Optimization of Selective Electrophoretic Deposition and Isostatic Compression of Titania Nanoparticles for Flexible Dye-Sensitized Solar Cells

Flexible photoanodes on PEN/PET based substrates for dye-sensitized solar cells (DSSC) by using electrophoretic deposition (EPD) method for the formation of titania nanoporous layer with titania nanoparticles (P-25) were produced. Considering commercially available titania nanoparticles containing both anatase and rutile phases, the undesired rutile nanoparticles, for DSSC applications, were almost eliminated from the coatings by selective pH adjustment of the EPD solutions without any binders. The coating characteristics and the selective coating capabilities of prepared ethanol and isopropanol based EPD solutions and their acetylacetone additive (as surfactant) alternatives were investigated using zeta potential measurements and mean colloid size analysis. As a subsequent complementary process, deposited films were compressed using Cold Isostatic Pressing (CIP) with an alternative clamping-effect pressure profile in order to increase the interparticular coherence and the overall adherence of the film onto substrates. Having obtained a 14-16 μm film thickness values, cells were assembled with active area values of 0.5 × 0.5 cm2, 1.0 × 1.0 cm2 and 2.5 × 2.5 cm2 and solar measurements were conducted, resulting in up to 4.22%, 4.13% and 4.00% efficiencies, relatively, under AM 1.5 conditions.