Issue Eur. Phys. J. Appl. Phys. Volume 32, Number 3, December 2005 Page(s) 187 - 192 Section Characterization of Materials: Imaging,\ Microscopy and Spectroscopy DOI 10.1051/epjap:2005085 Published online 30 November 2005

Eur. Phys. J. Appl. Phys. 32, 187-192 (2005)
DOI: 10.1051/epjap:2005085

N-type multicrystalline silicon wafers and rear junction solar cells

S. Martinuzzi¹, O. Palais¹, M. Pasquinelli¹ and F. Ferrazza<sup>2

1</sup>  UMR TECSEN, Université Paul Cézanne-Aix-Marseille III, 13397 Marseille Cedex 20, France
²  EniTecnologie, via d'Andrea 6, Nettuno, Italy

santo.martinuzzi@univ.u-3mrs.fr

(Received: 8 September 2005 / Accepted: 29 September 2005 / Published online: 30 November 2005 )

Abstract
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 p⁺n 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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