Pore-size effect on photovoltaic performance of dye-sensitized solar cells composed of mesoporous anatase-titania

Abstract

The effect of the pore size of mesoporous anatase-TiO 2 on the photovoltaic performance of dye-sensitized solar cells (DSSCs) is investigated. The mesoporous TiO 2 particles are synthesized by two different methods using a soft template of tri-block copolymer and a hard template of mesoporous ZnO/Zn(OH) 2-composite. These methods produce the same high surface area ( S BET ∼ 210 m 2 g −1) but different pore sizes of 6.8 and 3.0 nm, respectively. With the mesoporous TiO 2 having larger pores, the photo-conversion efficiency ( η) is increased significantly to 6.71%, compared with 5.62% that is typically achieved using P25 TiO 2 nanopowders. By comparison, only half the performance (3.05%) has been observed with mesoporous TiO 2 that has small pores. Mesoporous TiO 2 with suitable pore sizes (∼6.8 nm) makes the most of its high surface area and thereby allows a high uptake of dye to enhance the current density. In contrast, the low efficiency of mesoporous TiO 2 with small pores is attributed to the low uptake of dye due to the smaller pore size (∼3.0 nm), which blocks the diffusion and adsorption of dye molecules through the pores.