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N-type multicrystalline silicon wafers and rear junction solar cells
Published online by Cambridge University Press: 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 $\rm \Omega $ cm raw wafers lifetimes about 200 $\mu $s and diffusion lengths around 220 $\mu $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.
- Type
- Research Article
- Information
- The European Physical Journal - Applied Physics , Volume 32 , Issue 3 , December 2005 , pp. 187 - 192
- Copyright
- © EDP Sciences, 2005
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