Temperature Coefficient Imaging for Silicon Solar Cells

Abstract

As a usual procedure, silicon solar cells are characterized in test laboratories at standard testing conditions (STC) and are also optimized for these. However, as the cells’ performance parameters are dependent on temperature, which differs in real operation conditions to STC, extended characterization of solar cell current–voltage characteristics is necessary to calculate annual yields. In this paper, we study the temperature sensitivity of three multicrystalline silicon solar cells with different cell concepts and bulk material qualities but similar performance at STC. It is shown that at least for multicrystalline silicon solar cells the temperature sensitivity can only be understood by using spatially resolved characterization techniques. We apply temperature-dependent and spectrally resolved measurement techniques such as light-beam induced current, photoluminescence imaging, as well as quasi steady-state photoluminescence. Cell areas with high concentration of impurities show increased temperature sensitivity, especially of the open-circuit voltage $V_{{\text{OC}}}$ and the lifetime of excess charge carriers τ . Results gathered by averaging the spatially resolved measurements are in good agreement with global values which confirms the applicability of our approach. Our proposed method improves understanding of the influence of temperature on parameters of cell operation and enables a detailed analysis especially of multicrystalline silicon solar cells.