Stress and temperature coupling effects on dislocation density reduction in multicrystalline silicon

In multicrystalline silicon (mc-Si), the presence of dislocation-rich areas limits solar cell conversion efficiencies [1-2]. Previous studies have demonstrated that dislocation densities higher than 10⁶ cm ^-2 can dramatically decrease the minority carrier lifetime [3]. High dislocation densities, and their decoration with impurities, can limit minority carrier lifetime even after phosphorous diffusion or hydrogen passivation [4-5]. We previously proposed a method to remove dislocations from mc-Si by high-temperature annealing, demonstrating dislocation density reductions of 95% approximately [6]. We demonstrated that the dependence of dislocation density reduction on annealing temperature is much more pronounced that the dependence on annealing time [7]. In this contribution, we propose stress as an additional mechanism to enhance dislocation density reduction. We discuss the relationship between temperature, stresses and dislocation density in string ribbon.