One goal of nanotechnology is to improve photovoltaic solar electricity generation. The thermodynamic limit of 80% productivity is well beyond the capabilities of current photovoltaic technologies, whose performance now is only about 43%.
Devin Coldewey for TechCrunch: An experimental solar cell created by MIT researchers could massively increase the amount of power generated by a given area of panels, while simultaneously reducing the amount of waste heat. Even better, it sounds super cool when scientists talk about it: “with our own unoptimized geometry, we in fact could break the Shockley-Queisser limit.”
The Shockley-Queisser limit, which is definitely not made up, is the theoretical maximum efficiency of a solar cell, and it’s somewhere around 32 percent for the most common silicon-based ones.
You can get around this by various tricks like stacking cells, but the better option, according to David Bierman, a doctoral student on the team (and who is quoted above), will be thermophotovoltaics — whereby sunlight is turned into heat and then re-emitted as light better suited for the cell to absorb. Cont'd...
Invisibility cloaking may be a long way from reality, but the principle could help improve the performance of solar cells in the near term.
In a series of simulations, researchers at the Karlsruhe Institute of Technology have demonstrated how cloaks made of metamaterials or freeform surfaces could eliminate shadows cast by energy-harvesting components onto the active surfaces of solar cells.
Contact fingers, which extract electric current, cover up to one-tenth of the surface area of a solar cell. By guiding light around these features, more of the sun's energy could be captured by the solar cell.
"Our model experiments have shown that the cloak layer makes the contact fingers nearly completely invisible," said doctoral student Martin Schumann. Cont'd...
A team of researchers has come up with a solar cell that produces fuel rather than electricity. A material called gallium phosphide enables the solar cell to produce clean fuel hydrogen gas from liquid water.
To connect an existing silicon solar cell to a battery that splits the water may well be an efficient solution; but it is very expensive.
So, researchers were streamlining their search to a semi-conductor material that is able to both convert sunlight into an electrical charge and split water.
The team found gallium phosphide (GaP), a compound of gallium and phosphide, useful in this respect.
GaP has good electrical properties but the drawback is that it cannot easily absorb light when it is a large flat surface as used in GaP solar cells, said the study thatappeared in Nature Communications.
The researchers overcame this by making a grid of very small GaP nanowires, measuring five hundred nanometres (a millionth of a millimetre) long and ninety nanometres thick.
"That makes these kinds of cells potentially a great deal cheaper," said lead author Erik Bakkers from Eindhoven University of Technology, the Netherlands. Cont'd...
By Richard Martin for The MIT Technology Review: A group of Stanford researchers have come up with a nanoscale “designer carbon” material that can be adjusted to make energy storage devices, solar panels, and potentially carbon capture systems more powerful and efficient.
The designer carbon that has reached the market in recent years shares the Swiss-cheese-like structure of activated carbon, enhancing its ability to catalyze certain chemical reactions and store electrical charges; but it’s “designed” in the sense that the chemical composition of the material, and the size of the pores, can be manipulated to fit specific uses.
The designer carbon tested at Stanford is “both versatile and controllable,” according to Zhenan Bao, a professor of chemical engineering and the senior author of the study, which appeared in the latest issue of the journal ACS Central Science.
“Producing high-surface-area carbons with controlled chemical composition and morphology is really challenging,” says Bao. Other methods currently available, she says, “are either quite expensive or they don’t offer control over the chemical structure and morphology.” Cont'd...
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