Metamorphic tunnel junctions for high efficiency III-V/IV multi-junction solar cell technology

Through band gap engineering, metamorphic GaInP/GaAsP/Si multi-junction solar cells are theoretically capable of achieving a substantial increase in efficiency, with a significant decrease in cost, compared to current state-of-the-art Ge-based multi-junction solar cells. While the refinement of the necessary metamorphic materials and development of the associated sub-cells are obvious areas of focus, such devices also require high-performance tunnel junctions to minimize both optical and electrical sub-cell interconnection losses. Here we discuss efforts toward the development of these important component devices, including metamorphic materials growth and analysis, leading to the successful demonstration of metamorphic GaAs₀₉P₀₁ tunnel junctions with peak current densities exceeding 100 A/cm² and zero-bias resistance-area products of 4.5×10⁴ Ω·αη², indicating high-quality devices capable for use in future high-concentration GaInP/GaAsP/Si multi-junction devices.