1.5 eV GaInAsP Solar Cells Grown via Hydride Vapor-Phase Epitaxy for Low-Cost GaInP/GaInAsP//Si Triple-Junction Structures

Multijunction solar cells combining III-V and Si materials can provide high photoelectric conversion efficiency. Two-terminal III-V//Si triple-junction solar cells with an efficiency of 35.9% have already been developed using metal-organic vapor-phase epitaxy and the direct wafer bonding technique. This study, however, proposes the low-cost fabrication of III-V solar cells using hydride vapor-phase epitaxy (HVPE). GaInAsP solar cells are fabricated using HVPE to apply to middle cells in III-V//Si triple-junction structures. By controlling the partial pressure of the precursors, the optimal bandgap energy of 1.5 eV is obtained for the HVPE-grown GaInAsP quaternary alloys. The 1.5 eV GaInAsP single-junction solar cells show higher open-circuit voltage than the HVPE-grown GaAs solar cells. The open-circuit voltage of the GaInAsP solar cells fabricated with a GaInAsP growth rate of 77.6 mu m h(-1) reaches 1.1 V upon the formation of the rear-heterojunction structure. In addition, the external quantum efficiency spectra of the HVPE-grown GaInP/GaInAsP dual-junction solar cells show that the 1.5 eV GaInAsP solar cells are superior to the GaAs solar cells in terms of current matching for subcells in the III-V//Si triple-junction structures.