Identifying representative air masses for multi-junction solar cell bandgap optimization to maximize annual energy yield

Annual energy yield is calculated for multijunction solar cells with ideal bandgap combinations optimized for spectra between AM0.7d and AM3.1d. A “representative spectrum” can thus be defined, within the assumptions of the study, as that which corresponds to the air mass that resulted in the highest annual energy yield. Results show that the air mass of this representative spectrum does not correspond to the 50% cumulative energy air mass which has traditionally been used as a point of reference. Further, the optimal design point is shown to be different for cells with different numbers of junctions. Bandgap combinations that maximize clear sky annual energy yield in Boulder, USA and Ottawa, Canada are presented.