RED BANK, USA: Scientists at Natcore Technology Inc. have been able to demonstrate the effectiveness of the company's method to passivate the surface of standard commercial silicon solar cells on which a silica film has been grown using Natcore's liquid phase deposition (LPD) process.
Passivation is the process of filling the dangling atomic bonds at the surface of the solar cell, as well as reducing the numbers of defects that always exist in the upper region of the cell body. It is critical to enabling production of long-term, high-performance silicon solar cells.
Following an advance announcement on September 15, Natcore's R&D team at the Ohio State University now report that measurements of the effect of the Natcore surface passivation process on an important parameter called surface recombination velocity, or SRV, show that the SRV has been improved a factor of more than 25 times compared to its value for an untreated cell.
This result translates shows that Natcore's LPD passivation process achieves the same level of performance as the current industry standard technique. Importantly, it will be less costly to use in full-scale production compared to the hydrogenated silicon nitride passivation process now used in every silicon solar cell manufacturing line in the world.
In Natcore's refined LPD process, this necessary passivation is achieved using the same production steps normally applied to the solar cell to create its top and bottom metal contacts; no additional heating cycles are required. The synergistic nature of Natcore's technology with existing cell fabrication steps will greatly simplify the standard silicon solar cell manufacturing process.
Very importantly, recent developments in silicon solar cell manufacturing R&D have shown that significant gains in cell performance can be achieved with ever-thinner silicon wafers by passivating the rear surface of the cell with a layer of silica underneath the full-coverage aluminum back contact.
This step has not yet been included in actual manufacturing because it presently requires the deposition of the silica film by thermal vacuum processes that are too cumbersome and costly to implement. Natcore's new technology eliminates the need for that vacuum furnace, however, thereby lowering cost and environmental harm.
Natcore's patent-pending process can be implemented in a cost-effective manner as a simple add-on to equipment that already exists on the production floor. In the near future, Natcore will pursue discussions with existing suppliers of such equipment both at home and abroad to develop beta test sites in selected cell manufacturing facilities prior to full scale introduction of the technology to the global market.
"This is a significant advance in the performance of standard solar cells, and we're thrilled by it," says Natcore president and CEO Chuck Provini.
"Nevertheless, we continue to maintain our focus on our joint venture in China, our thin-film applications and, particularly, the development of our tandem solar cell. An all-silicon tandem solar cell would bring the greatest gains in solar cell efficiency to date. It remains our ultimate goal, and our scientists working at Rice University continue to make important progress toward achieving it."