Fabrication of monodisperse ITO submicro-spheres using l-Histidine-assisted one-step solvothermal method

Indium tin oxide (ITO), a representative transparent conducting oxide (TCO), is widely applied in photoelectric devices. In this work, monodisperse ITO submicro-spheres have been prepared using one-step solvothermal method at 250 °C. l -Histidine (L-His), triethylamine (TEA) and dimethylformamide (DMF) were used as shape controller, base agent and solvent, respectively. Significantly, the effect from process variables on the size and shape of submicro-spheres was studied systematically. L-His was used to promote the formation of spherical morphologies. When reaction time was prolonged from 12 to 24 h, nano-size particles eventually grew into submicron particles. After adding L-His, the size of ITO particles became smaller and the crystal tended to sphere-shape from cubic-shape. Meaningfully, the effect from particle size and morphology plays a key role in the resistivity of resultant powders. Compared with the resistivity of larger particles with mixed morphology prepared without L-His, the one of well-crystallized sphere-shaped small particles prepared with L-His was lower. The range of resistivity was between 0.4 and 0.7 Ω cm when 0.05 M L-His was added. Moreover, uniform spheres with a diameter of 0.29 μm have been obtained by one-step solvothermal method with 1 M TEA and 0.05 M L-His, which have potential application in photonic band gap crystals.