Supporting Information Lead-Free MA2CuClxBr4-x Hybrid Perovskites
Supporting Information
Lead-Free MA2CuClxBr4-x Hybrid Perovskites Daniele Cortecchia,1,2 Herlina Arianita Dewi,2 Jun Yin,3 Annalisa Bruno,2,3 Shi Chen,3 Tom Baikie,2 Pablo P. Boix,2 Michael Grätzel,4 Subodh Mhaisalkar,2,5 Cesare Soci,3 Nripan Mathews2,5*
1
Interdisciplinary Graduate School, Energy Research Institute at NTU (ERI@N) , Singapore 639798
2
Energy Research Institute @ NTU (ERI@N), Research Technoplaza, Nanyang Technological University, Nanyang Drive, Singapore 637553
3
Division of Physics and Applied Physics, Nanyang Technological University, Singapore 637371 4
Laboratory of Photonics and Interfaces, Department of Chemistry and
Chemical Engineering, Swiss Federal Institute of Technology, Station 6, CH1015 Lausanne, Switzerland 5
School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798. *[email protected]
S1
Sqrt(Counts)
I. X-Ray diffraction pattern of MA2CuBr4 and corresponding pawley fit:
The Pawley fit of the powder X-Ray diffraction pattern of MA2CuBr4 shows that its structure is consistent with the orthorhombic crystal system and space group Pbca. The refined lattice parametrs are: a = 7.8013(9) ; b = 7.6237(9) ; c = 19.1287(4) , with RB = 0.019. The reflections indicated with a star (*) don’t belong to the perovskite and indicate the presence of a secondary phase or impurities formed during the crystallization process. 420 400 380 360 340 320 300 280 260 240 220 200 180 160 140 120 100 80 60 40 20 0 -20 -40 -60 -80 8
hkl_Phase 0.00 %
MA2CuBr4 **
*
*
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
2Th Degrees
Figure S1 – Pawley fit of the powder X-Ray diffraction pattern of MA2CuBr4: observed (blue) and calculated (red) diffraction pattern by Pawley fitting. The grey line is the difference between the observed and calculated pattern.
S2
II. X-Ray diffraction pattern of MA2CuClxBr4-x and corresponding Pawley fit:Pawley fits
for the chlorine-stabilized copper perovskites MA2CuClxBr4-x. 350
hkl_Phase 0.00 %
a)
300
Sqrt(Counts)
250
MA2CuCl4
200 150 100 50 0 6
8
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
2Th Degrees 400
hkl_Phase 0.00 %
350
b)
Sqrt(Counts)
300
MA2CuCl2Br2
250 200 150 100 50 0 6
8
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
2Th Degrees
300
Sqrt(Counts)
250 200
hkl_Phase 0.00 %
c)
MA2CuClBr3
150 100 50 0
Sqrt(Counts)
6 260 240 220 200 180 160 140 120 100 80 60 40 20 0 -20 -40
8
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
2Th Degrees hkl_Phase 0.00 %
d)
6
8
MA2CuCl0.5Br3.5
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
2Th Degrees
Figure S2 – Pawley fit of the powder X-Ray diffraction pattern of the chlorine stabilized copper perovskite a) MA2CuCl4 ; b) MA2CuCl2Br2 ; c) MA2CuBr3 and d) MA2Cu0.5Cl3.5: observed (blue) and calculated (red) diffraction pattern by Pawley fitting. The grey line is the difference between the observed and calculated pattern.
S3
III. XRD study with increasing Br/Cl ratio: Due to the larger ionic radius of Br compared to Cl, the increase in Br/Cl ratio augments the unit cell dimensions, resulting in progressive peak shift to lower diffraction angles with Br addition from MA2CuCl4 to MA2CuCl0.5Br3.5 (Figure S3).
Figure S3- Peak shift toward smaller diffraction angles upon increase of Br/Cl ratio.
S4
IV. Thermogravimetric analysis (TGA): TGA of MA2CuCl2Br2 and MA2CuCl0.5Br3.5 are shown in Figure S4 a and b, respectively. The decomposition profile proceeds with two steps, and the first weight loss increases with higher Br content, indicating a major loss of Br compounds during this step, such as MABr and HBr, together with the release of MACl and HCl and CH3NH2. At higher temperatures, the decomposition is possibly accompanied with the formation of higher boiling point compounds such as CuCl2.
