In this work, the electronic structure and optical properties of Mg 1−x Zn x O (0 ≤ x ≤ 0.5) are investigated within the framework of the density functional theory (DFT), the GW method, and the Bethe-Salpeter equation (BSE). We find that zinc doping can lower the band gap of pure MgO via the Zn 4s states near the Fermi level and reduce the lattice symmetry, both of which will affect the optical properties. The energy of the first absorption peak decreases as the concentration of zinc increases, so are the exciton energy and binding energy of the lowest excited state. The results nicely fit to published experimental results and are compared to those of the simple hydrogen-like atom model for excitons. As the lowest excited state is closely related to light emission at that energy according to Kasha's rule, zinc doping will lower the light emission energy of pure MgO, while still exhibiting an exciton binding energy much higher than that of k B T at room temperature. This means that Mg 1−x Zn x O materials are perfectly suited for optoelectronic devices operating in the deep blue and near-ultraviolet (UV) range.

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In this work, the properties of Mg1-xZnxO thin films are investigated as an example of a protective layer material with a small bandgap in a plasma display panel, to analyze the impact of these kinds of materials on the discharge properties. Using the first principles calculation method, the electronic structure of Mg1-xZnxO crystal is analyzed, and an analytical formula is obtained for the values of the bandgap. A cubic structure is obtained for x between 0 and 0.625. The secondary electron emission coefficients γ of Neon and Xenon with the Mg1-xZnxO films are then evaluated based on Hagstrum’s theory. The γ value for Xe ions is zero, until a concentration of 0.375 is reached, when the bandgap is about 5.1 eV. At x = 0.375 and beyond the condition for Auger emission by xenon ions is fulfilled, and for x > 0.375 the γ value increases continuously until a value of 0.07 is reached for x = 0.625. The γ value for Ne increases from 0.25 to 0.38 when the ZnO proportion is increased from 0 to 0.625. The discharge characteristics of the SM-PDP with Mg1-xZnxO protective layer are then calculated using the fluid model. When increasing the x value, the working voltage is strongly reduced, while the discharge efficiency is enhanced by about 60% at 20% Xe for a change in x from 0 to 0.625. We find that this increase is mainly caused by increased electron excitation efficiency. Therefore mixed-oxide materials with a small bandgap like MgO-ZnO in principle enable the use of high xenon content plasma displays, while strongly increasing the discharge efficiency.