25.2% efficiency (1-sun, air mass 0) AlGaAs/GaAs/InGaAsP three-junction, two-terminal solar cell

A 25.2% efficiency measured under 1 sun, air mass 0 illumination has been achieved in a two-terminal AlGaAs/GaAs/InGaAsP three-junction solar cell. The cascade cell consists of a monolithic AlGaAs (Eg=1.93 eV)/GaAs two-junction mechanically stacked on an InGaAsP (Eg=0.95 eV) single-junction cell. The component cell of the AlGaAs/GaAs two-junction structure were electrically connected using a metal interconnect fabricated during post-growth processing. To minimize the obscuration effect introduced by the grid lines and metal interconnect, a prismatic cover glass was bonded to the AlGaAs/GaAs cascade cell. The results obtained with this structure represent the highest 1-sun, air mass 0 efficiency achieved in any solar cell operating under a two-terminal configuration. The implications of achieving this high efficiency in a two-terminal, three-junction solar cell for terrestrial and space applications are described as well.