In this article, we developed a microcrystalline silicon tunnel junction to be used as a tunnel recombination junction between a large-gap top cell and a silicon heterojunction bottom cell, in a monolithic tandem integration. This junction is composed of a p-type layer on the top of an n-type layer, deposited by plasma-enhanced chemical vapor deposition at low temperature (200 °C). Microcrystalline phase percentage was controlled with Raman spectroscopy and ellipsometry measurements. The total stack has a thickness of 40 nm and an average conductivity around 10 S/cm. Minority carrier lifetime measurements showed an improvement of the field effect and the passivation with the addition of this junction on top of silicon heterojunction solar cells. Moreover, implementation of microcrystalline layer on top of reference rear emitter silicon heterojunction solar cells improved the fill factor and did not induce parasitic absorption above 700 nm. Simple test structures were fabricated in order to characterize the tunnel junction and optimize it. Then, we carried out dark temperature-dependent I-V measurements on those test structures and observed peaks and valleys, characteristic of the junction tunnel behavior. The developed tunnel junction shows low contact resistivity and activation energies; these are promising results for the complete integration on the tandem device.

中文翻译：

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采用硅异质结技术的单片串联太阳能电池的微晶硅隧道结


在本文中，我们开发了一种微晶硅隧道结，用作单片串联集成中大间隙顶部电池和硅异质结底部电池之间的隧道复合结。该结由 n 型层顶部的 p 型层组成，通过等离子体增强化学气相沉积在低温 (200 °C) 下沉积。通过拉曼光谱和椭圆光度测量来控制微晶相百分比。总堆叠厚度为 40 nm，平均电导率约为 10 S/cm。少数载流子寿命测量表明，通过在硅异质结太阳能电池顶部添加该结，场效应和钝化得到改善。此外，在参考后发射极硅异质结太阳能电池顶部实施微晶层提高了填充因子，并且不会引起700 nm以上的寄生吸收。为了表征隧道结并对其进行优化，制作了简单的测试结构。然后，我们对这些测试结构进行了暗温度相关的 IV 测量，并观察了峰和谷，这是结隧道行为的特征。所开发的隧道结表现出较低的接触电阻率和活化能；这些对于在串联装置上的完全集成来说是有希望的结果。