First-Principles Calculations of the Electronic Structure and Optical Properties of Yttrium-Doped ZnO Monolayer with Vacancy.

Qian Wu,Yintang Yang,Han Yang,Yan Liu,Lixin Guo,Zhiyong Zhang,Ping Wang,Jingsi Cheng

doi:10.3390/ma13030724

Abstract

The electronic structures and optical characteristics of yttrium (Y)-doped ZnO monolayers (MLs) with vacancy (zinc vacancy, oxygen vacancy) were investigated by the first-principles density functional theory. Calculations were performed with the GGA+U (generalized gradient approximation plus U) approach, which can accurately estimate the energy of strong correlation semiconductors. The results show that the formation energy values of Y-doped ZnO MLs with zinc or oxygen vacancy (VZn, VO) are positive, implying that the systems are unstable. The bandgap of Y-VZn-ZnO was 3.23 eV, whereas that of Y-VO-ZnO was 2.24 eV, which are smaller than the bandgaps of pure ZnO ML and Y-doped ZnO MLs with or without VO. Impurity levels appeared in the forbidden band of ZnO MLs with Y and vacancy. Furthermore, Y-VZn-ZnO will result in a red-shift of the absorption edge. Compared with the pure ZnO ML, ZnO MLs with one defect (Y, VZn or VO), and Y-VZn-ZnO, the absorption coefficient of Y-VO-ZnO was significantly enhanced in the visible light region. These findings demonstrate that Y-VO-ZnO would have great application potential in photocatalysis.

Highlights

Since the third scientific and technological revolution, energy has become essential for economic development
ZnO ML was acquired by cutting the bulk wurtzite
The top view of the optimized ZnO ML is shown in Figure 1a, which illustrates a graphene-like structure

Summary

Introduction

Since the third scientific and technological revolution, energy has become essential for economic development. Fossil energy, such as oil, natural gas, and coal, is the most consumed energy in the world. The vigorous development of renewable energy is conducive for sustainable economic development and for alleviating the increasingly serious energy and environmental problems. As a potential renewable energy source, solar energy, especially visible light (which accounts for most of the solar energy), is believed to contribute to mitigating these problems through photocatalytic technology ( known as semiconductor-based photocatalytic technology) [1]. Semiconductor-based photocatalysis has attracted considerable attention due to its direct conversion of solar energy to stored hydrogen, as well as free secondary pollution [2,3]. The basic principle of semiconductor-based photocatalytic technology is the energy band theory of solids.

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Conclusion