Eur. Phys. J. Appl. Phys.
Volume 32, Number 3, December 2005
|Page(s)||187 - 192|
|Section||Imaging, Microscopy and Spectroscopy|
|Published online||30 November 2005|
N-type multicrystalline silicon wafers and rear junction solar cells
UMR TECSEN, Université Paul Cézanne-Aix-Marseille III, 13397 Marseille Cedex 20, France
2 EniTecnologie, via d'Andrea 6, Nettuno, Italy
Corresponding author: email@example.com
Accepted: 29 September 2005
Published online: 30 November 2005
N-type silicon presents several advantages compared to p-type material, among them, the most important is the small capture cross sections of metallic impurities, which are neatly smaller. As a consequence lifetime and also diffusion length of minority carriers should be neatly higher in n-type than in p-type, for a given impurity concentration. This is of a paramount interest for multicrystalline silicon wafers, in which the impurity-extended crystallographic defects interaction governs the recombination strength of minority carriers. It is experimentally verified that in 1.2 cm raw wafers lifetimes about 200 s and diffusion lengths around 220 m are measured. These values increase strongly after gettering treatments like phosphorus diffusion or Al-Si alloying. Scan maps reveal that extended defects are poorly active, although in regions where the density of dislocations is higher than 106 cm-2. Abrupt junctions are obtained by Al-Si alloying after annealing between 850 and 900 °C, which could be used for rear junction cells. Such cells can be processed by means of similar processing steps used to make conventional p-type base cells.
PACS: 72.20.Jv – Charge carriers: generation, recombination, lifetime and trapping
© EDP Sciences, 2005
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