A simple criterion for predicting multicrystalline Si solar cell performance from lifetime images of wafers prior to cell production

Abstract

The aim of this paper is to clarify which mean value can be used to predict multicrystalline Si (mc-Si) solar cell performance from lifetime distributions on wafers prior to production. Therefore, a numerical device simulation model is presented that predicts cell performance very precisely from lifetime distributions. This model is used to derive a simple lifetime averaging procedure, which can be used as a criterion for excluding low-quality wafers from production. Compared with standard mean values such as the arithmetic, harmonic, or geometric mean, the criterion derived here significantly reduces the number of mistakenly rejected wafers prior to cell production. In an exemplary case study where 1000 different lifetime distributions were analyzed, our new procedure misjudged only 13 wafers, in contrast with 158 wafers when using the arithmetic mean, 109 wafers when using the geometric mean, and 78 when using the harmonic mean. Further, the influence of lower lifetime regions on mc-cell performance is quantified, showing that low lifetime regions cannot be overcompensated with higher lifetimes in general.