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

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä

Date

2019-01-23

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en

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10

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ACS Applied Materials and Interfaces, Volume 11, issue 3, pp. 3024-3033

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.

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| 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