solar_power (3)

Silicon Sees the Light...

Silicon sees the light: Elham Fadaly (left) and Alain Dijkstra in their Eindhoven lab. (Courtesy: Sicco van Grieken/SURF)


Topics: Optics, Electrical Engineering, Nanotechnology, Research, Solar Power, Spectroscopy

A light-emitting silicon-based material with a direct bandgap has been created in the lab, fifty years after its electronic properties were first predicted. This feat was achieved by an international team led by Erik Bakkers at Eindhoven University of Technology in the Netherlands. They describe the new nanowire material as the “Holy Grail” of microelectronics. With further work, light-emitting silicon-based devices could be used to create low-cost components for optical communications, computing, solar energy and spectroscopy.

Silicon is the wonder material of electronics. It is cheap and plentiful and can be fabricated into ever smaller transistors that can be packed onto chips at increasing densities. But silicon has a fatal flaw when it comes to being used as a light source or solar cell. The semiconductor has an “indirect” electronic bandgap, which means that electronic transitions between the material’s valence and conduction bands involve vibrations in the crystal lattice. As a result, it is very unlikely that an excited electron in the conduction band of silicon will decay to the valence band by emitting light. Conversely, the absorption of light by silicon does not tend to excite valence electrons into the conduction band – a requirement of a solar cell.


Silicon-based light emitter is ‘Holy Grail’ of microelectronics, say researchers
Hamish Johnston, Physics World

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2D MXenes...

Helper two-dimensional metal-carbide layers could improve perovskite solar cell stability and help make these complex solar cells a viable green energy option. Credit: iStock Milos-Muller


Topics: Condensed Matter Physics, Green Tech, Materials Science, Metamaterials, Nanotechnology, Solar Power

With the reality of climate change looming, the importance of realistic green energy sources is higher than ever. Solar cells are one promising avenue, as they can convert readily available visible and ultraviolet energy into usable electricity. In particular, perovskite materials sandwiched between other support layers have demonstrated impressive power conversion efficiencies. Current challenges reside in optimizing perovskite/support layer interfaces, which can directly impact power conversion and cell degradation. Researchers Antonio Agresti et al. under the direction of Aldo Di Carlo at the University of Rome Tor Vergata in Italy have investigated how cells containing two-dimensional titanium-carbide MXene support layers could improve perovskite solar cell performance.

To obtain good power conversion within a perovskite solar cell, all layers and layer interfaces within the cell must have good compatibility. Typical cells contain the active perovskite material sandwiched between two charge transport layers, which are then adjacent to their corresponding electrodes. Support layers may also be added. Charge mobility, energy barriers, interface energy alignment, and interfacial vacancies all impact compatibility and subsequent cell performance and stability. Thus, engineering well-suited interfaces with the cell is paramount to cell success and long-term stability, an important criterion for potential commercialization.

Two-dimensional buffer materials could help to modify and promote useful interface interactions. MXenes, a growing class of two-dimensional transitional metal carbides, nitrides, and carbonitrides, have shown impressive electronic properties that are easily tuned via surface modification. For example, the band gap of an MXene can be modified by changing the surface termination group from an oxygen atom to a hydroxide molecule. Additionally, MXene composition impacts the overall material performance. This type of fine-tuning allows impressive control over MXene properties and makes them ideal for interface adjustments.


Two-dimensional MXenes improve perovskite solar cell efficiency
Amanda Carr, Physics World

#P4TC: MXenes...August 24, 2015

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Argonne and Oak Ridge scientists plan to demonstrate sensors for concentrating solar power plants – like the Crescent Dunes Solar Energy Project, shown here – that can monitor and safely maintain molten salt above 700 Celsius. (Image courtesy of SolarReserve and the U.S. Department of Energy.)


Topics: Alternative Energy, Green Energy, Green Technology, Solar Power

Scientists at Argonne and Oak Ridge national laboratories are drawing on decades of nuclear research on salts to advance a promising solar technology.

Nuclear power and solar power may seem like very different energy sources. Nuclear power stems from the energy released when neutrons crash into uranium atoms, splitting them apart. Solar power stems from the sunlight beaming down on earth. But some solar plants convert that light into heat, which can be used just like the heat of a nuclear reactor to generate steam to make electricity. And both energy sources often share a key ingredient: salt.

Engineers sometimes use molten salt to fuel and cool nuclear reactors. As nuclear fuel, salt is attractive because it withstands radiation and can operate at near-normal pressure and relatively low temperatures. Salt also remains fairly inert and stable within the nuclear fuel cycle. Now engineers from the U.S. Department of Energy’s (DOE) Argonne and Oak Ridge national laboratories are drawing on decades of nuclear research on salts to advance a solar technology called concentrating solar-thermal power (CSP).

In the heat of the light, Dave Bukey, Argonne National Laboratory

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