Enhancement of photo-sensing properties of CdS thin films by changing spray solution volume

Abstract

CdS is a IIIV family semiconductor chalcogenide that has been deposited on amorphous glass substrates as thin films form with various solution (precursor) volume (5, 10, and 15 mL) by employing a cost-effective spray technique using a nebulizer. The effect of the varying quantity of coating solution on the structural and optoelectronic properties has been studied. The X-ray diffraction (XRD) patterns reveal the polycrystalline nature of CdS with a hexagonal structure with preferential orientation along the c-axis. Atomic force microscope (AFM) demonstrated the film prepared with a 10 mL solution possesses uniform coating with spherical shaped nanograins. Energy dispersive X-ray analysis (EDX) reveals the coated film contains Cd and S elements. The direct bandgap values decreased with the increase in precursor volume and reached a minimum value for the film prepared with a 10 mL solution. Photoluminescence (PL) spectra revealed the two emission peaks in which a sharp dominant peak at 470 nm and a peak with a shoulder at 620 nm. The CdS film coated with a precursor spray volume of 10 mL resulted in better photo-sensitivity characteristics of the responsivity of 1.01 AW−1, detectivity of 2.21 × 1012 Jones, photo-sensitivity of ∼4.9 × 103, and external quantum efficiency (EQE) of 257 %. The film-coated with a solution volume of 10 mL was found to have good optical characteristics which make them suitable for photo-detector applications.