Structural, Optoelectronic, and Electrochemical Properties of Zn_1–<i>x</i>(Ga_0.5Al_0.5)_<i>x</i>O Nanoparticles for Supercapacitor Applications

Abstract

The structural, optoelectronic, and electrochemical properties of the sol–gel prepared Zn1–x(Ga0.5Al0.5)xO samples are explored for their possible supercapacitor applications. Rietveld analysis of X-ray diffraction patterns confirms that all samples crystallize in a single wurtzite structure. Ga and Al incorporation in ZnO leads to generate lattice strain in a host lattice, resulting in reduction in the crystalline nature of the samples. The variation in the band gap with increasing Ga and Al content was found to be better scaled with the lattice parameters. Photoluminescence studies suggest a defective lattice for x = 0.03, because of the formation of more defect states such as oxygen vacancies near the band-edges. X-ray photoelectron spectroscopy analysis at the O 1s edges supports the presence of oxygen-related defects in the samples. A varying color emission from yellow to orange was observed with the codoping as revealed from photoluminescence studies. However, oxygen interstitial defects result in enhanced conductivity for the x = 0.01 sample. The enhanced electrochemical performance was also achieved for the x = 0.01 sample with a higher specific capacitance. The simultaneous doping of Ga and Al gives a more extensive range of physical, optoelectronic, and electrochemical properties of ZnO nanoparticles for supercapacitor applications.