O thin films as transparent conducting oxides

Zn_1−xCd_xO thin films spanning the whole composition range have widely been explored as active region in optoelectronic devices. The precise control of the Cd concentration as well as its crystalline phase allowed to fully characterize their intrinsic properties. However, its application as a transparent conducting oxide material (TCO) is promising, and a complete analysis of this application is still missing. Here, we fabricated Zn_1−xCd_xO thin films via the spray pyrolysis method and confirmed their composition via Energy-dispersive X-ray spectroscopy (EDX) measurements. Also, we characterized the electric and optical properties through spectroscopy ellipsometry and transmittance measurements from 300 nm to 3200 nm wavelength range. As expected, we see a nonlinear red-shift of the optical band gap while increasing the Cd concentration. Moreover, we show that the thin films have an average transmittance of 0.8 over a wide range of the electromagnetic spectrum. We find that most of our samples were conductive with a sheet resistance as low as 19.8 Ω for a composition of Zn_0.25Cd_0.75O. The use of alloyed metal oxides as building blocks for organic solar cells with photonic crystal structures will also be discussed.