Radiation degradation and damage coefficients of InGaP/GaAs/Ge triple-junction solar cell by low-energy electrons

Imaizumi, Mitsuru*; Morioka, Chiharu*; Sumita, Taishi*; Oshima, Takeshi; Okuda, Shuichi*

InGaP single-junction and InGaP/GaAs/Ge triple-junction (3J) solar cells were irradiated with low energy electrons. The energy of electrons were selected around the threshold energy of Gallium and Indium recoiling in the InGaP system (300 keV). Simultaneous electron irradiation and current-voltage characteristics measurement of the cells revealed the fact that the short-circuit current (Isc) of InGaP cells and consequently the 3J cells does not degrade when the cells are irradiated with electrons with energies of less than 300 keV, while the open-circuit voltage (Voc) considerably degrades for both types of the cell, regardless of the electron energies. This result suggests that the effects of defects generated by the recoil of phosphorus are insufficient to decrease the minority-carrier lifetime in InGaP. In addition, the degradation of the Voc suggests an increase in surface recombination.