New Hampshire, United States [Photovoltaics World magazine] Innovalight recently announced that both NREL and the Fraunhofer Institute for Solar Energy Systems had certified that its silicon-ink processed solar cell, called the Cougar cell, has achieved an 18% conversion efficiency. The company’s CTO and VP of Engineering, Homer Antoniadis, presented results at the IEEE San Francisco Bay Area Nanotechnology Council Chapter meeting earlier this month (9/15). Though not yet ready to publicly announce its data, Antoniadis says that higher efficiencies than those made public have been obtained in the lab.
The company’s core technology is a proprietary silicon ink and a process to fabricate high-efficiency crystalline silicon (c-Si) cells. While reluctant to make many details public, Antoniadis discussed some of the technology details with PV World:
A standard cell process makes a uniform emitter; “By inserting only one additional step, using an industrial inkjet printer, we are able to enhance the overall efficiency of the solar cell.” A pattern is introduced onto the surface of the incoming c-Si substrate using an ink printing/drying process coupled with a thermal process to enable activation. Higher n-type doping is achieved under the metal layers (high conductivity), and lighter doping is achieved everywhere else (lower conductivity).
“The n-type doping pattern can easily be recognized by the cameras of the metallization tool via an auto-alignment capability without the need for fiducials,” Antoniadis said.
The Cougar cell architecture is key to improving the amount of absorbed photons that get utilized in the cell. “You need to drop the resistivity under the metal and increase it between the metal contacts, a fundamental property of this high-efficiency cell,” Antoniadis explains. The lighter doping lowers recombination losses; therefore, with fewer dopant atoms, surface recombination velocity is improved and more charges are generated at the surface of the cell.
“A standard cell has uniform doping throughout, which kills the photoresponse,” he noted.
It was also recently announced by JA Solar that it would be developing next-generation solar products using Innovalight’s silicon ink technology. Commercialization is planned for sometime in 2010.
(Read more at Photovoltaics World)