Optimisation of four-terminal GaAs//Si tandem solar cells using numerical simulation

Abstract

III–V//crystalline-silicon (c-Si) multi-junction solar cells exhibit great potential in the development of high-efficiency and cost-effective photovoltaic devices. Numerical simulation tools are fast and convenient approaches to optimise cell operation, compared to optimisation techniques involving costly extending experiments. In this study, optimisation of a four-terminal GaAs//c-Si tandem structure was modelled through automat for simulation of heterostructures (AFORS-HET) simulation. Various window layers, including AlGaAs, InGaP, AlInP, and AlGaInP layers, and absorber thicknesses were examined and compared to obtain the optimal light collection for the GaAs top cell. In addition, the absorber thicknesses and defect densities of the c-Si bottom cells were used to obtain optimal light absorption. The tandem operation was modelled by illuminating the top and bottom cells separately, with different spectral irradiance sources. The results indicated that the tandem structure with a 1.5 μm thick GaAs top and an AlGaAs window layer, in combination with 200-μm thick c-Si bottom cells, showed an optimal efficiency of 32.57%. These simulation results can be used as baselines for strictly experimental processes in the future. The cell operational mechanisms under these variations are detailed herein.