Unlocking Enhanced Photoluminescence Potential: Zinc (Zn)-Doped Cadmium Oxide (CdO) Thin Films for Superior
Habtamu Fekadu Etefa1, Francis Birhanu Dejene1
1Department of Physics, Walter Sisulu University, Private Bag X-1, Mthatha 5117, South Africa.
Abstract:
This study explores the impact of zinc (Zn) doping on the structural, morphological, optical, and photoluminescent properties of cadmium oxide (CdO) thin films synthesized via a cost-effective chemical bath deposition (CBD) method. Structural analysis using XRD reveals that Zn doping induces lattice strain, change crystallite size, and causes peak shifts, as confirmed by both Scherrer and Williamson-Hall methods. SEM images show that moderate Zn doping (3%) enhances grain connectivity, surface uniformity, and reduces porosity, which benefits charge transport. In contrast, excessive doping (4%) results in structural disorder. EDS analysis confirms the successful incorporation of Zn, with increasing Zn content without significant phase separation. The experimental and DFT optical characterization shows that Zn incorporation modifies the electronic structure and defect states of CdO, resulting in a bandgap narrowing to 1.95 eV at 3% Zn doping, which enhances visible-light absorption. Photoluminescence (PL) studies indicate enhanced emission at 550 nm due to Zn-induced defect modulation; however, higher doping levels introduce nonradiative centers that diminish emission intensity. The formation of a CdO/CdO-Zn heterojunction facilitates charge transfer mechanism, improving PL activity under visible light by enhancing the generation of reactive species such as •OH and H2O2. Optimal Zn doping significantly improves the structural, optical, and PL properties of CdO thin films, making them promising candidates for applications in PL, solar energy conversion, and environmental remediation technologies.
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