Noncontact crucible (NOC) method to grow Si ingots with a larger diameter than 45 cm is proposed as a novel crystal growth method, which has several merits comparing with the Czochralski (CZ) method such as larger diameter ratio defined as crystal diameter / crucibles diameter (near 0.9) and lower oxygen concentration. The solar cells prepared by the present Si ingots has the highest conversion efficiency of 19.6% and the average conversion efficiency of 18.9% using the same solar cell structure and process to obtain the conversion efficiency of 20.0% for CZ wafers. Kazuo Nakajima and coworkers at JST succeeded to control temperature in NOC method by using a carbon heat holder.
That is expected to lead about 30% cut in costs for manufacturing a high quality Si wafer.
MEXT FUTURE-PV Innovation (FUkushima Top-level United center for Renewable Energy research — PhotoVoltaics Innovation)
Research Theme “Si Nano-Wire Solar Cells”
K. Nakajima, S. Ono, R. Murai, Y. Kaneko, F. Jay, Y. Veschetti, and A. Jouini. “Growth of Si ingots for solar cells with 33 cm diameter using a small crucible with 40 cm diameter by Noncontact crucible method”. PVSEC-25, BEXCO, Busan, Korea, November 15-20 (2015).
Kazuo Nakajima, Ph.D.
Team Leader, FUTURE-PV Innovation, JST
Terutake Koizumi, Ph.D.
FUTURE-PV Innovation, Department of Green Innovation, JST