Sunday, 25 March 2012

LED can emit more optical power than the electrical power it consumes

(PhysOrg.com) -- For the first time, researchers have demonstrated that an LED can emit more optical power than the electrical power it consumes. Although scientifically intriguing, the results won't immediately result in ultra-efficient commercial LEDs since the demonstration works only for LEDs with very low input power that produce very small amounts of light.

The researchers, Parthiban Santhanam and coauthors from MIT, have published their study in a recent issue of Physical Review Letters.

As the researchers explain in their study, the key to achieving a power conversion efficiency above 100%, i.e., "unity efficiency," is to greatly decrease the applied voltage. According to their calculations, as the voltage is halved, the input power is decreased by a factor of 4, while the emitted light power scales linearly with voltage so that it's also only halved. In other words, an LED's efficiency increases as its output power decreases. (The inverse of this relationship - that LED efficiency decreases as its output power increases - is one of the biggest hurdles in designing bright, efficient LED lights.)