Supporting Information Reversible Halide Exchange Reaction of ...
Supporting Information
Reversible Halide Exchange Reaction of Organometal Trihalide Perovskite Colloidal Nanocrystals for Full-Range Band Gap Tuning Dong Myung Jang,† Kidong Park,† Duk Hwan Kim,† Jeunghee Park,*,†, Fazel Shojaei,‡ and Hong Seok Kang,§ Jae-Pyung Ahn,≠ Jong Woon Lee,# and Jae Kyu Song# †
Department of Chemistry, Korea University, Jochiwon 339-700, Korea
‡
Department of Chemistry and Bioactive Material Sciences and Research Institute of Physics and
Chemistry, Jeonbuk National University, Jeonju, Jeonbuk 560-756, Korea §
Department of Nano and Advanced Materials, College of Engineering, Jeonju University, Jeonju,
Jeonbuk 560-759, Korea ≠ #
Nano Materials Analysis Center, Korea Institute of Science and Technology, Seoul 136-791, Korea
Department of Chemistry, Kyung Hee University, Seoul 130-701, Korea
Contents I. Experimental Section II. Supporting Tables: Table S1-S6 III. Supporting Figures: Figure S1-S11 IV. Snapshots of Movie S1
S1
I. Experimental Section 1. Materials. Commercially available compounds PbCl2 (Aldrich), PbBr2 (Aldrich), PbI2 (Aldrich), HCl (36% in water, Aldrich), HBr (48% in water, Aldrich), HI (57% in water, Aldrich), CH3NH2 (40% in methanol, TCI), CH3(CH2)7NH2 (octylamine; OA, 99% Aldrich), and C17H34=CH2 (1octadecene; ODE, 90% Aldrich) were used without further purification. 2. Synthesis 2.1. Methylammonium halides (CH3NH3X, MAX, where X = Cl, Br, I): CH3NH3Br, CH3NH3Cl, and CH3NH3I were prepared by treating aqueous solutions of methylamine (CH3NH2) with the corresponding hydrogen halides, followed by recrystallization. CH3NH2 (0.27 mmol, 28 mL) and HBr (0.23 mmol, 26 mL) [or HI (0.23 mmol, 30 mL) or HCl (0.23 mmol, 23 mL)] were mixed and stirred for 2 h in an ice bath, followed by evaporation and recrystallization in an oil bath at 50–60 °C. In all cases, the precipitate was washed several times with diethyl ether, dried under vacuum, and used without further purification. 2.2. MAPbBr3: Two milliliters of ODE was stirred and heated at 80 °C (in an oil bath), and octylamine (17 µL, 0.1 mmol) was added. Next, MABr (11.2 mg, 0.1 mmol dissolved in 0.1 mL DMF) and PbBr2 (36.7 mg, 0.1 mmol dissolved in 0.1 mL DMF) were added, affording a yellow dispersion from which the nanoparticles were immediately precipitated by the addition of acetone followed by centrifugation (7000 rpm, 10 min). Finally, the MAPbBr3 nanocrystals were dispersed in toluene. They have a plate type morphology with an average length of 70 nm. For the reduced size of nanocrystals, oleylamine was used instead of octylamine and the size was controlled using the amount of oleylamine; the average length becomes 20, 10, and 5 nm for 2, 4, and 6 mmol of oleylamine. 2.3. Exchange reaction of MAPbBr3: MACl or MAI dissolved in isopropyl alcohol (IPA; 10 mL) was mixed with MAPbBr3 nanocrystals (0.04 mmol) in 2 mL toluene. Following table lists the quantities of MACl, MAI, and MAPbBr3 used for composition control. The Br exchange reaction time was 5–120 min. After the reaction, the NC products were precipitated by centrifugation of the reaction mixture. The NC precipitates were washed with IPA and dispersed in toluene for further characterization of their structure and composition.
