The semiconductor-based UV photodetectors are the most essential devices in the field of space observations, military, DNA sequencing, analysis of protein, medical imaging, checking of atmospheric pollution, optical communications radiation, etc. With such a wide range of possible applications, the nanostructured pristine and rare-earth (RE) doped NiO ((NiO: Gd(1%), NiO:Nd(1%), NiO:La(1%)) thin films were prepared and investigated for their suitability as UV photodetectors. The films were prepared by nebulized spray pyrolysis (NSP) at a substrate temperature of 450 °C. The x-ray diffraction studies confirm the cubic single phase with the polycrystalline nature of the prepared films. The spectroscopic studies such as absorbance and photoluminescence confirm that increase in the optical bandgap and 391 nm PL emission is attributed to the near band edge emission of the NiO. The x-ray photoelectron spectroscopy reveals the presence of nickel and the doped elements with their oxidation states. The UV photodetector performance of the prepared NiO films was carried out under the irradiation of 365 nm light. The NiO:Gd exhibits the best responsivity (0.353 AW ⁻¹ ), external quantum efficiency (120%), detectivity (1.72 × 10 ¹⁰ Jones) and rise time (2.0 s), and fall time (2.2 s). Importantly, strategies such as limited doping (1 at.%) and larger ionic radii of Gd incorporation into the host NiO cause a moderate increase in the lattice distortion and inhibit the recombination rate instead of behaving as a recombination center. In addition, the conduction band ( CB ) electrons are trapped by a greater number of oxygen vacancies residing at the Gd ³⁺ 4f state and cause a good separation of charge carriers. Overall, these modifications enhance the mean lifetime of electrons, consequently reducing the recombination rate and enhancing the photoresponse.

The current work investigates the influence of the substrate temperature on the photodetection capability of cadmium selenide (CdSe) thin films deposited through economically viable thermal evaporation technique on glass substrates. The substrate temperature varied from room temperature (30 °C to 250 °C). The existence of a single-phase of hexagonal structured CdSe was established from XRD patterns with dominant peaks along the (002) plane in all the samples. The SEM micrographs show the homogeneous surface of the films without any pinholes. The bandgap of the films was found to vary with the variation in the substrate temperature and the sample fabricated at 200 °C substrate temperature showed a bandgap of 2.00 eV. The light-dependent electrical analysis is also made to reveal the photodetection capability of the deposited CdSe films. The 200°C deposited CdSe film exhibits a higher responsivity of 8.07 × 10 ⁻² A W ⁻¹ and a maximum detectivity of 6.66 × 10 ⁹ Jones. The external quantum efficiency (EQE) was found to rise with the substrate temperature and a maximum value of 18.8% for the 200 °C deposited sample. The observed rise and decay times show a rapid response when the incident light intensity is changed from 1 to 5 mW cm ⁻² .