Pulsed Nd:YAG laser depositions of ITO and DLC films for OLED applications

Indium-tin oxide (ITO) films deposited on heated and non-heated glass substrates by a pulsed Nd:YAG laser at 355 nm and ∼2.5 J/cm2 were used in the fabrication of simple organic light-emitting diodes (OLEDs), ITO/(PVK + Alq3 + TPD)/Al. The ITO was deposited on heated glass substrates which possessed resistivity as low as ∼3 × 10−4 Ω cm, optical transmission as high as ∼92% and carrier concentration of about ∼5 × 1020 cm−3, were comparable to the commercial ITO. Substrate heating transformed the ITO microstructure from amorphous to polycrystalline, as revealed by the XRD spectrum. While the polycrystalline ITO produced higher OLED brightness, it was still lower than that on the commercial ITO due to surface roughness. A DLC layer of ∼1.5 nm deposited on this ITO at laser fluence of >12.5 J/cm2 improved its device brightness by suppressing the surface roughness effect.