Influence of laterally split spectral illumination on multi-junction CPV solar cell performance

An important concern in concentrator photovoltaics (CPV) is inhomogeneity in spectral distribution on the cell caused by the applied optical systems. This is particularly the case in building-integrated CPV (BICPV) applications, where the inhomogeneities generally are larger than in field-based systems, on account of design constraints by the building incorporation. In this study, the electrical parameters of CPV solar cells under severe laterally split spectra are investigated experimentally. The short-circuit current exhibits a reduction under spectral splitting associated with reduced cell illumination. For one sun illumination, the open circuit voltage and the fill factor show relatively small reductions with increasing spectral splitting. This is shown to occur because the carriers encounter a locally elevated series resistance as they travel laterally through the cell to compensate for local current mismatch. Also under concentrated light (>100X) the effect of extreme non-uniformity in spectral distribution was found to have only minor effects on the cell performance. Therefore, a fair degree of design freedom exists to combine photovoltaics with a variety of concentrating optics in order to meet the specific design challenges of the built environment.