Determination of subcell open circuit voltages and I_ph–V_oc curves in multijunction solar cells by sequentially pulsed, monochromatic illumination

The open circuit voltages V_oc 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 μs regime. The influence of luminescent coupling and semi-transparency on V_oc is eliminated by over-illuminating all subcells below this subcell with a preceding light pulse. By using a suns-V_oc 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.