Isotropic Grids Revisited: A Numerical Study of Solar Cell Electrode Geometries

Many contemporary solar cells utilize sparse front electrodes to gather charge carriers from the sun-facing side of their active material layers, deploying an H-bar shape to minimize shadowing and resistive losses in the cell material and metal lines. Isotropic grids, comprised of overlapping line arrays and forming triangular, square, or hexagonal shapes, are generally not recognized as outperforming H-bar type designs as front electrodes due to their increased shadowing. However, for solar cells where front-side charge carriers converge to single point sinks, and especially when transparent conductor (TC) sheet resistance is high, isotropic grids are capable of outperforming H-bars. We present a simple numerical framework for modeling the shadow and resistive losses in circular H-bar and isotropic grids and for optimizing the pitch and width of the designs. Using Griddler finite element (FE) software as validation, we demonstrate that isotropic grids produce more power for solar cells with high transparent conductive layer resistance and point sinks.