[Summary of experimental condition for the exchange reaction] S2
No. 1 2 3 4 5 6 7 8 9 10 11 12
Composition
MAPbBr3-xClx
MAPbBr3-xIx
x 0.5 1.0 1.5 2.0 2.5 3.0 0.5 1.0 1.5 2.0 2.5 3.0
MAPbBr3
1
mM (mmol/L) MACl 0.6 1.5 3 6 15 30
1
0
MAI
0
0.6 1.5 3 6 15 75
Reaction Time (min) 30 30 30 30 60 120 5 5 10 10 30 30
3. Characterization. The products were analyzed by field-emission transmission electron microscopy (TEM, Jeol JEM 2100F and FEI TECNAI G2 200 kV), high-voltage TEM (HVEM, Jeol JEM ARM 1300S, 1.25 MV), and energy-dispersive X-ray fluorescence spectroscopy (EDX). High-resolution X-ray diffraction (XRD) patterns were obtained using the 9B and 3D beam lines of the Pohang Light Source (PLS) with monochromatic radiation (λ=1.54595 Å). X-ray photoelectron spectroscopy (XPS) was performed using the 8A1 beam line of the PLS and a laboratory-based spectrometer (ESCALAB 250, VG Scientifics) using a photon energy of 1486.6 eV (Al Kα). For steady-state and time-resolved photoluminescence studies, samples were excited by the second harmonic (355 nm, 400 nm) or fundamental (710 nm) of a cavity-dumped oscillator (Mira/PulseSwitch, Coherent, 31.25 kHz, 150 fs). Emission was collected using the lens, spectrally resolved using a monochromator (Sciencetech 9055, Sciencetech), detected using a photomultiplier (PMA-182-P-M, PicoQuant), and recorded using a time-correlated single photon counter (PicoHarp300, PicoQuant). 4. Photocurrent Measurement. The Ti (20 nm)/Au (80 nm) electrode structure was deposited onto a Si substrate by photolithography with a 1 µm thick SiO2 layer by sputtering using a patterned mask. The gap between the electrodes was 2 µm. A spin coater was used to deposit the NCs (dispersed in toluene) as a film between the electrodes. The thickness was controlled to be in the range of 1–10 µm. We tested the devices on the probe station with parametric test equipment (Agilent E5270A) at room temperature. A light-emitting diode (Mightex S3
System LEDs, 365, 505, and 617 nm, 150-200 mW) was used as the light source. 5. Computation Methods. The geometric optimization and total energy calculation were done using the Vienna ab initio simulation package (VASP).S1,S2 Electron-ion interactions were described by the projector-augmented wave (PAW) method,S3 which is essentially a frozen-core all-electron calculation. The van der Waals interaction was estimated through the PBE-D2 calculation, which empirically includes these interactions using Grimme’s approach.S4 In most cases, our supercell consisted of 1×1×1 primitive cell. However, 2×2×2 supercell was employed for MAPbX2Y1, where two X ions cannot be placed at proper sites of a primitive cell. For example, in T-ae configuration of MAPbBr2Cl, two Br can be placed on different sites only when the supercell enlarges. When 2×2×2 supercell was employed, one Br can be placed at an axial site along the c axis with respect to the Pb, while the other Br can be placed at an equatorial site along the a or b axis, The k-point sampling was done using 8×8×8 - 13×13×13 points depending upon the size of the supercell.
References S1-S4: S1. Kresse, G.; Hafner, J. Ab Initio Molecular Dynamics for Liquid Metals. Phys. Rev. B 1993, 47, 558561. S2. Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54, 11169. S3. Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B 1999, 59, 1758-1775. S4. Grimme, S. Semiempirical GGA-type Density Functional Constructed with a Long-Range Dispersion Correction. J. Comp. Chem. 2006, 27, 1787–1799.
S4
II. Supporting Tables Table S1. Fitted parameters of the decay curve of the PL, measured for MAPbBr3-xClx and MAPbBr3-xIx films on the Si substrates, using three-exponential decay function. The average decay time 〈τ〉 was calculated using the equation, 〈τ〉 = Σi fiτi, where fi is the fraction of component i and τi is its decay time.
MAPbBr3-xClx
MAPbBr3-xIx
x
f1
τ1 (ns)
f2
τ2 (ns)
f3
τ3 (ns)
〈τ〉 (ns)
0
0.60
4.65
0.36
19.67
0.04
113.82
14.1
0.5
0.46
1.98
0.51
4.45
0.03
16.43
3.7
1.0
0.32
1.06
0.55
4.40
0.13
15.34
4.8
1.5
0.33
0.44
0.56
2.23
0.11
10.03
2.5
2.0
0.44
0.01
0.52
2.23
0.04
10.93
1.8
2.5
0.15
0.31
0.15
2.21
0.05
7.27
1.2
3.0
0.90
0.26
0.09
1.25
0.01
8.37
0.38
0.5
0.13
0.14
0.77
0.81
0.10
3.04
0.94
1.0
0.08
0.02
0.72
1.30
0.20
4.28
1.8
1.5
0.49
1.92
0.44
4.74
0.07
13.59
4.0
2.0
0.58
6.62
0.40
23.36
0.02
145.51
16.7
2.5
0.58
5.45
0.41
19.92
0.01
209.88
13.5
3.0
0.53
4.67
0.43
17.29
0.04
79.55
12.8
Table S2. Fitted parameters of the decay curve of the PL, measured for MAPbBr3-xClx and MAPbBr3-xIx in toluene, using three-exponential decay function. The average decay time 〈τ〉 was calculated using the equation, 〈τ〉 = Σi fiτi, where fi is the fraction of component i and τi is its decay time.
MAPbBr3-xClx
MAPbBr3-xIx
x
f1
τ1 (ns)
f2
τ2 (ns)
f3
τ3 (ns)
〈τ〉 (ns)
0
0.44
6.13
0.34
44.1
0.22
260.7
71.5
0.5
0.45
4.25
0.44
23.8
0.11
16.43
27.3
1.0
0.41
2.88
0.48
18.6
0.11
15.34
21.7
1.5
0.51
1.34
0.37
10.6
0.12
10.03
12.8
2.0
0.50
1.01
0.43
4.53
0.07
10.93
4.64
2.5
0.63
0.87
0.32
6.07
0.05
8.05
1.04
3.0
0.44
0.29
0.54
1.41
0.02
6.99
1.98
0.5
0.54
0.60
0.37
2.19
0.09
10.0
1.98
1.0
0.42
1.56
0.46
6.79
0.12
21.9
6.37
1.5
0.29
3.05
0.59
18.2
0.12
70.2
20.3
2.0
0.18
6.15
0.41
55.8
0.41
252.7
127.0
2.5
0.47
3.01
0.33
27.2
20.0
268.3
62.5
3.0
0.34
3.00
0.45
29.4
0.21
156.6
46.4
S5
Table S3. (a) Fitted parameters of the excitation photon energy (λ)- and intensity (I)-dependent decay curve of the PL, measured for MAPbBr3 and MAPbI3 in toluene, using three-exponential decay function. The average decay time 〈τ〉 was calculated using the equation, 〈τ〉 = Σi fiτi, where fi is the fraction of component i and τi is its decay time.
