Organic light-emittig diodes : four different technologies

Organic Light-Emitting Diodes (OLEDs) are electronic devices whose main component is an organic semiconductor capable of emitting light under the effect of an electric field. Since their discovery in 1987, they have been the subject of intense research by chemists, physicists and electronic engineers. These devices, some of which are already on the market, are increasingly gaining a foothold in the electronics market. Today, they can be found in all types of display systems, as well as in new electronic objects such as flexible and rollable screens, and some are even being used in future light walls.

While the first OLEDs were based on fluorescent molecules or polymers (1987), they gradually gave way to the more efficient phosphorescent emitter OLEDs (PhOLEDs) (1998). In a PhOLED, the platinum- or iridium-based organometallic phosphorescent component is present as a dopant in an organic host matrix. In 2009, a new emission mechanism was demonstrated: thermally activated delayed fluorescence (TADF OLED), making it possible to dispense with phosphorescent emitters while maintaining high emission yields. More recently, a fourth generation of hyperfluorescent OLEDs has emerged, combining the benefits of TADF and fluorescence (3rd and 1 ^re generations) and heralded as highly efficient, low-cost and superior color emission. The aim of this reference article is to provide an overview of these four generations of OLEDs through their different emission mechanisms, their performance and their limitations.

At the end of the article, readers will find a glossary and a table of acronyms and formulas used.