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

Abstract

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 μm, lengths of up to 130 nm, and widths of ∼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 ∼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.