Dislocation Density Reduction In Multicrystalline Silicon Solar Cell Material By High Temperature Annealing

We propose and demonstrate a method to remove performance-limiting dislocations from multicrystalline silicon (mc-Si) solar cell material, appropriate for wafers or bricks. Dislocation density reductions of > 95% are achieved in commercial mc-Si via high temperature annealing with an impurity diffusion barrier, with controlled ambient and time-temperature profiles. The dislocation density reduction follows temperature-dependent models developed by Kuhlmann [Proc. Phys. Soc., London, Sect. A 64, 140 (1951)] and Nes [Acta Metall. Mater. 43, 2189 (1995)]. It is believed that higher annealing temperatures (>1170 degrees C) allow dislocation movement unconstrained by crystallographic glide planes, leading to dislocation annihilation within minutes. (C) 2008 American Institute of Physics.