Effects of Multi-dimensional Defects on Optical and Thermoelectric Properties of Cerium-Doped ZnO Nanoparticles

Abstract

The thermoelectric properties of materials are often limited by various factors, and enhancing these properties through defect engineering is an effective strategy. In this study, pure and cerium (Ce)–doped ZnO nanostructures were synthesized by a facile hydrothermal method with varying Ce concentrations. The thermoelectric enhancement in the context of point and bulk defects was experimentally demonstrated by establishing a correlation with structural and optical properties. X-ray diffraction analysis confirmed a hexagonal, highly crystalline structure. Scanning electron microscopy revealed that the particles took on a nanorod shape, elongating with increased doping. Photoluminescence spectra showed near-band-edge and green emissions for all samples, with the optical band gap decreasing as Ce doping increased. The absolute value of electrical conductivity and Seebeck coefficient depicted an increasing trend with the rise in Ce doping concentration. Our outcomes reveal that the addition of 1.2% of Ce into ZnO leads to improvements in the Seebeck coefficient to a maximum value of ~ 98 μV/K at 400 K, along with Figure-of-merit (ZT) improvement, which directly correlates with thermoelectric efficiency and oxygen vacancies along with secondary phase are thought to be the main reasons for that augmentation as supported by XRD and photoluminescence studies. Our study possibly possesses twofold advancements, first providing an opportunity to explore other rare earth–doped ZnO systems specifically for improved thermoelectric efficiency, second, it could be viable for better design of future thermoelectric materials via inspecting the role of defects.