SUPPORTING INFORMATION
Microstructural analysis of 9.7% efficient Cu2ZnSnSe4 thin film solar
cells
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M. Buffière
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, G. Brammertz , M. Batuk , C. Verbist , D. Mangin , C. Koble , J. Hadermann , M.
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Meuris , J. Poortmans
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Department of Electrical Engineering (ESAT), KU Leuven, Kasteelpark Arenberg 10, 3001 Heverlee, Belgium
imec- partner in Solliance, Kapeldreef 75, 3001 Leuven, Belgium
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imec division IMOMEC - partner in Solliance, Wetenschapspark 1, 3590 Diepenbeek, Belgium
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Institute for Material Research (IMO) Hasselt University, Wetenschapspark 1, 3590 Diepenbeek, Belgium
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Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp,
Belgium
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Institut Jean Lamour, Université de Lorraine, Parc de Saurupt, CS 50840, 54011 Nancy cedex, France
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Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
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Further TEM-EDX analysis were performed on the same Cu2ZnSnSe4 (CZTSe) based solar cell
in order to support the conclusions of the article. Figure S1 shows the EDX spectra acquired on the
inclusions phases pointed with arrows in Figure 3 of the main text. These EDX analysis were used to
determine the chemical composition of both types of particles. The [Zn]/[Se] atomic ratio calculated
for the top spectrum is 1:1 giving the ZnSe composition. The atomic ratio between Cu and Se at the
bottom spectrum is close to 2:1, giving the composition Cu2Se. Small additional peaks on the EDX
spectra can be due to the overlap with near grains. The formation of the ZnSe phase was further
confirms by ED analysis presented in Figure S2, showing the ED pattern taken from the individual
ZnSe grain. The pattern corresponds to the cubic phase: #37-1463, space group F-43m, a = 5.6688 Å.
TEM image taken from this ZnSe grain oriented along the [110] zone axis is also available. Figure S3
shows the EDX elemental maps taken from another TEM specimen prepared from the same CZTSe
solar cell. Here again, we observed the presence of ZnSe grains at the Mo/CZTSe interface, as well as
the CuxSe based underlying layer. Note that the S-K and Mo-L lines on the EDX spectra overlap. On
Figure S4, the EDX elemental maps taken from the absorber/buffer layer interface shows that the
ZnO/CdS and CZTSe/CdS interfaces are quite well defined without any preferential inter-diffusion. A
CdS inclusion is observed in the ZnO layer, likely due to the roughness of the buffer layer. Note that
the Cu inclusions that can be found in the buffer layer could be formed during the preparation of the
TEM specimen. Finally, Figure S5 shows a larger view of the TEM specimen used for the Mo/CZTSe
interface study (i.e. Figure 4 of the main text). The carbon layer at the surface of the CZTSe grain is
marked with a red arrow, inclusions of the ZnSe grains at the top part of the CZTSe layer are pointed
with blue arrows.
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Figure S1: EDX spectra from the inclusion phases pointed with arrows in Figure 3 of the main text.
The Zn/Se atomic ratio calculated for the top spectrum is 1:1 giving the ZnSe composition. The
atomic ratio between Cu and Se at the bottom spectrum is close to 2:1, giving the composition Cu2Se.
Small additional peaks on the EDX spectra can be due to the overlap with near grains.
Figure S2: (left) Electron diffraction pattern taken from the individual ZnSe grain. The pattern
corresponds to the cubic phase: #37-1463, space group F-43m, a = 5.6688 Å. (right) TEM image
taken from the ZnSe grain oriented along the [110] zone axis.
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Figure S3: EDX elemental maps taken from the CZTSe solar cell (elements detected: Cu, Zn,
Sn, Se, Cd, S, O, and Mo) and a mixed map. Arrows point the ZnSe grains at the Mo/CZTSe
interface. Note that the S-K and Mo-L lines on the EDX spectra overlap.
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Figure S4: EDX elemental maps taken from the absorber/buffer layer interface.
Figure S5: EDX elemental maps taken from the CZTSe solar cell (elements detected: Cu, Zn,
Sn, Se, Cd, S, Mo, O, and C) and a mixed map. The carbon layer at the surface of the CZTSe grain is
marked with a red arrow, inclusions of the ZnSe grains at the top part of the CZTSe layer are pointed
with blue arrows. Note that the S-K and Mo-L lines on the EDX spectra overlap.
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