Figure S4- TGA analysis for the compounds MA2CuCl2Br2 and MA2CuCl0.5Br3.5
S5
V. Annealing study: Annealing of MA2CuCl0.5Br3.5 films at 100 °C results in the loss of reflections characteristic of the perovskite structure, and extra reflections appear between 10° and 30° 2θ (Figure S5). Samples annealed at 70°C for 30 min display residual MABr, which is minimized with prolonged annealing at 70°C for 1h.
Figure S5 – Effect of annealing temperature and time on the perovskite formation.
S6
VI. Band Gap Determination: Tauc Plot construction for the determination of perovskite’s direct band gap associated to CT transitions (Figure S6a) and schematic representation of the electronic transitions exemplified with the absorption spectrum of MA2CuCl2Br2 (Figure S6b).
Figure S6- a) Tauc plots for the determination of band-gaps associated to charge transfer (CT) transitions; b) representation of the electronic transitions for MA2CuCl2Br2: charge transfer transitions 1 and 2 (𝑪𝒍, 𝑩𝒓_𝒑𝝈 → 𝑪𝒖_𝒅𝒙𝟐 −𝒚𝟐 𝒂𝒏𝒅 𝑪𝒍, 𝑩𝒓_𝒑𝝅 → 𝑪𝒖_𝒅𝒙𝟐 −𝒚𝟐 ) and d-d transition 3 (𝑪𝒖_𝒅𝒙𝒚 → 𝑪𝒖_𝒅𝒙𝟐 −𝒚𝟐 ).
S7
VII. Low Temperature Absorption:
Figure S7- Low temperature absorption measurement for a) MA2CuCl4 and b) MA2CuClBr3. Narrowing of the bands is observed at 78 K, together with blue-shift of the bandgap of about 20 nm and peak splitting of the main CT band. The observed behavior is in agreement with the thermochromism previously observed in similar compounds. 1
S8
VIII. X-Ray photoelectron spectroscopy (XPS): XPS analysis of MA2CuCl2Br2, MA2CuCl0.5Br3.5 and MA2CuBr4 (Figure S8). In Cu 2p spectra, samples with chlorine show satellite peaks, indicating the presence of Cu2+ ions. In pure bromine sample, the absence of a satellite peak suggest the surface of this sample changes to Cu+.
Figure S8 – XPS analysis of the series MA2CuClxBr4-x.
S9
IX. Perovskite Band structure
Figure S9 – Electronic band structure from DFT simulation for a) MA2CuCl2Br2 and b) MA2CuCl0.5Br3.5.
S10
X. Density of states based on DFT calculations: Projected density of states (PDOS) of the four copper pervoskite compounds (a) MA2CuCl4, (b) MA2CuCl2Br2, (c) MA2CuClBr3, and (d) MA2CuCl0.5Br3.5 from DFT calculations (Figure S10).
Figure S10- PDOS for (a) MA2CuCl4, (b) MA2CuCl2Br2, (c) MA2CuClBr3, and (d) MA2CuCl0.5Br3.5
S11
XI. Cu-based d-d transitions:
Figure S11- a) Details of Cu-based d-d transitions for MA2CuClBr3with 3-peaks fitting identifying
the
expected
transitions
𝒂𝟏𝒈 (𝒛𝟐 ) → 𝒃𝟏𝒈 (𝒙𝟐 − 𝒚𝟐 ) ; 𝒃𝟐𝒈 (𝒙𝒚) → 𝒃𝟏𝒈 (𝒙𝟐 −
𝒚𝟐 ) ; 𝒆𝒈 (𝒙𝒛, 𝒚𝒛) → 𝒃𝟏𝒈 (𝒙𝟐 − 𝒚𝟐 ) at 12111 cm-1, 12918 cm-1 and 13606 cm-1 respectively. b) energy level diagram for the d9 electronic configuration in octahedral (Oh) and tetragonal (D4h) crystal field showing the effect of Jahn-Teller distortion on the energy level splitting. Based on the experimental values of the transitions, it is possible to define the value of 10Dq = 12918 cm 1
and the splitting of eg levels due to Jahn-Teller stabilization De = 12111 cm-1. The determined
values are in excellent agreement with those reported in similar compounds. 2-3
S12
XII: SEM images of infiltration of TiO2 with the Cu perovskite: SEM images of mesoporous TiO2 infiltrated with MA2CuCl2Br2 using DMSO solution of different concentration: 1M (a, c) and 2M (b, d) (Figure S12).
