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Supporting Information
Interfacial Bonding and Electronic Structure between
Copper Thiocyanate and Hybrid Organohalide Lead
Perovskites for Photovoltaic Application
Bingcheng Luo1,2,*, Yuan Yao1, Enke Tian1,*, Kun Shen1, Hongzhou Song3, Haifeng
Song3, Baiwen Li3
1 School of Science, China University of Geosciences, Beijing 100083, P. R. China
2 Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United
Kingdom
3 Institute of Applied Physics and Computational Mathematics, Beijing 100094, P. R.
Computational Methods
The present calculations of MAPbI3/CuSCN heterostructure were carried out using the
density functional theory (DFT) frame work as implemented Vienna ab initio simulation program (VASP) 1-3. MAPbI
3/CuSCN heterostructures is built by building
up supercells consisting of surface-located CuSCN layers and perovskite MAPbI3
layered slabs following the previous modeling4-5.
CuSCN has a Pbca space group with the lattice parameter a = 10.994 Å, b = 7.224 Å and c = 6.662 Å for one formula unit per unit cell, while tetragonal MAPbI3 has the
lattice parameter a = b = 8.8 Å and c = 13.0475 Å for one formula unit per unit cell. Previous calculations have reported that (001) surfaces can be efficient intermediates of hole transfer to HTM and be most studied in organic-inorganic halide perovskites6-9.
The CuSCN (001) surfaces were reported to yield the lowest value of surface energies, 2.79 J/m2, to cleave the Cu-N bond, compared to cleaving the semi-ionic bond of S–Cu
(3.92 J/m2), the covalent bond between S–C (4.14 J/m2), or the strong cyanide bond
(11.99 J/m2)10. Since the (001) surfaces have been experimentally observed in CuSCN
films grown by electrochemical deposition11-12 and confirmed to be most stable
surfaces10, 13, we adopted (001) surface to model the interface interaction with
perovskites. In order to investigate the local interfacial properties of MAPbI3/CuSCN
heterostructures, bottom three layers of MAPbI3 perovskite and top four layers of
CuSCN were both fixed during the geometrized relaxation. To decrease the lattice misfit of MAPbI3/CuSCN heterostructures, a 10% strain is employed on the [100] and
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142 atoms based on the CuSCN 1×1×2 supercell and MAPbI3 1×1×2 supercell. Both
CuSCN and MAPbI3 were optimized respectively before they connect. A vacuum layer
with thickness about 15 Å is adopted.
The generalized gradient approximation (GGA) with the PBEsol exchange-correlation functional for solid was employed. We have adopted SCAN meta-GGA functional14 is
adopted to improve the band structure15-16. It is worth mentioning that the employed
computational approach at the GGA level, correctly predicts the band gap for the bulk MAPbI3 and FAPbI3 perovskite 17-19, due to a fortuitous cancellation of errors between
relativistic, spin−orbit coupling and electronic correlation, as widely reported in the literature 20-22. Cut-off energy of 500 eV23 and Monkhorst-Pack mesh grid of 3×3×1 for
structure optimization and 9×9×1 for properties calculations were employed. To achieve the global minimum energy, the energy tolerance was 1×10−6 eV/atom and
force tolerance is 0.01 eV/Å. The pseudopotentials were constructed by the electron configurations as Cu 3d10 4s1 states, S 3s2 3p4 states, I 5s2 5p5 states, Pb 5d10 6s2
Supporting Tables
Table S 1 Copper atomic relaxation of PbI-interface and MAI-interface along [100], [010] and [001] direction. Label of each atom is shown in Figure S 2.
PbI-interface MAI-interface Layer Atoms [100] [010] [001] Layer Atoms [100] [010] [001] 1 Cu1 -0.00 -0.00 0.00 1 Cu1 -0.00 -0.02 0.00 1 Cu8 -0.00 -0.00 0.00 1 Cu8 -0.00 -0.02 0.00 2 Cu3 -0.01 -0.01 0.00 2 Cu3 -0.00 -0.02 0.00 2 Cu6 -0.00 -0.01 0.00 2 Cu6 -0.00 -0.02 0.00 3 Cu2 -0.01 -0.01 0.00 3 Cu2 -0.00 -0.03 0.00 3 Cu7 -0.01 -0.01 0.00 3 Cu7 -0.00 -0.03 0.00 4 Cu4 -0.01 -0.01 0.00 4 Cu4 -0.00 -0.04 0.00 4 Cu5 -0.01 -0.01 0.00 4 Cu5 -0.00 -0.04 0.00 5 Cu9 0.01 -0.05 0.01 5 Cu11 -0.20 -0.06 -0.01 5 Cu16 -0.03 -0.03 0.00 5 Cu14 0.01 -0.05 -0.02 6 Cu11 -0.05 -0.02 0.01 6 Cu10 -0.23 -0.18 -0.02 6 Cu14 -0.01 -0.01 0.01 6 Cu12 0.20 -0.28 -0.05 7 Cu10 0.04 -0.07 0.00 7 Cu13 -0.02 -0.03 -0.02 7 Cu15 0.00 0.01 0.01 7 Cu15 0.10 -0.16 0.01 8 Cu12 -0.03 0.03 0.01 8 Cu9 -0.05 0.09 0.11 8 Cu13 0.00 0.01 0.01 8 Cu16 -0.03 0.13 0.16
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Table S 2 Lead atomic relaxation of PbI-interface and MAI-interface along [100], [010] and [001] direction. Label of each atom is shown in Figure S 2.
