Band-Gap Widening at the Cu(In,Ga)(S,Se)2 Surface: A Novel Determination Approach Using Reflection Electron Energy Loss Spectroscopy

详细信息    查看全文

• 作者：Dirk Hauschild ; Evelyn Handick ; Sina Göhl-Gusenleitner ; Frank Meyer ; Holger Schwab ; Andreas Benkert ; Stephan Pohlner ; Jörg Palm ; Sven Tougaard ; Clemens Heske ; Lothar Weinhardt ; Friedrich Reinert
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：August 17, 2016
• 年：2016
• 卷：8
• 期：32
• 页码：21101-21105
• 全文大小：327K
• 年卷期：0
• ISSN：1944-8252

文摘

Using reflection electron energy loss spectroscopy (REELS), we have investigated the optical properties at the surface of a chalcopyrite-based Cu(In,Ga)(S,Se)₂ (CIGSSe) thin-film solar cell absorber, as well as an indium sulfide (In_xS_y) buffer layer before and after annealing. By fitting the characteristic inelastic scattering cross-section λK(E) to cross sections evaluated by the QUEELS-ε(k,ω)-REELS software package, we determine the surface dielectric function and optical properties of these samples. A comparison of the optical values at the surface of the In_xS_y film with bulk ellipsometry measurements indicates a good agreement between bulk- and surface-related optical properties. In contrast, the properties of the CIGSSe surface differ significantly from the bulk. In particular, a larger (surface) band gap than for bulk-sensitive measurements is observed, providing a complementary and independent confirmation of earlier photoelectron spectroscopy results. Finally, we derive the inelastic mean free path λ for electrons in In_xS_y, annealed In_xS_y, and CIGSSe at a kinetic energy of 1000 eV.