Using the cast furnace, p-type solar cells with the conversion efficiency and yield as high as those of the p-type CZ solar cells can be obtained by the noncontact crucible (NOC) method for the first time. The NOC method was developed to obtain uniform large Si single ingots with sufficient quality to obtain such solar cells using a cast furnace. In this method, the Si melt has a large low-temperature region in its upper central part to grow ingots inside the Si melt without contact with the crucible wall. Using the same solar cell structure and process to obtain the conversion efficiency of 19.1% for p-type CZ wafers (The FREA (Fukushima Renewable Energy Institute, AIST) standard process with Al-BSF), the highest conversion efficiency of 19.14% and the average conversion efficiency of 19.0% were obtained for our wafers. The yield of the regular solar cells with the conversion efficiency higher than 18.8% was 100% for the present method. The conversion efficiency and yield were much higher and quite uniform comparing with those of the solar cells prepared by the high-performance cast method. The present method is promising as an advanced cast method for obtaining uniform large Si single ingots with sufficient quality to obtain high-efficiency solar cells with a high yield in the mega solar market.
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, Y. Kaneko, R. Murai, K. Shirasawa, T. Fukuda, H. Takato, M. A. Jensen, A. Youssef, E. Looney, T. Buonassisi, M. Benoit, S. Dubois, and A. Jouini. “Applications based on novel effects derived to the Si bulk crystal growth inside Si melt without contact to crucible wall using noncontact crucible method”. The 18th International Conference on Crystal Growth and Epitaxy (ICCGE-18), Nagoya, Japan, August 7-12 (2016).
Kazuo Nakajima, Ph.D.
Team Leader, FUTURE-PV Innovation, JST
Terutake Koizumi, Ph.D.
FUTURE-PV Innovation, Department of Green Innovation, JST