Effect of Annealing Temperature on the Structural, Morphological, and Optical Properties of CdSeTe Nanoparticles for Optoelectronic Applications

Abstract

This study investigates the influence of annealing temperature on the structural, morphological, and optical properties of CdSeTe nanoparticles synthesized via a co-precipitation method. Samples were annealed between 100°C and 400°C to examine thermally induced changes in the crystal structure, morphology, and optical behaviour. X-ray diffraction reveals a temperature-driven transition from a hexagonal CdSeTe phase in the as-prepared and 100°C sample to a mixed hexagonal–cubic structure at 200°C, followed by a complete transformation to a cubic CdTe-rich phase at higher temperatures. The crystallite size increases from 12 nm (as-prepared sample) to 33 nm (400°C sample), indicating thermally assisted structural reorganization. Scanning electron microscopy shows a progression from rod-like particles to irregular agglomerated structures with increasing temperature, while energy-dispersive X-ray spectroscopy confirms the presence of Cd, Se, and Te with uniform elemental distribution. Diffuse reflectance spectra (DRS) indicate enhanced absorption as annealing temperature increases, and bandgaps determined using the Kubelka-Munk method decrease from 2.63 to 2.12 eV up to 300°C, with a slight rise at 400°C due to possible Te loss or compositional shifts. Photoluminescence shows emission peak shifts associated with defect and structural changes. CIE chromaticity analysis places emissions in the yelgreen region.