The effects of the solvent ratio on the electron transport for non-sintering flexible TiO2 photoanodes

Chemically modified TiO2 colloidal paste with a mixed solvent of water and t-butanol are developed for preparation of dye-sensitised photoanodes on plastic indium-tin oxide (ITO)-coated polyethylene-naphthalate (PEN) substrates. The effects of the solvent ratio on the rheological behaviour of the binder-free paste and the contact angle between the paste and the substrate for TiO2 photoanodes are scrutinised. First, tests of the rheological behaviour revealed that the increasing content of water leads to a decrease in the viscosity of the paste. Second, the dependence of the contact angle on the content of t-butanol is attributed to the trends of surface tension. Third, both the rheological properties and the contact angle influence the microstructure and morphology of the TiO2 coating on the ITO-PEN surface. Finally, the EIS results confirm that electron transport and recombination are significantly influenced for the mixed case. All of these results enable the optimisation of the connection in the photoanodes, achieving the highest energy conversion efficiency of 5.30%.