Identification of Killer Defects in Kesterite Thin-Film Solar Cells,ACS Energy Letters

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Identification of Killer Defects in Kesterite Thin-Film Solar Cells
ACS Energy Letters ( IF 19.3 ) Pub Date : 2018-02-01 00:00:00 , DOI: 10.1021/acsenergylett.7b01313
Sunghyun Kim ₁ , Ji-Sang Park ₁ , Aron Walsh _{1,

2}

Affiliation

Nonradiative electron–hole recombination is the bottleneck to efficient kesterite thin-film solar cells. We have performed a search for active point defect recombination centers using first-principles calculations. We show that the anion vacancy in Cu₂ZnSnS₄ (CZTS) is electrically benign without a donor level in the band gap. V_S can still act as an efficient nonradiative site through the aid of an intermediate excited state involving electron capture by Sn. The bipolaron associated with Sn⁴⁺ to Sn²⁺ two-electron reduction stabilizes the neutral sulfur vacancy over the charged states; however, we demonstrate a mechanism whereby nonradiative recombination can occur via multiphonon emission. Our study highlights that defect-mediated recombination does not require a charge transition level deep in the band gap of a semiconductor. We further identify Sn_Zn as the origin of persistent electron trapping/detrapping in kesterite photovoltaic devices, which is suppressed in the selenide compound.

中文翻译：

钾长石薄膜太阳能电池杀手缺陷的鉴定

非辐射电子-空穴复合是高效硅藻土薄膜太阳能电池的瓶颈。我们已经使用第一性原理计算来搜索活性点缺陷重组中心。我们表明，Cu ₂ ZnSnS ₄（CZTS）中的阴离子空位是电良性的，在带隙中没有供体能级。V_小号仍可以作为通过中间激发态涉及电子捕获的由Sn中的助剂的有效非辐射点。与Sn ⁴⁺到Sn ²⁺相关的双极化子二电子还原可在带电状态下稳定中性硫的空位；但是，我们证明了一种通过多声子发射可以发生非辐射重组的机制。我们的研究着重指出，缺陷介导的重组并没有要求在半导体的带隙的电荷变化程度深。我们进一步确定Sn _Zn是在钾钛矿型光伏器件中持久电子俘获/俘获的源头，在硒化物化合物中可以抑制这种现象。

更新日期：2018-02-01

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