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Reliable wet-chemical cleaning of natively oxidized high-efficiency Cu(In,Ga)Se-2 thin-film solar cell absorbers

Lehmann, Jascha; Lehmann, Sebastian LU ; Lauermann, Iver; Rissom, Thorsten; Kaufmann, Christian A.; Lux-Steiner, Martha Ch.; Baer, Marcus and Sadewasser, Sascha (2014) In Applied Physics Reviews 116(23).
Abstract
Currently, Cu-containing chalcopyrite-based solar cells provide the highest conversion efficiencies among all thin-film photovoltaic (PV) technologies. They have reached efficiency values above 20%, the same performance level as multi-crystalline silicon-wafer technology that dominates the commercial PV market. Chalcopyrite thin-film heterostructures consist of a layer stack with a variety of interfaces between different materials. It is the chalcopyrite/buffer region (forming the p-n junction), which is of crucial importance and therefore frequently investigated using surface and interface science tools, such as photoelectron spectroscopy and scanning probe microscopy. To ensure comparability and validity of the results, a general... (More)
Currently, Cu-containing chalcopyrite-based solar cells provide the highest conversion efficiencies among all thin-film photovoltaic (PV) technologies. They have reached efficiency values above 20%, the same performance level as multi-crystalline silicon-wafer technology that dominates the commercial PV market. Chalcopyrite thin-film heterostructures consist of a layer stack with a variety of interfaces between different materials. It is the chalcopyrite/buffer region (forming the p-n junction), which is of crucial importance and therefore frequently investigated using surface and interface science tools, such as photoelectron spectroscopy and scanning probe microscopy. To ensure comparability and validity of the results, a general preparation guide for "realistic" surfaces of polycrystalline chalcopyrite thin films is highly desirable. We present results on wet-chemical cleaning procedures of polycrystalline Cu(In1-xGax)Se-2 thin films with an average x = [Ga]/([In] + [Ga]) = 0.29, which were exposed to ambient conditions for different times. The hence natively oxidized sample surfaces were etched in KCN- or NH3-based aqueous solutions. By x-ray photoelectron spectroscopy, we find that the KCN treatment results in a chemical surface structure which is - apart from a slight change in surface composition - identical to a pristine as-received sample surface. Additionally, we discover a different oxidation behavior of In and Ga, in agreement with thermodynamic reference data, and we find indications for the segregation and removal of copper selenide surface phases from the polycrystalline material. (C) 2014 AIP Publishing LLC. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Applied Physics Reviews
volume
116
issue
23
publisher
American Institute of Physics
external identifiers
  • wos:000346634500011
  • scopus:84920280507
ISSN
0021-8979
DOI
10.1063/1.4903976
language
English
LU publication?
yes
id
4096ef0a-0a37-4574-9978-8015b155eac5 (old id 4941629)
date added to LUP
2015-01-28 08:24:44
date last changed
2017-11-19 03:19:44
@article{4096ef0a-0a37-4574-9978-8015b155eac5,
  abstract     = {Currently, Cu-containing chalcopyrite-based solar cells provide the highest conversion efficiencies among all thin-film photovoltaic (PV) technologies. They have reached efficiency values above 20%, the same performance level as multi-crystalline silicon-wafer technology that dominates the commercial PV market. Chalcopyrite thin-film heterostructures consist of a layer stack with a variety of interfaces between different materials. It is the chalcopyrite/buffer region (forming the p-n junction), which is of crucial importance and therefore frequently investigated using surface and interface science tools, such as photoelectron spectroscopy and scanning probe microscopy. To ensure comparability and validity of the results, a general preparation guide for "realistic" surfaces of polycrystalline chalcopyrite thin films is highly desirable. We present results on wet-chemical cleaning procedures of polycrystalline Cu(In1-xGax)Se-2 thin films with an average x = [Ga]/([In] + [Ga]) = 0.29, which were exposed to ambient conditions for different times. The hence natively oxidized sample surfaces were etched in KCN- or NH3-based aqueous solutions. By x-ray photoelectron spectroscopy, we find that the KCN treatment results in a chemical surface structure which is - apart from a slight change in surface composition - identical to a pristine as-received sample surface. Additionally, we discover a different oxidation behavior of In and Ga, in agreement with thermodynamic reference data, and we find indications for the segregation and removal of copper selenide surface phases from the polycrystalline material. (C) 2014 AIP Publishing LLC.},
  articleno    = {233502},
  author       = {Lehmann, Jascha and Lehmann, Sebastian and Lauermann, Iver and Rissom, Thorsten and Kaufmann, Christian A. and Lux-Steiner, Martha Ch. and Baer, Marcus and Sadewasser, Sascha},
  issn         = {0021-8979},
  language     = {eng},
  number       = {23},
  publisher    = {American Institute of Physics},
  series       = {Applied Physics Reviews},
  title        = {Reliable wet-chemical cleaning of natively oxidized high-efficiency Cu(In,Ga)Se-2 thin-film solar cell absorbers},
  url          = {http://dx.doi.org/10.1063/1.4903976},
  volume       = {116},
  year         = {2014},
}