Effect of acidic additives on the structure and performance of TiO2 films prepared by a commercial nanopowder for dye-sensitized solar cells

Two strong acids (hydrochloric, HCl and nitric, HNO3), a weak one (acetic acid, CH3COOH) and a ketone (acetylacetone, C5H8O2) were used in turn. The properties of the films were dependent on the concentration and the kind of the acid. With increasing concentration the coagulation of the nanoparticles also increases, thus affecting the efficiency of the devices. Of all the additives used, HNO3 gave the best results and a 40% increment in efficiency was observed, compared to the standard dispersing agent that is acetylacetone. The improved homogeneity of the nanoparticle size (24 nm for anatase and 21.5 nm for rutile) and the better connectivity between them were responsible for the improvement in efficiency.