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Old Posted Dec 8, 2015, 1:50 AM
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Join Date: Aug 2007
Location: Naugatuck, CT/Worcester,MA
Posts: 3,506
Quote:
“Molecular Soccer Ball” Perovskite Solar Cell Already At 20.5% Efficiency
November 30th, 2015 by Tina Casey

Perovskite solar cells could be the next big thing to touch off another downward surge in the cost of solar energy, and a Swiss research team is reporting that it is on track to make it happen. The team has developed a low cost way to manufacture thin film solar cells that use a layer of “molecular soccer balls” to hold perovskite in place.

The new perovskite solar cell comes from Empa, the Swiss Federal Laboratories for Materials Science and Technology. When the Empa team incorporated it into a “tandem” thin film solar cell, it reported a solar conversion efficiency of 20.5 percent. While that’s peanuts compared to the best silicon solar cells, the relative simplicity and low cost of manufacturing the new cell would make it a bargain.

At a conversion efficiency of 20.5 percent the new perovskite/CIGS solar cell may not look that much of an improvement, but that’s just for starters. In addition to lowering manufacturing costs with cheaper substrates, the team is eyeing that practical maximum mark of 30 percent or more.

http://cleantechnica.com/2015/11/30/...-5-efficiency/
Quote:
Nanopillars Hide Solar Wiring
By Dexter Johnson
Posted 1 Dec 2015 | 21:00 GMT


Silicon nanopillars funnel light through a gold metal contact to a sheet of silicon underneath.

Photovoltaics convert the photons from light into a voltage—thus the name. And anything that reduces the number of photons that strike the electric field of the semiconducting P-N junction inside the solar cell will reduce the voltage it generates.

One of things that curtail the amount of photons interacting with the solar cell is the design of the device’s outer layer. In many silicon solar cell designs, a grid of metal wires is employed in order to get the electricity to and from the device. The problem: the wires reflect light away from the surface, reducing the amount of photons that are absorbed. (It should be noted that in some photovoltaics, indium tin oxide is used to create transparent conducting films that stand in for the metal wire grids.)

Researchers at Stanford University have taken a novel approach to addressing this problem by creating a nanostructure comprising so-called nanopillars that rise above the metal surfaces. The nanopillars direct the light into the solar cell in a way that avoids reflection by the metal, effectively making the metal invisible to the incoming light.

In research published in the journal ACS Nano, the researchers were able to fabricate the nanopillars in a one-step chemical process. They started with a 16-nanometer-thick film of gold that had been layered onto a flat sheet of silicon. The gold film was covered with an array of nanoscale holes.

“We immersed the silicon and the perforated gold film together in a solution of hydrofluoric acid and hydrogen peroxide,” said Thomas Hymel, a Stanford graduate student who co-authored the ACS Nano article, in a press release. “The gold film immediately began sinking into the silicon substrate, and silicon nanopillars began popping up through the holes in the film.”

Once the gold-coated silicon is dipped in the chemicals, the metal is transformed from a shiny gold to a dark red, which indicates that the material will no longer reflect light. You can watch a demonstration of this process in the video below:

Video Link


The results of this change are dramatic. The Stanford researchers estimate that this could increase the efficiency of some silicon solar cells by as much as 22 percent.

http://spectrum.ieee.org/nanoclast/s...e-solar-wiring
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