Researchers at the University of Cambridge have developed an LED smart lighting system using a combination of printed nanotechnology, colour science and advanced computational methods.
Using quantum dots, the team found that by using more than the three primary lighting colours used in typical LEDs, they were able to reproduce daylight more accurately through both wide colour controllability and high colour rendering capability.
The researchers developed an architecture for the quantum dot LEDs that combines system-level colour optimisation, device-level optoelectronic simulation, and material-level parameter extraction.
The researchers produced a computational design framework from a colour optimisation algorithm used for neural networks in machine learning, together with a new method for charge transport and light emission modelling.
The system uses multiple colours to more accurately mimic white light. By choosing quantum dots of a specific size – between three and 30 nanometres in diameter – the researchers were able to overcome some of the practical limitations of LEDs and achieve the emission wavelengths they needed to test their predictions.
The structure of the QD-LED white lighting developed by the Cambridge team is scalable to large area lighting surfaces, as it is made with a transfer printing process using cadmium selenide (CdSe) quantum dots for red, green, cyan, and blue light. These are driven by a single common control voltage to achieve the full colour temperature range.
The team then validated their design by creating a new device architecture of QD-LED based white lighting. The test showed excellent colour rendering, a wider operating range than current technology, and a wide spectrum of white light shade customisation.
The system showed a correlated colour temperature (CCT) range from 2243K (reddish) to 9207K (bright midday sun), compared with current LED-based smart lights which have a CCT between 2200K and 6500K. The colour rendering index (CRI) – a measure of colours illuminated by the light in comparison to daylight (CRI=100) – of the QD-LED system was 97, compared to current smart bulb ranges, which are between 80 and 91.
“This is a world-first: a fully optimised, high-performance quantum-dot-based smart white lighting system,” said Professor Jong Min Kim from Cambridge’s Department of Engineering, who co-led the research. “This is the first milestone toward the full exploitation of quantum-dot-based smart white lighting for daily applications.”
“The ability to better reproduce daylight through its varying colour spectrum dynamically in a single light is what we aimed for,” said Professor Gehan Amaratunga, who co-led the research. “We achieved it in a new way through using quantum dots. This research opens the way for a wide variety of new human responsive lighting environments.”
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