Finite Element Simulation of Electrical Intradevice Physics of Thin-Film Solar Cells and Its Implications on the Efficiency

One key aspect to further improve thin-film photovoltaic devices is the optimal sizing of the different layers, such as grids, transparent conducting oxides (TCOs), back contacts, and absorber materials, with respect to their mutual electrical influences. This article describes a novel quasi-3-D finite element method (FEM) tool on a digital twin, which is capable of simulating all electrical influences from a holistic perspective from semiconductor materials to device level. It yields a spatially resolved intradevice distribution of electrical potentials and currents, helping to understand the physical processes within solar cell devices. Experimentally inaccessible data, such as the breakdown of different loss mechanisms, can be provided. Moreover, the internal cell properties can be used for forecasting calculations of characteristic
I–V
curves. This process can also be reversed in a procedure called reverse engineering fitting. It allows to calculate backward from the external cell properties to the internal loss-exempt semiconductor material characteristics. Our approach is verified by semitransparent cells with a perovskite absorber, a silver rear metalization grid, and indium zinc oxide as a rear TCO. Our simulation predicts characteristic
I–V
curves with a coefficient of determination of well above 0.99 with respect to experimentally measured cells. The power conversion efficiency (PCE) can be forecast within a mean error of 0.18%
$_{\mathrm{abs}}$
at absolute PCEs around 13% for different TCO and grid thicknesses. The advantage of our FEM approach in contrast to a single-diode equivalent circuit model is demonstrated by considering
I–V
curve predictions for different cell sizes.