λ (nm)
I (µJ/cm2)
f1
τ1 (ns)
f2
τ2 (ns)
f3
τ3 (ns)
〈τ〉 (ns)
355
0.05
0.44
6.13
0.34
44.1
0.22
260.7
71.5
0.25
0.76
4.79
0.21
19.8
0.03
125.1
10.9
0.5
0.89
2.26
0.10
9.58
0.01
62.14
3.4
0.05
0.36
10.39
0.44
46.66
0.20
239.4
72.2
0.25
0.82
4.50
0.16
20.2
0.02
124.9
9.6
0.5
0.89
0.10
0.10
12.1
0.01
87.06
4.5
0.05
0.34
3.00
0.45
29.4
0.21
165.6
46.4
0.25
0.37
4.43
0.49
24.1
0.14
125.5
30.6
0.5
0.48
4.89
0.42
25.2
0.10
131.1
25.5
0.25
0.39
2.78
0.30
50.2
0.31
342.6
122.3
0.5
0.29
2.84
0.37
51.2
0.34
309.8
125.1
2.5
0.21
3.72
0.51
37.5
0.26
203.8
72.9
MAPbBr3
400
MAPbI3
355
710
(b) Fitted parameters of the decay curve of the PL, measured for MAPbCl3 in toluene, upon excitation of 400 nm (0.05 µJ/cm2), and MAPbBr3-xIx in toluene, upon excitation of 710 nm (0.25 µJ/cm2). x
f1
τ1 (ns)
f2
τ2 (ns)
f3
τ3 (ns)
〈τ〉 (ns)
MAPbBr3-xClx
3
0.70
0.59
0.24
2.63
0.06
13.03
1.8
MAPbBr3-xIx
1.8
0.28
23.35
0.48
63.57
0.24
273.43
102.7
2.0
0.34
10.83
0.37
67.36
0.29
440.30
156.3
2.5
0.21
5.61
0.42
57.55
0.37
298.89
135.9
3.0
0.39
2.78
0.30
50.16
0.31
342.63
122.3
S6
Table S4. (a) Fitted parameters of the size (d = diameter) -dependent decay curve of the PL, measured for MAPbBr3 in toluene (355 nm excitation, 0.05 µJ/cm2), using three-exponential decay function. The average decay time 〈τ〉 was calculated using the equation, 〈τ〉 = Σi fiτi, where fi is the fraction of component i and τi is its decay time.
MAPbBr3
d (nm)
f1
τ1 (ns)
f2
τ2 (ns)
f3
τ3 (ns)
〈τ〉 (ns)
80
0.44
6.13
0.34
44.4
0.22
260.7
71.5
20
0.35
6.69
0.53
29.52
0.12
120.51
32.4
10
0.58
7.32
0.41
19.1
0.01
108.51
13.5
5
0.49
6.01
0.49
6.01
0.02
21.14
6.4
(b) Fitted parameters of the PL decay curves, measured for MAPbBr3-xClx and MAPbBr3-xIx NCs (size=10 nm) in toluene.
MAPbBr3-xClx
MAPbBr3-xIx
x
f1
τ1 (ns)
f2
τ2 (ns)
f3
τ3 (ns)
〈τ〉 (ns)
0
0.58
7.32
0.41
19.10
0.01
108.51
13.5
1.0
0.53
5.39
0.46
14.98
0.01
141.36
10.6
2.0
0.52
6.44
0.47
14.53
0.01
159.86
10.7
3.0
0.39
2.39
0.47
10.70
0.14
35.09
10.9
1.0
0.30
2.44
0.46
7.68
0.24
16.16
8.1
2.0
0.38
9.98
0.60
24.63
0.02
121.64
20.8
3.0
0.29
13.95
0.66
32.29
0.05
116.54
30.8
S7
Table S5. Summary of characteristics of previous MAPbI3 photodetectors.
