Investigating local inhomogeneity effects of silicon wafer solar cells by circuit modelling

Abstract

Local inhomogeneity effects such as shunts, inhomogeneous sheet resistance and inhomogeneous recombination rate are typical phenomena for silicon wafer solar cells. Some widely used solar cell simulators (for example Sentaurus TCAD and PC1D) have limitations in modelling these effects, since they are, for practical reasons, often restricted either to only one or two dimensions, or to small scales. In this work, circuit modelling is used to simulate local inhomogeneity effects of a silicon wafer solar cell. A distributed circuit model has the advantage that it can take large-scale lateral transport of carriers into account. First, the method of constructing the distributed circuit model is described. Then some local inhomogeneities, such as local shunts and broken fingers, are introduced into the circuit model. Finally, the global I-V characteristics and voltage distribution of the modelled cell are calculated. It is found that local inhomogeneities have an influence on the efficiency of a solar cell, and that this kind of influence can be quantified by circuit modelling. For example, it was calculated that a broken finger reduced the fill factor of the simulated solar cell by about 1.1% relative, and local shunt reduced the fill factor by about 3.2% relative. © 2013 Published by Elsevier Ltd. Selection.