Examination of optimized structures for a-Si:H based triple junction solar cells

We have examined a-Si:H based triple junction solar cells by using the AMPS computer program. We have found that, although the a-SiC:H material has wider band-gap, it does not yield better performance than a-Si:H absorber as the first absorber in the triple junctions because of the severely degraded material quality of today's a-SiC:H in the stabilized state. Moreover, for the stabilized state, we find that the optimized thickness distributions of a-Si:H based triple junctions are thinner than those determined in the annealed state. Our results for optimized stable efficiencies show that (1) with today's a-SiC:H materials, stabilized cell efficiencies can be better with a-Si:H top cells, (2) sub-cell layers need to be thinner than generation current matching would suggest, and (3) because of the need for thinner i-layers, the window losses become critical (to keep Jsc up).