Impact of temperature difference on the features of spray deposited yttrium doped cobalt selenide (YCoSe) thin films for photovoltaic application

Abstract

In this investigation, spray deposited yttrium doped cobalt selenide (YCoSe) thin materials were synthesized in soda lime glass and the impact of substrate temperature (140 ^oC, 160 ^oC, 180 ^oC and 200 ^oC) on their elemental composition, surface morphology, structural, electrical and optical properties were investigated using scanning electron microscopy-SEM X-ray diffraction –XRD, four-point probe and UV-VIS spectrophotometer respectively. The EDX plots of the deposited undoped and Y-doped cobalt selenide revealed the major elements: cobalt, selenium and yttrium. This confirms the deposition of CoSe and Y-doped CoSe thin materials. The morphology of undoped CoSe thin materials was very rough containing randomly oriented non-uniform thin particles while addition of Y dopant (0.1 mol%) at substrate temperature of 140 ^oC gave a homogenous distribution of compact rectangular-like nanograins. The XRD result shows that the films are cubic polycrystalline in nature and the film grown at substrate temperature of 180 ^oC was seen to give the most excellent crystalline quality and a preferential orientation along (111) direction. From electrical results it was observed that increase in substrate temperature increased the film thickness with decreased resistivity and increased conductivity. The optical properties were found to vary with substrate temperature despite the fact that the variation was not totally linear, as the film deposited at substrate temperature of 160 ^oC deviated from the linearity in all the optical properties. The energy band gap of the deposited samples ranges from 1.25 eV–1.75 eV. The materials produced could be used in the production of photovoltaic devices.