Optical properties of ZnO

Abstract

Zinc oxide (ZnO) is a compound semiconductor (belonging to the IIb-VI family of compounds) with a large exciton binding energy that makes it valuable for various optoelectronic applications. This chapter presents an overview of the various optical properties of ZnO in bulk and nanostructures. The effect of particle sizes on the optical bandgap, near-band-edge emission, photoluminescence (PL) Stokes shift, electron-phonon interaction, and nonlinear optical properties have been discussed. The low-temperature PL spectrum of ZnO possesses various emission peaks corresponding to free excitons, bound excitons, and donor-acceptor pairs. On the other hand, the room-temperature PL shows broad emission peaks in the visible region, along with the near-band-edge emission, which originates from various intrinsic defects. The stimulated emission and various dopants strategies to tailor the electrical conductivity, magnetic properties, and PL emission have been described. There remain a number of avenues for research in ZnO nanostructures, therefore; finally we present future prospects. © 2021 Elsevier Inc. All rights reserved.