Structural, morphological, optical, and electrical properties of Ni–Cr dual-doped CdSe thin films: potential for photovoltaic applications

The present study is aimed at investigating the effect of Ni-Cr dual doping on the structural, morphological, optical and electrical properties of cadmium selenide (CdSe) thin films prepared by the chemical bath deposition (CBD) technique on glass substrates. Pure, single-doped (Ni and Cr) and Ni-Cr dual-doped CdSe thin films have been characterised by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), UV-Vis spectroscopy and electrical conductivity measurements. The XRD analysis revealed that the pure and single-doped CdSe thin films crystallised in the hexagonal phase, but the 4% Ni–Cr dual-doped CdSe thin film showed a phase transformation to the cubic structure. More importantly, Ni–Cr dual-doping reduced the crystallite size from 47 nm for pure CdSe to 17 nm and modified the lattice constant and dislocation density. SEM images showed uniform and compact film morphology, while EDX analysis confirmed the successful incorporation and homogeneous distribution of Ni and Cr in the CdSe thin films. The optical band gap of the prepared annealed pure CdSe thin film was 1.43 eV, which was reduced to 1.16 eV after Ni–Cr dual-doping. Furthermore, the 4% Ni–4% Cr dual-doped CdSe thin film showed the highest DC electrical conductivity of 5 × 10⁻ 3 S·cm⁻¹. The reduction of optical band gap with the increased optical absorption and electrical conductivity indicates that the dual doping of Ni–Cr is an effective way to tune the optoelectronic properties of the CdSe thin films, making them promising absorber materials for the upcoming photovoltaic and optoelectronic applications.