15:30 〜 15:45
▲ [14p-2M-9] Dependence of internal radiative efficiencies on radiative damages in multi-junction tandem solar cells via absolute electroluminescence measurements
キーワード：III-V solar cells,Multi-junction solar cells,Radiation effects
In multi-junction (MJ) tandem solar cells for space use, the degradation by radiation is a serious problem. The high-energy particles in space colliding with atoms in cells cause atomic displacements, which can act as non-radiative recombination centers. This leads to significantly reduced minority carrier lifetimes and the cell performance. Therefore, the basic understanding of radiation effects is very important for space-cell development.
The dependences of subcell characteristics (short circuit current, open circuit voltage, and efficiency, etc) on the incident particles’ type, energy and fluence have been reported previously. In this work, we characterize degradations of internal radiative efficiency in subcells in proton-induced GaInP/GaAs/Ge triple-junction and electron-induced GaInP/GaAs double-junction solar cells via absolute electroluminescence (EL) measurement method.[3] We show their dependence on energy and fluence, and explain them by a simple calculation model. The results exhibit that subcell internal radiative efficiency is a sensitive and quantitative indicator of radiation damage, since it purely represents material-quality change due to radiation damage, independently from small differences in the band-gap energy due to alloy composition fluctuations and in other cell structures. A detailed fluence-dependence study on 2-junction cells shows that the data of internal radiative efficiency versus fluence in moderate and high fluence regions are very similar and almost independent of the subcell material, while the difference in beginning-of-life values of subcell internal radiative efficiency cause dominant difference in sensitivity to the low radiation damages.
The dependences of subcell characteristics (short circuit current, open circuit voltage, and efficiency, etc) on the incident particles’ type, energy and fluence have been reported previously. In this work, we characterize degradations of internal radiative efficiency in subcells in proton-induced GaInP/GaAs/Ge triple-junction and electron-induced GaInP/GaAs double-junction solar cells via absolute electroluminescence (EL) measurement method.[3] We show their dependence on energy and fluence, and explain them by a simple calculation model. The results exhibit that subcell internal radiative efficiency is a sensitive and quantitative indicator of radiation damage, since it purely represents material-quality change due to radiation damage, independently from small differences in the band-gap energy due to alloy composition fluctuations and in other cell structures. A detailed fluence-dependence study on 2-junction cells shows that the data of internal radiative efficiency versus fluence in moderate and high fluence regions are very similar and almost independent of the subcell material, while the difference in beginning-of-life values of subcell internal radiative efficiency cause dominant difference in sensitivity to the low radiation damages.