N-type multicrystalline silicon wafers and rear junction solar cells

S. Martinuzzi (1) , O. Palais (2, 1) , M. Pasquinelli (1) , F. Ferrazza (3)

1 TECSEN - Laboratoire de thermodynamique, propriétés électriques, contraintes, structures aux échelles nanométriques
2 IM2NP - Institut des Matériaux, de Microélectronique et des Nanosciences de Provence
3 EniTecnologie SpA

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.

Domains: Physics [physics]

S. Martinuzzi, O. Palais, M. Pasquinelli, F. Ferrazza. N-type multicrystalline silicon wafers and rear junction solar cells. European Physical Journal: Applied Physics, 2005, 32 (3), pp.187-192. ⟨10.1051/epjap:2005085⟩. ⟨hal-03350281⟩