Effect of coating temperature on the properties of CdS thin films coated by nebulizer spray pyrolysis method for photodetection applications

Nanostructured CdS-based photodetectors have been focused on recent years because of their high photosensitivity and quick response time. This work reports the photodetector characteristics of CdS thin films prepared using a nebulizer-assisted spray pyrolysis technique by varying substrate temperatures. The X-ray diffraction (XRD) pattern of CdS films exhibits hexagonal structure with orientation along the (0 0 2) plane and CdS films deposited at 450 °C exhibits a higher crystallite size of 53 nm. Morphological analysis shows that the small grains become large spherical flakes at higher substrate temperatures. The optical studies showed that around the visible region, the films exhibit solid optical absorbance, and when substrate temperatures rise to 450 °C, the energy bandgap value decreases to 2.29 eV. The photoluminescence (PL) spectra exhibit two emission peaks: a broad peak at 525 nm and a sharp dominant peak at 680 nm. The CdS thin film deposited at 450 °C produced the highest photoresponsivity (R) of 37.1 × 10^-2 A/W, detectivity (D*) of 268 x10⁸ Jones, external quantum efficiency (EQE) of 120 %, and response/recovery times of 0.92/0.28 s under 532 nm illumination. The study suggests that CdS thin films are suitable for visible photodetector applications due to their simple and cost-effective production process.