Abstract Technologies based on organic semiconductors may answer the increasing demands that consumers make in the areas of large-area electronics, lightweight displays, and portable computing. Advances in scientific understanding, technology, and device performance have occurred particularly rapidly in the area of polymer light-emitting diodes (LEDs). Material properties and economic considerations suggest that polymer LEDs are the devices most likely to win the race to applications that produce light on inorganic substrates such as glass and silicon, as well as plastic substrates. The field of semiconducting polymers has its root in the 1977 discovery of the semiconducting properties of polyacetylene 1 . This breakthrough earned Alan Heeger, Alan MacDiarmid, and Hideki Shirakawa the 2000 Nobel Prize in Chemistry for ‘the discovery and development of conductive polymers’ 2–5 . Other review articles capture how more than two decades of developments in the physical and chemical understanding of these novel materials has led to new device applications as active and passive electronic and optoelectronic devices ranging from diodes and transistors to polymer LEDs, photodiodes, lasers, and solar cells 6–11 . Much interest in plastic devices derives from the opportunities to use clever control of polymer structure combined with relatively economical polymer synthesis and processing techniques to obtain simultaneous control over electronic, optical, chemical, and mechanical features 5 . This article focuses on the advances leading to polymer LEDs 12–14 .