Good article.
National Renewable Energy Lab Bets On Black Silicon Solar Power
Photo of Natcore's tandem solar panels.
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TINA CASEY
Just when you think silicon is getting nudged aside as the material of choice for making photovoltaic cells, along comes the National Renewable Energy Laboratory (NREL).
The NREL on Tuesday announced it’s entered into an agreement with Natcore Technology Inc., a Red Bank, NJ-based company, to develop a low cost way to manufacture high efficiency solar cells using NREL’s latest innovation, a black silicon antireflective layer on solar cells.
The agreement calls for relatively small spending on the part of NREL and Natcore, at least to begin with: Each company will spend $150,000 over the next year to reach their stated goals of cutting the cost of panels between 2 and 3 percent and increasing the energy output of the panels throughout one day of operation by 3 to 10 percent. The agreement allows the companies to decide later if they want to increase funding together.
“Our technology will create a new American industry,” says Natcore President and CEO Chuck Provini, in a news release on Tuesday. “We’ve been trying for two years to get financial support from the Department of Energy. This is a meaningful first step.”
NREL expects a huge bang for its buck. Last December the lab granted Natcore exclusive rights to develop its black silicon patents into commercial products. The new agreement combines NREL’s work with Natcore’s own proprietary treatment for boosting silicon solar cell efficiency.
Black silicon does not actually refer to the color of the panels per se. It describes the appearance of a silicon wafer after it has been etched with tiny pores.
Researchers have found that the pores enable a silicon solar cell to capture more sunlight throughout the day, including morning and afternoon hours when the sun is not at an optimal angle.
NREL has demonstrated that a typical silicon solar cell treated with its black silicon process has a solar conversion efficiency of almost 17 percent, compared to the 11 to 15 percent commonly seen in standard polysilicon solar panels.
NREL’s new etching process, which won a top award from R&D Magazine in 2010, consists of a one-step immersion in a chemical bath. The low-cost bath (just a few cents per watt, according to NREL) replaces hazardous gases that are used in conventional silicon etching.
In the chemical bath, nanoparticles of gold form in a mixture of chloroauric acid (a hydrogen-chlorine-gold combo), hydrogen peroxide and hydrofluoric acid. The gold sparks a series of chemical reactions that etch tiny pores - tiny, as in a billionth of a meter in diameter - into the surface of a silicon wafer.
As described by NREL, the pores: “are much smaller than the wavelength of the incident light, so they suppress reflection across the full spectrum of sunlight.”
NREL continues:
“As the tiny holes deepen, they make the metallic gray silicon appear increasingly dark until it becomes almost pure black, absorbing nearly all frequencies of sunlight. The surface becomes riddled with minute pores of varying depths with no sharp interfaces that would reflect light, creating a highly absorbent silicon wafer.” The whole process takes about three minutes at room temperature, saving both time and energy. If a higher throughput is desired, a boost to 100 degrees Fahrenheit speeds the process up to less than a minute.
Natcore’s contribution to the effort is a patented “liquid phase deposition” (LPD) process that will boost efficiency even further. LPD is a type of passivation technology, that is, a technology to chemically treat the surface of the solar cells to make sure that the sides of the pores don’t stop electricity from migrating throughout the panel.
Like NREL’s chemical bath, Natcore’s technology is based on a low cost, low energy liquid process. In addition to increasing solar cell efficiency, Natcore’s LPD process can also help create a more durable, long lasting surface.
As Natcore proudly explains on its website: “We think LPD is the future of solar. It is at the core of everything we do. It results in solar cells of higher quality, and is safer, cleaner and less expensive,” than the alternative processes of passivating solar cells used by Natcore’s competitors.
Overall, Natcore’s and NREL’s emphasis on low manufacturing costs is a key element of President Obama’s SunShot Initiative, which calls for achieving price parity between solar energy and fossil fuels within ten years.
http://idealab.talkingpointsmemo.com/2012/03/national-renewable-energy-lab-bets-on-black-silicon-solar-power.php?ref=fpblg |
