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

Thermal annealing effects of InGaAs(1.0 eV)and InGaAs(0.7 eV)sub-cells of inverted metamorphic four junction(IMM4J)solar cells under 1 MeV electron irradiation

本文为研究1 MeV电子辐照倒置四结(IMM4J)太阳电池InGaAs(1.0 eV)和InGaAs(0.7 eV)关键子电池的退火效应,将辐照后的两种子电池在60—180℃温度范围累计退火180 min,并对不同退火温度、退火时间下的两种子电池进行了光IV测试、暗IV测试和光谱响应测试.实验结果表明两种子电池的开路电压Voc、短路电流Isc和最大输出功率Pmax随着退火时间的延长逐渐恢复,温度越高,恢复程度越大.在相同的退火条件下,InGaAs(1.0 eV)子电池的恢复程度比InGaAs(0.7 eV)子电池小.本文通过对暗特性曲线进行双指数模型拟合,得到不同退火条件下两种子电池的串联电阻Rs、并联电阻Rsh、扩散电流Is1、复合电流Is2.结果表明在退火过程中两种子电池的Rsh逐渐增大,Rs,Is1和Is2逐渐减小.温度越高,退火时间越长,恢复程度越大.在退火60 min后两种子电池的Voc,Isc和Pmax恢复程度均可达到整体恢复程度的85%以上.InGaAs(1.0 eV)子电池的Is1和Is2的恢复程度远大于InGaAs(0.7 eV).本文建立了短路电流密度Jsc和缺陷浓度N的等效模型,以此计算得到InGaAs(1.0 eV)和InGaAs(0.7 eV)两种子电池的热退火激活能分别为0.38 eV和0.26 eV.

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 Voc,short-circuit current Isc,and maximum power Pmax 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 Rs,the parallel resistant Rsh,the diffusion current Is1 and the recombination current Is2).It is found that Rs,Is1 and Is2 of two sub-cells decrease gradually and Rsh increases during annealing and the rate of recovery increases with annealing temperature rising.However,the recovery of Is1 and Is2 of InGaAs(1.0 eV)are much greater than that of InGaAs(0.7 eV).The equivalent model between short-circuit current density(Jsc)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.