High-performance dye-sensitized solar cells based on hierarchical yolk-shell anatase TiO2 beads

Yolk-shell TiO2 beads consisting of nanoparticles are synthesized by using a facile hydrothermal method. The influences of hydrothermal reaction temperature on the size of TiO2 particles and the photovoltaic performance of dye-sensitized solar cells (DSSCs) have been investigated in detail. A DSSC based on the yolk-shell TiO2 bead photoelectrode (similar to 15 mu m) exhibits an energy conversion efficiency of 9.05%, which is much higher than that of P25 (7.56%). This can be mainly attributed to the fast electron transport and long electron lifetime resulting in a larger electron diffusion coefficient and higher charge collection efficiency for the former, which are confirmed by intensity-modulated photocurrent spectroscopy (IMPS), intensity-modulated photovoltage spectroscopy (IMVS), and electrochemical impedance spectroscopy (EIS). In addition, the superior light scattering ability of hierarchical yolk-shell TiO2 beads compared to P25 film measured by UV-vis diffuse spectrum also contributes to higher photocurrent and photovoltaic performance.