Proton Damage Effects Of In_xGa_1-xAs Solar Cells And Trpl-based Investigation Of The Carrier Behaviors

The efficient and lightweight IMM multi-junction cell has the potential to replace the GaInP（1.90ev）/GaAs（1.42ev）/Ge（0.67ev）LM3J solar cell as the next generation space solar cell.As a new type of space solar cells,In_xGa_1-xAs subcells of IMM multi-junction solar cells is still at the primary stage of research on its radiation damage effect,especially on proton radiation damaging behaviors.Therefore,In_x Ga_1-xAs（x=0.3,0.5）single junction solar cell was chosen as the research object.We studied the degradation characteristicsof electrical properties of In_xGa_1-xAs（x=0.3,0.5）solar cells,and revealed the evolution behavior and damage mechanism of minority carrier lifetime,which provides theoretical guidance for the structural optimization and on-orbit behavior prediction of IMM multi-junction solar cells through proton irradiation test,supplemented by time resolved photoluminescence spectrum,light/dark property test spectral response test,steady-state fluorescence spectrum test and other analytical means.The results showed that for In_0.3 Ga_0.7As solar cells,both 1 MeV proton and 3 MeV protons caused damage to the cells.The short circuit current,open circuit voltage and maximum power of proton irradiated In_0.3Ga_0.7As solar cells meet the degradation law of y=1-Clog(D_d/D_d,o),and the degradation coefficients of C_Isc、C_Voc and C_Pmax are 0.095,0.075 and 0.098,respectively.For In_0.5Ga_0.5As solar cells,the short circuit current,open circuit voltage and maximum power of In_0.5Ga_0.5As solar cells meet the degradation law of y=1-Clog（φ/φ_o）,the degradation coefficients of C_Isc、C_Voc and C_Pmax are 0.062,0.012 and 0.064,respectively.The dark characteristic analysis shows that the dark current,parallel resistance and series resistance of In_x Ga_1-xAs（x=0.3,0.5）solar cells have similar degradation laws after proton irradiation:the dark current and series resistance increase,while the parallel resistance decreases.The study also showed tha the electrical degradation degree of In_0.5Ga_0.5As solar cells was greater than that of In_0.3Ga_0.7As solar cells under the same irradiation condition(3 MeV,10¹² cm^-2),this is because the In_0.3Ga_0.7As material in the upper layer of In_0.5G_a0.5As solar cells will produce obvious fluorescence coupling effect under the original conditions of the cells,which improves the nominal conversion efficiency of the original In_0.5Ga_0.5As solar cells,so its relative degradation rate after irradiation is relatively large.The photoluminescence spectrum analysis showed that the photoluminescence intensity of In_0.3Ga_0.7As materials and In_0.3Ga_0.7As solar cells decreased rapidly after proton irradiation,indicating that the defects introduced by irradiation in materials and the solar cells reduced the lattice integrity.Through the test results and simulation of TRPL of In_0.3Ga_0.7As materials,it is revealed that the deep level defect introduced by proton irradiation is the main reason for the significant reduction of the lifetime of the minority carriers,and the physical relationship between carrier lifetime and radiation defect is established.Based on the above results,the attenuation coefficient of minority carrier lifetime of In_0.3Ga_0.7As cells k_{τ,solar cell} is 0.1 g/（MeV?s?cm³）.