Atomic scale structure and its impact on the band gap energy for Cu2Zn(Sn,Ge)Se4 kesterite alloys
Atomic scale structure and its impact on the band gap energy for Cu2Zn(Sn,Ge)Se4 kesterite alloys
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DOI：
10.1088/2515-7655/ab9d8b
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发表时间：
2020-07
期刊：
影响因子：
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通讯作者：
K. Ritter;S. Eckner;Cora Preiß;G. Gurieva;T. Bischoff;E. Welter;S. Botti;S. Schorr;C. Schnohr
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文献类型：
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作者：
K. Ritter;S. Eckner;Cora Preiß;G. Gurieva;T. Bischoff;E. Welter;S. Botti;S. Schorr;C. Schnohr
Kesterite基材料获得越来越多的相关性在追求实惠，高效和灵活的薄膜光伏吸收材料。用Ge合金化Cu2ZnSnSe4可以实现Cu(In,Ga)(S,Se)2基太阳能电池的可控带隙工程。采用低温扩展x射线吸收精细结构光谱研究了Cu2Zn(Sn,Ge)Se4合金的局部原子排布。元素特定键长与x射线衍射数据结合，得到了不同局部构型的阴离子位置。通过从头算理论计算，预测了阴离子位置和晶格常数等结构参数对带隙能的影响。结合实验和理论研究结果表明，合金化引起的结构变化对带隙弯曲的总体影响显著，但小于带隙能量的非线性总变化。因此，我们得出结论，带隙弯曲源于结构和电子的变化。
Kesterite based materials gain more and more relevance in the pursuit of affordable, efficient and flexible absorber materials for thin film photovoltaics. Alloying Cu2ZnSnSe4 with Ge could allow controlled band gap engineering as already established for Cu(In,Ga)(S,Se)2 based solar cells. This study investigates the local atomic arrangements of Cu2Zn(Sn,Ge)Se4 alloys by means of low temperature Extended x-ray Absorbtion Fine Structure Spectroscopy. The element specific bond lengths are used together with x-ray diffraction data to derive the anion positions of the different local configurations. Ab initio theoretical calculations are performed to predict the influence of structural parameters such as anion position and lattice constants on the band gap energy. Combining the results of the experimental and theoretical studies suggests that the overall influence of the structural changes on the band gap bowing due to alloying is significant yet smaller than the total non-linear change of the band gap energy. Consequently, it is concluded, that band gap bowing stems from both structural and electronic changes.