Electroluminescent panel is most used as backlight for LCDs in watches, PDAs and other devices where a thin lightsource is needed. The optimum voltage is between 100V and 150V AC at a frequency of 60Hz to 1Khz. This is created by using a stepup transformer. The EL panel is built up like this:
__________________ electrode
================== plastic layer
****************** Phosphor layer
------------------ transparent electrode
================== Plastic or glass substrate

The electrode is transparent like the ones in LCDs. After all the layers are stacked the whole thing might be sealed in plastic to protect it, though is not done to all panels since this increases the thicknes of it.

When the AC power supply is connected to the electrodes, the energy exites the phosphor atoms and they in turn starts to emit light. The plastic layer between the phosphor and one of the electrodes prevents arching. This technology is also used in the electroluminescent display and the Active Matrix ElectroLuminescent Display.