Effects of Thallium–Aluminum‐Codoped Zinc Oxide Thin Film as a New Transparent Conducting Oxide

Herein, the electro–optical properties of sol–gel spin‐coated “thallium–aluminum‐codoped zinc oxide (TAZO)” focusing on the effects of thallium are investigated. It is shown that the amount of thallium (Tl) has a significant effect on improving the electrical properties of TAZO as a new transparent conducting oxide (TCO). The optimum results are achieved by adding 1 at% of Tl to aluminum‐doped zinc oxide (AZO), after which the sheet resistance ( R s ) value is reduced from 30.21 to 2.832 KΩ sq −1 . Although less R s is recorded in all amounts of Tl used (from 1 to 4 at%) than in Tl‐free samples, R s also increases as the amount of Tl increases, which is related to the degradation of the crystal structure at higher values of Tl. In view of a trade‐off between electrical conductivity and optical transparency, a decrease in transparency in the presence of Tl is a predictable issue, but while the Tl‐free samples record 90% transparency, the uniform thin film of 1 at% Tl‐AZO is able to achieve 85% transparency. This small amount of reduction in transparency shows the high potential of Tl to improve the properties of AZO as a TCO.