a
Ref 32
Devices Film
λ (nm)a 633 laser
Intensity 0.07-6.78 µW
33
Film
365 780
0.05-4.5 mW/cm2
34
MAPbI3/TiO2
0.5 mW/cm2
35
MAPbI3/graphene
AM1.5 (100 mW/cm2 Xe lamp) 400-980 laser
36
ITO/MAPbI3/Mo O3/Ag
Xe lamp
10-7-10 mW/cm2
Ipb 40 nA at 1.0 kV/cm (area: L = 5-50 µm; W = 100 µm) 0.8 µA at 3 V (365 nm under 0.21 mW/cm2) 10 nA at 4 V (under 0.5 mW/cm2)
Sc --
Rd 5 mA/W
Ge
--
3.49 0.0367
1.19×103 5.84
--
0.49 (µA/W)
1.5 mA at 0.2 V (under 1 µW) (Idark = 3 mA)
--
180
1-2000 µW
10-5-1000 µA
--
5×104
299 (350 nm) 203 (530 nm) 242 (740 nm)
c
Wavelength; b Photocurrent; S = Photosensitivity = (Ilight- I0(=dark))/I0 = ∆I/I0, where ∆I is photocurrent;
d
R (A/W) = Responsitivity = ∆I/P, where ∆I = Ilight - I0(=dark) = photocurrent, P = light intensity (W); e G = Gain = number of electrons detected per incident photon = R (hν/q); hν = photon energy, q = electron charge. [References] 32. Horváth, E.; Spina, M.; Szekrényes, Z.; Kamarás, K.; Gaal, R.; Gachet, D.; Forró, L. Nanowires of Methylammonium Lead Iodide (CH3NH3PbI3) Prepared by Low Temperature Solution-Mediated Crystallization. Nano Lett. 2014, 14, 6761-6766. 33. Hu, X.; Zhang, X.; Liang, L.; Bao, J.; Li, S.; Yang, W.; Xie, Y. High-Performance Flexible Broadban d Photodetector Based on Organolead Halide Perovskite. Adv. Funct. Mater. 2014, 24, 7373-7380. 34. Xia, H. R.; Li, J.; Sun, W. T.; Peng, L. M. Organohalide Lead Perovskite Based Photodetectors with Much Enhanced Performance. Chem. Commun. 2014, 50, 13695. 35. Lee, Y.; Kwon, J.; Hwang, E.; Ra, C. H.; Yoo, W. J.; Ahn, J. H.; Park, J. H.; Cho, J. H. HighPerformance Perovskite–Graphene Hybrid Photodetector. Adv. Mater. 2015, 27, 41-46. 36. Dong, R.; Fang, Y.; Chae, J.; Dai, J.; Xiao, Z.; Dong, Q.; Yuan, Y.; Centrone, A.; Zeng, X. C.; Huang, J. High-Gain and Low-Driving-Voltage Photodetectors Based on Organolead Triiodide Perovskites. Adv. Mater. 2015, 27, 1912-1918.
S8
Table S6. Number of atoms (N), cell size, and stoichiometry in a primitive cell for various configurations of MAPbBr3–xClx and MAPbBr3–xIx.
MAPbBr3-xClx
x 0 1 2
MAPbBr3-xIx
3 1
2
3
*
Structure C TS TE-aa TE-ae TE-aa TE-ae C TS-ae (1) TS-aa TS-ae (2) TS-ee TS-ae (3) TE-ae TE-aa TS-ae (1) TS-ae (3) TS-aa S T -ae (2) TS-ee TE-ae TE-aa TS C
N 12 48 12 96 12 96 48 48 48 48 48 48 96 12 48 48 48 48 48 96 12 48 12
Cell size 1×1×1 1×1×1 1×1×1 2×2×2 1×1×1 2×2×2 1×1×1 1×1×1 1×1×1 1×1×1 1×1×1 1×1×1 2×2×2 1×1×1 1×1×1 1×1×1 1×1×1 1×1×1 1×1×1 2×2×2 1×1×1 1×1×1 1×1×1
Stoichiometry* MAPbBr3 (MAPb)4Br12 MAPbBr2Cl (MAPb)8Br16Cl8 MAPbBrCl2 (MAPb)8Br8Cl16 MAPbCl3 (MAPb)4Br8I4 (MAPb)4Br8I4 (MAPb)4Br8I4 (MAPb)4Br8I4 (MAPb)4Br8I4 (MAPb)8Br16I8 MAPbBr2I (MAPb)4Br4I8 (MAPb)4Br4I8 (MAPb)4Br4I8 (MAPb)4Br4I8 (MAPb)4Br4I8 (MAPb)8Br8I16 MAPbBrI2 (MAPb)4I12 MAPbI3
Stoichiometry of atoms in each primitive cell. Primitive cells are derived from more than one primitive cells of
MAPbX3 depending upon the system. For example, the primitive cells of TS configurations of MAPbBr3-xIx basically consisted of
2 × 2 × 2 primitive cells of MAPbBr3, by substituting appropriate number of Br
atoms with I atoms.
S9
III. Supporting Figures Figure S1. (a) XRD pattern of MAPbBr3−xClx NCs over the full 2θ range, where x = 0, 0.5, 1, 1.5, 2, 2.5, and 3, synthesized by the exchange reaction of MAPbBr3. (b) (200)C and (c) (210)C peaks in a magnified scale. The peaks of the MAPbCl3 and MAPbBr3 were indexed using the references: a = 5.675 Å for C-phase MAPbCl3; a = 5.90 Å for C-phase MAPbBr3. As x increases, the peaks shift from those of MAPbBr3 to those of MAPbCl3. The (200)C and (210)C peaks were well fitted to a Voigt function. We determined the particle size (d) using the Scherrer equation; d = 0.9λ/βcosθ, where β is the full-width at half-maximum, and θ is the Bragg angle.
