Low temperature chemically sintered nano-crystalline TiO2 electrodes for flexible dye-sensitized solar cells

Chemically sintered, mesoporous TiO2 electrodes with improved interparticle contact and bond strength were prepared on indium tin oxide (ITO) coated plastic substrates in the absence of any organic binders, using hydrochloric acid as the sole reagent to encourage interparticle connectivity. The degree of chemical sintering as a function of the HCl concentration was evaluated using a newly developed nanoscratch technique. The theological properties of the titania paste was influenced by the HCl as was the resultant bonding of the TiO2 grains both to each other and to the substrate. The mechanism for the low temperature chemical sintering could be due to the surface modification of titania particles during the HCl treatment and subsequent improved chemical bonding at particle contact points. The improved strength and chemical bonding of the particle network led to improved photovoltaic properties of the resulting solar cells. The highest value of light to electrical energy conversion efficiency obtained was 5% for the plastic-based dye-sensitized solar cells, under 1 sun (100 mW cm(-2)). This thus represents a novel method for ensuring the appropriate titania nanomorphology using room temperature treatment on a flexible substrate, as compared to the required thermal treatments in excess of 400 degrees C normally required in conventional ITO glass-based dye-sensitized solar cell devices. (C) 2010 Elsevier B.V. All rights reserved.