Freeze-casted TiO2 photoelectrodes with hierarchical porous structures for efficient light harvesting ability in dye-sensitized solar cells

Abstract Hierarchical porous TiO2 photoelectrodes fabricated using freeze-casting method were introduced for efficient light scattering effect in dye-sensitized solar cells (DSSCs). Unique porous microstructures (lamellar or interconnected pore structures) were obtained by controlling the concentrations of slurry and binder. The freeze-casted photoelectrodes exhibited stronger light scattering effects than conventionally screen-printed mesoporous photoelectrode. This is attributed to a great number of scattering sites (interconnected pores with the size range of 50–500 nm), which are uniformly distributed throughout the entire freeze-casted photoelectrodes, resulting in an enhancement of the light pathway. As a result, despite a lower dye adsorption and less kinetically efficient charge transport, DSSCs based on freeze-casted photoelectrodes showed significant conversion efficiencies (3.64%) compared with those of DSSCs based on conventionally screen-printed photoelectrodes (2.57%). This study suggests that the hierarchical porous photoelectrodes fabricated using the freeze-casting are promising candidates for highly efficient DSSCs.