The effect of diffusion-limited lifetime on implied current voltage curves based on photoluminescence data

Abstract

Quasi-steady-state photoconductance measurements and Suns-photoluminescence are useful techniques in predicting the electrical terminal characteristics of partially finished solar cells in contactless mode even prior to the junction formation. In both techniques, a measured average minority carrier density in the bulk is correlated with the carrier density at the edge of the junction and thereby with an implied voltage. This paper discusses experimental artifacts in such experiments that can be caused by the diffusion-limited effective minority carrier lifetime. Here these effects are discussed theoretically and demonstrated experimentally in relation to the Suns-photoluminescence technique only, because the range of implied voltages that is affected is generally not accessible via photoconductance measurements. A simple technique is proposed to correct the curves and increase the range of voltages measured accurately by the Suns-photoluminescence technique. It is concluded that the influence of diffusion-limited lifetime must be considered when interpreting Suns-photoluminescence curves, particularly in samples with a surface that is passivated by a shunted junction. © 2007 American Institute of Physics.