Determination of subcell open circuit voltages and Iph-Voc curves in multijunction solar cells by sequentially pulsed, monochromatic illumination

The open circuit voltages Voc of individual subcells in a multijunction solar cell are measured by illuminating a given subcell with a pulse of spatially homogeneous, nearly monochromatic light with a rising edge in the ms regime. The influence of luminescent coupling and semi-transparency on Voc is eliminated by over-illuminating all subcells below this subcell with a preceding light pulse. By using a suns-Voc approach, the two-diode model dark saturation currents of each subcell are extracted. The proposed method is verified experimentally as well as through simulations on three and four-junction solar cells.