New phosphor blend for LEDs could crank up Li-Fi speed

Adding perovskite to the material that converts blue LED light into white boosts visible light communication modulation rates by a factor of 40, researchers find, improving the capabilities of Li-Fi.

LED-based data speeds could operate 40 times faster than they do today if manufacturers alter the design of the phosphors that convert light from blue LEDs into the white light of LED lamps and luminaires, researchers have concluded.

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A team of scientists at King Abdullah University of Science and Technology in Saudi Arabia found that a color converter made from a combination of a red phosphor and perovskite nanocrystals supports visible light communication (VLC) modulation rates of nearly 500 MHz, which they said is 40 times faster than what conventional phosphor material allows.

By adding perovskite to the phosphor mix, Li-Fi might easily exceed Wi-Fi speeds. (Source: ACS Photonics.)

VLC uses the invisible modulations in LED lightwaves to transmit data via the lightwaves. It is the technology behind Li-Fi, the light-based alternative to radio-based Wi-Fi, for wireless Internet transmission. It is also one of several technologies that can be used in lighting-based indoor positioning systems which help track people, products, and assets around factories, stores, workplaces, and other environments.

The red phosphor and perovskite material modulates faster than conventional yttrium aluminum garnet (YAG) phosphor because it has shorter “excited-state lifetimes,” the researchers stated.

“The conventional lighting phosphors that are typically integrated with LEDs have limited modulation bandwidth and thus cannot provide the bandwidth required to realize the potential of VLC,” the team said in the journal ACS Photonics. “In this work, we present a promising light converter for VLC by designing solution-processed CsPbBr₃ perovskite nanocrystals (NCs) with a conventional red phosphor. The fabricated CsPbBr₃ NC phosphor-based white light converter exhibits an unprecedented modulation bandwidth of 491 MHz, which is about 40 times greater than that of conventional phosphors.”

The perovskite material supports data transmission rates of up to 2 Gbit/sec, the team said. The paper did not state whether that is also up to 40 times faster than the transmission rates of VLC using today's phosphors. But according to Phys.org, 2 Gbit/sec is significantly faster than Wi-Fi, which “can reach speeds of only a few tens of Mbits/second.”

Supporters of Li-Fi and its underlying VLC technology say that it will add enormous capacity to wireless communications, because the visible light spectrum is 10,000 times larger than the radio frequency spectrum that Wi-Fi uses. They also say that it has a much higher data density than Wi-Fi, and that it is less prone to electromagnetic interference. It does, however, have a shorter range than Wi-Fi.

Li-Fi could become an important artery in the Internet of Things (IoT). Last spring, Germany's Fraunhofer Institute of Telecommunications, Heinrich Hertz Institute (HHI) demonstrated how Li-Fi could help visually inspect cars on the factory floor at an automobile plant.

As our sister publication Lux Review has reported, the Paris Metro looks set to deploy Li-Fi, as does the Sogeprom real estate office building, also in Paris and part of banking company Société Générale. The Golden State Warriors basketball team will also install it at its new arena, planned to open next year in San Francisco.

Perovskite is a mineral with potential to improve performance across a range of products including LEDs, solar cells, and photodetectors.

MARK HALPERis a contributing editor for LEDs Magazine, and an energy, technology, and business journalist ([email protected]).