Figure S12 – SEM characterization for different concentrations of the spin coating solution for MA2CuCl2Br2
S13
XIII. Dark Current of Mesoporous Solar Cells:
Currend Density [A/cm2]
5 0 -5 -10 -15
MA2CuCl2Br2 dark MA2CuCl0.5Br3.5 dark
-20 -25
-4
-3
-2
-1
0
1
2
3
4
Voltage [V]
Figure S13 – Dark current of mesoporous solar cells sensitized with MA2CuCl2Br2 and MA2CuCl0.5Br3.5 showing the rectifying behavior of the cells under dark condition.
S14
XIV. Binding Energy and Work Function determination: Binding energy (BE) and work function (WF) determination for MA2CuCl2Br2 and MA2CuCl0.5Br3.5 by ultraviolet photoelectron spectroscopy (UPS).
Figure S14 – UPS analysis for MA2CuCl2Br2 and MA2CuCl0.5Br3.5
S15
XV. Impedance analysis of the Cu perovskite:
Figure S15 - a) Example impedance spectra under 1 sun at 0.25 V for both analyzed samples, the inset represents the equivalent circuit employed for the fitting. b) Series resistance extracted from the fitting of the impedance spectrum measured under 1 sun.
S16
XVI. Inverted solar cell: Copper perovskite-based solar cell with inverted structure PEDOT:PSS/ MA2CuCl2Br2/PCBM (Figure S16).
Figure S16 – IV curves for a flat-junction solar cell based on MA2CuCl2Br2 as light harvester.
References (1) Bloomquist, D. R.; Pressprich, M. R.; Willett, R. D. J. Am. Chem. Soc. 1988, 110, 7391-7398. (2) Valiente, R.; Rodríguez, F. Phys. Rev. B 1999, 60, 9423-9429. (3) Jaffe, A.; Lin, Y.; Mao, W. L.; Karunadasa, H. I. J. Am. Chem. Soc. 2015, 137, 1673-1678
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Lead-Free MA2CuClxBr4-x Hybrid Perovskites Daniele Cortecchia,1,2 Herlina Arianita Dewi,2 Jun Yin,3 Annalisa Bruno,2,3 Shi Chen,3 Tom Baikie,2 Pablo P. Boix,2 Michael Grätzel,4 Subodh Mhaisalkar,2,5 Cesare Soci,3 Nripan Mathews2,5*
1
Interdisciplinary Graduate School, Energy Research Institute at NTU (ERI@N) , Singapore 639798
2
Energy Research Institute @ NTU (ERI@N), Research Technoplaza, Nanyang Technological University, Nanyang Drive, Singapore 637553
3
Division of Physics and Applied Physics, Nanyang Technological University, Singapore 637371 4
Laboratory of Photonics and Interfaces, Department of Chemistry and
Chemical Engineering, Swiss Federal Institute of Technology, Station 6, CH1015 Lausanne, Switzerland 5
School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798. *[email protected]
S1
Sqrt(Counts)
I. X-Ray diffraction pattern of MA2CuBr4 and corresponding pawley fit:
The Pawley fit of the powder X-Ray diffraction pattern of MA2CuBr4 shows that its structure is consistent with the orthorhombic crystal system and space group Pbca. The refined lattice parametrs are: a = 7.8013(9) ; b = 7.6237(9) ; c = 19.1287(4) , with RB = 0.019. The reflections indicated with a star (*) don’t belong to the perovskite and indicate the presence of a secondary phase or impurities formed during the crystallization process. 420 400 380 360 340 320 300 280 260 240 220 200 180 160 140 120 100 80 60 40 20 0 -20 -40 -60 -80 8
hkl_Phase 0.00 %
MA2CuBr4 **
*
*
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
2Th Degrees
Figure S1 – Pawley fit of the powder X-Ray diffraction pattern of MA2CuBr4: observed (blue) and calculated (red) diffraction pattern by Pawley fitting. The grey line is the difference between the observed and calculated pattern.
