APIVT Epitaxial Growth on Zone-Melt Recrystallized Silicon: Preprint

Single-junction thin-film silicon solar cells require large grain sizes to ensure adequate photovoltaic performance. Using 2D silicon solar cell simulations on the quantitative effects of grain-boundary recombination on device performance, we have found that the acceptable value of effective grain boundary recombination velocity is almost inversely proportional to grain size. For example, in a polycrystalline silicon thin film with an intragrain bulk minority-carrier lifetime of 1 s, a recombination velocity of 104 cm/s is adequate if the grain is 20 m across, whereas a very low recombination velocity of 103 cm/s must be accomplished to achieve reasonable performance for a 2-m grain. For this reason, large grain size on the order of hundreds of m is currently a prerequisite for efficient solar cells, although a more effective grain-boundary passivation technique may be developed in the future.