Simulating the Effect of Lifetime Non-uniformity on Solar Cell Performance Using cmd-PC1D 6 and Griddler 2

Abstract

In this paper we present a novel approach to investigate the influence of non-uniformity in the minority carrier lifetime of c-Si wafers on solar cell efficiency. By using a combination of one-dimensional device modelling (cmd-PC1D 6) and finite element circuit modelling (Griddler 2) we are able to simulate the total IV characteristics of a solar cell based on input from minority carrier lifetime images. With suitable input regarding the optical properties, doping profiles, recombination behaviour and sheet resistance of the passivated and metallized surfaces involved this combined model can be used to predict the total cell efficiency of mc-Si solar cells and other cells with significant lateral variations in wafer quality. Several artificial test cases are investigated in order to determine the sensitivity of the method and the magnitude of the effect of lifetime distribution. We find that using the weighted average of the two-diode parameters J01, J02 and Jlight in most cases provides a good description of total cell performance, correctly describing the IV parameters within an error of ∼0.1 - 0.2% relative as compared to simulations taking the complete lateral distribution over the wafer into account. The deviation was however observed to be up to 1.5% for extreme, artificial cases. By instead assuming an average carrier lifetime over the wafer larger errors are observed, due to the non-linear relation between the two-diode parameters and the bulk lifetime.