倒置四结砷化镓太阳电池的电子辐照性能研究及其仿真分析

发布时间：2019-01-23 19:14

【摘要】：由于四结太阳电池相比三结阳电池具有更高的光电转换效率,将逐步取代目前普遍使用的三结太阳电池。目前多结太阳电池主要应用于太空中航天器的供电系统,而其间存在的高能粒子的持续轰击将导致其性能逐步降低,因此太阳电池的耐辐照性能在很大程度上决定了航天器的寿命。目前三结太阳电池相关的辐照损伤研究已经开展10年以上且还在持续被研究中,但是四结太阳电池的相关研究还属于空白领域。多结太阳电池辐照效应研究需要从实验测试和理论分析两方面进行。测试方面涉及的方向很多,本工作主要关注电学性能的衰减,因此本文主要测量四结太阳电池的辐照前后的短路电流密度Jsc和开路电压Voc的衰减。理论方面需要原子级别的高能粒子轰击半导体的仿真软件和器件级别的计算机辅助软件。对于原子级别的仿真,本工作选用基于第一性原理的Casino软件对高能粒子注入到多层薄膜中的能量吸收进行计算;器件的性能仿真,采用加拿大Crosslight公司的Apsys软件进行分析。本工作分为实验和理论分析两部分。实验方面,参与制备出了四结太阳电池并通过合理选择辐照电子的能量和注量,测试了辐照前后的Jsc和Voc。考虑到统计学因素,选择了5组相近的测量结果计算其平均值,得到Jsc在辐照后从15.69mA/cm2衰减为13.55mA/cm2,Voc从3276.76mV衰减到2902.64mV。理论分析分为辐照前和辐照后两部分。辐照前的理论分析使用Apsys软件进行器件仿真。考虑到工艺中产生的缺陷问题,提出“多结太阳电池的单结分析法”,分析了少数载流子寿命和陷阱密度对各子结Jsc的影响趋势,结果表明:第三结子电池的Jsc对缺陷最敏感,从而判断其为四结太阳电池的电流限制结。少数载流子寿命分析是普遍采用的方法,陷阱密度的分析属于首次采用,而陷阱密度更能体现晶格中的缺陷情况。在确定电流限制结后,通过调整其它三个子结的陷阱密度,得到了拟合实验的结果,仿真得到的Jsc和Voc的误差只有0.1%左右。辐照后的理论分析首先使用Casino软件进行高能电子辐照仿真,接着使用Apsys软件进行仿真分析。由于Casino软件不能完整仿真四结太阳电池的薄膜结构,因此使用各子结电池吸收高能粒子能量的“能量损失递减”方法,由此得到在1MeV电子辐照的情况下,各子结的吸收平均能量分别为27.3 keV,28.24keV,27.8keV和29.3keV。电子辐照产生的晶格缺陷在载流子的输运过程中表现为陷阱。为了体现每个子结吸收的电子能量转化为陷阱的能力,本文尝试采用“吸收能量和陷阱密度表征的方法”,其相应的Apsys软件仿真分析得出,第3结子电池依然是辐照后的电流限制结。通过改变各个子结的吸收电子能量转化陷阱能力的表征值,同样得到了拟合实验的结果,仿真得到的J-V曲线非常逼近辐照后的实验测量J-V曲线。四结太阳电池分析工作还处于初期阶段,后续可以开展许多方面的完善性工作,比如测量各层薄膜材料的电学性质和各子结吸收材料的折射率谱以得到电池的精确仿真结果,以此为前提进行电池的精确优化工作。本文中提出的一系列理论结合实验的分析方法不限于应用于四结太阳电池,对于将来五结太阳电池甚至六结太阳电池的分析和优化都是行之有效的方法。
[Abstract]:Because the four-junction solar cell has higher photoelectric conversion efficiency compared with the three-junction solar cell, the three-junction solar cell currently commonly used is gradually replaced. At present, the multi-junction solar cell is mainly applied to the power supply system of the spacecraft in space, and the continuous bombardment of the high-energy particles in the space can lead to a gradual reduction in the performance of the solar cell, so that the radiation resistance performance of the solar cell largely determines the life of the spacecraft. At present, the research on the radiation damage associated with the three-junction solar cell has been carried out more than 10 years and is still under study, but the related research of the four-junction solar cell also belongs to the blank field. The study of the radiation effect of multi-junction solar cells needs to be carried out from both experimental and theoretical analysis. In this paper, the short-circuit current density (Jsc) and the open-circuit voltage (Voc) before and after the irradiation of the four-junction solar cell are mainly measured. The theoretical aspect requires the atomic level of high-energy particles to bombard the semiconductor's simulation software and device-level computer-aided software. For the simulation of the atomic level, the energy absorption of high-energy particles into the multi-layer film is calculated by the Casino software based on the first principle, and the performance simulation of the device is carried out by using the Apsys software of Crosslight, Canada. This work is divided into two parts: experimental and theoretical analysis. In the experimental aspect, the four-junction solar cell was prepared and the energy and the injection quantity of the irradiated electrons were selected reasonably, and the Jsc and Voc before and after irradiation were tested. Taking into account the statistical factors, the average value of 5 groups of similar measurements was selected to obtain the average value of Jsc from 15. 69mA/ cm2 to 13.55mA/ cm2 after irradiation and from 3276.76mV to 2902. 64mV. The theoretical analysis is divided into two parts before and after irradiation. The theoretical analysis before irradiation uses the Apsys software for device simulation. In this paper, the influence of minority carrier lifetime and trap density on sub-junction Jsc is analyzed, and the effect of minority carrier lifetime and trap density on sub-junction Jsc is analyzed. The results show that the Jsc of the third junction cell is most sensitive to the defect, so as to judge the current limiting junction of the four-junction solar cell. The analysis of minority carrier lifetime is a widely used method. The analysis of the trap density belongs to the first use, and the trap density can reflect the defects in the lattice. After the current limit junction is determined, the trap density of the other three sub-junctions is adjusted, and the result of the fitting experiment is obtained, and the error of the obtained Jsc and Voc is only 0.1%. The theoretical analysis after irradiation firstly uses the Casino software for high-energy electronic irradiation simulation, and then uses the Apsys software to carry out the simulation analysis. Since the Casino software does not fully simulate the thin-film structure of the four-junction solar cell, the 鈥渆nergy loss decrements鈥，

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