Jul 5 2013
Light emitting capacitor (LEC) is an electroluminescent device in which the active layer is an electroluminescent polymer - a polymer which emits photons when an electrical current is passed through it. The polymers used are conjugated polymers, meaning the chemical and electronic structure of the material allow it to act as an ionic conductor, giving it the electronic and optical properties of a semiconductors.
LECs provide mulitple advantages - they are compatible with inexpensive manufacturing processes, eliminate the need for a transparent anode, and are independent of the difference in the work function of the electrodes. This article will elaborate on the working, construction and applications of LECs.
Working
The active polymer layer consists of electronic and ionic conductors. This layer is in between the two electrodes. When an electric charge is applied on the electrodes, electrons and holes are released and they accumulate around the polymer layer. The recombination of the electron hole pairs causes the polymer layer to emit light.
Construction
The polymer layer of the LEC is sandwiched between the two electrodes. The polymer layer is an ionic conducting layer, made of conjugated polymers like poly (ethylene oxide), MEH-PPV, etc.
In recent years, a number of LECs have been developed having different configurations as listed below:
- Planar LECs
- Bilayer LECs – capable of emitting different colors at forward and reverse bias
- Frozen p-i-n junction LECs – capable of functioning like diodes
- Phosphorescent LECs
Applications
Some of the typical applications of LECs are given below:
- Information displays
- High-brightness lighting
- Flexible flat-panel displays