(b) MAPbBr3
(c)
(210)C
(200)C
(311)
(220)
(300)
(112)
(210)
(200)
(100)
(a)
(110)
The size is ca. 60–100 nm, which is consistent with the size of square plates.
x=0
Intensity (arb. units)
x = 0.5 x = 1.0 x = 1.5 x = 2.0 x = 2.5
40
50 30
31
Degree (2θ)
S10
(210)C
MAPbCl3
(200)C
(300)
(220)
30
(112)
20
(210)
(200)
10
(110)
(100)
x = 3.0
34
35
Figure S2. Survey-scan XPS of (a) MAPbBr3−xClx and (b) MAPbBr3−xIx, where x = 0, 0.5, 1, 1.5, 2, 2.5, and 3, synthesized by the exchange reaction of MAPbBr3. The x value was determined using Pb 4f, Br 3d, Cl 2p, and I 3d peaks, and correlated well with the x
Intensity (arb. units)
x = 2.5
Br 3d I 4d
Pb 4f
x = 2.5
x=2
x=2
x = 1.5
x = 1.5
x=1
x=1
x = 0.5
x = 0.5
x=0
x=0
600
C 1s
x=3
N 1s
I 3d
(b) Br 3d
Cl 2p
C 1s
x=3
N 1s
(a)
Pb 4f
values determined by the XRD peak position.
500
400
300
200
100
0
600
500
400
300
200
100
Binding Energy (eV)
(a) MAPbBr3-xClx
3.0
2.5
(b) MAPbBr3-xIx
2.5
x = I (XPS)
x = Cl (XPS)
3.0
2.0 1.5 1.0
2.0 1.5 1.0
0.5
0.5
0.0
0.0 0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.0
0.5
1.0
1.5
2.0
x = I (XRD)
x = Cl (XRD)
S11
2.5
3.0
0
Figure S3. EDX spectra of MAPbBr3−xClx (x = 0.5, 1, 1.5, and 2.0) and MAPbBr3−xIx (x = 0.5, 1, and 2). The corresponding scanning TEM (STEM) images are shown in the inset. The composition was calculated using the Pb L shell, Cl K shell, Br K, and I L shell peaks. The STEM and EDX mapping of MAPbBr3 using the Pb L shell, Br K shell, and C K shell peak shows the homogeneous composition distribution over the NCs.
2
4
6
8
10 12
Energy (keV)
8
2
2
4
6
8
4
6
8
2
4
6
8
10 12
Energy (keV)
Energy (keV)
S12
0
2
Pb L Br K
Br L
Cu K
Pb M Cl K
Pb : Br : I = 1 : 1 : 2
10 12 0
Pb : Br : Cl = 1 : 1 : 2
Pb L Br K 10 12
Energy (keV)
Pb M IL
0
Cu K
Br L Pb M Cl K
10 12 0
Pb L Br K
6
Pb : Br : I = 1 : 2 : 1 Br L
Cu K Pb L Br K
IL
Br L
Pb M
Pb : Br : I = 1 : 2.5 : 0.5
0
4
Energy (keV)
Cu K
2
Cu K Pb L Br K
Br L Pb M Cl K
Pb L Br K
10 12 0
IL
8
Br L
6
Energy (keV)
Pb M
4
Pb : Br : Cl = 1 : 1.5 : 1.5
Pb L Br K
2
Pb : Br : Cl = 1 : 2 : 1
Cu K
0
Cu K
Cl K
Br L
Pb M
Pb : Br : Cl = 1 : 2.5 : 0.5
4
6
8
10 12
Energy (keV)
Figure S4. UV–visible absorption and PL spectra of (a) MAPbBr3−xClx and (b) MAPbBr3−xIx NCs in toluene under low excitation power (10 µW) of 355 nm. The
Intensity (arb. units)
concentration was adjusted to have an absorbance (A) = 0.5 at the absorption peak.
(a)
(b) MAPbBr3-xClx
MAPbBr3-xIx
MAPbBr3-xIx
MAPbBr3-xClx
400
500
600
700
400
800
Wavelength (nm)
500
600
700
800
Wavelength (nm)
Figure S5. PL decay curves of (a) MAPbBr3−xClx and (b) MAPbBr3−xIx in toluene, upon excitation at 355 nm with the lowest excitation intensity (0.05 µJ/cm2). The fitting parameters are summarized in Table S2.
(a) MAPbBr3-xClx
0
PL Intensity (arb. units)
10
0 0.5 1 1.5 2 2.5 3
(b) MAPbBr3-xIx
0
10
-1
10
-2
10
0 0.5 1 1.5 2 2.5 3
-1
10
-2
10
0
100
200
300
400
500
Decay Time (ns)
0
100
200
300
Decay Time (ns)
S13
400
500
Figure S6. PL decay curves of MAPbBr3 upon excitation at (a) 355 nm (0.05, 0.25, and 2.5 µJ/cm2) and (b) 400 nm (0.05, 0.25, and 0.5 µJ/cm2) in toluene; MAPbI3 upon excitation at (c) 355 nm (0.05, 0.25, and 2.5 µJ/cm2) and (d) 710 nm (0.25, 0.5 and 2.5 µJ/cm2) in toluene. The fitting parameters are summarized in Table S3. As the laser intensity increases, the decay time decreases. We used the lowest intensity 0.05 µJ/cm2 for 355 nm and 400 nm, and 0.25 µJ/cm2 for 710 nm to study the compositiondependence of the PL decay time.
