It took nearly 30 years, but those applications finally did show up in the marketplace.  Today, in the form of "Indiglo" technology, electroluminescence has gained a firm foothold in consumer products, mainly in wristwatches, but also in nightlights.  In addition, it is appearing in such uses as automobile instrument gauges and palmtop computer screens, and the technology is likely to find additional applications soon.

Electroluminescence is a very efficient means of converting electricity into light.  In Indiglo watches, a thin layer of phosphorescent material (zinc sulfide doped with copper) is sandwiched between two thin layer electrodes, one of which is transparent.  When a sufficiently high AC voltage is applied to the electrodes, the atoms of the phosphorescent material absorb energy and are raised to an excited state.  They subsequently decay to a lower energy state (i.e., lose that energy) and emit photons.  Although this phenomenon had been known for many years (well before I wrote my senior thesis), its use in a wristwatch only became possible through the development of very small batteries that provide the electricity and microchips that transform it to the necessary voltage and control its application to the electrodes.