#indium
Turning heat energy into a viable fuel source
A new device being developed by Washington State University physicist Yi Gu could one day turn the heat generated by a wide array of electronics into a usable fuel source.
The device is a multicomponent, multilayered composite material called a van der Waals Schottky diode. It converts heat into electricity up to three times more efficiently than silicon – a semiconductor material widely used in the electronics industry. While still in an early stage of development, the new diode could eventually provide an extra source of power for everything from smartphones to automobiles.
“The ability of our diode to convert heat into electricity is very large compared to other bulk materials currently used in electronics,” said Gu, an associate professor in WSU’s Department of Physics and Astronomy. “In the future, one layer could be attached to something hot like a car exhaust or a computer motor and another to a surface at room temperature. The diode would then use the heat differential between the two surfaces to create an electric current that could be stored in a battery and used when needed.”
Gu recently published a paper on the Schottky diode in The Journal of Physical Chemistry Letters.
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See-through circuitry: New method makes AZO a viable and cheap alternative for transparent electronics
Indium tin oxide (ITO) is the current material of choice for electronics because it combines optical transparency with electrical conductivity. Its use ranges from touch-sensitive smartphone screens to light-harvesting solar panels. Indium is in short supply, however, and as demand increases for ITO-containing devices, so does the price of indium.
One promising low-cost ITO alternative is a transparent material known as aluminum-doped zinc oxide (AZO).
“The elements that make up this material are more abundant than indium, making AZO a commercially sensible option,” said Professor Husam Alshareef from the KAUST Physical Science and Engineering Division who also led the research. “However, electronic devices made using AZO have traditionally shown inferior performance to devices made using ITO.”
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Going cubic halves the efficiency droop in InGaAlN light-emitting diodes
Today, it is widely accepted that the large Auger coefficient is the main cause for the large (~50%) efficiency droop in traditional hexagonal-phase InGaAlN LEDs. Yet, this explanation is inadequate to account for the low efficiency droop in gallium arsenide- and gallium phosphide-based LEDs, as those have similar Auger coefficients.
InIEEE Transactions on Electron Devices, Can Bayram, Jean-Pierre Leburton and Yi-Chia Tsai at the University of Illinois at Urbana-Champaign show that the coexistence of strong internal polarization and large carrier effective mass accounts for ~51% of the efficiency droop under high current densities in hexagonal-phase green InGaAlN LEDs (h-LEDs) compared to cubic-phase InGaAlN green LEDs (c-LEDs).
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New efficiency record for solar hydrogen production is 14 percent
An international team has succeeded in considerably increasing the efficiency for direct solar water splitting with a tandem solar cell whose surfaces have been selectively modified. The new record value is 14 percent and thus tops the previous record of 12.4 percent, broken now for the first time in 17 years. Researchers from Helmholtz-Zentrum Berlin, TU Ilmenau, Fraunhofer ISE and California Institute of Technology participated in the collaboration. The results are published in Nature Communications.
Solar energy is abundantly available globally, but unfortunately not constantly and not everywhere. One especially interesting solution for storing this energy is artificial photosynthesis. This is what every leaf can do, namely converting sunlight to chemical energy. That can take place with artificial systems based on semiconductors as well. These use the electrical power that sunlight creates in individual semiconductor components to split water into oxygen and hydrogen. Hydrogen possesses very high energy density, can be employed in many ways and could replace fossil fuels. In addition, no carbon dioxide harmful to the climate is released from hydrogen during combustion, instead only water. Until now, manufacturing of solar hydrogen at the industrial level has failed due to the costs, however. This is because the efficiency of artificial photosynthesis, i.e. the energy content of the hydrogen compared to that of sunlight, has simply been too low to produce hydrogen from the sun economically.
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