Correlation of pre-breakdown sites and bulk defects in multicrystalline silicon solar cells

Strong correlation between the pre-breakdown sites visible in dark lock-in thermography due to local heating and the intensity of spatially resolved electroluminescence of reverse-biased solar cells was observed. By comparing differently texturised solar cells we could show that the pre-breakdown sites are not correlated to the surface morphology, e.g. etch pits resulting in local field enhancement. The positions of the pre-breakdown sites are identical for acidic and alkaline texturised solar cells and therefore are directly related to bulk defects in the wafer. Neverthless, the breakdown voltage is lower for acidic texturised solar cells; the parameters of breakdown are influenced by the texture in contrast to the position. Also pre-breakdown sites are observed in areas without specific surface features for alkaline texturised solar cells. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim