Title: Illuminated versus dark lock-in thermography investigations of solar cells

Authors: Otwin Breitenstein

Addresses: Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany

Abstract: In this paper, after describing the basics of lock-in thermography investigations of solar cells, the application of this imaging technique for the characterisation of silicon wafer-based solar cells is reviewed. In particular, the differences between various variants of this technique working with and without light illumination are discussed. It is found that, for imaging and a detailed local investigation of leakage currents, both under forward and reverse bias, the application of dark lock-in thermography is most useful. On the other hand, illuminated lock-in thermography provides some unique possibilities, like the investigation of shunts in non-metallised solar cells or without contacting the cells, local efficiency imaging, and the imaging of the local avalanche multiplication factor under reverse bias. A special variant of illuminated lock-in thermography enables the imaging of the minority carrier lifetime distribution and of trapping centres in bare silicon wafers.

Keywords: solar cells; leakage current; imaging technique; lock-in thermography; LIT; carrier density imaging; CDI; infrared lifetime mapping; ILM; dark lock-in thermography; DLIT; illuminated lock-in thermography; ILIT; silicon wafers.

DOI: 10.1504/IJNP.2013.054983

International Journal of Nanoparticles, 2013 Vol.6 No.2/3, pp.81 - 92

Published online: 31 Mar 2014 *

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