The degradation of inverted metamorphic four-junction (GaInP/GaAs/In_0.3Ga_0.7As/In_0.58Ga_0.42As, IMM4J) solar cells irradiated by 1-MeV electrons was investigated via their spectral responses and the characterization of their electrical properties. As in the case of traditional three-junction (TJ) GaInP/GaAs/Ge solar cells, the electrical properties (I_sc, V_oc, and P_max) decrease with the logarithmic change of the electron fluence. The degradation of open-circuit voltage (V_oc) is slightly more pronounced than that of I_sc in IMM4J solar cells because of the sum rule for V_oc and the limit rule for I_sc. The spectral response analysis showed that an In_0.3Ga_0.7As subcell was the most damaged subcell in the irradiated IMM4J solar cell, but an In_0.58Ga_0.42As subcell had the lowest initial short-circuit current density (J_sc), which was maintained throughout the irradiation test. We therefore focused on the In_0.58Ga_0.42As subcell. Deep-level transient spectroscopy (DLTS) experiments were realized to study emission and capture processes in two special full configurations of In_0.58Ga_0.42As and In_0.3Ga_0.7As subcells of the IMM4J solar cell. DLTS measurements reveal a dominant electron trap at 0.52 eV below the conduction band (E_c) of In_0.58Ga_0.42As, and the electron trap gradually evolved into E_c-0.46eV and E_c-0.58eV after 1-MeV electron irradiation. Based on the first-principles calculation, E_c-0.46 eV and E_c-0.58 eV can be assigned as ${\bf V}_{{\bf Ga}}^{\bf 0}/{\bf V}_{{\bf Ga}}^{{\rm{ - }}1}$ and ${\bf V}_{{\bf In}}^{\bf 0}/{\bf V}_{{\bf In}}^{{\bf - 1}}$, respectively. However, only one shallow level E_c-0.03eV was observed within the bandgap of In_0.3Ga_0.7As after irradiation with DLTS detection. We summarize the issues faced for the space application of IMM4J solar cells by comparing the spectral responses of IMM3J, IMM4J, and TJ solar cells. Finally, the optimization of the design and fabrication of IMM solar cells are proposed.

中文翻译：

---

倒变质四结太阳能电池的电子辐照效应及缺陷分析

通过其光谱响应和电性能表征研究了由 1-MeV 电子辐照的倒变质四结 (GaInP/GaAs/In _0.3 Ga _0.7 As/In _0.58 Ga _0.42 As, IMM4J) 太阳能电池的退化。与传统的三结 (TJ) GaInP/GaAs/Ge 太阳能电池一样，电性能 (一世_SC，伏_oc , 和磷_max ) 随电子注量的对数变化而减小。开路电压的退化（伏_oc ) 比一世在 IMM4J 太阳能电池中的_sc是因为伏_oc和极限规则一世_秒。光谱响应分析表明In _0.3 Ga _0.7 As子电池是辐照IMM4J太阳能电池中损坏最严重的子电池，而In _0.58 Ga _0.42 As子电池的初始短路电流密度（J _sc）最低，并保持不变在整个辐照试验过程中。因此，我们专注于 In _0.58 Ga _0.42 As 子电池。实现了深能级瞬态光谱 (DLTS) 实验以研究 In _0.58 Ga _0.42 As 和 In _0.3 Ga _0.7两种特殊完整配置的发射和捕获过程作为 IMM4J 太阳能电池的子电池。DLTS 测量显示在 In _0.58 Ga _0.42 As的导带 (E _c )以下 0.52 eV 处存在主要电子陷阱，并且在 1-MeV 电子辐射后，电子陷阱逐渐演变为 E _c -0.46eV 和 E _c -0.58eV。根据第一性原理计算，E _c -0.46 eV 和 E _c -0.58 eV 可表示为${\bf V}_{{\bf Ga}}^{\bf 0}/{\bf V}_{{\bf Ga}}^{{\rm{ - }}1}$ 和 ${\bf V}_{{\bf In}}^{\bf 0}/{\bf V}_{{\bf In}}^{{\bf - 1}}$， 分别。然而，在用DLTS检测照射后，在In _0.3 Ga _0.7 As的带隙内仅观察到一个浅能级E _c -0.03eV 。我们通过比较 IMM3J、IMM4J 和 TJ 太阳能电池的光谱响应，总结了 IMM4J 太阳能电池在空间应用中面临的问题。最后，提出了IMM太阳能电池设计和制造的优化方案。