ABSTRACT
In this chapter the basics of an OLED device are explained followed by description of the main constrains to their wide-spread use. The specific necessities for special applications are focused.
2.1 The Organic-LED BasicsOrganic LEDs have a more complex structure than inorganic ones for two main reasons. Firstly, the low-carrier mobility and the electrical conduction process impose a new device structure; secondly, the much different carrier mobility between electron transport material (“n-type”) and hole transport material (“p-type”), the last being several orders of magnitude higher. In turn, the benefits of using an organic-based self-emissive layer that allows very thin film devices (in some cases below 100 nm), the much sought after flexibility result in devices with unique properties that move the interest of the scientific community.The traditional LED from inorganic semiconductors is typically a p-n junction, were a hole injected from anode and an electron injected from cathode diffuses in the respective semiconductor type to recombine at the interface resulting in light emission. In this kind of semiconductors, the carrier mobilities are relatively Organic Light-Emitting Diodes: The Use of Rare-Earth and Transition Metals Luiz Pereira Copyright © 2012 Pan Stanford Publishing Pte. Ltd. www.panstanford.com
similar, the device structure can be kept simple, and one needs to only worry about the electrode contacts and the p-n interface. The III-V semiconductors (due to the bandgap in the visible region) are the best and cheapest choice as basic materials for inorganic LED. Figure 2.1 shows a simple scheme.
