Scientists at the University of Illinois Urbana-Champaign have discovered something surprising about light-emitting diodes (LEDs).
They found that the efficiency of LEDs, specifically blue ones made of a material called indium gallium nitride (InGaN), may not be as perfect as we thought.
Usually, it’s assumed that the efficiency of these LEDs is perfect (100%) at low temperatures. Efficiency here is about how good LEDs are at turning electricity into light.
But this new research, published in Applied Physics Letters, found that the efficiency could be as low as 27.5%.
LEDs are super popular because they are energy-efficient and cost-effective. They work by allowing electric current to flow through them, which produces light. The kind of light – or color – produced is determined by the energy of the light particles (photons) produced.
InGaN-based blue LEDs are important because they provide bright, energy-saving white light. The switch to LEDs has helped to cut down on energy use and greenhouse gas emissions. But, we still need to make LEDs more efficient to meet future energy saving targets.
For example, the U.S. Department of Energy wants to increase the efficiency of blue LEDs from 70% to 90% by 2035, which would save a huge amount of energy and reduce CO2 emissions significantly.
So, how do we make LEDs even better? Professor Can Bayram says we need to understand their absolute efficiency, not just relative efficiency. Basically, we need to know how efficient LEDs are in a way that we can compare different LEDs with each other.
One way to measure the efficiency of LEDs is to look at how many light particles (photons) are created for each electron used. It was believed that at very low temperatures, every electron used would result in a photon being created (100% efficiency).
However, this research suggests that even at these low temperatures, not all the electrons result in light – some energy might be lost as heat.
In their research, Professor Bayram and a graduate student, Yu-Chieh Chiu, came up with a different way to find out the efficiency of blue LEDs at low temperatures. They used a new model and found that the efficiency was much lower than previously assumed.
Chiu explains that their new model takes a broader view of what happens inside the LED. It considers the different paths that the electric current can take within the LED, some of which may result in light, others may result in heat.
This is important because understanding these different paths can help improve the overall efficiency of the LEDs.
As we continue to study and improve LEDs, it’s important to understand their absolute efficiency. This way, scientists can compare results and build on each other’s work. Also, even a small increase in efficiency can result in large energy savings and reductions in CO2 emissions.
Therefore, having a clear picture of the efficiency of LEDs will help us make better and more energy-efficient devices.
Source: Beckman Institute for Advanced Science and Technology.
