Performance analysis of GaAsBi/InGaAs heterostructure for III-V multi-junction solar cells

Abstract

This study analyses the dilute GaAsBi as a candidate for the nominally 1.0 eV bandgap subcell in III-V multi-junction solar cells. The GaAsBi/InGaAs heterojunction solar cells are grown by molecular beam epitaxy pseudomorphically on thin InGaAs buffer layers to reduce GaAsBi lattice-mismatch with a GaAs substrate. We demonstrate a power conversion efficiency of 6.2%, one of the highest reported in GaAsBi-based solar cells thus far. The experimental photovoltaic and quantum efficiency measurements of the solar cells with intrinsic and n-type doped GaAsBi are modelled numerically to determine non-radiative recombination effects as well as optimal layer thickness and doping concentration to improve the performance. This work advances the GaAsBi-based device design and shows that current-matching conditions for a 3-junction inverted-growth solar cell could be achieved using a 1.0 eV GaAsBi bottom junction. • GaAsBi-based solar cells are considered as a candidate for the nominally 1.0 eV bandgap subcell in III-V multi-junction photovoltaics. • A heterojunction GaAsBi/InGaAs solar cells are grown pseudomorphically by MBE on thin InGaAs buffer layers. • We demonstrate so far the highest achieved power conversion efficiency of 6.2% in GaAsBi-based solar cells. • Numerical modelling of the J-V and quantum efficiency allows for the elucidation of charge carrier lifetimes and optimal device polarity. • The optimal doping concentration and GaAsBi absorber layer thickness are determined to improve the cells' V oc and J sc .