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Gizmorama - January 22, 2018

Good Morning,

Electrons are so hot right now! But not when it comes to boosting solar cell efficiency. The article below will explain.

Learn about this and more interesting stories from the scientific community in today's issue.

Until Next Time,

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*-- Hubble image showcases cluster with mass of three million billion suns --*

A new image captured by the Hubble Space Telescope shows what the mass of three million billion suns looks like. The image, shared Tuesday by NASA, features ACT-CLJ0102-4915, a massive cluster known as El Gordo -- Spanish for "The Fat One."

El Gordo is the biggest, brightest and hottest galaxy cluster found in the distant universe. It's located 7 billion light-years from Earth.

As revealed by a trio of telescopes in 2012, including NASA's Chandra X-ray Observatory, El Gordo is actually the product of two galaxy clusters, which are in the millions-of-years-long process of colliding.

The formation and evolution of galaxy clusters is thought be heavily influenced by dark matter. The study of galaxy clusters can help astrophysicists better understand dark matter and dark energy.

"Evidence suggests that El Gordo's 'normal' matter -- largely composed of hot gas that is bright in the X-ray wavelength domain -- is being torn from the dark matter in the collision," NASA said in a news update. "The hot gas is slowing down, while the dark matter is not."

The new image was captured by Hubble's Advanced Camera for Surveys and Wide-Field Camera 3. El Gordo is one of 41 giant galaxy clusters surveyed as part of the RELICS project, aimed at identifying faraway clusters for the James Webb Space Telescope to study. JWST is set to be launched in 2019.

*-- Study: To boost solar cell efficiency, curb 'hot electrons' --*

New research suggests the key to improving the efficiency of solar cells is the reduction of so-called hot electrons.

When photos with energy levels greater than the solar cell's band gap are absorbed by the semiconductor, hot electrons are produced. The extra energy is quickly converted into thermal energy and is lost.

Researchers at the University of Groningen in the Netherlands have developed a way to keep hot electrons around for a while longer, so that their energy might be converted into electricity.

A semiconductor's bandgap refers the range of energy at which absorbed photons are converted into free electrons, which form an electric current that can be funneled out and used.

When photons with too much energy hit the solar cell, they cause the photovoltaic material to vibrate, generating thermal energy.

"This energy loss puts a limit to the maximum efficiency of solar cells," Maria Antonietta Loi, a professor of photophysics and optoelectronics at Groningen, said in a news release.

Loi has developed a unique solar cell material that solves the problem of energy loss. The material is made of organic-inorganic hybrid perovskites. All perovskites boast the basic chemical formula of ABX3. The structure features an octahedron of anions, the X, which binds an outer cube of larger A atoms to smaller B atoms in the center.

Most perovskites feature lead, which is toxic, but Loi and her colleagues designed a perovskite material featuring tin.

"When we studied this material further, we observed something strange," Loi explained. "The hot electrons gave off their energy after several nanoseconds instead of some hundred femtoseconds. Finding such long-lived hot electrons is what everybody in this field is hoping for."

The technology effectively expands the material's bandgap. The longer the excess energy lingers, the more likely it is to get converted into electricity. The breakthrough could inspire solar cells capable of producing much higher voltages, as well as provide an efficiency boost of between 33 to 66 percent.

"These tin-based perovskites could be a game changer, and could ultimately make a big contribution to providing clean and sustainable energy in the future," Loi said.

She and her research partners shared their discovery this week in the journal Nature Communications.

The researchers are now working to better understand why the addition of tin effectively slows down the energy dissipation of hot electrons.


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