Point-Defects Assisted Zn-Diffusion in AlGaInP/GaInP Systems During the MOVPE Growth of Inverted Multijunction Solar Cells
Point-Defects Assisted Zn-Diffusion in AlGaInP/GaInP Systems During the MOVPE Growth of Inverted Multijunction Solar Cells
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倒置多结太阳能电池 MOVPE 生长期间 AlGaInP/GaInP 系统中的点缺陷辅助 Zn 扩散
DOI：
10.1109/jphotov.2020.3043849
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发表时间：
2020
影响因子：
3
通讯作者：
C. Algora
中科院分区：
文献类型：
--
作者：
M. Hinojosa;Iv'an Garc'ia;S. Dadgostar;C. Algora
我们研究了MOVPE生长的AlGaInP/GaInP系统中Zn扩散的动力学，通过比较不同的结构来模拟集成到倒置多结太阳能电池结构中的GaInP子电池的背表面场（BSF）和基极层。通过二次离子质谱、电化学电容-电压和光谱分辨阴极发光的分析，我们提供了实验证据：1）在隧道结阴极层生长过程中注入的点缺陷增强了Zn的扩散，2）这一过程的强度取决于阴极掺杂水平，并且对于不同的阴极材料都是如此; 3）移动的Zn带正电荷; 4）扩散机制降低了GaInP中CuPt的有序性。我们证明，使用阻挡层的点缺陷的扩散可以减轻，使它们不会达到Zn掺杂层，防止其扩散。最后，通过比较不同浓度下的I-V曲线，评估了Zn扩散对具有不同Zn剖面的太阳能电池的影响。结果排除了在BSF中引入内部势垒，但说明了在典型生长条件下Zn扩散如何到达发射极并显著影响串联电阻等效应。
We investigate the dynamics of Zn diffusion in MOVPE-grown AlGaInP/GaInP systems by the comparison of different structures that emulate the back-surface field (BSF) and base layers of a GaInP subcell integrated into an inverted multijunction solar cell structure. Through the analysis of secondary ion mass spectroscopy, electrochemical capacitance–voltage and spectrally resolved cathodoluminescence measurements, we provide experimental evidence that 1) the Zn diffusion is enhanced by point defects injected during the growth of the tunnel junction cathode layer; 2) the intensity of the process is determined by the cathode doping level and it happens for different cathode materials; 3) the mobile Zn is positively charged; and 4) the diffusion mechanism reduces the CuPt ordering in GaInP. We demonstrate that using barrier layers the diffusion of point defects can be mitigated, so that they do not reach Zn-doped layers, preventing its diffusion. Finally, the impact of Zn diffusion on solar cells with different Zn-profiles is evaluated by comparing the electrical I–V curves at different concentrations. The results rule out the introduction of internal barriers in the BSF but illustrate how Zn diffusion under typical growth condition can reach the emitter and dramatically affect the series resistance, among other effects.