Combining drift-diffusion and equivalent-circuit models for efficient 3D tandem solar cell simulations

For upscaling silicon based tandem solar cells from small laboratory sizes to full size formats compatible with industrial production, two-dimensional (2-D) and 3-D effects like metal grid layout, perimeter design, and lateral inhomogeneities gain importance for tandem cell development. For understanding and quantifying such effects, 3-D tandem modeling is helpful, but the capabilities of existing solar cell simulation tools is limited in this respect. In this article, we describe a numerically efficient 3-D tandem modeling approach implemented in the solar cell simulation software Quokka3. It combines a 1-D equivalent-circuit (EQC) model of the top cell within the front side’s boundary condition with either the quasi-neutral 3-D drift-diffusion model or an EQC model for the bottom cell’s bulk carrier transport. This way the addition of a top cell to a single-junction silicon bottom cell model in Quokka3 adds little effort in terms of computational time and is thus compatible with large-area 3-D simulations up to full cell geometries.We showcase the usefulness of this approach by investigating various perimeter designs of small-area silicon-perovskite cells.