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Perovskite the mineral contains calcium, titanium and oxygen arranged in a crystal structure. It was discovered in the 1800s, but people later realised that they could make other kinds of perovskites that shared the same structure while having different elements or molecules as the components.<\/p>\n
Depending on the materials chosen, perovskites can be really good at, for example, conducting electricity or emitting light.<\/p>\n
\u201cBy slightly tuning the chemical composition you can cover the full visible spectrum,\u201d says Dr Braga, explaining that making perovskites is a relatively simple and cheap process. \u201cIf you think about mass production, this is gigantic.\u201d<\/p>\n
There are some problems, though. <\/p>\n
PeLEDs are notoriously unstable \u2013 they go bad with exposure to moisture or oxygen, for instance. Loreta Muscarella at VU Amsterdam, a university, is working to develop new kinds of PeLEDs.<\/p>\n
She says that if you leave a PeLED lying around for a few hours or days, the colour of light it emits will gradually degrade or shift to a less pure version of, say, green, than the green you want.<\/p>\n
And this undermines the whole point of perovskites. They are desirable in part because they can be tuned to emit a very specific, very pure form of red, green or blue \u2013 the key hues required for full colour digital displays.<\/p>\n<\/div>\n
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To keep them stable, PeLEDs can be encapsulated in glue or resin, says Prof Gao. But researchers are still working on ensuring that the technology does not falter over a long period.<\/p>\n
Dr Muscarella says that traditional LEDs have lifetimes of 50,000 hours or more whereas PeLED lifespans are still in the hundreds to thousands of hours range.<\/p>\n
It could be years before you buy a commercial product that contains a PeLED, she adds.<\/p>\n
But there\u2019s a different type of light-emitting perovskite that you might see on the market first.<\/p>\n
It relies on photoluminescence. This isn\u2019t an LED as such but rather a filter or film-like material that absorbs and re-emits light in a particular colour.<\/p>\n
In some TV\u2019s on the market today, a coloured filter supplies the crucial red, green and blue colours used in every pixel on the screen.<\/p>\n
It\u2019s by mixing those colours at different levels that you can get the range of hues required to display a full picture.<\/p>\n
The red, green and blue filters are lit up by an LED backlight. But today\u2019s filters actually block a lot of that light.<\/p>\n
Photoluminescent perovskites, in contrast, let almost all the light through, which would mean a big increase in brightness and efficiency.<\/p>\n
Helio, a British company, is working on this. A video on their website shows how a red or green coloured perovskite film can re-emit blue light as either red or green almost perfectly.<\/p>\n<\/div>\n\n