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Atom swapping could lead to ultra-bright, flexible next generation LEDs

Mon, 07/06/2021 - 16:25

The researchers, led by the University of Cambridge and the Technical University of Munich, found that by swapping one out of every one thousand atoms of one material for another, they were able to triple the luminescence of a new material class of light emitters known as halide perovskites.  

This ‘atom swapping’, or doping, causes the charge carriers to get stuck in a specific part of the material’s crystal structure, where they recombine and emit light. The results, reported in the Journal of the American Chemical Society, could be useful for low-cost printable and flexible LED lighting, displays for smartphones or cheap lasers.

Many everyday applications now use light-emitting devices (LEDs), such as domestic and commercial lighting, TV screens, smartphones and laptops. The main advantage of LEDs is they consume far less energy than older technologies.

Ultimately, also the entirety of our worldwide communication via the internet is driven by optical signals from very bright light sources that within optical fibres carry information at the speed of light across the globe.

The team studied a new class of semiconductors called halide perovskites in the form of nanocrystals which measure only about a ten-thousandth of the thickness of a human hair. These ‘quantum dots’ are highly luminescent materials: the first high-brilliance QLED TVs incorporating quantum dots recently came onto the market.

The Cambridge researchers, working with Daniel Congreve’s group at Harvard, who are experts in the fabrication of quantum dots, have now greatly improved the light emission from these nanocrystals. They substituted one out of every one thousand atoms with another – swapping lead for manganese ions – and found the luminescence of the quantum dots tripled.

A detailed investigation using laser spectroscopy revealed the origin of this observation. “We found that the charges collect together in the regions of the crystals that we doped,” said Sascha Feldmann from Cambridge’s Cavendish Laboratory, the study’s first author. “Once localised, those energetic charges can meet each other and recombine to emit light in a very efficient manner.”

“We hope this fascinating discovery: that even smallest changes to the chemical composition can greatly enhance the material properties, will pave the way to cheap and ultrabright LED displays and lasers in the near future,” said senior author Felix Deschler, who is jointly affiliated at the Cavendish and the Walter Schottky Institute at the Technical University of Munich.

In the future, the researchers hope to identify even more efficient dopants which will help make these advanced light technologies accessible to every part of the world.

 

Reference:
Sascha Feldmann et al. ‘Charge carrier localization in doped perovskite nanocrystals enhances radiative recombination.’, Journal of the American Chemical Society (2021). DOI: 10.1021/jacs.1c01567

An international group of researchers has developed a new technique that could be used to make more efficient low-cost light-emitting materials that are flexible and can be printed using ink-jet techniques.

Ella Maru StudioArtist’s impression of glowing halide perovskite nanocrystals


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Yes

Mind Over Chatter: What is the future?

Thu, 27/05/2021 - 14:22
Season 2, episode 1

This second series of Mind Over Chatter is all about the future - and in this first episode we’re going to be considering what the future even is… Have you ever wondered how time works? It turns out, the answer is a lot more complicated than we thought.

Join our wondering and wonderful conversation with philosopher of science Dr Matt Farr, whose work focuses particularly on what it means for time to have a direction, professor of psychology Nicky Clayton, who looks at the evolution and development of intelligence in non-verbal animals and pre-verbal children, and professor of linguistics and philosophy, Kasia Jaszczolt whose research interests combine semantics, pragmatics, and the metaphysics of time 

We’ll be talking about everything from physics to linguistics… and from broken eggs to Einstein’s theory of relativity. 

Subscribe to Mind Over Chatter

Key points

[04:28] - Does time actually go from past to present to future? And does time really ‘flow’?

[09:53] - How do B-theorists deal with entropy? Can you un-break an egg?

[14:12] - Recap of the first portion of the episode, reviewing A-theory, B-theory and C-theory of time

[18:58] - How the mind understands the subjective concept of time

[27:11] - The Sapir-Whorf Hypothesis and how the way you talk about language affects the way you perceive and think about things

[30:21] - Recap of the second portion of the episode 

[34:02] - How do the mental and linguistic concepts around time fit with philosophical concepts and physics of time?

[45:46] - Is there a conflict between the psychological and linguistic models of time and the way physics handles time?

[48:20] - Recap of the last portion of the episode

Mind Over Chatter: The Cambridge University Podcast