MOCVD-Derived Highly Transparent, Conductive Zinc- and Tin-Doped Indium Oxide Thin Films: Precursor Synthesis, Metastable Phase Film Growth and Characterization, and Application as Anodes in Polymer Light-Emitting Diodes

Four diamine adducts of bis(hexafluoroacetylacetonato)zinc [Zn(hfa)2·(diamine)] can be synthesized in a single-step reaction. Single crystal X-ray diffraction studies reveal monomeric, six-coordinate
structures. The thermal stabilities and vapor phase transport properties of these new complexes are
considerably greater than those of conventional solid zinc metal−organic chemical vapor deposition
(MOCVD) precursors. One of the complexes in the series, bis(1,1,1,5,5,5-hexafluoro-2,4-pentadionato)(N,N‘-diethylethylenediamine)zinc, is particularly effective in the growth of thin films of the transparent
conducting oxide Zn−In−Sn−O (ZITO) because of its superior volatility and low melting point of 64 °C.
ZITO thin films with In contents ranging from 40 to 70 cation % (a metastable phase) were grown by low-pressure MOCVD. These films exhibit conductivity as high as 2900 S/cm and optical transparency
comparable to or greater than that of commercial Sn-doped indium oxide (ITO) films. ZITO films with the
nominal composition of ZnIn2.0Sn1.5Oz were used in fabrication of polymer light-emitting diodes. These
devices exhibit light outputs and current efficiencies almost 70% greater than those of ITO-based control
devices.