Gallium-Doped Zinc Oxide Nanoparticle Thin Films as Transparent Electrode Materials with High Conductivity

Gallium-doped zinc oxide (GZO) nanoparticles (NPs) have been synthesized by a solvothermal synthesis method using gallium chloride and zinc chloride as precursors in anhydrous methanol along with bases. Systematic investigations have revealed that H2O, formed through the condensation of metal hydroxides to obtain GZO NPs, not only enhances the production of layered compounds as byproducts but also accelerates Ostwald ripening to reduce the amount of doped gallium ions. To overcome H2O generation during NP growth, we first applied sodium methoxide (NaOMe) as a base for the synthesis of GZO NPs. As a result, high-performance GZO NPs were successfully obtained in a single phase, and the mean particle size of the GZO NPs was controlled from 10 to 35 nm by changing the molar ratio of the sodium hydroxide (NaOH) and NaOMe in the reaction mixture. We further applied the obtained GZO NPs to prepare GZO NP-based transparent conductive metal oxide (TCO) films using an NP-mist deposition strategy as our developed NP-coating method on substrates. The resistivity and transparency of the deposited GZO thin films were compared with those of conventional thin films prepared by a dispersion coating method, showing that NP-mist deposition is a promising method for fabricating high-performance GZO NP-based TCO thin films on substrates under mild atmospheric conditions.