S2
II. X-Ray diffraction pattern of MA2CuClxBr4-x and corresponding Pawley fit:Pawley fits
for the chlorine-stabilized copper perovskites MA2CuClxBr4-x. 350
hkl_Phase 0.00 %
a)
300
Sqrt(Counts)
250
MA2CuCl4
200 150 100 50 0 6
8
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
2Th Degrees 400
hkl_Phase 0.00 %
350
b)
Sqrt(Counts)
300
MA2CuCl2Br2
250 200 150 100 50 0 6
8
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
2Th Degrees
300
Sqrt(Counts)
250 200
hkl_Phase 0.00 %
c)
MA2CuClBr3
150 100 50 0
Sqrt(Counts)
6 260 240 220 200 180 160 140 120 100 80 60 40 20 0 -20 -40
8
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
2Th Degrees hkl_Phase 0.00 %
d)
6
8
MA2CuCl0.5Br3.5
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
2Th Degrees
Figure S2 – Pawley fit of the powder X-Ray diffraction pattern of the chlorine stabilized copper perovskite a) MA2CuCl4 ; b) MA2CuCl2Br2 ; c) MA2CuBr3 and d) MA2Cu0.5Cl3.5: observed (blue) and calculated (red) diffraction pattern by Pawley fitting. The grey line is the difference between the observed and calculated pattern.
S3
III. XRD study with increasing Br/Cl ratio: Due to the larger ionic radius of Br compared to Cl, the increase in Br/Cl ratio augments the unit cell dimensions, resulting in progressive peak shift to lower diffraction angles with Br addition from MA2CuCl4 to MA2CuCl0.5Br3.5 (Figure S3).
Figure S3- Peak shift toward smaller diffraction angles upon increase of Br/Cl ratio.
S4
IV. Thermogravimetric analysis (TGA): TGA of MA2CuCl2Br2 and MA2CuCl0.5Br3.5 are shown in Figure S4 a and b, respectively. The decomposition profile proceeds with two steps, and the first weight loss increases with higher Br content, indicating a major loss of Br compounds during this step, such as MABr and HBr, together with the release of MACl and HCl and CH3NH2. At higher temperatures, the decomposition is possibly accompanied with the formation of higher boiling point compounds such as CuCl2.
Figure S4- TGA analysis for the compounds MA2CuCl2Br2 and MA2CuCl0.5Br3.5
S5
V. Annealing study: Annealing of MA2CuCl0.5Br3.5 films at 100 °C results in the loss of reflections characteristic of the perovskite structure, and extra reflections appear between 10° and 30° 2θ (Figure S5). Samples annealed at 70°C for 30 min display residual MABr, which is minimized with prolonged annealing at 70°C for 1h.
Figure S5 – Effect of annealing temperature and time on the perovskite formation.
S6
VI. Band Gap Determination: Tauc Plot construction for the determination of perovskite’s direct band gap associated to CT transitions (Figure S6a) and schematic representation of the electronic transitions exemplified with the absorption spectrum of MA2CuCl2Br2 (Figure S6b).
Figure S6- a) Tauc plots for the determination of band-gaps associated to charge transfer (CT) transitions; b) representation of the electronic transitions for MA2CuCl2Br2: charge transfer transitions 1 and 2 (𝑪𝒍, 𝑩𝒓_𝒑𝝈 → 𝑪𝒖_𝒅𝒙𝟐 −𝒚𝟐 𝒂𝒏𝒅 𝑪𝒍, 𝑩𝒓_𝒑𝝅 → 𝑪𝒖_𝒅𝒙𝟐 −𝒚𝟐 ) and d-d transition 3 (𝑪𝒖_𝒅𝒙𝒚 → 𝑪𝒖_𝒅𝒙𝟐 −𝒚𝟐 ).
S7
VII. Low Temperature Absorption:
Figure S7- Low temperature absorption measurement for a) MA2CuCl4 and b) MA2CuClBr3. Narrowing of the bands is observed at 78 K, together with blue-shift of the bandgap of about 20 nm and peak splitting of the main CT band. The observed behavior is in agreement with the thermochromism previously observed in similar compounds. 1
S8
VIII. X-Ray photoelectron spectroscopy (XPS): XPS analysis of MA2CuCl2Br2, MA2CuCl0.5Br3.5 and MA2CuBr4 (Figure S8). In Cu 2p spectra, samples with chlorine show satellite peaks, indicating the presence of Cu2+ ions. In pure bromine sample, the absence of a satellite peak suggest the surface of this sample changes to Cu+.
