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

Abstract

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.

A Nanoparticle-Mist Deposition Method: Fabrication of High-Performance ITO Flexible Thin Films under Atmospheric Conditions

“…Unless otherwise noted, all the characterization tests were performed under atmospheric conditions based on our previous studies. [5,37,41] The average temperature was 28 °C. The crystallographic structures of the ITO powders were identi ed by a Rigaku Ultima-IV XRD measurement system using a Cu Kα radiation source (40 kV, 40 mA) equipped with a D/teX Ultra detector.…”

“…More recently, we demonstrated the preparation of galliumdoped zinc oxide (GZO) on glass substrates as TCO thin lms by the GZO NP-mist deposition method. [37] Here, GZO NPs controlled in mean particle size were originally synthesized by a solvothermal method using a mixture of NaOH/NaOMe as bases. [37] The transparency, haze, and resistivity of the GZO NP-mistdeposited thin lms on glass substrates were more than 99% at 600 nm, 0.3%, and 5 x 10 -2 Ω•cm after annealing at 300 °C, respectively.…”

“…[37] Here, GZO NPs controlled in mean particle size were originally synthesized by a solvothermal method using a mixture of NaOH/NaOMe as bases. [37] The transparency, haze, and resistivity of the GZO NP-mistdeposited thin lms on glass substrates were more than 99% at 600 nm, 0.3%, and 5 x 10 -2 Ω•cm after annealing at 300 °C, respectively. Despite extensive investigations, heat treatment at 300 °C under a reducing atmosphere was an essential step to induce low resistivity in the GZO NP-based thin lms.…”

A nanoparticle-mist deposition method: fabrication of high-performance ITO flexible thin films under atmospheric conditions

“…Watanabe 35 and Kim 36 et al reported the preparation of porous TiO 2 films from preheated and dried spray mists, respectively. More recently, we demonstrated the preparation of gallium-doped zinc oxide (GZO) on glass substrates as TCO thin films by the GZO NP-mist deposition method 37 . Here, GZO NPs controlled in mean particle size were originally synthesized by a solvothermal method using a mixture of NaOH/NaOMe as bases 37 .…”

“…More recently, we demonstrated the preparation of gallium-doped zinc oxide (GZO) on glass substrates as TCO thin films by the GZO NP-mist deposition method 37 . Here, GZO NPs controlled in mean particle size were originally synthesized by a solvothermal method using a mixture of NaOH/NaOMe as bases 37 . The transparency, haze, and resistivity of the GZO NP-mist-deposited thin films on glass substrates were more than 99% at 600 nm, 0.3%, and 5 × 10 −2 Ω cm after annealing at 300 °C, respectively.…”