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

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(In{sub 1-x}Ga{sub x})Se{sub 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 NH{sub 3}-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 withmore » thermodynamic reference data, and we find indications for the segregation and removal of copper selenide surface phases from the polycrystalline material.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ; ; ; ;  [1] ;  [1] ;  [4] ;  [1] ;  [5]
  1. Renewable Energies, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin (Germany)
  2. (PIK), 14473 Potsdam (Germany)
  3. (Sweden)
  4. (Germany)
  5. (Portugal)
Publication Date:
OSTI Identifier:
22402803
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 23; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; AMMONIA; AQUEOUS SOLUTIONS; CHALCOPYRITE; CLEANING; COPPER; EFFICIENCY; PHOTOVOLTAIC EFFECT; P-N JUNCTIONS; POLYCRYSTALS; SILICON; SOLAR CELLS; SURFACES; THIN FILMS; X-RAY PHOTOELECTRON SPECTROSCOPY