UofT researchers’ new hybrid crystal opens door to hyper-efficient LEDs

Researchers at the University of Toronto’s Edward S. Rogers Sr. Department of Electrical & Computer Engineering announced the invention of a crystalline material that could soon lead to hyper energy efficient LED technology.

The new black crystal is the result of combining colloidal quantum dots – luminescent nanoparticles that efficiently convert electricity to light and vise versa – with a family a materials called Perovskites, another promising solar energy material that allow easy electron flow with minimal loss.

“It’s a pretty novel idea to blend together these two optoelectronic materials, both of which are gaining a lot of traction,” says Xiwen Gong, a PhD candidate working with UofT professor Ted Sargent and one of the lead authors of group’s study published recently in the journal Nature. “We wanted to take advantage of the benefits of both by combining them seamlessly in a solid-state matrix.”

Within this matrix, the perovskite lattice helps channel electrons into the quantum dots, which efficiently convert the flowing electricity to light. The trick, say the researchers, was achieving heteroexpitaxy, a state in which the atomic edges of both crystalline structures align smoothly.

“We started by building a nano-scale scaffolding ‘shell’ around the quantum dots in solution, then grew the perovskite crystal around that shell so the two faces aligned,” explained coauthor Dr. Zhijun Ning, who contributed to the work while a post-doctoral fellow at UofT and is now a faculty member at ShanghaiTech.

According the UofT research team, the combined crystal materials eliminate self-absorption, energy is reabsorbed by the material emitting it. In addition, their material has been designed to be compatible with existing inexpensive and commercially viable solution-processing techniques. Their next step, they say, will be to build LEDs with the new crystal in an attempt to beat the current LED efficiency record.
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