Low-temperature flexible Ti/TiO_2 photoanode for dye-sensitized solar cells with binder-free TiO_2 paste

摘要

An energy-economical dye-sensitized solar cell (DSSC) with highly flexible Ti/TiO_2 photoanode was developed through a low-temperature process, using a binder-free TiO_2 paste. Ti foils, coated with the binder-free TiO_2 films were annealed at various temperature. Scanning electron microscopic (SEM) images of the films show uniform, mesoporous and crack-free surface morphologies as well as interpenetrated TiO_2 network. DSSCs with binder-free TiO_2 films annealed at 450, 350, 250 and 120°C show solar-to-electricity conversion efficiencies (η) of 4.33,4.34, 3.72 and 3.40%, respectively, which are comparable to the efficiency of 4.56% obtained by using a paste with binder and annealing it at 450°C;;this observation demonstrates the benefits of a binder-free TiO_2 paste for the fabrication of energy-fugal DSSCs. On the other hand, when organic binder was used in the TiO_2 paste for film preparation, a drastic deterioration in the cell performance with decreasing annealing temperature is noticed. Laser-induced photo-voltage transient technique is used to estimate the electron lifetime in various Ti/TiO_2 films. Electrochemical impedance spectroscopic (EIS) analysis shows that the lower the annealing temperature of the TiO_2 coated Ti foil, the larger the charge transfer resistance at the TiO_2/dye/electrolyte interface (R_(ct2)).