Measurement of the limiting subcell in multijunction space solar devices by restricted-wavelength-range illumination

During their employment in space applications, InGaP/InGaAs/Ge‐based multijunction solar cells undergo strong particle bombardments that decrease their performances. As InGaP is more resistant to radiation, the whole device is usually designed in “top‐limited” configuration. Then the development of high‐efficiency and reliable devices needs standard techniques for identifying the limiting subcell before and after irradiation. We here present a specific method to determine the limiting subcell and matching current in multijunction solar cell. This approach is based on using simultaneously a solar simulator and a suitable supplemental lamp for illuminating the cell in a restricted wavelength range where the top subcell only responds. The technique is tested on beginning‐of‐life and irradiated 3‐junction InGaP/InGaAs/Ge solar cells, and its reliability is discussed.