Nd:YAG Laser Annealing: Impact on the Photoconductive Properties of CdS Thin Films

This study investigates the effects of pulsed Nd:YAG laser annealing at a wavelength of 532 nm on the photoconductivity properties of cadmium sulfide (CdS) thin films prepared by thermal evaporation. In addition, measurements at room temperature showed an ohmic behavior in the voltage-current characteristics of the CdS thin films. It was observed that after laser irradiation, the photosensitivity of the film increased due to the improved crystallinity and decreased defect density of the thin films, as shown by the increase in the ratio of light to dark current (Iph/Id) from 0.35 to 0.42. The photocurrent also follows the relationship (Iph∝FγI), with γ-values of 1.037 and 1.047 after annealing due to monomolecular recombination, reduced grain boundaries and enhanced recrystallization. The spectral response peaked at 585 nm, which corresponds to the optical band gap of the CdS thin film. The transient photoconductivity, which describes the time-dependent change in the electrical conductivity of the material when exposed to light, was measured and showed significantly increased decay rates. The differential lifetime (τd) decreased from (90.8 sec) to (39.2 sec) after Nd:YAG laser annealing, which can be attributed to a lower density of defect states and an improvement in film quality. The results highlight the ability of Nd:YAG laser annealing to maximize the photonic and electronic properties of CdS thin films through structural and carrier recombination dynamics, increasing their use in optoelectronic devices.