Non-optimal yet useful bandgap combinations for multijunction solar cells

The optimal bandgap combinations for multijunction solar cells are well known. The bandgaps used in practical devices may deviate from these optimal values depending on the availability of suitable materials. This work explores the non-ideal but still useful bandgap combinations that exist for multijunction cells with up to six subcells. It is found that principal component analysis can be utilized to establish rules of thumb for how the bandgaps in multijunction devices should be collectively adjusted to maintain high efficiency. This realization allows bandgap configurations with high theoretical efficiency to be identified with a few easy calculations, as demonstrated by a practical example.