Chemical bath deposition of vertically aligned TiO2 nanoplatelet arrays for solar energy conversion applications

We report a facile, scalable, and low cost chemical bath deposition of vertically aligned TiO2 nanoplatelet arrays on various substrates including fluorine-doped tin oxide coated glass substrates and their applications for photoelectrochemical (PEC) water splitting and dye sensitized solar cells. The TiO2 arrays consisting of single crystal rutile nanoplatelets with heights (film thicknesses) of up to 1 mu m, lengths of up to 130 nm, and widths of similar to 5 nm were grown via controlling oxidation and hydrolysis of TiCl3 at low pH (0.71-0.85) and low TiCl3 concentration (8-40 mM). As a photoanode for water oxidation in a PEC water splitting cell, the TiO2 nanoplatelets show excellent charge separation characteristics with a saturated photocurrent in 1 M KOH electrolyte under AM 1.5 G illumination of similar to 0.4 mA cm(-2) reached at an exceptionally low bias of -0.6 V vs. Ag/AgCl (0.4 V vs. reversible hydrogen electrode). Dye sensitized solar cells assembled using N719 dye sensitized-TiO2 nanoplatelet arrays also show promising performance with photoconversion efficiencies of 1.28% for as-synthesized (no thermal post-treatment) and 3.7% for annealed TiO2 nanoplatelets.