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Title: The order-disorder transition in Cu{sub 2}ZnSnS{sub 4}: A theoretical and experimental study

Abstract

In this work the Cu/Zn order-disorder transition in Cu{sub 2}ZnSnS{sub 4} kesterites on Wyckoff positions 2c and 2d was investigated by a structural and electronic analysis in theory and experiment. For experimental investigations stoichiometric samples with different Cu/Zn order, annealed in the temperature range of 473–623 K and afterwards quenched, were used. The optical gaps were determined using the Derivation of Absorption Spectrum Fitting (DASF) method. Furthermore, the order-disorder transition was examined by DFT calculations for a closer analysis of the origins of the reduced band gap, showing a good agreement with experimental data with respect to structural and electronic properties. Our studies show a slight increase of lattice parameter c in the kesterite lattice with increasing disorder. Additionally, a reduced band gap was observed with increasing disorder, which is an effect of newly occurring binding motifs in the disordered kesterite structure. - Highlights: • Experimental and theoretical investigation on the order-disorder transition in kesterites. • Slight enlargements of lattice constants due to disorder in experiment and theory. • Strong band gap fluctuations with decreasing order. • Electronic structure deviations due to changing binding motifs. • Disorder as possible main source of low open-circuit voltages.

Authors:
 [1];  [2];  [1];  [2];  [3];  [4]
  1. Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin (Germany)
  2. (Germany)
  3. Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany)
  4. Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin (Germany)
Publication Date:
OSTI Identifier:
22658298
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 250; Other Information: Copyright (c) 2017 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTRA; COMPUTERIZED SIMULATION; COPPER IONS; ELECTRIC POTENTIAL; ELECTRONIC STRUCTURE; EXPERIMENTAL DATA; LATTICE PARAMETERS; ORDER-DISORDER TRANSFORMATIONS; SULFIDES; TEMPERATURE RANGE 0400-1000 K; TIN COMPOUNDS; ZINC COMPOUNDS

