Band-Gap Widening at the Cu(In,Ga)(S,Se)2 Surface: A Novel Determination Approach Using Reflection Electron Energy Loss Spectroscopy
Document Type
Article
Publication Date
1-1-2016
Publication Title
ACS Applied Materials and Interfaces
Volume
8
Issue
32
First page number:
21101
Last page number:
21105
Abstract
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 (InxSy) buffer layer before and after annealing. By fitting the characteristic inelastic scattering cross-section λK(E) to cross sections evaluated by the QUEELS-(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 InxSy 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 InxSy, annealed InxSy, and CIGSSe at a kinetic energy of 1000 eV. © 2016 American Chemical Society.
Keywords
band gap; Cu(In; Ga)(S; Se)2; EELS; optical spectroscopy; thin-film solar cell
Language
English
Repository Citation
Hauschild, D.,
Handick, E.,
Göhl-Gusenleitner, S.,
Meyer, F.,
Schwab, H.,
Benkert, A.,
Pohlner, S.,
Palm, J.,
Tougaard, S.,
Heske, C.,
Weinhardt, L.,
Reinert, F.
(2016).
Band-Gap Widening at the Cu(In,Ga)(S,Se)2 Surface: A Novel Determination Approach Using Reflection Electron Energy Loss Spectroscopy.
ACS Applied Materials and Interfaces, 8(32),
21101-21105.
http://dx.doi.org/10.1021/acsami.6b06358