Researchers from North Carolina State University and the University of Texas have developed and demonstrated a new approach for designing photonic devices. The new method enabled the team to control the direction and polarization of light from thin-film LEDs, overcoming the widely known obstacles of beam shaping that arise from their Lambertian nature. Such LEDs with directional and polarized light emission could be useful for many photonic applications.

'This is a fundamentally new device architecture for photonic devices,' says Franky So, corresponding author of a paper describing the work and Professor of Materials Science and Engineering at NC State. 'And we've demonstrated that, using our approach, directional and polarized emissions from an organic LED or a perovskite LED without external optical elements can be realized'.

A research team, led by University of Minnesota Professor K. Andre Mkhoyan, has made a discovery that blends the best of two sought-after qualities for touchscreens and smart windows'transparency and conductivity.

The atomic arrangement of both the BaSnO3 crystal and the metallic line defect. Image credit UMN

The researchers have observed metallic lines in a perovskite crystal. Perovskites are abundant in the Earth's center, and barium stannate (BaSnO₃) is one such crystal. However, it has not been studied extensively for metallic properties because of the prevalence of more conductive materials like metals or semiconductors. The finding was made using advanced transmission electron microscopy (TEM), a technique that can form images with magnifications of up to 10 million.

China-based Zhijing Nanotech develops perovskite-QD film (PQDF) technologies for the display industry, and the company demonstrated its first prototypes in 2018.

Perovskite-Info has talked with the company's management, which updated us that it recently concluded a successful pilot with TCL. TCL, in collaboration with Zhijing Nanotech, produced 500 75-inch QD-enhanced LCD TVs (TCL 4K 75M10) with Zhijing's PQDF films. The company reports that the TVs featured a wide color gamut, 147% BT709 - which is higher than most QD TV's on the market, and higher than TCL's original 75M10 TVs.

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UK-based Quantum Solutions published this video below that demonstrates its latest perovskite QD film for LCD color conversion:

Quantum Solutions now offers its QDot SharpGreen Perovskite QDs Film, which is a polymer composite with embedded QDot SharpGreen Perovskite QDs. It is designed to be used in LCD backlighting units and sensor devices for X-rays and UV lights. The material has green emission 520-535 nm (depending on the concentration), high PLQY (up to 80-100 %) and narrow FWHM ( 70-80 % of initial photoluminescence within 1000 hours of exposing by heat (85 °C and blue light 10 mW/cm² exposure) and high relative humidity (90 % RH at 60 °C).

Researchers at The University of Cambridge and Zhejiang University recently created highly efficient LEDs by depositing mixed-dimensional perovskites on a thin lithium fluoride interface. The fabrication method they used reportedly resulted in LEDs with impressive external quantum efficiencies, while also enabling the deposition of perovskites on a material that they are typically incompatible with.

Image from Nature Electronics

The researchers have been conducting research into perovskite-based LEDs for a few years now. Back in 2018, they created a near-infrared LED using perovskite-polymer heterostructures that achieved external quantum efficiencies of over 20% and internal quantum efficiencies of almost 100%.

Researchers from Russia-based ITMO University have created a perovskite-based surface that can turn normal glass into a smart surface. The surface will also be able to convert solar energy into electricity.

"Perovskite films are successfully implemented in LED production. We want to use these films to create surfaces that could be potentially used in AR screens. They have to be transparent enough for users to be comfortable looking through them. At the same time, they have to radiate light to display the necessary information on the screen," explains Sergey Makarov, lead researcher at ITMO's Faculty of Physics and Engineering.

An exciting application for perovskite QDs, which is likely to be the first commercial adoption of pQDs, is for the display market - films that convert blue LED LCD backlight to green.

Switzerland-based nanomaterial developer Avantama told us that the company passed the OEM qualification with its green pQD film, together with a KSF phosphor solution on the LED chip. Avantama expects the first commercial LCD display to adopt this solution to hit the market in 2021.

A team of researchers at the Ulsan Institute of Science and Technology (UNIST) and Korea University, led by Professors Myung-Hoon Song, Sang-Gyu Kwak and Han-Young Woo, recently announced the development of a PeLED - a perovskite-based LED device, that emits blue light.

The team explained that the perovskite light emitting device, which uses perovskite as a color material, is more than three times more efficient than before and has a high color purity, enabling a clear blue color.

Researchers at Northwestern University have developed a new method for synthesizing halide perovskite nanocrystals.

The synthesis process for the halide perovskite nanocrystal arrays. Image from Science Advances

'This method could be used to create optical displays with 'true' reds, greens, and blues that completely outshine current LEDs,' said Northwestern's Chad A. Mirkin. 'From color purity to pixel density, these nano-LEDs point toward a potentially dramatic improvement over current LEDs.'