High-efficiency, one-sun (22.3% at air mass 0; 23.9% at air mass 1.5) monolithic two-junction cascade solar cell grown by metalorganic vapor phase epitaxy

A high-efficiency monolithic two-junction solar cell consisting of an Al0.37Ga0.63As (Eg =1.93 eV) upper cell and a GaAs lower cell has been grown by metalorganic vapor phase epitaxy. Since both component cells have the n-on-p configuration, the unwanted p-n junction has been eliminated with the use of metal-interconnect contact during post-growth processing. As a two-terminal device, an efficiency of 22.3% has been achieved under 1 sun, air mass 0 illumination conditions, whereas an efficiency of 23.9% was obtained when the cascade cell was operated as a three-terminal device under 1 sun, air mass 1.5 illumination. This result represents the highest 1 sun efficiency ever reported. The advantages of utilizing this multijunction solar cell for terrestrial and space applications are also described.