Theoretical analysis of AlxGa1−xAs-GaAs graded band-gap solar cell

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Abstract
A practical theoretical analysis of an n/p graded band‐gap AlxGa1−xAs‐GaAs solar cell indicates that the presence of a built‐in electric field acting on holes in the surface layer increases the hole collection efficiency of a nearly optimum cell to a maximum of 97.8%. The electric field is created by the band‐gap gradient and serves to reduce the surface hole recombination by 97% and reduce the bulk hole recombination by 80%, compared to a similar GaAs cell. These reduced losses increase cell response substantially for wavelengths less than 0.59 μm and yield a maximum air‐mass‐zero efficiency of 17.7% (not corrected for a 13% front‐surface contact). The model includes an optimized antireflection coating, series resistance, and junction‐recombination current.