Improved Method of Device Area Scale-up for SWNT/Silicon Hybrid Solar Cells Using Silver Nanowires
Recently, Li, et.al, from the Taylor group in the Chemical and Environmental Engineering Department at Yale University, reported on a approach to significantly improve the performance for scaling up cell area for hybrid single walled carbon nanotubes (SWNT)/Silicon solar cells. In this work, the authors utilized p-type SWNTs cast onto n-type silicon as a dense film approximately 15 nm in thickness. For small cell areas on the order of 1-2 mm2, cell performance was significantly improved in comparison to other hybrid approaches due to the low Rs of the SWNT film. For larger cell areas, the Rs increased substantially to kilo-ohm/square, resulting in decreased cell efficiency. While increasing the SWNT film thickness could potentially lower Rs, the trade-off would be a reduction in optical transparency for the film, which would still reduce cell efficiency during scale-up. Patterning of metal conductor traces over the SWNT film was considered as a means to reduce Rs, but the evaporation of metal over the SWNT film resulted in cell shorting as some of the metal penetrated the pores in the film to the silicon junction. Instead, a strategy of casting silver nanowires (AgNWs) from solution at medium densities was investigated as a means to lower Rs while maintaining reasonable optical transparency during cell area scale-up.
References: Device Area Scale-Up and Improvement of SWNT/Si Solar Cells Using Silver Nanowires. Xiaokai Li, Yeonwoong Jung, Jin-Shun Huang, Tenghooi Goh, and André D. Taylor; Advanced Energy Materials 2014. DOI: 10.1002/aenm.201400186
Images reprinted with permission from John Wiley and Sons; Advanced Energy Materials; Device Area Scale-Up and Improvement of SWNT/Si Solar Cells Using Silver Nanowires; © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim; Xiaokai Li,Yeonwoong Jung,Jing-Shun Huang,Tenghooi Goh,André D. Taylor.