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Valence band offsets at Cu(In,Ga)Se 2 /Zn(O,S) interfaces
Author(s) -
Adler Tobias,
Botros Miriam,
Witte Wolfram,
Hariskos Dimitrios,
Menner Richard,
Powalla Michael,
Klein Andreas
Publication year - 2014
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201330353
Subject(s) - conduction band , x ray photoelectron spectroscopy , analytical chemistry (journal) , band offset , valence band , chemical bath deposition , materials science , chemical composition , solar cell , fermi level , sulfide , thin film , band gap , chemistry , electron , optoelectronics , metallurgy , nanotechnology , nuclear magnetic resonance , physics , organic chemistry , chromatography , quantum mechanics
The energy band alignment at interfaces between Cu‐chalcopyrites and Zn(O,S) buffer layers, which are important for thin‐film solar cells, are considered. Valence band offsets derived from X‐ray photoelectron spectroscopy for Cu(In,Ga)Se 2 absorber layers with CdS and Zn(O,S) compounds are compared to theoretical predictions. It is shown that the valence band offsets at Cu(In,Ga)Se 2 /Zn(O,S) interfaces approximately follow the theoretical prediction and vary significantly from sample to sample. The integral sulfide content of chemical bath deposited Zn(O,S) is reproducibly found to be 50–70%, fortuitously resulting in a conduction band offset suitable for solar cell applications with Cu(In,Ga)Se 2 absorber materials. The observed variation in offset can neither be explained by variation of the Cu content in the Cu(In,Ga)Se 2 near the interface nor by local variation of the chemical composition. Fermi level pinning induced by high defect concentrations is a possible origin of the variation of band offset.