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Non‐vacuum deposition of Cu(In,Ga)Se 2 absorber layers from binder free, alcohol solutions
Author(s) -
Uhl Alexander R.,
Fella Carolin,
Chirilă Adrian,
Kaelin Marc R.,
Karvonen Lassi,
Weidenkaff Anke,
Borca Camelia N.,
Grolimund Daniel,
Romanyuk Yaroslav E.,
Tiwari Ayodhya N.
Publication year - 2012
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.1246
Subject(s) - copper indium gallium selenide solar cells , thermogravimetric analysis , deposition (geology) , absorption (acoustics) , layer (electronics) , materials science , absorption spectroscopy , chemical engineering , analytical chemistry (journal) , chemistry , inorganic chemistry , organic chemistry , nanotechnology , optics , composite material , paleontology , physics , engineering , sediment , biology
Non‐vacuum methods for Cu(In,Ga)Se 2 (CIGS) absorber deposition have gained wide interest because of their inherent cost and energy saving potential. Here, a solution‐based processing route for CIGS absorber layers is presented that employs binder‐free solutions of metal salts in non‐toxic, alcohol solvents. Despite the low‐boiling‐point nature of the employed solvents, a residual carbon‐rich layer is observed between the CIGS and metal back contact. Based on comprehensive investigations by scanning electron microscopy, energy‐/wavelength dispersive X‐ray spectroscopy, X‐ray fluorescence, X‐ray diffraction, thermogravimetric analysis, differential thermal analysis, and extended X‐ray absorption fine structure spectroscopy, a formation reaction mechanism through intermediate metal–organic complexes is proposed. In this route, the CIGS layer is formed in selenium atmosphere via a gradual decomposition of the carbon‐rich layer comprising carboxylic chelate complexes of metals. A compositional gradient occurs in the CIGS absorber, whereas a significant amount of metals remains in the carbon‐rich layer. The incorporation of Ga into CIGS is affected by the initial salt concentration and the selenization temperature. Fabricated solar cells exhibit active area efficiencies of up to 7.7% on 0.3 cm 2 area without anti‐reflection coating, which is among the highest reported efficiencies for solar cells from a solution process with non‐explosive gases or solvents. Copyright © 2012 John Wiley & Sons, Ltd.