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Researchers explain visible light from 2-D lead halide perovskites



 Jiming Bao, associate professor of electrical and computer engineering at the University of Houston, is a researcher in the field of 2D lead halide perovskites bromine what to emit a strong green light. Credit: University of Houston
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<p> Researchers drew attention three years ago when they reported a two-dimensional perovskite-a material with a specific crystal structure-composed of cesium, lead and bromine emitted a strong green light. Crystals that produce light on the green spectrum are desirable because green light, while valuable in themselves, can therefore be used to make light-emitting devices diagnostic tools.<br />
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But there is no agreement on how the crystal, CsPb 2 Br 5 produced the green photoluminescence.

Now, however, researchers from the United States, Mexico and China, led by an engineer from the University of Houston, have reported in the journal Advanced Materials

They initially synthesized CsPb 2 Br 5 [CsPbBr 3 3 [Foundedin [found in the catalog] 2 Br 5 crystals. While CsPbBr 3 the base crystal, is three-dimensional and appears green under ultraviolet light, the new material, CsPb 2 Br 5 has a layered structure and is optically inactive.

"Now that the mechanism is understood, it may be replicated," said Jiming Bao, Associate Professor of Electrical and Computer Engineering at UH and corresponding author of the paper.

Potential applications range from solar cells to LED lighting and other electronic devices.

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9 researchers from UH and institutions in China and Mexico started working on the problem in 2016. At the time, there were two schools of scientific thought on the light emission from the cesium crystal: that it emitted green light due to a defect, mainly a varnish of bromine, rather than the material itself, or that a variation had been unintentionally been introduced , resulting in the emission. powder in water, resulting in sharper-edged crystals. Bao said.

The researchers then used an optical microscope to study the individual crystals of the compound, which is said to be transparent, "something was going on at the edge, resulting in the photoluminescence. "

They relied on Raman spectroscopy-an optical technique that uses information about how to determine the material's lattice properties-to identify nanocrystals of the original source material, CsPbBr 3 along the edges of the crystal as the source of the light.

Bao said CsPbBr 3 is too unstable to use on its own, but the stability of the converted form isn

The researchers said the new understanding of light emission is yielding new opportunities to design and fabricate novel optoelectronic devices. The techniques used to understand the cesium-lead-halide compound can also be applied to other optical materials to learn more about how they emit light, Bao said.
                                                                                                                        


Probing semiconductor crystals with a sphere of light


More information:
Chong Wang et al, Extrinsic Green Photoluminescence from the Edges of 2D Cesium Lead Halides, Advanced Materials (2019). DOI: 10.1002 / adma.201902492

Provided by
University of Houston




Citation :
                                                 Researchers explain visible light from 2-D lead halide perovskites (2019, June 24)
                                                 retrieved 25 June 2019
                                                 from https://phys.org/news/2019-06-visible-d-halide-perovskites.html
                                            

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