Design and simulation of double-heterojunction solar cells based on Si and GaAs wafers

This article demonstrates the novel designs of Si and GaAs wafer-based double-heterojunction (DH) solar cells using SCAPS-1D simulator. Simple five-layer solar cells are proposed here: cells comprised of a cathode metal layer, three layers of semiconductor materials in the III-V, II-VI and group IV families--and a layer of anode metal. The device structures have been optimized for the analysis of the power-conversion efficiency (PCE) of the Si and GaAs solar cells considering high defect densities at and near each heterojunction. The PCEs predicted are 38% and 38.9% for n-ZnSe/p-Si/p (+)-Al0.8Ga0.2Sb and n-ZnSe/p-GaAs/p (+)-AlAs0.9Sb0.1 cells, respectively which stay entirely within the PCE limits set by the Shockley-Queisser theory of multi-junction cell. These results reveal that high efficiency and hence cost-effective Si and GaAs wafer-based DH solar cells can be fabricated in the near future.