Soap molecule could help make alternative LED tech commercially viable

Adding a molecule normally used in detergent to an infrared LED could make devices that are easier to manufacture, require less energy and display richer colours than existing ones.

Solar cells and LEDs made from perovskite, a titanium and calcium crystal, have long held promise as being more efficient and easier to produce than commonly used silicon-based devices, but making them both stable and efficient enough to rival silicon’s commercial success has proved difficult.

Now, Dawei Di at Zhejiang University in China and his colleagues have developed an infrared perovskite LED device that lasts for more than 10,000 hours, similar to typical silicon LEDs, while also matching on efficiency. The next best perovskite LEDs had only lasted for a few hundred hours before becoming unstable.

“Before we saw our LEDs operating for months without degrading, I personally thought it was impossible,” says Di. “But now we think OK, near-infrared perovskite LEDs can last for a very long time.”

The key to this improved stability, says Di, is the introduction of a molecule called sulfobetaine 10 (SFB10), which is typically used as a detergent. The molecule attracts positive and negative ions that would normally move freely around in the perovskite crystal structure and compromise its stability. But with SFB10, the ions are prevented from moving.

“If we don’t use this dipolar molecular stabiliser, the ions can move and the structure of the perovskite can change… eventually it will decompose into, for example, lead iodide and other organic compounds, which are completely useless for light emission,” says Di.

While infrared LEDs aren’t suitable for ordinary lighting, it should be possible to apply the same techniques to produce visible light LEDs. “There shouldn’t be any problem in principle for us to achieve similar stability results for the green, and for the red,” says Di, though blue light may prove more difficult.

The efficiency and stability results from this new perovskite cell are very impressive, says Kyle Frohna at the University of Cambridge. “I think this sort of approach should be immediately tried in some visible LEDs because it’s very promising,” he says.