We all know that LED light bulbs are vastly more energy efficient than incandescent bulbs, but there’s a quirk in that efficiency that most folks may not realize. As higher currents are fed to LEDs, past a certain point they become way less efficient — a phenomenon known as “LED droop.”
Researchers James Speck and Claude Weisbuch of the Center for Energy Efficient Materials at UC Santa Barbara have finally figured out what causes this “LED Droop,” though, and have published their results in a paper called Direct Measurement of Auger Electrons Emitted from a Semiconductor Light-Emitting Diode under Electrical Injection: Identification of the Dominant Mechanism for Efficiency Droop in the journal Physical Review Letters. Unfortunately, as is all too often the case with intriguing scientific papers, this one is behind a pay wall (Grr! Seriously, people, embrace PLoS as the future!), but UC Santa Barbara’s engineering website has a nice overview for the less scientifically inclined:
In 2011, UCSB professor Chris van de Walle and colleagues theorized that a complex non-radiative process known as Auger recombination was behind nitride semiconductor LED droop, whereby injected electrons lose energy to heat by collisions with other electrons rather than emitting light.
A definitive measurement of Auger recombination in LEDs has now been accomplished by Speck, Weisbuch, and their research team.
The experiment used an LED with a specially prepared surface that permitted the researchers to directly measure the energy spectrum of electrons emitted from the LED. The results unambiguously showed a signature of energetic electrons produced by the Auger process.
The researchers say that this discovery will lead to new ways of designing LED bulbs that avoid droop and produce higher light output at higher currents.
Combine this innovation with the continuing drop in LED bulb pricing, and the increase in products that support LED dimming, and our lighting woes may soon be over.