Degradation behavior of electrical properties of GaInAs (1.0 eV) and GaInAs (0.7 eV) sub-cells of IMM4J solar cells under 1-MeV electron irradiation.

In this work the degradation effects of the GaInAs (1.0 eV) and GaInAs (0.7 eV) sub-cells for IMM4J solar cells are investigated after 1-MeV electron irradiation by using spectral response and photoluminescence (PL) signal amplitude analysis, as well as electrical property measurements. The results show that, compared with the electrical properties of traditional single junction (SJ) GaAs (1.41 eV) solar cell, the electrical properties (such as , , and of the newly sub-cells degrade similarly as a function of , where represents the electron fluence. It is found that the degradation of is much more than that of in the irradiated GaInAs (0.7 eV) cells due to the additional intrinsic layer, leading to more serious damage to the space charge region. However, of the three types of SJ cells with the gap widths of 0.7, 1.0, and 1.4 eV, the electric properties of the GaInAs (1.0 eV) cell decrease largest under each irradiation fluence. Analysis on the spectral response indicates that the of the GaInAs (1.0 eV) cell also shows the most severe damage. The PL amplitude measurements qualitatively confirm that the degradation of the effective minority carrier life-time ( in the SJ GaInAs cells is more drastic than that of SJ GaAs cells during the irradiation. Thus, the output current of GaInAs sub-cell should be controlled in the irradiated IMM4J cells. [ABSTRACT FROM AUTHOR]