Organic Light-Emitting Diodes (OLEDs): Working Principles and Device Technology

Organic electronics is a field of material science that has encountered a rapid advance over the last few decades and has now reached the commercial marketplace. Its most relevant example is represented by Organic Light-Emitting Diodes (OLEDs) technology, able to combine the device low energy consumption and low production costs with many additional appealing features, such as large emitting surfaces, transparency and flexibility, color-tunability and color-quality. These unique properties of OLEDs allow to design low cost, large area flexible displays and white lighting sources that can fit to many different environmental requirements, resulting in tremendous benefits in imaging, lighting, automotive, transportation, communication, agriculture and medicine. This chapter provides an overview on the basic working principles of the devices with the analysis of the different kinds of emission mechanisms and the methods to improve quantum efficiency by optimization of the device architecture. The main classes of materials employed in OLED technology are presented focusing on few representative examples while the challenges to be faced by future research on material and device stability are discussed in view of commercialization applications. Some of the outstanding results recently obtained in white OLEDs (WOLEDs), able to produce a revolution in the next generation lighting industry, are also presented at the end of the chapter.