Requirements for a GaAsBi 1 eV sub-cell in a GaAs-based multi-junction solar cell

T Thomas, A Mellor, N P Hylton, M Führer, D Alonso-Álvarez, A Braun, N J Ekins-Daukes, J P R David, S J Sweeney
2015 Semiconductor Science and Technology  
Multi-junction solar cells achieve high efficiency by stacking sub-cells of different bandgaps (typically GaInP/GaAs/Ge) resulting in efficiencies in excess of 40%. The efficiency can be improved by introducing a 1 eV absorber into the stack, either replacing Ge in a triplejunction configuration or on top of Ge in a quad-junction configuration. GaAs 0.94 Bi 0.06 yields a direct-gap at 1 eV with only 0.7% strain on GaAs and the feasibility of the material has been demonstrated from GaAsBi
more » ... from GaAsBi photodetector devices. The relatively high absorption coefficient of GaAsBi suggests sufficient current can be generated to match the sub-cell photocurrent from the other sub-cells of a standard multi-junction solar cell. However, minority carrier transport and background doping levels place constraints on both p/n and p-i-n diode configurations. In the possible case of short minority carrier diffusion lengths we recommend the use of a p-i-n diode, and predict the material parameters that are necessary to achieve high efficiencies in a GaInP/GaAs/GaAsBi/Ge quad-junction cell.
doi:10.1088/0268-1242/30/9/094010 fatcat:bh7e4exvnzbabf5txroahhgcs4