Structure, binding energy and optoelectrical properties of p-type CuI thin films: The effects of thickness

Abstract

Ultra-high transparent p-type copper iodide (CuI) thin films were fabricated by solid iodization of evaporated Cu precursor layers at room temperature. The effect of the thickness on microstructure, binding energy and optoelectrical properties is systematically studied. X-ray diffraction measurements show the polycrystalline nature of the CuI thin films with zincblende type structure. The X-ray photoelectron spectroscopy (XPS) analysis indicates that the oxidation state of Cu is +1 and the estimated value of [Cu]/[I] at 100 nm is 0.87. Excess iodide ions trap considerable holes, causing CuI thin films to exhibit the p-type conductivity, which is consistent with the results of the Hall effect measurement and the non-linear characteristics of the CuI/ITO structure. Moreover, the CuI thin films with thickness of 100 nm exhibits an ultra-high optical transmittance of 95.5% in the wavelength of 380–780 nm and an excellent conductivity of 34 S/cm. These results prove the great potential of CuI as a promising p-type optoelectronic material.