Dirk Hauschild1,2,Luisa Both1,Ralph Steininger1,Elizaveta Pyatenko1,Mary Blankenship2,Wolfram Witte3,Rico Gutzler3,Dimitrios Hariskos3,Michael Powalla3,Clemens Heske1,2,Lothar Weinhardt1,2
Karlsruhe Institute of Technology (KIT)1,University of Nevada, Las Vegas (UNLV)2,Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW)3
Dirk Hauschild1,2,Luisa Both1,Ralph Steininger1,Elizaveta Pyatenko1,Mary Blankenship2,Wolfram Witte3,Rico Gutzler3,Dimitrios Hariskos3,Michael Powalla3,Clemens Heske1,2,Lothar Weinhardt1,2
Karlsruhe Institute of Technology (KIT)1,University of Nevada, Las Vegas (UNLV)2,Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW)3
The introduction of alkali post-deposition treatments (PDTs) for Cu(In,Ga)Se<sub>2 </sub>(CIGSe)-based thin-film solar cells has paved the way for efficiencies above 23 % on a laboratory scale.<sup>1</sup> For the next big step in solar-cell performance, new approaches need to be pursued. In recent studies, the incorporation of silver in CIGSe, i.e., forming (Ag,Cu)(In,Ga)Se<sub>2 </sub>(ACIGSe), has been identified as a promising route.<sup>2</sup> The addition of Ag increases the absorber band gap, which could increase the open circuit Voltage (V<sub>OC</sub>).<sup>3</sup> However, the impact of Ag on the chemical and electronic structure of the absorber surface, in particular with a PDT, is not yet understood.<br/>In this contribution, we investigate in-line deposited and industrially relevant RbF-PDT ACIGSe absorbers and their interfaces with the molybdenum back contact as a function of the Ag/(Ag+Cu) (AAC)-ratio. For this purpose, the deeply-buried ACIGSe/Mo interface was accessed using sample cleaving and studied by synchrotron-based soft <i>and</i> hard x-ray photoelectron spectroscopy (PES and HAXPES, respectively), as well as laboratory-based x-ray and UV PES (XPS and UPS, respectively) and inverse photoemission (IPES). A detailed picture of the chemical and electronic structure of the ACIGSe surface and the ACIGSe/Mo interface as a function of the AAC-ratio is painted and will be discussed in view of the device performance.<br/><br/>(1) Nakamura, M.; Yamaguchi, K.; Kimoto, Y.; Yasaki, Y.; Kato, T.; Sugimoto, H. Cd-Free Cu(In,Ga)(Se,S)<sub>2</sub> Thin-Film Solar Cell With Record Efficiency of 23.35%. <i>IEEE J. of Photovoltaics</i> <b>2019</b>, <i>9</i> (6), 1863–1867. https://doi.org/10.1109/JPHOTOV.2019.2937218.<br/>(2) Keller, J.; Sopiha, K. V.; Stolt, O.; Stolt, L.; Persson, C.; Scragg, J. J. S.; Törndahl, T.; Edoff, M. Wide-Gap (Ag,Cu)(In,Ga)Se<sub>2</sub> Solar Cells with Different Buffer Materials—A Path to a Better Heterojunction. <i>Prog. Photovoltaics</i> <b>2020</b>, <i>28</i> (4), 237–250. https://doi.org/10.1002/pip.3232.<br/>(3) Edoff, M.; Jarmar, T.; Nilsson, N. S.; Wallin, E.; Högström, D.; Stolt, O.; Lundberg, O.; Shafarman, W.; Stolt, L. High V<sub>oc</sub> in (Cu,Ag)(In,Ga)Se<sub>2</sub> Solar Cells. <i>IEEE J. of Photovoltaics</i> <b>2017</b>, <i>7</i> (6), 1789–1794. https://doi.org/10.1109/JPHOTOV.2017.2756058.