Analysing Solar Cells by Circuit Modelling

Abstract

Solar cell models implemented in simulation packages (for example Sentaurus TCAD) are typically restricted either to only one or two dimensions, or to small scales. They therefore neglect effects of local inhomogeneities or large scale phenomena such as lateral transport to fingers or busbars. In this paper, we use a distributed circuit model to investigate lateral inhomogeneity effects on silicon wafer solar cells. The circuit is constructed of different unit elements based on the one-diode model. To calculate the characteristics of the circuit, we use the freely available software LTspice IV (Linear Technology Corp). The presented model is used to simulate the distributed current flow in a solar cell. First, the design of the distributed circuit model is described. Then, the current-voltage characteristics obtained by the distributed circuit model are compared with those obtained from measurements. Finally, one kind of large-scale lateral effect, the voltage distribution across the solar cell area, is analysed. Due to lateral ohmic voltage drops, the electric potential at the cell surface is shown to be higher in the middle between two busbars or fingers than close to them.