Clare Kenyon
Finding a more natural light might take a big step forward with quantum dots.
LED (Light-emitting diode) technology has brought about a revolution in lighting — particularly in terms of efficiency and colour. But there’s still daylight between what traditional LEDs can produce and what we get when we step outside into the sun. They in turn are a big step up from fluorescent, halogen and incandescent bulbs.
LEDs produce “white” light either by conversion from blue light via a phosphor coating or by combining three separate LEDs, each with one of the three primary colours of light (red, blue and green).
Now, a research group from the University of Cambridge has delved into the tiny world of quantum dots (semiconductors just tens of atoms across) to design smart, colour-controllable white light devices able to produce white light and replicate a wider range of colours than current smart lighting technology.
Professor Gehan Amaratunga from Cambridge’s Department of Engineering, who co-led the research, says this increases the potential for a positive impact on human health and well-being, as they can be fine-tuned to respond to individual mood and circadian rhythms.
“It opens the way for a wide variety of new human responsive lighting environments,” Amaratunga says.
So, Quantum… whats? Let me try to ahem…enlighten…ahem…you.
Quantum dots are sometimes known as artificial atoms because their crystal or lattice structures mimic the discrete electronic energy levels found in isolated atoms. A photon (or packet of light) is produced when an electron and a “hole” (where there is no electron) combine within a quantum dot and this can be controlled by applying a laser beam or electric or magnetic field. The wavelength (or colour) of the light produced is effectively determined by the size of the quantum dot material.
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By choosing quantum dots that are between three and 30 nanometres in diameter, the Cambridge University team achieved correlated colour temperature (CCT) of between 2243 K (reddish) to 9207 K (bright, midday sun) which far outshines the 2200 K–6500 K CCT range achieved by LEDs.
CCT is the lighting colour equivalent of weather forecast “feels like” temperature ranges.
Although quantum dots as light sources have been investigated for almost 30 years, this innovative approach is scalable to large area lighting systems and can be made with a printing process. “This is a world-first: a fully optimised, high-performance quantum-dot-based smart white lighting system,” says Professor Jong Min Kim from Cambridge’s Department of Engineering who also co-led the research. It’s the “first milestone toward the full exploitation of quantum-dot-based smart white lighting for daily applications”.