倒置四结(IMM4J)太阳电池中InGaAs(1.0 eV)和InGaAs(0.7 eV)子电池高能电子辐照退火效应

In this work, thermal annealing effects of InGaAs (1.0 eV) and InGaAs (0.7 eV) sub-cells for inverted metamorphic four junction (IMM4J) solar cells after being irradiated by 1 MeV electrons are investigated by using light I-V characteristic, dark I-V characteristic and spectral response. Annealing temperature range is 60-180 ℃ and annealing time is 0-180 min. The results indicate that the open-circuit voltage V_oc, short-circuit current I_sc, and maximum power P_max of two sub-cells are gradually recovered with annealing time increasing, and the rate of recovery increases with annealing temperature increasing. Besides, the recovery rate of InGaAs (1.0 eV) sub-cell is less than that of InGaAs (0.7 eV) sub-cell under the same annealing temperature and time. Double exponential model is used to fit the dark I-V curve for the key parameters (the serial resistant R_s, the parallel resistant R_sh, the diffusion current I_s1 and the recombination current I_s2). It is found that R_s, I_s1 and I_s2 of two sub-cells decrease gradually and R_sh increases during annealing and the rate of recovery increases with annealing temperature rising. However, the recovery of I_s1 and I_s2 of InGaAs(1.0 eV) are much greater than that of InGaAs(0.7 eV). The equivalent model between short-circuit current density (J_sc) and defect concentration (N) induced by irradiation and annealing is established. N changes follow the first reaction kinetics, and the rate constant follows the Arrhenius equation with the annealing temperature. Therefore, the thermal annealing activation energy of InGaAs(1.0 eV) and InGaAs(0.7 eV) sub-cells are 0.38 eV and 0.26 eV, respectively. These efforts will contribute to the IMM4J solar cells, in particular, to space-based applications.