Supplementary material
Rationally designed CuSb1-xBixS2 as a promising photovoltaic
material: theoretical and experimental study
Bo-In Park a,b,†, Minyeong Je c,†, Jihun Oh a,d,e,*, Heechae
Choi c,*, Seung Yong Leeb,e,*
a Department of Materials Science and Engineering, Korea
Advanced Institute of Science andTechnology (KAIST), Daejeon 34141,
Republic of Korea
b Center for Materials Architecturing, Korea Institute of
Science and Technology (KIST), Seoul 02792, Republic of Korea
c Theoretical Materials & Chemistry Group, Institute of
Inorganic Chemistry, University of Cologne, Greinstrasse 6, Cologne
50939, Germany
d Graduate School of Energy, Environment, Water, and
Sustainability (EEWS), Korea Advanced Institute of Science and
Technology (KAIST), Daejeon 34141, Republic of Korea
e KAIST Institute for NanoCentury (KINC), KAIST, Daejeon 34141,
Republic of Korea
f Nanomaterials Science and Engineering, Korea University of
Science and Technology(UST), Daejeon 34113, Republic of Korea
*Corresponding authors: [email protected],
[email protected], [email protected]
1. Experimental section
1.1. Calculation Methods
All calculations were performed using density functional theory
(DFT) calculations, as implemented in the plane VASP code [1, 2].
The ionic-interactions were described by the projector-augmented
wave (PAW) method [3]. The exchange-correlation interaction is
treated using the generalized gradient approximation (GGA) with in
the Perdew-Burke-Ernzerhof form [4, 5]. The energy cutoff for
plane-wave basis set was taken as 400 eV. The Monkhorst-Pack Method
was used and the supercell was simulated with center k-points mesh
of 222 [6]. Lattice constant and all atomic position for CuSbS2,
CuBiS2, and CuSbxBi1-xS2 are fully optimized until all
Hellmann-Feynman forces are smaller than 0.02 eV/. The energy
criterion for self-consistency was set to less than 10-6 eV.
Hyed-Scuseria-Ernzerhof (HSE06) hybrid functional are used for
calculating electronic properties [7].
1.2. Synthesis of CuSb1-xBixS2 nanocrystals
Cu(Sb1-xBix)S2 nanocrystals were synthesized by a
mechanochemical method (MCM) with a planetary ball-mill machine
(Fritsch GmBH, pulverisette 5). Cu (Alfa Aesar, 99.9%), Sb (Sigma
aldrich, 99.98%), Bi (Alfa Aesar, 99.999%), and sulfur (Sigma
Aldrich, 99.99%) as elemental precursors were weighed by a
predetermined ratio as a function of each molar ratio of
CuSb1-xBixS2. The precursors mixture (~20 g in total) was contained
into a round-ended stainless steel jar (80 mL in volume) with ZrO2
balls (25 g of 5-mm-diameter and 25g of 10-mm-diameter balls).
Ball-milling process was conducted without any chemical and
solvents at a speed of 500 rpm within 5 h.
1.3. Characterization of materials
High-magnification images, selected-area electron diffraction
(SAED) patterns, and energy dispersion spectroscopy (EDS) data were
obtained using a TEM (FEI Titan 80-300 microscope) with scanning
transmission electron microscopy-energy dispersive X-ray
spectroscopy (STEM-EDS). The compositions of the as-synthesized
Cu(Sb1-xBix)S2 (CABS) nanocrystals (NCs) were determined by EDS
(EDAX PV97-61850-ME). The crystal structure and phase purity were
examined by X-ray diffraction (XRD; Bruker D3 Advance) with Cu Kα
radiation (λ = 1.5406 Å) and Raman spectroscopy (Horiba Jobin-Yvon
LabRam Aramis spectrometer) equipped with an Ar-ion laser
excitation source (λ = 514.5 nm). The diffuse reflectance of the
obtained CABS NCs were characterized by a VARIAN Cary 5000
UV/Vis/NIR spectroscopy apparatus.
Table. S1. Calculated CuSbS2, CuSb0.54Bi0.46S2 and
CuSb0.21Bi0.79S2 lattice parameter and HSE band gaps
CuSbS2
CuSb0.54Bi0.46S2
CuSb0.21Bi0.79S2
CuSbS2
a/
12.26
12.41
12.52
b/
11.50
11.67
11.80
c/
14.47
14.50
14.46
90
90
90
Eg (eV, HSE)
1.67
1.45
1.35
Fig. S1. Supercells of CuSbS2, CuSb0.54Bi0.46S2,
CuSb0.21Bi0.79S2. The yellow, blue, brown, and violet spheres are
S, Cu, Sb, and Bi atoms, respectively.
Fig. S2. The crystallite size calculated by Scherr’s equation
from XRD data in Fig 2a
Fig. S3. STEM-EDS elemental mapping results for the
as-synthesized CABS nanocrystals: CuSb0.2Bi0.8S2 (a),
CuSb0.4Bi0.6S2 (b), CuSb0.5Bi0.5S2 (c), and CuSb0.4Bi0.6S2 (d).
Reference
[1] G. Kresse, J. Furthmüller, Comput. Mater. Sci. 6(1) (1996)
15-50.
[2] G. Kresse, J. Furthmüller, Phys. Rev. B 54(16) (1996)
11169.
[3] G. Kresse, D. Joubert, Phys. Rev. 59(3) (1999) 1758.
[4] C. PerdewJP, H. VoskoS, Phys. Rev. B 46(11) (1992)
6671-6687.
[5] J. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett 77(18)
(1996) 3865-3868.
[6] H. Monkshort, J. Pack, Phys. Rev. B 13 (1976) 5188-5192.
[7] J. Heyd, G.E. Scuseria, M. Ernzerhof, J. Chem. Phys. 118(18)
(2003) 8207-8215.
0.00.10.20.30.40.50.6
13
14
15
16
17
CAS
x = 0.2
x = 0.4
x = 0.5
x = 0.6
Crystallite size (nm)
[Bi]/[Bi]+[Sb]
increase up
