Irradiation Effects in Space Solar Cells Made of Multiple Absorbers

Solar cells made of multiple absorbers are a commonly used approach for improving efficiency due to their extended range of spectral sensitivity. Indeed, efficiencies nearing the theoretical maximum have been achieved with a triple-junction device made of In_0.51Ga_0.49P (InGaP₂), GaAs, and Ge solar cells connected in series. For extraterrestrial applications, there is the added requirement of radiation tolerance. The main challenge for space power-generation is therefore the development of highly efficient and radiation-tolerant devices. We have investigated several aspects of the radiation response of solar cells made of multiple absorbers, such as multijunction devices and quantum-well solar cells. Novel possibilities such as quantumdot solar cells and ordered-disordered heterostructures are proposed.