A coordination chemistry approach for shape controlled synthesis of indium oxide nanostructures and their photoelectrochemical properties

Abstract

Indium oxide (In₂O₃) is an important wide band-gap semiconductor having applications in a variety of optoelectronic devices. We report here on the low temperature solution deposition of In(OH)₃ and In(SO₄)(OH)·H₂O architectures with various shapes such as cubes, maize corns and giant crystals. The In₂O₃ nanostructures are then obtained by solid state transformation of In(OH)₃ and In(SO₄)(OH)·H₂O architectures. Shape control is achieved by controlling the local concentration of In³⁺ ions available for reaction by applying the principles of coordination chemistry, thereby obviating the need of any shape controlling agents. The phase and surface composition is obtained by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. The XPS is used to probe the defect structure of In₂O₃ architecture. Optical properties of the films, studied by UV-Vis absorption and photoluminescence (PL) spectroscopy measurements, show that the different morphologies have different band-gaps. Furthermore current–voltage characteristics of In₂O₃–CdSe photoelectrochemical cells are studied, which show that cube–CdSe samples display excellent photovoltaic behaviour, exhibiting a short circuit current density in excess of 10 mA cm⁻². The charge transport properties of the In₂O₃–CdSe photoanodes are studied by impedance spectroscopy, which shows that cube–CdSe samples have lowest resistance to charge transfer.