Last year I had the opportunity to attend two big international Photovoltaics (PV) conferences.  The keynote speeches at both conferences discussed the future of crystalline silicon (c-Si) and ideas for high efficiency low cost c-Si PV technology. With less expensive organic PVs in the market and efficiency mark of thick crystalline silicon cells jammed at ~ 26% , these issues have been the hottest break-time discussion topics among people working in c-Si PV.

Recently, a very interesting article on “exotic silicon” by researchers at University of California, Davis on January 25, 2013 in Physical Review letters stirred up excitement in c-Si PV world. This exotic silicon, also called BC8 silicon, is a type of silicon that can be formed under extremely high pressure and is still capable of maintaining its stability at normal pressures. So what’s exotic about this silicon?? It can produce multiple electron hole pairs per incident photon in contrast with one e-h pair/photon generation in normal c-Si! The simulations run through the National Energy Research Scientific Supercomputing Center at the Lawrence Berkeley Laboratory predicted ~ 42 % efficiency in BC8 silicon solar cells under one sun that can be increased to ~ 70% by concentrating sunlight on the cell.

Wondering if you can actually make this exotic silicon? The answer is yes! Joint research between MIT and Harvard University shows that one can convert ordinary c-Si into high efficiency exotic silicon merely by shining it with laser light or by applying chemical pressure.

Conclusion: Silicon is an exotic element.  I think c-si will keep holding its share in future PV market with its surprising properties and contribution from researchers.

Check out the links and papers below for more information on this exciting research

  1. Lin, Yu-Ting,  Sher, Meng-Ju, Winkler, Mark T., Mazur, Eric,  Gradecak, Silvija Pressure-induced phase transformations during femtosecond-laser doping of silicon, Journal of Applied Phyics 5-110 (2011)
  2. Sher, Meng-Ju, Franta, Benjamin, Lin, Yu-Ting, Mazur, Eric, Gradecak, Silvija The origins of pressure-induced phase transformations during the surface texturing of silicon using femtosecond laser irradiation, Journal of Applied Phyics 8-112 (2012)

Kitty Kumar

-Kitty Kumar

Ph.D Candidate, Year 4

University of Toronto, Toronto, Ontario