PbI-interface MAI-interface Layer Atoms [100] [010] [001] Layer Atoms [100] [010] [001] 9 Pb3 -0.08 0.14 -0.01 10 Pb1 -0.05 0.00 -0.00 9 Pb5 0.06 0.12 -0.01 10 Pb5 0.00 -0.14 -0.00 11 Pb1 0.04 0.02 0.00 12 Pb3 -0.11 -0.06 -0.00 11 Pb7 0.08 0.12 -0.00 12 Pb4 -0.11 -0.11 -0.00 13 Pb4 -0.02 -0.04 0.00 14 Pb2 -0.02 -0.16 0.00 13 Pb6 -0.03 -0.04 0.00 14 Pb6 -0.02 -0.16 0.00 15 Pb2 -0.03 -0.05 0.00 15 Pb8 -0.03 -0.05 0.00
Table S 3 Iodine atomic relaxation of PbI-interface and MAI-interface along [100], [010] and [001] direction. Label of each atom is shown in Figure S 2.
PbI-interface MAI-interface Layer Atoms [100] [010] [001] Layer Atoms [100] [010] [001] 9 I5 0.07 0.03 0.00 9 I15 0.00 0.73 -0.00 9 I11 0.02 -0.03 0.01 9 I17 0.93 -0.13 -0.01 9 I13 -0.11 0.01 0.00 10 I1 0.05 -0.23 -0.00 9 I15 -0.04 -0.01 0.01 10 I3 -0.06 -0.12 -0.01 10 I18 -0.05 0.05 0.00 10 I6 -0.06 -0.15 0.02 10 I20 0.08 0.06 -0.00 10 I8 -0.08 -0.19 -0.04 11 I1 -0.04 0.05 0.02 11 I13 0.02 -0.01 -0.00 11 I3 0.07 -0.05 -0.00 11 I19 -0.13 -0.13 -0.00 11 I7 -0.08 0.01 0.00 12 I5 -0.03 -0.11 0.01 11 I9 0.00 0.03 0.00 12 I10 -0.17 -0.23 -0.01 12 I17 -0.11 -0.01 -0.00 12 I11 -0.11 -0.16 -0.01 12 I22 -0.02 0.03 -0.00 12 I12 0.05 -0.24 -0.00 13 I6 -0.03 -0.04 0.00 13 I16 -0.02 -0.14 0.00 13 I12 -0.03 -0.04 0.00 13 I18 -0.02 -0.13 0.00 13 I14 -0.02 -0.04 0.00 14 I2 -0.02 -0.16 0.00 13 I16 -0.02 -0.04 0.00 14 I4 -0.02 -0.16 0.00 14 I19 -0.03 -0.04 0.00 14 I7 -0.02 -0.16 0.00 14 I21 -0.03 -0.04 0.00 14 I9 -0.02 -0.16 0.00 15 I2 -0.03 -0.05 0.00 15 I14 -0.02 -0.17 0.00 15 I4 -0.03 -0.05 0.00 15 I20 -0.02 -0.13 0.00 15 I8 -0.03 -0.05 0.00 15 I10 -0.03 -0.05 0.00
7 Supporting Figures
Figure S 1 Scheme of atomistic model of MAPbI3/CuSCN heterostructures. (a) initial and (b)
Figure S 2 Atomic relaxed model of (a) PbI-interface and (b) MAI interface. Cu, Pb, and I atoms are labeled with numbers.
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Figure S 3 Band structure of (a) PbI-interface and (b) MAI-interface along the high symmetry K-points in the first Brillion zone, solid line represents the use of GGA-PBE functional, dot line represents the use of SCAN Meta-GGA functional; (c) Projected band structure of Pb ions from perovskite layer in PbI-interface; (d) Projected band structure of Pb ions from perovskite layer in MAI -interface; (e) Band structure of pristine MAPbI3 along the high symmetry; (f)
Figure S 4 Density of states (DOS) of MAPbI3/CuSCN heterostructure. (a) total DOS of
PbI-interface, (b-c) partial DOS of (b) Cu atoms and (c) Pb atoms with various orbitals for PbI-interface, (d) total DOS of MAI-interface, (e-f) partial DOS of (e) Cu atoms and (f) Pb atoms with various orbitals for MAI-interface, (g-h) partial DOS of iodine atoms with various
orbitals for (g) interface and (h) MAI-interface. (i) partial DOS of N atoms for PbI-interface
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Figure S 5 Plane-averaged charge density difference of (a) PbI-interface and (b) MAI-interface.
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Figure S 9 Partial density of states of sulfur atoms with s, px, py, pz orbitals for (a) PbI
Figure S 10 Partial density of states of hydrogen atoms for (a) PbI interface and (b)MAI interface
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Figure S 11 Partial density of states of carbon atoms with s, px, py, pz orbitals for (a) PbI
interface and (b)MAI interface
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