Larsen Jes K, Sopiha Kostiantyn V, Persson Clas, Platzer-Björkman Charlotte, Edoff Marika
Division of Solar Cell Technology, Department of Materials Science and Engineering, Uppsala University, Box 534, Uppsala, SE-75237, Sweden.
Centre for Materials Science and Nanotechnology/Department of Physics, University of Oslo, Blindern, Box 1048, Oslo, NO-0316, Norway.
Adv Sci (Weinh). 2022 Aug;9(23):e2200848. doi: 10.1002/advs.202200848. Epub 2022 Jun 20.
The chalcopyrite Cu(In,Ga)S has gained renewed interest in recent years due to the potential application in tandem solar cells. In this contribution, a combined theoretical and experimental approach is applied to investigate stable and metastable phases forming in CuInS (CIS) thin films. Ab initio calculations are performed to obtain formation energies, X-ray diffraction (XRD) patterns, and Raman spectra of CIS polytypes and related compounds. Multiple CIS structures with zinc-blende and wurtzite-derived lattices are identified and their XRD/Raman patterns are shown to contain overlapping features, which could lead to misidentification. Thin films with compositions from Cu-rich to Cu-poor are synthesized via a two-step approach based on sputtering from binary targets followed by high-temperature sulfurization. It is discovered that several CIS polymorphs are formed when growing the material with this approach. In the Cu-poor material, wurtzite CIS is observed for the first time in sputtered thin films along with chalcopyrite CIS and CuAu-ordered CIS. Once the wurtzite CIS phase has formed, it is difficult to convert into the stable chalcopyrite polymorph. CuIn S and NaInS accommodating In-excess are found alongside the CIS polymorphs. It is argued that the metastable polymorphs are stabilized by off-stoichiometry of the precursors, hence tight composition control is required.
近年来，由于在串联太阳能电池中的潜在应用，黄铜矿Cu(In,Ga)S重新引起了人们的关注。在本论文中，采用理论与实验相结合的方法来研究CuInS（CIS）薄膜中形成的稳定相和亚稳相。进行了从头算计算以获得CIS多型体及相关化合物的形成能、X射线衍射（XRD）图谱和拉曼光谱。识别出了具有闪锌矿和纤锌矿衍生晶格的多种CIS结构，并且它们的XRD/拉曼图谱显示出包含重叠特征，这可能导致误识别。通过基于从二元靶材溅射然后进行高温硫化的两步法合成了从富铜到贫铜组成的薄膜。发现采用这种方法生长材料时会形成几种CIS多晶型物。在贫铜材料中，首次在溅射薄膜中观察到纤锌矿CIS以及黄铜矿CIS和CuAu有序CIS。一旦形成纤锌矿CIS相，就很难转化为稳定的黄铜矿多晶型物。在CIS多晶型物旁边还发现了容纳过量In的CuInS和NaInS。有人认为，亚稳多晶型物通过前驱体的非化学计量比得以稳定，因此需要严格控制成分。
