Properties of TCO anodes deposited by APCVD and their applications to OLEDs

摘要

Doped ZnO is one of the materials currently being considered in industrial applications as a possible replacement for ITO as a transparent conducting oxide. The properties of doped ZnO anodes prepared at Arkema Inc. are analyzed in 3D using high-throughput mapping tools. The 2D resistivities of the coatings measured by 4-point probe compare well with the resistivity values calculated from the spectroscopic ellipsometer measurements. It was found that the dependence of effective mass of doped ZnO on Hall-electron concentration influences optically-calculated mobilities and electron concentrations. To study the variation of the film properties along z-axis, the films are polished using mechanical planarization technique. The electrical and crystallographic depth profiles for these films are studied by differential Hall-effect and grazing-angle x-ray spectroscopy. The electron mobility increases continuously from the glass-film interface (12 cm /Vs) to the ZnO film surface (19 cm~2/Vs). The electron concentration depth profile has bell-like dependence with a maximum at 1.55 × 10~(21) cm~(-3). In addition to the increasing grain size, the texture coefficients for the (002) reflection decrease and (103) reflection increase towards the air-film interface. Examples of the applications of the doped ZnO anodes in the OLED structures suggest improvement of external quantum efficiency with introduction of an A1_2O_3 undercoat.