“…At present, as good alternatives to ITO, many research groups have studied ZnO based materials such as Al doped ZnO (AZO) which are non-toxic, inexpensive source materials and abundant for thin-film transparent electrode applications [17,18]. In addition, when impurity elements of group III in the periodic table (B, Al, Ga, and In), especially Al, are incorporated, ZnO becomes an n-type material with the improvement of electrical [19] and optical properties because of the increase in the carrier concentration and mobility.…”