Influence of the base layer thickness and the graded buffer layer thickness on the conversion efficiency of a metamorphic triple-junction solar cell

摘要

Metamorphic multiple-junction soalr cells based on III-V compound semiconductor have advantages of more degree of freedom in selection of bandgaps of subcells. Recently, Spectrolab, Inc. reported a high conversion efficiency of 40.7% in a triple junction Ga_(0.44)In to Ge substrate. Optimization of device structure of such metamorphic Ga_(0.44)In_(0.56)P/Ga_(0.92)In_(0.08)As/Ge solar cell is important to increase its efficiency. In this work, two-dimensional simulation has been performed on the metamorphic Ga_(0.44)In_(0.56)P/Ga_(0.92)In_(0.08)As/Ge solar cell. Efficiency dependence of the Ga_(0.44)In_(0.56)P/Ga_(0.92)In_(0.08) As/Ge triple junction solar cell on the base layer thickness and the InGaAs graded buffer layer thickness has been investigated. It has been found that the efficiency depends significantly on the thickness of the GaInP base layer. The metamorphic triple junction solar buffer layer connecting the Ge substrate and GainAs middle-cell are 0.35 gm, 2.5 gm and 0.15 gm, respectively.