Silicon heterojunction (SHJ) solar cell device structures use carrier-selective contacts that enable efficient collection of majority carriers while impeding the collection of minority carriers. However, these contacts can also be a source of resistive losses that degrade the performance of the solar cell. In this article, we evaluate the performance of the carrier-selective hole contact—hydrogenated amorphous silicon (a-Si:H)(i)/a-Si:H(p)/indium tin oxide (ITO)/Ag—by simulating transport in SHJ solar cell transfer length method structures. We study contact resistivity behavior by varying the a-Si:H(i) layer thickness, ITO(n+) and a-Si:H(p) layer doping, temperature, and interface defect density at the a-Si:H(i)/ crystalline silicon (c-Si) interface. In particular, we consider the effect of ITO/a-Si:H(p) and the a-Si:H(i)/c-Si heterointerfaces on contact resistivity as they play a crucial role in modulating transport through the hole contact structure. Transport models such as band-to-band tunneling, and thermionic emission models were added to describe transport across the heterointerfaces. Until now, most simulation studies have treated the ITO as a Schottky contact; in this article, we treat the ITO as an n-type semiconductor. Our simulations match well with corresponding experiments conducted to determine contact resistivity. As the a-Si:H(i) layer thickness is increased from 4 to 16 nm, the simulated contact resistivity increases from 0.50 to 2.1 Ωcm2, which deviates a maximum of 8% from the experimental measurements. It should be noted that we calculate the contact resistivity for the entire hole contact stack, which takes into account transport across the a-Si:H(p)/c-Si and ITO/a-Si:H(p) heterointerface. Corresponding experiments on cell structures showed a fill factor degradation from 77% to 70%. Our simulations indicate that a highly doped n-type ITO layer facilitates tunneling at the ITO/a-Si:H(p) heterointerface, which leads to low contact resistivities.

中文翻译：

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通过模拟 TLM 结构了解硅异质结太阳能电池的空穴接触中的传输

硅异质结 (SHJ) 太阳能电池器件结构使用载流子选择性接触，可有效收集多数载流子，同时阻止少数载流子的收集。然而，这些触点也可能是降低太阳能电池性能的电阻损耗的来源。在本文中，我们评估了载流子选择性空穴接触——氢化非晶硅 (a-Si:H)(i)/a-Si:H(p)/氧化铟锡 (ITO)/Ag——的性能——通过模拟SHJ太阳能电池传输长度方法结构中的传输。我们通过改变 a-Si:H(i) 层厚度、ITO(n+) 和 a-Si:H(p) 层掺杂、温度和 a-Si:H(i) 处的界面缺陷密度来研究接触电阻率行为)/ 晶体硅 (c-Si) 界面。我们特别考虑 ITO/a-Si:H(p) 和 a-Si 的影响：H(i)/c-Si 异质界面对接触电阻率的影响，因为它们在调节通过空穴接触结构的传输中起着至关重要的作用。添加了诸如带间隧穿和热离子发射模型之类的传输模型来描述跨异质界面的传输。到目前为止，大多数仿真研究都将 ITO 视为肖特基接触；在本文中，我们将 ITO 视为 n 型半导体。我们的模拟与为确定接触电阻率而进行的相应实验非常匹配。随着 a-Si:H(i) 层厚度从 4 nm 增加到 16 nm，模拟的接触电阻率从 0.50 增加到 2.1 Ωcm2，这与实验测量值的最大偏差为 8%。应该注意的是，我们计算了整个空穴接触叠层的接触电阻率，这考虑了跨 a-Si:H(p)/c-Si 和 ITO/a-Si:H(p) 异质界面的传输。对单元结构的相应实验表明填充因子从 77% 下降到 70%。我们的模拟表明，高度掺杂的 n 型 ITO 层促进了 ITO/a-Si:H(p) 异质界面处的隧穿，从而导致低接触电阻率。