Electron transportation and optical properties of microstructure TiO2 films: applied in dye-sensitized solar cells

Micro-structure of TiO2 films in dye-sensitized solar cells (DSSCs) can affect light absorption and electron transportation that impact on the characteristics of current-voltage (J-V). In this paper, films with different surface area, pore size and porosity were obtained by adding different ratio of ethyl cellulose (Ec-S) to pastes, and a photo-electric conversion efficiency (eta) of 7.55% with a short-circuit current density (Jsc) of 16.81 mA . cm(-2) was obtained when the ratio of Ec-S was 10:5. BET results showed that film with this optimum ratio had the most suitable pore size and surface area for good properties of photovoltaic, which had a low reflectivity and high transmission rate, and the efficiency of light utilization was improved. Moreover, measurements by intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS) implied that the electron transport time (tau(d)) increased as the content of Ec-S increased, which was related to the larger surface area. Results of steady-state cyclic voltammetry indicated that diffusion-limited current density (J(lim)) of I-3(-) in TiO2 film increased with its porosity, which revealed that the transportation of redox mediators in the electrolyte was speeded up.