This chapter discusses the physics of weak- and strong-coupling light–matter regimes between light and organic molecules with a special focus on organic electroluminescent device applications. It explains three kinds of devices and related applications: white organic light-emitting diodes (OLEDs) in weak coupling for lighting, polariton light-emitting diodes under strong and ultrastrong-coupling regime, and organic polariton lasers. As the total thickness of an OLED is comparable to the wavelength of the emitted light, this class of devices can be integrated in an optical cavity made by two metallic or dielectric mirrors. A typical OLED is made by several thin organic layers deposited by solution or thermal evaporation processes, embedded between two electrodes: a high work function anode, typically indium tin oxide, and a low work function metallic layer, such as Ag or Al. The dynamics of organic polariton electroluminescence are very similar to that previously reported for photoluminescence.