Alkali Postdeposition Treatment-Induced Changes of the Chemical and Electronic Structure of Cu(In,Ga)Se2 Thin-Film Solar Cell Absorbers

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2019-01-23
Major/Subject
Mcode
Degree programme
Language
en
Pages
10
3024-3033
Series
ACS Applied Materials and Interfaces, Volume 11, issue 3
Abstract
The effects of alkali postdeposition treatment (PDT) on the valence band structure of Cu(In,Ga)Se2 (CIGSe) thin-film solar cell absorbers are addressed from a first-principles perspective. In detail, experimentally derived hard X-ray photoelectron spectroscopy (HAXPES) data [ Handick, E.; et al. ACS Appl. Mater. Interfaces 2015, 7, 27414-27420 ] of the valence band structure of alkali-free and NaF/KF-PDT CIGSe are directly compared and fit by calculated density of states (DOS) of CuInSe2, its Cu-deficient counterpart CuIn5Se8, and different potentially formed secondary phases, such as KInSe2, InSe, and In2Se3. The DOSs are based on first-principles electronic structure calculations and weighted according to element-, symmetry-, and energy-dependent photoionization cross sections for the comparison to experimental data. The HAXPES spectra were recorded using photon energies ranging from 2 to 8 keV, allowing extraction of information from different sample depths. The analysis of the alkali-free CIGSe valence band structure reveals that it can best be described by a mixture of the DOS of CuInSe2 and CuIn5Se8, resulting in a stoichiometry slightly more Cu-rich than that of CuIn3Se5. The NaF/KF-PDT-induced changes in the HAXPES spectra for different alkali exposures are best reproduced by additional contributions from KInSe2, with some indications that the formation of a pronounced K-In-Se-type surface species might crucially depend on the amount of K available during PDT.
Description
| openaire: EC/H2020/641004/EU//Sharc25
Keywords
chalcopyrite thin-film solar cells, DFT, HAXPES, KF-PDT, KInSe
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Citation
Malitckaya , M , Kunze , T , Komsa , H P , Havu , V , Handick , E , Wilks , R G , Bär , M & Puska , M J 2019 , ' Alkali Postdeposition Treatment-Induced Changes of the Chemical and Electronic Structure of Cu(In,Ga)Se 2 Thin-Film Solar Cell Absorbers : A First-Principle Perspective ' , ACS Applied Materials and Interfaces , vol. 11 , no. 3 , pp. 3024-3033 . https://doi.org/10.1021/acsami.8b18216