Natcore Technology’s black silicon wafers have now been processed into actual working solar cells in a production line, rather than a laboratory setting, for the first time. This has been done by one of the world’s largest photovoltaic manufacturers, which is located in China’s Hunan province.
Five batches of the silicon wafers with a black silicon etch were produced in the trial run. Impressively, the conversion efficiencies of the trial-run solar cells hit 15.7% — a figure that can likely be easily increased as the process is optimized.
The achievement represents an important step towards the commercialization of the technology — showing, quite clearly, that the process can be made to be commercially viable in an actual production line.
The specifics are detailed below:
Five batches of silicon wafers with a black silicon etch — prepared by Natcore’s scientists at their R&D Center in Rochester, NY, under an exclusive license from the National Renewable Energy Laboratory — were supplied to the Chinese company for cell finishing and testing. Two of the batches were used as controls to help interpret results. Of the three test batches, one had a diffusion using phosphorous oxychloride (POCl3) applied by Natcore; the remaining test batches were diffused by the Chinese company. In all cases, the Chinese performed the final steps necessary to turn the wafers into solar cells and to test them.
“We put these cells through the Chinese manufacturer’s process with essentially no modification to the process itself, except for the fact that certain steps were completely removed,” states Dr David Levy, Natcore’s Director of Research & Technology. “And the removal of these steps projects to yield cost savings of as much as 23.5%.”
“We came out with an efficiency of 15.7% on this first trial. The Chinese team said they were very impressed, as we were, with this result. Conventional cells made in a similar industrial process do have efficiencies in the range of 17 to 19%. But considering the results of this first attempt, the Chinese engineers feel that we could easily push our black cell efficiency into the high teens.”
“Cells made from wafers using our POCl3 diffusion outperformed the cells made with the Chinese diffusion, which was a bit of a surprise to us. The open circuit voltages of the black cells were in the ballpark of 0.63 V, very close to results obtained on conventional control cells that were made with a silicon nitride passivation layer. That speaks to the good passivation that can be obtained on our black etch,” Levy continued.
“I can’t overstate the importance of this development,” says Chuck Provini, Natcore’s president and CEO. “It demonstrates that our black silicon process is commercially viable in a real production line. It also shows that our process could be integrated into a production line without fear of contamination by the chemicals that our process uses.”
“This is a huge step toward commercialization. It proves our earlier contention that our technology can easily be retrofitted into existing solar cell production lines and can just as easily be incorporated into a new line. Black silicon seems poised to become an important new approach for the industry.”
After completion, the solar cells were shipped back to Natcore for further testing.
For some background — black silicon wafers are (typically) simply silicon wafers etched with billions of nano-sized holes per square inch. These holes and the silicon walls around them are smaller than the light wavelengths hitting them, and so, as a result, there isn’t all that much reflectivity.
Natcore has been pursuing the commercialization and improvement of the technology for quite some time now, as we have reported previously a great deal. Most recently, the company has released information about its efforts to reduce the costs of the black silicon cells through the use of a new low temperature laser process.
For some other Natcore stories, see: