Spectrum splitting photovoltaics: Materials and device parameters to achieve ultrahigh system efficiency

We describe an approach for spectrum splitting solar module design using 8 independently connected subcells with optimized band gaps. Modified detailed balance calculations using parameters to account for nonideal absorption and recombination behavior are used to identify the efficiency of spectrum splitting modules with 2 to 20 subcells. Potential optical designs for solar spectrum splitting among subcells are briefly described. Spectrum splitting improves use of the power in the solar spectrum by decreasing thermalization losses. A multijunction design utilizing independently connected subcells employed in a concentrator photovoltaic receiver allows flexibility in subcell selection, fabrication and operating power point optimization when a large number of subcells are employed.