(a) MAPbBr3 (at 355 nm)
Intensity (arb. units)
0
-1
10
(b) MAPbBr3 (at 400 nm)
10
2
0.05 µJ/cm 2 0.25 µJ/cm 2 0.5 µJ/cm
Intensity (arb. units)
0
10
-2
10
-3
10
-4
10
-1
10
-2
10
-3
10
-4
0
100
200
300
400
10
500
0
100
Time (ns)
300
400
500
Intensity (arb. units)
10
-2
10
-3
10
2
(d) MAPbI3 (at 710 nm)
10
2
0.05 µJ/cm 2 0.25 µJ/cm 2 0.5 µJ/cm
-1
200
Time (ns)
0
(c) MAPbI3 (at 355 nm)
0
10
Intensity (arb. units)
2
0.05 µJ/cm 2 0.25 µJ/cm 2 0.5 µJ/cm
0.25 µJ/cm 2 0.5 µJ/cm 2 2.5 µJ/cm
-1
10
-2
10
-3
10
-4
10
0
100
200
300
400
500
0
100
200
300
Time (ns)
Time (ns)
S14
400
500
Figure S7. PL decay curves of (a) MAPbBr3 and MAPbCl3 in toluene, upon excitation at 400 nm (0.05 µJ/cm2); (b) MAPbBr3−xIx in toluene, upon excitation at 710 nm (0.25 µJ/cm2). (c) Average value of decay time (〈τ〉 in ns) versus composition (x), MAPbBr3−xClx and MAPbBr3−xIx. The fitting parameters are summarized in Table S3. The MAPbBr3 and MAPbCl3 have 〈τ〉 = 72.2 ns and 1.8 ns, respectively, showing a decrease with increasing x. The 〈τ〉 of MAPbBr3−xIx series is 102.7, 156.3, 135.9, and 122.3 ns for x = 1.8, 2, 2.5, and 3, respectively, which shows an increase-to-decrease with increasing x. The maximum value is obtained for x = 2. Both MAPbBr3−xClx and MAPbBr3−xIx series exhibit similar
0
10
(a)
(b)
at 400 nm
at 710 nm
0
10
MAPbBr3
-1
10
-1
10 -2
10
MAPbCl3
3.0 2.5 2.0 1.8
MAPbBr3-xIx -2
10
-3
10
0
100
200
300
400
500
0
100
Time (ns) 150
(ns)
PL Intensity (arb. units)
composition dependence of 〈τ〉 for two different photon energies.
(c)
100
200
Time (ns) MAPbBr3-xIx 355 nm 710 nm MAPbBr3-xClx 355 nm 400 nm
50
0 0.0
300
0.5
1.0
1.5
2.0
X (Cl or I) S15
2.5
3.0
400
500
Figure S8. (a) PL decay curves of MAPbBr3 NCs having an average size of 5, 10, 20, and 80 nm, dispersed in toluene upon excitation at 355 nm (0.05 µJ/cm2). The fitting parameters are summarized in Table S4. (b) The average decay time (〈τ〉 in ns) is plotted as a function of size, showing that the average decay time increases with increasing the size. (c) HRTEM images of MAPbBr3 NCs shows the average size of 5, 10, and 20 nm. The synthesis method was described in the Experimental Section. 80 0
10
(a)
(b) 70 60
20 nm
-1
10
50
10 nm
(ns)
Intensity (arb. units)
80 nm
-2
10
5 nm
40 30
-3
10
20 10
-4
10
0 0
20
40
60
80
100
0
10
5 nm
30
40
50
60
70
80
90
Size (nm)
Time (ns)
(c)
20
10 nm
S16
20 nm
Figure S9. PL decay curves of (a) MAPbBr3−xClx and (b) MAPbBr3−xIx NCs (size = 10 nm) in toluene, upon excitation at 355 nm with the lowest excitation intensity (0.05 µJ/cm2). The fitting parameters are summarized in Table S4. Average value of decay time (〈τ〉 in ns) versus composition (x) for (c) MAPbBr3−xClx and (d) MAPbBr3−xIx NCs. The MAPbBr3 exhibits 〈τ〉 = 13.5 ns. The 〈τ〉 of MAPbBr3−xClx series decreases to 10.9 ns with increasing x to 3. The 〈τ〉 of MAPbBr3−xIx series is 8.1, 20.8, and 30.8 ns for x = 1, 2, and 3, respectively. It initially decreases (x = 1) and then increases with increasing x. Both series exhibit similar composition dependence of 〈τ〉 for two different size of
Intensity (arb. units)
nanoplates; 70 nm and 10 nm.
0
10
(a) MAPbBr3-xClx
0 1.0 2.0 3.0
-1
10
0
10
(b) MAPbBr3-xIx
-1
10
-2
10
-2
-3
10
-4
10
10
-3
10
-4
10
0
20
40
60
80
100
0
20
40
60
80
100
Time (ns)
Time (ns) 13
0 1.0 2.0 3.0
35
(c) MAPbBr3-xClx
30
(d) MAPbBr3-xIx
(ns)
25 12
20 15
11
10 5 0
1
2
3
0
X (Cl)
1
2
X (I)
S17
3
Figure S10. Photocurrents of MAPbBr3 and MAPbBrI2 films as a function of film thickness, at a bias voltage of 2 V under 365 nm (60 mW/cm2). SEM images shows the morphology and thickness (T) of the film.
