The organic films consist of a hole-injection layer, a hole transport layer, an emissive layer and an electron-transport layer. While voltage is applied to the OLED cell, the injected positive and negative charges recombine in the emissive layer and make electro luminescent light. Unlike LCDs, which require backlighting, OLED displays are emissive devices they emit light rather than modulate transmitted or reflected light.

OLED technology was invented by Eastman Kodak in the early on 1980s. It is start to replace LCD technology in handheld devices like PDAs and cellular phones as the technology is brighter, thinner, faster and lighter than LCDs, use less power, present higher contrast and are cheaper to produce. An important step in the evolutionary process starts with the use of thin-film organic layers. The first EL slim film device used a single organic layer sandwiched between two injecting electrodes.