Investigation on the I2:CuI thin films and its stability over time

Iodine-doped copper (I) iodide (I-2:CuI) at different doping concentrations (i.e., 20%, 40%, 60%, and 80%) was prepared on glass substrate by mist atomization technique. The structural, electrical, and optical properties were studied. The X-ray diffraction results were found to depend on the doping concentration. The I-2:CuI film shows a gamma-phase CuI with strong orientation of (1 1 1) with a nano-scale crystallite size. The improvement of surface morphology measured by field emission scanning electron microscopy was indicated by the reduction of grain boundaries at a higher doping concentration. The electrical resistivity shows a parabolic pattern, with 60% of iodine doping having the highest resistivity at 4.56 x 10(1) Omega cm caused by the surface traps created by iodine doping. The degradation of I-2:CuI films after 5 weeks were caused by the Cu and I-2 deficiency. The transmittance for all samples was found to be below 50% in the visible wavelength. The energy band gap was determined by using the direct transition of n = 2. The maximum band gap observed was 2.90 eV at 80% doping concentration because of the quantum confinement effect. (c) 2013 Elsevier B.V. All rights reserved.