Spectrometric Characterization for Triple-Junction Solar Cells

Spectrometric characterization allows for accurate determination of the current matching point and investigation of sub-cell properties of multi-junction solar cells. It has been widely used for dual-junction solar cells. Although the concept has been suggested for triple-junction solar cells, it has only been applied for the variation of two sub-cells. In this work we present the applicability and evaluation procedure for a systematic variation of all three sub-cells of a triple-junction solar cell. Clearly defined measurement conditions are derived which allow for meaningful characterization and comparisons of different triple-junction devices. The presented procedure is exemplarily tested on a III-V on Silicon triple-junction solar cell using an LED-based solar simulator where all needed spectral conditions can be calculated in advance and accordingly adjusted. Spectral conditions around the AM1.5g spectrum are chosen and a fit routine to determine the current matching point from the discrete measurement points is proposed and validated by a measurement with a higher resolution around the current matching point. Finally, it is shown that the spectral conditions applied during the measurement also reflect outdoor conditions. This highlights the relevance of the presented procedure beyond the determination of the current matching conditions.