Photo current (nA)
250 200
MAPbBr3
150 100
MAPbBrI2 50 0 3
6
9
12
15
18
21
24
Thickness (µm)
S18
27
Figure S11. Two different views (projected onto the a-b and a-c planes) of PBE-D2 structures for configurations (a) C- MAPbX3, (b) TE-ae, (c) TS-ae(1), (d) TS-aa, and (e) TS-ae(3). For example, in the TS-ae(1-3) configuration of MAPbBr2I, two Pb cations are coordinated with twelve anions (eight Br and four I), two of four I are located at axial sites, while other two I are located at equatorial sites. In the TS-aa configuration, all I are located at axial sites. Other configurations of the organic backbone are possible, but the corresponding band gap is quite different from the reference value.
(a) C-MAPbX3 a-b
a-c
S19
(b) TE-ae a-c
a-b
(c) TS-ae(1) a-b
a-c
(d) TS-aa S20
a-b
a-c
(e) TS-ae (3) a-b
a-c
S21
IV. Snapshots of Movie S1 (total time is 1 min, 30X of 30 min movie) Snapshots were taken for 0, 0.5, 1, 5, 15, and 30 min, for the exchange reaction of MAPbBr3 → MAPbI3; MAPbBr3 → MAPbCl3; MAPbCl3 → MAPbI3; MAPbCl3 → MAPbBr3. We prepared the MAPbBr3 film on ITO substrate (1 cm × 1 cm) with a thickness of 10 µm, and each piece was immersed in 0.1 M MAI and MACl dissolved IPA solution (5 mL). The time taken for the complete change into MAPbI3 and MAPbCl3 is about 5 min and 30 min, respectively. The MAPbCl3 film (prepared by the exchange reaction of MAPbBr3 → MAPbCl3) was immersed in 0.1 M MAI and MABr dissolved IPA solution to produce the MAPbI3 and MAPbBr3, respectively. The time takes about 1 min and 30 min, respectively.
S22
Reversible Halide Exchange Reaction of Organometal Trihalide Perovskite Colloidal Nanocrystals for Full-Range Band Gap Tuning Dong Myung Jang,† Kidong Park,† Duk Hwan Kim,† Jeunghee Park,*,†, Fazel Shojaei,‡ and Hong Seok Kang,§ Jae-Pyung Ahn,≠ Jong Woon Lee,# and Jae Kyu Song# †
Department of Chemistry, Korea University, Jochiwon 339-700, Korea
‡
Department of Chemistry and Bioactive Material Sciences and Research Institute of Physics and
Chemistry, Jeonbuk National University, Jeonju, Jeonbuk 560-756, Korea §
Department of Nano and Advanced Materials, College of Engineering, Jeonju University, Jeonju,
Jeonbuk 560-759, Korea ≠ #
Nano Materials Analysis Center, Korea Institute of Science and Technology, Seoul 136-791, Korea
Department of Chemistry, Kyung Hee University, Seoul 130-701, Korea
Contents I. Experimental Section II. Supporting Tables: Table S1-S6 III. Supporting Figures: Figure S1-S11 IV. Snapshots of Movie S1
S1
I. Experimental Section 1. Materials. Commercially available compounds PbCl2 (Aldrich), PbBr2 (Aldrich), PbI2 (Aldrich), HCl (36% in water, Aldrich), HBr (48% in water, Aldrich), HI (57% in water, Aldrich), CH3NH2 (40% in methanol, TCI), CH3(CH2)7NH2 (octylamine; OA, 99% Aldrich), and C17H34=CH2 (1octadecene; ODE, 90% Aldrich) were used without further purification. 2. Synthesis 2.1. Methylammonium halides (CH3NH3X, MAX, where X = Cl, Br, I): CH3NH3Br, CH3NH3Cl, and CH3NH3I were prepared by treating aqueous solutions of methylamine (CH3NH2) with the corresponding hydrogen halides, followed by recrystallization. CH3NH2 (0.27 mmol, 28 mL) and HBr (0.23 mmol, 26 mL) [or HI (0.23 mmol, 30 mL) or HCl (0.23 mmol, 23 mL)] were mixed and stirred for 2 h in an ice bath, followed by evaporation and recrystallization in an oil bath at 50–60 °C. In all cases, the precipitate was washed several times with diethyl ether, dried under vacuum, and used without further purification. 2.2. MAPbBr3: Two milliliters of ODE was stirred and heated at 80 °C (in an oil bath), and octylamine (17 µL, 0.1 mmol) was added. Next, MABr (11.2 mg, 0.1 mmol dissolved in 0.1 mL DMF) and PbBr2 (36.7 mg, 0.1 mmol dissolved in 0.1 mL DMF) were added, affording a yellow dispersion from which the nanoparticles were immediately precipitated by the addition of acetone followed by centrifugation (7000 rpm, 10 min). Finally, the MAPbBr3 nanocrystals were dispersed in toluene. They have a plate type morphology with an average length of 70 nm. For the reduced size of nanocrystals, oleylamine was used instead of octylamine and the size was controlled using the amount of oleylamine; the average length becomes 20, 10, and 5 nm for 2, 4, and 6 mmol of oleylamine. 2.3. Exchange reaction of MAPbBr3: MACl or MAI dissolved in isopropyl alcohol (IPA; 10 mL) was mixed with MAPbBr3 nanocrystals (0.04 mmol) in 2 mL toluene. Following table lists the quantities of MACl, MAI, and MAPbBr3 used for composition control. The Br exchange reaction time was 5–120 min. After the reaction, the NC products were precipitated by centrifugation of the reaction mixture. The NC precipitates were washed with IPA and dispersed in toluene for further characterization of their structure and composition.
