New records are being set and surpassed in short order as the quest to make solar photovoltaic (PV) modules and panels ever more efficient continues. Reducing the amount of sunlight reflected from the surface of solar panels is one promising pathway that’s being explored. Making them black would appear to be a simple solution, but doing so isn’t so simple… or cheap.
Natcore Technology Oct. 25 announced that it has fabricated an “Absolute Black” silicon PV cell — from wafer to finished product — using a proprietary processes “amenable to low-cost mass production.”
The Blackest Black
Natcore scientists first created the “blackest” silicon solar cell surface ever recorded. Natcore technicians then took over, employing the Red Bank, NJ-based company’s liquid phase deposition (LPD) process to create the finished Absolute Black silicon PV cell.
Reducing the reflectivity of solar cells ten-fold yields up to 3% more usable light and an identical boost in PV cell efficiency, according to Natcore. “This is a major milestone for Natcore and the entire solar industry. A low-cost, scalable production process was the missing piece in making black silicon solar cells viable. We now look forward to providing this key capability,” company Chairman Brien Lundin stated.
The entire process was completed at Natcore’s R&D Center in Rochester, NY — the first time the company fabricated one of its black silicon PV cells from start to finish. Due to lack of equipment and technical capacity, Natcore had previously farmed out aspects of the process to other labs, including Arizona State University, the Photovoltaic R&D Center at the University of Toledo, and the US Dept. of Energy National Renewable Energy Lab (NREL).
That changed in July when Natcore was able to raise $2.5 million in capital to commercialize its black silicon technology. Some of the proceeds were invested “in the brainpower and lab equipment needed to execute its work quickly and in-house,” according to Natcore’s press release. “This black silicon solar cell, made entirely in our lab, is the first fruit of that investment,” commented Natcore president and CEO Chuck Provini.
Achieving such a high state of “blackness,” Natcore’s black silicon wafers have “near-zero reflectivity,” which means that virtually 100% of the sunlight striking the cell gets absorbed and is available for conversion to electricity. The wafers are only the substrate for the finished product, however. They need to be “fashioned into solar cells” before they’re able to convert sunlight into electricity.
Solar R&D Public-Private Partnership
Enter NREL, with whom Natcore has a Cooperative Research & Development Agreement (CRADA). NREL recently produced black silicon PV cells with a conversion efficiency of 18.2%, but these black silicon solar cells were fabricated using a thermal deposition process too expensive for production in commercial quantities. Natcore’s LPD, by contrast, is a chemical process.
As per the terms of the CRADA, Natcore and NREL will work together and make use of their respective technologies “to achieve or exceed that efficiency with Natcore’s black silicon solar cells.” This entails combining Natcore’s patented LPD technology with “NREL’s technologies for creating a black silicon antireflective layer integrated into high-efficiency solar cells.”
“The feasibility of the combined technologies working together has already been demonstrated in a preliminary Natcore/NREL effort that produced a small-area, lab-scale black silicon solar cell with 16.5% efficiency,” Natcore notes.
“We have a good synergy with Natcore on black silicon technology,” commented NREL Research Scientist Dr. Hao-Chih Yuan. “A silicon surface, without proper coating, is detrimental to the energy conversion efficiency of the solar cell. It is not unusual to grow silicon dioxide coatings on black silicon surfaces for this purpose, but the growth is typically at very high temperatures. Natcore’s coating uses chemistry. They are the ones who can passivate a black silicon surface cheaply.”
Regular CleanTechnica readers will know that other than Natcore and NREL, researchers in Germany at the Fraunhofer-Gesellschaft institute are working on improving and perhaps commercializing black silicon solar cells. Natcore seems the closest to commercialization at this point, but the work of all of these scientists may help us in the long run.
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