Researchers have designed smart, color-controllable white-light devices from quantum dots — tiny semiconductors only a few billionths of a meter in size — that are more efficient and have better color saturation than LEDs. standard, and can dynamically replicate daylight conditions in a single light.
The researchers, from the University of Cambridge, designed the next-generation smart lighting system using a combination of nanotechnology, color science, advanced computing methods, electronics and a unique manufacturing process .
The team found that by using more than the three primary lighting colors used in typical LEDs, they were able to reproduce daylight more accurately. Early testing of the new design showed excellent color rendering, a wider operating range than current smart lighting technology, and a wider spectrum of white light customization. The results are published in the journal Nature Communication.
As the availability and characteristics of ambient light are linked to well-being, the widespread availability of smart lighting systems may have a positive effect on human health since these systems can respond to individual mood. Smart lighting can also respond to circadian rhythms, which regulate the daily sleep-wake cycle, so light is reddish-white in the morning and evening, and bluish-white during the day.
When a room has sufficient natural or artificial lighting, good glare control and a view of the outside, it is said to have a good level of visual comfort. In indoor environments under artificial light, visual comfort depends on the accuracy of color rendering. Since the color of objects is determined by lighting, smart white lighting must be able to accurately express the color of surrounding objects. Current technology achieves this by using three different colors of light simultaneously.
Quantum dots have been studied and developed as light sources since the 1990s, due to their high tunability and color purity. Due to their unique optoelectronic properties, they exhibit excellent color performance in both wide color controllability and high color rendering ability.
Cambridge researchers have developed an architecture for next-generation smart white lighting based on quantum dot light-emitting diodes (QD-LEDs). They combined system-level color optimization, device-level optoelectronic simulation, and material-level parameter extraction.
Researchers produced a computational design framework from a color optimization algorithm used for neural networks in machine learning, as well as a novel method for charge transport and emission modeling. light.
The QD-LED system uses several primary colors – beyond the commonly used red, green and blue – to more accurately mimic white light. By choosing quantum dots of a specific size – between 3 and 30 nanometers 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 team then validated their design by creating a new QD-LED-based white lighting device architecture. The test showed excellent color rendition, a wider operating range than current technology, and a wide range of white light hue customization.
The QD-LED system developed by Cambridge showed a correlated color temperature (CCT) range of 2243K (reddish) to 9207K (bright midday sun), compared to current LED-based smart lights that have a CCT between 2200K and 6500K. The Color Rendering Index (CRI) – a measure of colors illuminated by light compared to daylight (CRI=100) – of the QD-LED system was 97, compared to current smart bulb ranges , which are between 80 and 91 .
The design could pave the way for more efficient and precise smart lighting. In a smart LED bulb, the three LEDs must be individually controlled to achieve a given color. In the QD-LED system, all quantum dots are driven by a single common drive voltage to achieve the full color temperature range.
“This is a world’s first: a fully optimized, high-performance smart white lighting system based on quantum dots,” said Professor Jong Min Kim of Cambridge’s Department of Engineering, who co-led the research. . “This is the first step towards fully exploiting quantum dot-based smart white lighting for everyday applications. »
“The ability to better dynamically reproduce daylight through its varying color spectrum in a single light is what we were looking for,” said Professor Gehan Amaratunga, who co-led the research. “We achieved this in a new way through the use of quantum dots. This research paves the way for a wide variety of new reactive lighting environments for humans. »
The structure of the QD-LED white light developed by the Cambridge team is scalable for large lighting surfaces, as it is manufactured with a printing process and its control and drive is similar to that of a screen. With standard point source LEDs requiring individual control, this is a more complex task.
The research was partly funded by the European Union and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI).
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