Figure S8 – XPS analysis of the series MA2CuClxBr4-x.
S9
IX. Perovskite Band structure
Figure S9 – Electronic band structure from DFT simulation for a) MA2CuCl2Br2 and b) MA2CuCl0.5Br3.5.
S10
X. Density of states based on DFT calculations: Projected density of states (PDOS) of the four copper pervoskite compounds (a) MA2CuCl4, (b) MA2CuCl2Br2, (c) MA2CuClBr3, and (d) MA2CuCl0.5Br3.5 from DFT calculations (Figure S10).
Figure S10- PDOS for (a) MA2CuCl4, (b) MA2CuCl2Br2, (c) MA2CuClBr3, and (d) MA2CuCl0.5Br3.5
S11
XI. Cu-based d-d transitions:
Figure S11- a) Details of Cu-based d-d transitions for MA2CuClBr3with 3-peaks fitting identifying
the
expected
transitions
𝒂𝟏𝒈 (𝒛𝟐 ) → 𝒃𝟏𝒈 (𝒙𝟐 − 𝒚𝟐 ) ; 𝒃𝟐𝒈 (𝒙𝒚) → 𝒃𝟏𝒈 (𝒙𝟐 −
𝒚𝟐 ) ; 𝒆𝒈 (𝒙𝒛, 𝒚𝒛) → 𝒃𝟏𝒈 (𝒙𝟐 − 𝒚𝟐 ) at 12111 cm-1, 12918 cm-1 and 13606 cm-1 respectively. b) energy level diagram for the d9 electronic configuration in octahedral (Oh) and tetragonal (D4h) crystal field showing the effect of Jahn-Teller distortion on the energy level splitting. Based on the experimental values of the transitions, it is possible to define the value of 10Dq = 12918 cm 1
and the splitting of eg levels due to Jahn-Teller stabilization De = 12111 cm-1. The determined
values are in excellent agreement with those reported in similar compounds. 2-3
S12
XII: SEM images of infiltration of TiO2 with the Cu perovskite: SEM images of mesoporous TiO2 infiltrated with MA2CuCl2Br2 using DMSO solution of different concentration: 1M (a, c) and 2M (b, d) (Figure S12).
Figure S12 – SEM characterization for different concentrations of the spin coating solution for MA2CuCl2Br2
S13
XIII. Dark Current of Mesoporous Solar Cells:
Currend Density [A/cm2]
5 0 -5 -10 -15
MA2CuCl2Br2 dark MA2CuCl0.5Br3.5 dark
-20 -25
-4
-3
-2
-1
0
1
2
3
4
Voltage [V]
Figure S13 – Dark current of mesoporous solar cells sensitized with MA2CuCl2Br2 and MA2CuCl0.5Br3.5 showing the rectifying behavior of the cells under dark condition.
S14
XIV. Binding Energy and Work Function determination: Binding energy (BE) and work function (WF) determination for MA2CuCl2Br2 and MA2CuCl0.5Br3.5 by ultraviolet photoelectron spectroscopy (UPS).
Figure S14 – UPS analysis for MA2CuCl2Br2 and MA2CuCl0.5Br3.5
S15
XV. Impedance analysis of the Cu perovskite:
Figure S15 - a) Example impedance spectra under 1 sun at 0.25 V for both analyzed samples, the inset represents the equivalent circuit employed for the fitting. b) Series resistance extracted from the fitting of the impedance spectrum measured under 1 sun.
S16
XVI. Inverted solar cell: Copper perovskite-based solar cell with inverted structure PEDOT:PSS/ MA2CuCl2Br2/PCBM (Figure S16).
Figure S16 – IV curves for a flat-junction solar cell based on MA2CuCl2Br2 as light harvester.
References (1) Bloomquist, D. R.; Pressprich, M. R.; Willett, R. D. J. Am. Chem. Soc. 1988, 110, 7391-7398. (2) Valiente, R.; Rodríguez, F. Phys. Rev. B 1999, 60, 9423-9429. (3) Jaffe, A.; Lin, Y.; Mao, W. L.; Karunadasa, H. I. J. Am. Chem. Soc. 2015, 137, 1673-1678
S17
