A silicon testing system developed by the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL) to aid solar cell manufacturers was among the year's most significant technology innovations, as judged by Research & Development (R&D) Magazine. The Sinton QSSPC Silicon Evaluation System is a method of detecting impurities and defects in silicon boules—the material from which solar cells are made—early in the manufacturing process.
In this system, a boule tester sends short pulses of infrared light into the boule and measures minority-carrier lifetime in p- or n-type silicon. Using radio frequency (RF) sensing, the tester determines quasi-steady-state photoconductance (QSSPC), then uses this information to calculate the bulk minority-carrier lifetime. Next, it calibrates the results of the photoconductance analysis to determine the absolute lifetime, and then determines grain structure and calculates levels of unwanted impurities.
This process gives manufacturers information to identify substandard silicon before it is made into cells, thereby increasing the number of efficient cells produced, boosting yields and reducing manufacturing costs. The evaluation system will enable the solar industry to keep up with product demand and growth.
The award is shared by NREL and Sinton Consulting Inc. NREL researchers who worked on this project are David Mooney and Katie Brown.
For further information contact NREL Public Affairs at (303) 275-4090