Researchers in Professor Dan Congreve’s lab are testing methods that boost the brightness and efficiency of perovskite LEDs, or PeLEDs. Their findings were published in Device, "Trade-off between efficiency and stability in Mn2+-doped perovskite light-emitting diodes."

By tinkering with the material makeup of perovskite LEDs, a cheaper and more easily-made type of LED, they hope to address the laborious and expensive manufacturing process of LEDs. Their enhancements, however, caused the lights to fizzle out within minutes, demonstrating the careful trade-offs that must be understood to advance this class of materials.

"We took some big steps towards understanding why it’s degrading. The question is, can we find a way to mitigate that while keeping the efficiency? If we can do that, I think we can really start to work towards a viable commercial solution," reports Professor Dan Congreve.

In simplest terms, LEDs transform electrical energy into light by passing electric current through a semiconductor – layers of crystalline material that emits light with an applied electric field. But creating those semiconductors gets complex and costly compared to less energy-efficient lights like incandescents and fluorescents.

"A lot of these materials are grown on expensive surfaces such as a four-inch sapphire substrate," says Sebastian Fernández, a PhD student in Congreve’s lab and the paper’s lead author. "Just to purchase this substrate costs a few hundred dollars."

PeLEDs use a semiconductor known as metal halide perovskites, composed of a blend of different elements. Engineers can grow perovskite crystals on glass substrates, saving a significant sum compared to normal LEDs. They can also dissolve perovskites in solution and "paint" it onto glass to create a light-emitting layer, a simpler production process than regular LEDs call for.

The Congreve Lab is working to address other limitations of PeLEDs, too, such as their difficulty with producing violet and ultraviolet light. In another recent paper in the journal Matter led by PhD student Manchen Hu (who is also a co-author of the Device paper), the team found that by adding water to the solution in which the perovskite crystals form, they could produce PeLEDs that emitted bright violet light five times more efficiently. With further improvements, ultraviolet PeLEDs could sterilize medical equipment, purify water, and help grow indoor crops – all more affordably than current LEDs allow.

Authors include Sebastian Fernández (PhD candidate), William Michaels (BS candidate), Manchen Hu (PhD candidate), Pournima Narayanan (PhD candidate), Natalia Murrietta (BS candidate), Arynn O. Gallegos (PhD candidate), Ghada H. Ahmed (postdoc researcher), Junrui Lyu (MS candidate), Mahesh K. Gangishetty (Mississippi State University), Prof. Daniel N. Congreve.

Excerpted from Stanford News, “A molecular additive enhances next-gen LEDs – but shortens their lifespans."