The potential for increasing the efficiency of photovoltaic systems by using multiple cell concepts

Two techniques have been investigated to increase the conversion efficiencies in concentration systems by the use of two or three different bandgap material cells. The technique of putting cells in optical series with the highest-gap material first, could lead to efficiencies of about 30-35% if a high efficiency cell with a bandgap of about 2.0 eV could be developed. Using selective mirrors to divide the solar spectrum into energy bands that selected cells could respond to has special advantages from a design point of view and could lead to comparable efficiencies as for optical series arrangements.