Citation Formats

Quennet, Marcel, E-mail: marcel.quennet@fu-berlin.de, Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Ritscher, Anna, Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Lerch, Martin, and Paulus, Beate. The order-disorder transition in Cu{sub 2}ZnSnS{sub 4}: A theoretical and experimental study. United States: N. p., 2017. Web. doi:10.1016/J.JSSC.2017.03.018.
Quennet, Marcel, E-mail: marcel.quennet@fu-berlin.de, Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Ritscher, Anna, Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Lerch, Martin, & Paulus, Beate. The order-disorder transition in Cu{sub 2}ZnSnS{sub 4}: A theoretical and experimental study. United States. doi:10.1016/J.JSSC.2017.03.018.
Quennet, Marcel, E-mail: marcel.quennet@fu-berlin.de, Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Ritscher, Anna, Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Lerch, Martin, and Paulus, Beate. Thu . "The order-disorder transition in Cu{sub 2}ZnSnS{sub 4}: A theoretical and experimental study". United States. doi:10.1016/J.JSSC.2017.03.018.
@article{osti_22658298,
title = {The order-disorder transition in Cu{sub 2}ZnSnS{sub 4}: A theoretical and experimental study},
author = {Quennet, Marcel, E-mail: marcel.quennet@fu-berlin.de and Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin and Ritscher, Anna and Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin and Lerch, Martin and Paulus, Beate},
abstractNote = {In this work the Cu/Zn order-disorder transition in Cu{sub 2}ZnSnS{sub 4} kesterites on Wyckoff positions 2c and 2d was investigated by a structural and electronic analysis in theory and experiment. For experimental investigations stoichiometric samples with different Cu/Zn order, annealed in the temperature range of 473–623 K and afterwards quenched, were used. The optical gaps were determined using the Derivation of Absorption Spectrum Fitting (DASF) method. Furthermore, the order-disorder transition was examined by DFT calculations for a closer analysis of the origins of the reduced band gap, showing a good agreement with experimental data with respect to structural and electronic properties. Our studies show a slight increase of lattice parameter c in the kesterite lattice with increasing disorder. Additionally, a reduced band gap was observed with increasing disorder, which is an effect of newly occurring binding motifs in the disordered kesterite structure. - Highlights: • Experimental and theoretical investigation on the order-disorder transition in kesterites. • Slight enlargements of lattice constants due to disorder in experiment and theory. • Strong band gap fluctuations with decreasing order. • Electronic structure deviations due to changing binding motifs. • Disorder as possible main source of low open-circuit voltages.},
doi = {10.1016/J.JSSC.2017.03.018},
journal = {Journal of Solid State Chemistry},
number = ,
volume = 250,
place = {United States},
year = {Thu Jun 15 00:00:00 EDT 2017},
month = {Thu Jun 15 00:00:00 EDT 2017}
}
  • In this work a series of stoichiometric Cu{sub 2}ZnSnS{sub 4} (CZTS) samples annealed at different temperatures in the range of 473–623 K were investigated. The temperature dependence of the Cu/Zn-order-disorder behavior was analyzed by neutron powder diffraction measurements. Cu fully occupies the 2a and Sn the 2b position within the whole temperature range. For Zn and the remaining Cu on sites 2d and 2c, a clear change from ordered to disordered kesterite structure is found. The critical temperature T{sub c} for this Landau-type second order transition was determined as 552±2 K. It was found that in Cu{sub 2}ZnSnS{sub 4} verymore » long annealing times are necessary to reach equilibrium at low temperatures. - Graphical abstract: The order-disorder transition in Cu{sub 2}ZnSnS{sub 4} was investigated using neutron diffraction techniques on samples annealed in the temperature range of 473–623 K. The critical temperature T{sub c} for this Landau-type second order transition was determined as 552±2 K. Display Omitted - Highlights: • The order-disorder transformation of Cu{sub 2}ZnSnS{sub 4} follows a Landau‐type behavior for a second order transition. • The critical exponent β is 0.57±0.06. • The critical temperature was determined as 552±2 K. • A fully ordered (within the standard deviation) Cu{sub 2}ZnSnS{sub 4} sample was synthesized.« less
  • The interest in Cu2ZnSn(S,Se)4 (CZTS) for photovoltaic applications is motivated by similarities to Cu(In,Ga)Se2 while being comprised of non-toxic and earth abundant elements. However, CZTS suffers from a Voc deficit, where the Voc is much lower than expected based on the band gap, which may be the result of a high concentration of point-defects in the CZTS lattice. Recently, reports have observed a low-temperature order/disorder transition by Raman and optical spectroscopies in CZTS films and is reported to describe the ordering of Cu and Zn atoms in the CZTS crystal structure. To directly determine the level of Cu/Zn ordering, wemore » have used resonant-XRD, a site, and element specific probe of long range order. We used CZTSe films annealed just below and quenched from just above the transition temperature; based on previous work, the Cu and Zn should be ordered and highly disordered, respectively. Our data show that there is some Cu/Zn ordering near the low temperature transition but significantly less than high chemical order expected from Raman. To understand both our resonant-XRD results and the Raman results, we present a structural model that involves antiphase domain boundaries and accommodates the excess Zn within the CZTS lattice.« less
  • We report that the interest in Cu 2ZnSn(S,Se) 4 (CZTS) for photovoltaic applications is motivated by similarities to Cu(In,Ga)Se 2 while being comprised of non-toxic and earth abundant elements. However, CZTS suffers from a V oc deficit, where the V oc is much lower than expected based on the band gap, which may be the result of a high concentration of point-defects in the CZTS lattice. Recently, reports have observed a low-temperature order/disorder transition by Raman and optical spectroscopies in CZTS films and is reported to describe the ordering of Cu and Zn atoms in the CZTS crystal structure. Tomore » directly determine the level of Cu/Zn ordering, we have used resonant-XRD, a site, and element specific probe of long range order. We used CZTSe films annealed just below and quenched from just above the transition temperature; based on previous work, the Cu and Zn should be ordered and highly disordered, respectively. Our data show that there is some Cu/Zn ordering near the low temperature transition but significantly less than high chemical order expected from Raman. Finally, to understand both our resonant-XRD results and the Raman results, we present a structural model that involves antiphase domain boundaries and accommodates the excess Zn within the CZTS lattice.« less
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