LEDs, or light-emitting diodes, are used in a swathe of technologies and applications, such as the backlights in electronic displays, light-based communication, and even medical sterilisation equipment. Theyâre altogether an omnipresent technology that holds much promise for the future.
Now, working in collaboration with the Indian Institute of Technology (IIT) Guwahati, a team of researchers from Imperial College London (ICL) claims to have found a new way to boost the amount of light that LEDs produce while extending their shelf life. The teamâs research was published in Light: Science & Applications in July 2020.
A Layer of Nanoparticles
By introducing a meta-grid of sub-wavelength-sized plasmonic nanoparticles into existing semiconductor LEDs, the researchers say that the transmission of light across the LED chip/encapsulant interface can be enhanced.
Imperial College Londonâs (ICL) diagram, which shows a side-on view of its light-emitting diode (represented by the overall dome shape), embedded with nanoparticles (represented by the grey spots in alignment). Image Credit: ICL, via Nature Communications.
The âtwo-dimensionalâ layer of nanoparticles was placed between the light-producing semiconductor chip and the transparent casing, which, despite being necessary to prevent damage, can cause the light emitted by the chip to be reflected (thus reducing the amount of light that escapes).
In response to the above, ICL and IITâs addition of the finely tuned nanoparticles reduced such problematic light reflections, allowing up to 20% more light to be emitted as a result. This also reduced the amount of heat inside the LEDâanother pitfall caused by the initial reflection of lightâwhich was found to help the semiconductor chip to last longer, increasing device longevity.
Suitable for Existing Manufacturing Processes
This study isnât the first time that LED casing improvements have been suggested. However, as the projectâs co-author Dr Debabrata Sikdar explains, these have typically made the LED more bulky or difficult to manufacture. This diminishes the economic effect of the improvement. The ICL and IIT researchers believe that, based on the theory and analysis behind the study, their LED innovation âcould be introduced into existing manufacturing processes with little disruption or added bulkâ.
The studyâs co-author, Professor Sir John Pendry from ICL, said: âThe simplicity of the proposed scheme, and the clear physics underpinning it, should make it robust, and, hopefully, easily adaptable to the existing LED manufacturing processâ.
With larger light emission efficiency, the collaborating universitiesâ LEDs could lead to greater energy savings, which, together with better device longevity, could well have a positive impact on the multi-billion-dollar global LED market and the wider environment. The researchers believe that the principles of this study can be used alongside existing schemes for enhancing the light extraction efficiency of LEDs. They also believe their solution could be applied to other optical devices, such as solar cells, where light transmission across interfaces also takes place.
Future Research and Development Potential
The next challenge for the manufacturers will be to develop a prototype LED with a nanoparticle layer and test the theoretical configurations accordingly. This includes their research into the size, shape, material, and spacing of the deviceâs nanoparticles, as well as the question of how far this layer should be from the semiconductor chip.