Silicon-based 2 Terminal Tandem Solar Cells with Lattice-Matched Buffer Layers

Abstract

A novel structure for a Si-based 2-terminal tandem solar cell was proposed. The structure was optimized to get high efficiency considering the realistic material parameters. Gallium arsenide phosphide (GaAs₁₋xPx) and indium gallium phosphide (In₁₋xGaxP) were suggested as a top-cell material. A semi-empirical method was proposed to calculate the absorption coefficients of GaAs₁₋xPx and In₁₋xGaxP at any value of the composition x. The conversion efficiency of the cell was calculated by simulating its voltage-current characteristics. It was shown that an efficiency of 33.1% can be obtained for a GaAs.₇₃P.₂₇/Si cell and 34.2% for an In.₅₇Ga.₄₃P/Si cell. In₁₋xGaxP was shown to be more promising because of its larger absorption coefficient than GaAs₁₋xPx's.