A doctoral student at the University of Manchester has discovered a material that could dramatically improve the performance of smartphone displays – as well as reducing their cost. MM sat down with soon-to-be Dr Charlotte Riley to learn more.
New science is often the result of catching something unexpected. Diving into results and scouring data to find, surprisingly, something shimmering sapphire-like in a side product. Well, that at least was the case for Charlotte Riley.
Charlotte, who is currently completing a PhD, was trying to make a different molecule altogether when she found traces of a new host material in her data. You can imagine her excitement as things began to look, unexpectedly, more and more promising.
She is entirely transparent about what happened: “The discovery was completely serendipitous.
“After realising it had several properties that made it an excellent candidate for a host I went back to optimise the synthesis and make it on purpose.”
It’s one of those scientific discoveries which feels gilded by fate.
What Charlotte had uncovered was a material which encourages blue light emission in LEDs more efficiently than anything currently available. Less electricity, more power.
And if you think that sounds niche – just consider how often you use your phone.
Minuscule LEDs lie beneath a phone screen – small specks of energy that power your Instagram, TikTok and email display, similar to those which Charlotte has spent her PhD researching.
Organic LEDs were invented in 1987 by scientists Ching Wan Tang and Steven Van Slyke, a discovery which gave them a spot in the National Inventors Hall of Fame. They showed in organic materials, that when an electron had been given enough energy to jump up an energy level, it emitted green light when it hopped back down. OLEDs, as they’re called, were set to cause an overhaul to the display industry.
Accelerate forward to recent years, and the flexible, foldable and rollable screens now available owe all their glory to OLEDs. They have become adept at light production and the future of displays is bright.
A screen display needs three types of light: red, green and blue. As your battery percentage dwindles during a three-hour long doom scroll, the tiny colourful OLEDs behind your phone’s glass screen leach energy to power themselves.
Only the blue OLEDs are greedier than red and green. Whilst electrons can emit energy as light, they can also travel back down to their original energy in other ways without doing so, hopping across and down alternate energy routes that don’t release light. In blue OLEDs electrons are particularly good at finding these other pathways.
Avoiding energy leakages is usually expensive and complicated.
So as it stands, blue OLEDs need more electricity to produce the same amount of light. You can blame blue light, in part, as the reason you’re reaching for your charging cable quite so often.
That’s what makes Charlotte’s one-step sapphire discovery so useful. Recently published in Communications Chemistry, her research at the University of Manchester in partnership with the University of Eastern Finland presents a way to produce blue light emitting materials in LED displays in one simple step. And, even better, more cost-effectively.
Charlotte’s synthesis created a material which results in OLEDs with a competitive 21% efficiency in converting electricity to light, and a purer blue colour than those currently available.
She said: “Our synthesis only having a single step that takes three hours means that this material is considerably cheaper than other OLEDs.”
Condensing the multiple reactions currently used into one single reaction to create blue-emitting OLED materials not only produces a better colour, but has the potential to be more environmentally friendly. Less waste, greater efficiency.
“The reaction that produces the material is a fairly well known procedure but before this work no one had used it to make a molecule like ours,” she said.
Charlotte admits that the material isn’t perfect: “At high voltages, efficiency dropped significantly indicating that there is an issue with the stability of the material.
“There are a number of chemical changes we can make to the host to try and improve this, but achieving high efficiencies with such a simple molecule is a very promising place to start.”
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