Abstract
Organic electroluminescent (EL) materials are currently under intense investigation due to their potential application in low-cost full color displays.Over the past ten years, research efforts have been directed towards improvement of organic light-emitting diodes (OLEDs) by means of molecular engineering and improved device architectures. Existing organic EL materials can be divided into three main classes: small molecules, conjugated polymers, and, more recently, dendrimers. Among them, fluorescent small-molecule-based OLED devices have been studied for longest and were first to become commercially available. The most efficient OLED devices reported to date are based on small molecules that are phosphorescent rather than fluorescent, with peak external quantum efficiencies (EQEs) in the range 10-20 % being reported.