Characteristics of ZnS nanocolumn arrays and their effect on the light outcoupling of OLEDs

Wide band gap semiconductor zinc sulfide (ZnS) nanocolumn arrays were prepared on the glass side of ITO substrates by glancing angle deposition (GLAD) technology. The SEM images show the formation of ZnS nanocolumn arrays when the glancing angle was set to 80°; however, continuous ZnS thin films were fabricated under normal deposition (0°). The XRD spectra of the films show that the most intensive diffraction peak changed from (2 2 0) to (1 1 1) when the incidence angle was set to 0° and 80°. The transmitting ability of ITO substrate coated with ZnS nanocolumn arrays was enhanced compared with continuous ZnS thin films coated ITO substrate and bare ITO substrate in the visible range. Organic light emitting diodes (OLEDs) were simultaneously fabricated on these three kinds of substrates. The electroluminescence (EL) intensity of OLEDs based on the ITO substrate coated with ZnS nanocolumn arrays was about 1.3 times bigger than that of devices based on the other substrates (continuous ZnS film coated ITO substrates and bare ITO substrates) under the same driving voltage.