Spectral performance of non-optimally matched two-cell tandem solar cells

CdTe and CuInSe₂ solar cells have nonoptimally matched bandgaps for efficient utilization of the solar spectrum in a two-cell tandem configuration. To provide current matching between the two cells, part of the bottom cell may be exposed to the incident radiation. Since changes in the solar spectrum tend to predominantly occur at long wavelengths, if some of the short-wavelength incident radiation is allowed to penetrate the bottom cell, the tandem cell should perform more consistently with changing insolation conditions than in a regular tandem structure. The author shows through theoretical modeling that while the efficiency of nonoptimally matched cells does improve under varying insolation conditions when the bottom cell is exposed to the incident radiation, the enhancement in the cell´s output power is negligible