Development of radiation hard Ga0.50In0.50P/Ga0.99In0.01As/Ge space solar cells with multi quantum wells

The efficiency of today´s Ga_0.5In_0.5P/Ga_0.99In_0.01As/Ge triple-junction space solar cells can be improved by the incorporation of multi-quantum wells to extend the absorption of the GaInAs middle cell. In this paper, the effect of high energy electron irradiation on the device performance of quantum well single- and triple-junction devices was investigated. For GaAs single-junction solar cells it could be shown that the degradation is predominantly in voltage and not in current as for conventional p-n solar cells. This result was also confirmed for triple-junction quantum well solar cells. An excellent remaining factor in short-circuit current density of over 97% was measured after irradiation with 1 MeV electrons at a fluence of 10¹⁵ cm^-2. Also the remaining factor for V_oc was high with 91%. However, the fillfactor of this cell degraded 20% leading to a low overall end of life (EOL) efficiency. This may be due to a low shunt resistance of the device.