Funnel-structured TiO ₂ electrode for improved charge extraction in dye-sensitized solar cell

We here show that the current density and efficiency of dye-sensitized solar cell (DSSC) can be much enhanced by generating more bulky-structured funnels inside the typical TiO ₂ electrode. This approach is fundamentally based on the pulsed laser-induced desorption and melting of TiO ₂ nanoparticles. Three-beam interference was utilized to fabricate the periodic electrode structure. While the dye coverage was little influenced by this process because a small volume fraction of the electrode was converted into the bulky structure, the photoexcited electrons could be more effectively extracted owing to the prolonged diffusion length. As a result, the photocurrent density and efficiency of DSSCs were much improved. The enhancement of both factors was reliably ascertained by the multiple-cell characterization. The funnel cells exhibited an average short-circuit current density of 19.77 mA/cm ² and an efficiency of 9.44%, while 17.30 mA/cm ² and 8.27% were obtained from the reference cells.