Designing Tandem Photovoltaics for Energy Production

Changes in the incident spectrum under varying atmospheric conditions can degrade the performance of series connected tandem solar cells that are optimized for performance under the AM1.5D standard spectrum. We present a case study of optimizing series connected tandem solar cells with two to eight subcells for energy production using representative spectra that capture the variation of incident spectra with cumulative irradiance level. Combined with the National Solar Radiation Database information on the frequency of cumulative irradiance levels at locations across the United States, these 20 direct spectra allow us to predict the energy production of spectrum splitting photovoltaic systems across the United States. Series connected tandems optimized to maximize energy production at a local level can generate up to 3% more energy per year than the AM1.5D based design.