Generalized Synthesis to Produce Transparent Thin Films of Ternary Metal Oxide Photoelectrodes

Developing facile approaches to prepare non-light-scattering ternary oxide thin film photoelectrodes is an important goal for solar water splitting tandem cells. Herein, a novel synthesis route is reported that employs ethylenediaminetetraacetic acid (EDTA) to enable compatible water solubility of diverse metal cations, which affords transparent films by solution processing. By using BiVO₄ as a model material, a remarkable improvement in transparency is demonstrated, quantified by the direct transmittance at 600 nm of >80 % versus the <10 % observed with state-of-the-art electrodeposited thin films while maintaining reasonable solar-driven oxidation photocurrents (1.75 mA cm^-2 in the presence of a sulfite hole scavenger). Furthermore, it is demonstrated that the synthesis technique can be applied in a general fashion towards the synthesis of diverse n- and p-type metal oxide materials, such as ZnFe₂ O₄ and CuFeO₂ .