Defects and dopants assisted optoelectronic and electrochemical performance of ZnO nanostructures

Abstract

ZnO is widely recognized as an ideal semiconductor for optoelectronic applications and most of the recent interests in ZnO material have been focused on the future potentials of light-emitting devices (LED), lasers, and transparent conducting oxides (TCO’s). In addition, ZnO is promising for phosphor applications due to its strong luminescence in the visible region of the spectrum. The most important features of ZnO can be listed as follows [1, 2]: 1) ZnO has a wide bandgap energy of 3.37 eV at room temperature [3]. 2) It has an extremely large exciton binding energy of 60 meV [4]. This is much larger than the thermal energy (26 meV) at room temperature. This is one of the key parameters that enable ZnO to be applicable in UV laser diodes and other exciton-related light-emitting devices at room temperature [5, 6]. 3) High transparency in the visible and near-infrared spectral regions [7]. 4) Low material costs, nontoxicity, and abundance in the earth's crust. 5) Possibility to synthesize ZnO nanomaterials with different economical synthesis routes at low temperatures. In particular, the polar surface of ZnO is very stable and has been used to induce the formation of different types of nanostructures such as nanowires, nanorods, nanorings, nanohelices, nanobelts, and nanotubes [8]. It is easy to tune the properties of the ZnO nanostructures e.g. size and morphology, by controlling the synthesis technique and conditions. These properties of ZnO have led researchers to pursue and modify the synthesis process and different doping elements, to obtain desired and customed tailored materials for high performance nanoscale devices.