New efficiency record for a commercial-scale solar cell module arrives in the form of a flexible thin film semiconductor

March 13, 2013

The vast majority of commercially available solar panels available today are heavy, stiff, and only 10-15% efficient at converting incident sunlight to electric power. A start-up company called Alta Devices based in Santa Clara, California aims to dramatically change this norm by replacing the thick silicon cells with thin layers of gallium-arsenide (GaAs). GaAs, a compound semiconductor composed of the two elements gallium and arsenic, is much more effective at both absorbing sunlight and converting that absorbed sunlight to electricity than is silicon. The thin layer can then bend at much larger angles before breaking. In a paper presented at this year’s IEEE Photovoltaics Specialists Conference (38th PVSC), Alta demonstrated a new full-scale panel efficiency record of 23.5%, as verified by scientists at the National Renewable Energy Labs. Alta’s GaAs cells, at just 1% the thickness of comparable silicon, had set a single-semiconductor cell efficiency record at the previous PVSC of 27.6%. The extremely low cell thickness is achieved by depositing the semiconductor onto a GaAs substrate then lifting off this layer and bonding it to a flexible carrier material. The substrate, Alta then claims, can be reused for subsequent cell fabrication. This flexible, high efficiency cell technology offers promise for future markets in solar power. The competition, however, is fierce. The price of silicon has dropped dramatically in the last 10 years and solar power prices have followed suit. Alta’s success will likely hinge on their ability to achieve a very high yield with their lift-off process and convince buyers that their higher-performing flexible panels are worth the price premium over their silicon competitors.

1). Brendan M. Kayes, Hui Nie, Rose Twist, Sylvia G. Spruytte, Frank Reinhardt, Isik C. Kizilyalli, and Gregg S. Higashi (2011) 27.6% Conversion efficiency, a new record for single-junction solar cells under 1-sun illumination, Proceedings of the 37th IEEE Photovoltaic Specialists Conference. DOI:10.1109/PVSC.2011.6185831 

2). Laila S. Mattos, Shawn R. Scully, Maria Syfu, Eric Olson, Linlin Yang, Chris Ling, Brendan M. Kayes and Gang He (2012) New module efficiency record: 23.5% under 1-sun illumination using thin-film single-junction GaAs solar cells, Proceedings of the 38th IEEE Photovoltaic Specialists Conference. DOI:10.1109/PVSC.2012.6318255