Solar cell produced on EpiWafer yield 20 percent efficiency

September 16, 2015 // By Paul Buckley
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE in co-operation with NexWafe have optimized all production steps for the EpiWafer which is seen as a drop-in replacement for conventional Cz wafers.

The solar cells have been demonstrated to achieve a short-circuit current of 39.6 mA/cm2 which claims to be a world-record value for epitaxially grown silicon solar cells. The new results will be presented during the coming European PVSECconference in Hamburg.

Analysis of the new n-doped EpiWafers shows that mean minority carrier lifetimes are above 1000 µs, indicating the same quality as n-type Cz wafers. Solar cells processed on the EpiWafers have been shown to yield 20% efficiency which has been independently confirmed at the Fraunhofer ISE CalLab.

NexWafe GmbH, a spin-out company of Fraunhofer ISE, was formed with the aim of bringing the Institute’s kerfless EpiWafer technology to the market and implementing a rapid commercialization of the technology.

In the EpiWafer technology, a thick crystalline silicon layer is epitaxially deposited and subsequently detached after growth to produce a freestanding wafer of standard thickness. Due to the radical changes in the manufacturing value chain, EpiWafers can be produced at an appreciably lower cost compared to the traditional wafer manufacturing process. The EpiWafer is a direct substitute for conventional n- or p-doped silicon mono-crystalline wafers.

“I am elated about this fantastic result,” said Dr. Stefan Janz, Head of the Department of Silicon Materials. “This success attests to our fast progress made in only a few months since focusing on EpiWafers.”