiO 2 -HMSs precursor (H0) based film solar cell (3.75%) with the same film thickness by a factor of 1.6. The improved photoelectric conversion efficiency of TiO 2 -HMSs-NSs based solar cell was attributed to the unique hierarchical hollow structure, which results in a good contact between TiO 2 and FTO glass, enlarged pore volume, enhanced adsorption to sensitizer and improved light scattering ability.