GaAs/silicon mechanically stacked, multijunction solar cell

A GaAs/silicon mechanically stacked, multijunction solar cell has been experimentally and theoretically investigated. Theoretical calculations predict efficiencies over 30% for this cell and indicate that the penalty for using a non-optimal combination of bandgaps is small when the cells are operated independently. Preliminary experiments achieved 24.7% at 70X. A detailed analysis of the experimental results allowed estimation of the various loss mechanisms in the stack and projection of the performance of an optimized stacked cell. An optimized GaAs/silicon MSMJ cell should be able to achieve efficiencies near 30% under concentration.