Origin of the low conversion efficiency in Cu2ZnSnS4 kesterite solar cells: the actual role of cation disorder,Energy & Environmental Science

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Origin of the low conversion efficiency in Cu2ZnSnS4 kesterite solar cells: the actual role of cation disorder
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2021-4-20 , DOI: 10.1039/d1ee00260k
Wei Chen _{1,

2,

3,

4} , Diana Dahliah _{1,

2,

3,

4} , Gian-Marco Rignanese _{1,

2,

3,

4} , Geoffroy Hautier _{1,

2,

3,

4,

5}

Affiliation

The controversial role of cation disorder in the extraordinarily low open-circuit voltage (V_OC) of the Cu₂ZnSnS₄ (CZTS) kesterite absorber is examined through a statistical treatment of disorder within the cluster-expansion method. It is demonstrated that the extensive Cu–Zn disorder alone cannot be responsible for the large Urbach tails observed in many CZTS solar cells. While the band gap is reduced as a result of the Gaussian tails formed near the valence-band edge due to Cu clustering, band-gap fluctuations contribute only marginally to the V_OC deficit, thereby excluding Cu–Zn disorder as the primary source of the low efficiency of CZTS devices. On the other hand, the extensive disorder stabilizes the formation of Sn_Zn antisite and its defect complexes, which as nonradiative recombination and minority carrier trapping centers dominate the V_OC loss in CZTS. Our analysis indicates that current CZTS devices might have already approached the maximum conversion efficiency (14%) given the limited growth conditions and the remnant cation disorder even after postannealing. In view of the improved efficiency achieved with CZTS-derived kesterite absorbers, the methodology presented in this work offers an avenue to understanding and optimizing these emerging kesterite solar devices towards higher efficiency.

中文翻译：

Cu2ZnSnS4硅藻土太阳能电池转换效率低的根源：阳离子无序的实际作用

通过对簇扩展方法中无序的统计处理，研究了阳离子无序在Cu ₂ ZnSnS ₄（CZTS）钾盐吸收器的极低开路电压（V _OC）中的争议作用。事实证明，在许多CZTS太阳能电池中，仅广泛的Cu-Zn紊乱并不能导致大的Urbach尾巴。虽然由于Cu聚集而在价带边缘附近形成了高斯尾部，带隙有所减少，但带隙波动仅对V _OC产生很小的贡献缺陷，从而排除了Cu-Zn障碍作为CZTS器件效率低下的主要根源。另一方面，广泛的无序稳定了Sn _Zn反位点及其缺陷复合物的形成，这是非辐射复合和少数载流子俘获中心控制了CZTS中V _OC的损失。我们的分析表明，即使在退火后，由于有限的生长条件和残留的阳离子紊乱，当前的CZTS器件可能已经达到最大转换效率（14％）。鉴于使用CZTS衍生的钾长石吸收器可提高效率，本工作介绍的方法为理解和优化这些新兴的钾长石太阳能装置提供了一条途径，以实现更高的效率。

更新日期：2021-05-12

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