Light-emitting diodes based on organic semiconductors show promising features for display and lighting applications. A vertical in-line deposition technique for organic light-emitting diode (OLED) manufacturing was developed. OLED devices with electrically doped transport layers show low operating voltage, high efficiency and long lifetime. The preparation of p-i-n type devices was performed with the in-line fabrication tool resulting in highly efficient OLED with low operating voltage. The lowest operating voltage was achieved for green diodes with 2.9 V for 100 cd/m(2). This demonstrates that the p-i-n device concept can be applied under manufacturing conditions. In-line manufactured highly efficient red, green and blue OLED are presented. One important aspect for fabrication cost is the used ground contact, which is commonly made by indium tin oxide (ITO). For low cost fabrication an alternative for ITO has to be used. In this work, ITO was replaced by aluminium doped zinc oxide (ZAO). The results are comparable to OLEDs using ITO as transparent conductive oxide. (C) 2007 Elsevier B.V. All rights reserved.