The influence of surface morphology of TiO2 coating on the performance of dye-sensitized solar cells

The optimization of solar energy conversion efficiency of dye-sensitized solar cells (DSSCs) was investigated by the tuning of TiO2 photoelectrode's surface morphology. Double-layered TiO2 photoelectrodes with four different structures were designed by the coating of TiO2 suspension, incorporated with low and high molecular weight poly(ethylene glycol) as a binder. Among these four systems, P2P1, where P1 and P2 correspond to the molecular weight of 20,000 and 200,000, respectively, showed the highest efficiency under the conditions of identical film thickness and constant irradiation. This can be explained by the larger pore size and higher surface area of P2P1 TiO2 electrode than the other materials as revealed by scanning electron microscopic (SEM) and Brunauer–Emmett–Teller (BET) analyses. Electrochemical Impedance Spectroscopy (EIS) analysis shows that P2P1 formulation displayed a smaller resistance than the others at the TiO2/electrolyte interface. The best efficiency (η) of 9.04% with the short-circuit photocurrent density (Jsc) and open-circuit voltage (Voc) of 18.9 mA/cm2 and 0.74 V, respectively, was obtained for a solar cell by introducing the light-scattering particles to the TiO2 nanoparticles matrix coated on FTO electrode having the sheet resistivity of 8 Ω/sq.