Effects of luminescent coupling in single- and 4-junction dilute nitride solar cells

A novel method for incorporating the effects of luminescent coupling and photon recycling in numerical simulations of planar devices is described. The carrier generation is incorporated directly in the device simulator as an additional term in the continuity equation, so that no additional iterations are required. The method is applied to single- and four-junction solar cells containing ~1.0 eV dilute nitride material. We find that luminescent coupling increases the short-circuit current (J_SC) of the 1-junction dilute nitride cell by 2.4% due to coupling with the Al_0.05Ga_0.95As filter. In the 4-junction design, there is significant photon recycling within the GaAs and GaInP sub-cells, providing a 60 mV increase in open-circuit voltage. There is a 1.9% relative increase in calculated efficiency to 44.4%.