Aboulfadl Hisham, Sopiha Kostiantyn V, Keller Jan, Larsen Jes K, Scragg Jonathan J S, Persson Clas, Thuvander Mattias, Edoff Marika
Division of Microstructure Physics, Department of Physics, Chalmers University of Technology, 41296 Göteborg, Sweden.
Division of Solar Cell Technology, Department of Materials Science and Engineering, Uppsala University, 75121 Uppsala, Sweden.
ACS Appl Mater Interfaces. 2021 Feb 17;13(6):7188-7199. doi: 10.1021/acsami.0c20539. Epub 2021 Feb 3.
Silver alloying of Cu(In,Ga)Se absorbers for thin film photovoltaics offers improvements in open-circuit voltage, especially when combined with optimal alkali-treatments and certain Ga concentrations. The relationship between alkali distribution in the absorber and Ag alloying is investigated here, combining experimental and theoretical studies. Atom probe tomography analysis is implemented to quantify the local composition in grain interiors and at grain boundaries. The Na concentration in the bulk increases up to ∼60 ppm for [Ag]/([Ag] + [Cu]) = 0.2 compared to ∼20 ppm for films without Ag and up to ∼200 ppm for [Ag]/([Ag] + [Cu]) = 1.0. First-principles calculations were employed to evaluate the formation energies of alkali-on-group-I defects (where group-I refers to Ag and Cu) in (Ag,Cu)(In,Ga)Se as a function of the Ag and Ga contents. The computational results demonstrate strong agreement with the nanoscale analysis results, revealing a clear trend of increased alkali bulk solubility with the Ag concentration. The present study, therefore, provides a more nuanced understanding of the role of Ag in the enhanced performance of the respective photovoltaic devices.
用于薄膜光伏的Cu(In,Ga)Se吸收体的银合金化可提高开路电压，特别是与最佳碱处理和特定的镓浓度相结合时。本文结合实验和理论研究，研究了吸收体中碱分布与银合金化之间的关系。采用原子探针断层扫描分析来量化晶粒内部和晶界处的局部成分。与不含银的薄膜相比，[Ag]/([Ag] + [Cu]) = 0.2时，体相中钠浓度增加至约60 ppm，而不含银的薄膜约为20 ppm；[Ag]/([Ag] + [Cu]) = 1.0时，钠浓度增加至约200 ppm。采用第一性原理计算来评估(Ag,Cu)(In,Ga)Se中碱在I族缺陷（其中I族指Ag和Cu）上的形成能，作为Ag和Ga含量的函数。计算结果与纳米级分析结果显示出很强的一致性，揭示了随着银浓度增加碱体相溶解度增加的明显趋势。因此，本研究对银在相应光伏器件性能增强中的作用提供了更细致入微的理解。
