Optical Properties of Synthesized Hexagonal CdTe Nanoparticles Having Hexagonal Phase: Density Functional Theory‐Supported Calculation of Bandgap and Density of States

Abstract

Hexagonal CdTe nanoparticles with hexagonal phase are chemically prepared. Transmission electron microscopic analysis shows that the prepared nanoparticles are hexagonal in shape. Again, in the selected‐area electron diffraction pattern, ring‐shaped identical patterns containing sharp bright spots are observed, which confirm that nanoparticles are polycrystalline in nature. The observed X‐ray diffraction (XRD) peaks on matching with the standard data confirm the formation of hexagonal phase. Again, from the observed absorption peak at 449 nm, the bandgap is calculated as 2.4 eV using Tauc's equation, which is found to be slightly higher compared with the reported bandgap of cubic CdTe nanoparticles. Further, Urbach energy is found as 534 meV, which indicates the presence of defect states in the nanoparticles, and the refractive index of synthesized nanoparticles is calculated as 2.6. Rietveld refinement of X‐ray data is performed for the determination of lattice structural parameters, which is then used for the computation of density functional theory (DFT)‐based bandgap using Quantum ESPRESSO code. Finally, the bandgap obtained from the theoretical study and experimental study is compared. The innovation herein lies in the use of experimental XRD data for bandgap calculation using DFT.