Organic lighting is one of the first conjugated, semiconducting polymer technoligies to make it to the commercial market. Our group has been researching their use long before the technology was commerically viable, and even now there are plenty of unanswered research questions.
Polymer LEDs work on the same principles as polymer photovoltaics (here) but with an opposite goal. Instead of trying to separate the neutral exciton at an interface, polymer LEDs take advantage of the exciton's short lifetime. When the exciton radiatively recombines it emits light, with a color specific to the bandgap of that polymer. The ability to color-tune the emission of polymer LEDs is a huge advantage over traditional inorganics such as GaAs.