Monday, April 30, 2012

Blackest Solar Cell to Date Absorbs 99.7% of Light

Blackest Solar Cell to Date Absorbs 99.7% of Light:



Natcore Tech and National Renewable Energy Lab (NREL) scientists have created the “blackest” solar cell to date, a black silicon solar cell that absorbs an incredible 99.7% of the light that hits its surface. “Today’s solar cells absorb about 95 percent of the sun’s radiation,” NREL notes.
NREL actually holds the record for a black silicon solar cell — 18.6% — “but they had to make it using a passivation technology that requires thermal oxidation,” Natcore notes. “Natcore will replace that cumbersome step with its LPD oxide process.”
solar cell black silicon
With a very low reflectance (average of 0.3%), Natcore’s black solar cells perform about as well in cloudy weather as sunny weather, a significant advantage. The company has now received signed a Cooperative Research & Development Agreement with NREL, which will investment $150,000 in this project. The goals of the agreement are that Natcore and NREL work together to:
  1. Reduce solar cell costs by 2%-3%, and;
  2. Increase solar panel energy output from 3% to 10% over the course of a day without the aid of a solar tracking mechanism.
“These goals would be accomplished by combining Natcore’s patented liquid phase deposition (LPD) technology with NREL’s technologies for creating a black silicon antireflective layer integrated into high-efficiency solar cells…. The combination of the two technologies could significantly exceed NREL’s record cell efficiency.”

Currently, the agreement is for one year. Hopefully, in that time, or soon after, Natcore and NREL will be able to significantly improve the solar cell efficiency of black silicon cells. That could mean big things in the solar cell industry.
“This technology will play an important role in moving forward the availability of solar technologies,” NREL Vice President for Commercialization & Technology Transfer William Farris said. “It is one more step to help bolster the Department of Energy’s SunShot Initiative to make solar energy cost competitive with other forms of energy by the end of the decade.”
“Our technology will create a new American industry,” says Natcore President and CEO Chuck Provini. “We’ve been trying for two years to get financial support from the Department of Energy. This is a meaningful first step.”
We’ll see.
In the meantime, here’s a little more from Natcore on what “black silicon” is:
“Black silicon” refers to the apparent color of the surface of a silicon wafer after it has been etched with nano-scale pores. The etching takes place in a matter of a few minutes in a liquid solution at room temperature; the black color is not a color at all but results from the absence of reflected light from the porous wafer surface.

A panel made from black silicon solar cells will produce a significantly greater amount of energy (KwHrs) on a daily basis than will a panel made from cells using the industry standard thin film coating, not only because the reflectance is lower but also because the angular dependence of the reflectance from black silicon is much lower as well. The latter fact means a black silicon panel will perform better during the morning and afternoon hours when the sun hits at an angle and will also outperform standard cell panels on cloudy days. The combination of lower cost and higher energy output per kilowatt of installed array peak power should quickly make black silicon the antireflection control technology of choice in the industry.
h/t TreeHugger

Images: © Natcore Technology

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