Pertinent white light-emitting source materials using Zn_xCu_1 − xO (0.0 ≤ x ≤ 1.0) nanoparticles: synthesis, spectral investigations and device modeling

Nanocrystalline Zn_xCu_1 – xO (0.0 ≤ x ≤ 1.0) samples were synthesized through phytochemical (chrysin) mediated chemical reduction method. The samples were annealed at 600 °C for 4 h with the aim of aging and further studied the crystallographic characteristics, structure, morphology and optical properties using measurements such as X-ray diffraction, FESEM, UV–Visible spectroscopy and photoluminescence spectra. The crystallographic plane reflections analogous to the formation of monoclinic end-centered phase of copper (II) oxide (CuO) under the space group C2/c (15) and hexagonal primitive lattice of zinc (II) oxide (ZnO) phase under the space group P63mc (186) were obtained, respectively, for x = 0.0 and x = 1.0 samples. Gradual phase changes were observed in the intermediate compositions from x = 0.3 to 0.7. The strain separated effective crystallite size of the samples was estimated using Halder–Wagner method. The parameter, micro-strain, was calculated and used to study the defect structure and to analyze the effect of zinc substitution in the copper (II) oxide lattice in arbitrating the conducting nature of lattices. The optical direct band gaps were estimated through Tauc plot employing Kubelka–Munk function and UV-reflection data. Using PL spectra, CIE chromaticity diagram was drawn, from which photometric properties like chromaticity coordinates, correlated color temperature, color rendering index (CRI), color purity and luminaire efficacy of radiation were calculated. The CRI value for x = 0.0 and 0.3 samples is above 95, which signifies their perfect color appearance and the efficacy as the pertinent material for applications in white light-emitting sources. A prototype sketch for electroluminescent double heterojunction device structure is also discussed.