[Summary of experimental condition for the exchange reaction] S2
No. 1 2 3 4 5 6 7 8 9 10 11 12
Composition
MAPbBr3-xClx
MAPbBr3-xIx
x 0.5 1.0 1.5 2.0 2.5 3.0 0.5 1.0 1.5 2.0 2.5 3.0
MAPbBr3
1
mM (mmol/L) MACl 0.6 1.5 3 6 15 30
1
0
MAI
0
0.6 1.5 3 6 15 75
Reaction Time (min) 30 30 30 30 60 120 5 5 10 10 30 30
3. Characterization. The products were analyzed by field-emission transmission electron microscopy (TEM, Jeol JEM 2100F and FEI TECNAI G2 200 kV), high-voltage TEM (HVEM, Jeol JEM ARM 1300S, 1.25 MV), and energy-dispersive X-ray fluorescence spectroscopy (EDX). High-resolution X-ray diffraction (XRD) patterns were obtained using the 9B and 3D beam lines of the Pohang Light Source (PLS) with monochromatic radiation (λ=1.54595 Å). X-ray photoelectron spectroscopy (XPS) was performed using the 8A1 beam line of the PLS and a laboratory-based spectrometer (ESCALAB 250, VG Scientifics) using a photon energy of 1486.6 eV (Al Kα). For steady-state and time-resolved photoluminescence studies, samples were excited by the second harmonic (355 nm, 400 nm) or fundamental (710 nm) of a cavity-dumped oscillator (Mira/PulseSwitch, Coherent, 31.25 kHz, 150 fs). Emission was collected using the lens, spectrally resolved using a monochromator (Sciencetech 9055, Sciencetech), detected using a photomultiplier (PMA-182-P-M, PicoQuant), and recorded using a time-correlated single photon counter (PicoHarp300, PicoQuant). 4. Photocurrent Measurement. The Ti (20 nm)/Au (80 nm) electrode structure was deposited onto a Si substrate by photolithography with a 1 µm thick SiO2 layer by sputtering using a patterned mask. The gap between the electrodes was 2 µm. A spin coater was used to deposit the NCs (dispersed in toluene) as a film between the electrodes. The thickness was controlled to be in the range of 1–10 µm. We tested the devices on the probe station with parametric test equipment (Agilent E5270A) at room temperature. A light-emitting diode (Mightex S3
System LEDs, 365, 505, and 617 nm, 150-200 mW) was used as the light source. 5. Computation Methods. The geometric optimization and total energy calculation were done using the Vienna ab initio simulation package (VASP).S1,S2 Electron-ion interactions were described by the projector-augmented wave (PAW) method,S3 which is essentially a frozen-core all-electron calculation. The van der Waals interaction was estimated through the PBE-D2 calculation, which empirically includes these interactions using Grimme’s approach.S4 In most cases, our supercell consisted of 1×1×1 primitive cell. However, 2×2×2 supercell was employed for MAPbX2Y1, where two X ions cannot be placed at proper sites of a primitive cell. For example, in T-ae configuration of MAPbBr2Cl, two Br can be placed on different sites only when the supercell enlarges. When 2×2×2 supercell was employed, one Br can be placed at an axial site along the c axis with respect to the Pb, while the other Br can be placed at an equatorial site along the a or b axis, The k-point sampling was done using 8×8×8 - 13×13×13 points depending upon the size of the supercell.
References S1-S4: S1. Kresse, G.; Hafner, J. Ab Initio Molecular Dynamics for Liquid Metals. Phys. Rev. B 1993, 47, 558561. S2. Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54, 11169. S3. Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B 1999, 59, 1758-1775. S4. Grimme, S. Semiempirical GGA-type Density Functional Constructed with a Long-Range Dispersion Correction. J. Comp. Chem. 2006, 27, 1787–1799.
S4
II. Supporting Tables Table S1. Fitted parameters of the decay curve of the PL, measured for MAPbBr3-xClx and MAPbBr3-xIx films on the Si substrates, using three-exponential decay function. The average decay time 〈τ〉 was calculated using the equation, 〈τ〉 = Σi fiτi, where fi is the fraction of component i and τi is its decay time.
MAPbBr3-xClx
MAPbBr3-xIx
x
f1
τ1 (ns)
f2
τ2 (ns)
f3
τ3 (ns)
〈τ〉 (ns)
0
0.60
4.65
0.36
19.67
0.04
113.82
14.1
0.5
0.46
1.98
0.51
4.45
0.03
16.43
3.7
1.0
0.32
1.06
0.55
4.40
0.13
15.34
4.8
1.5
0.33
0.44
0.56
2.23
0.11
10.03
2.5
2.0
0.44
0.01
0.52
2.23
0.04
10.93
1.8
2.5
0.15
0.31
0.15
2.21
0.05
7.27
1.2
3.0
0.90
0.26
0.09
1.25
0.01
8.37
0.38
0.5
0.13
0.14
0.77
0.81
0.10
3.04
0.94
1.0
0.08
0.02
0.72
1.30
0.20
4.28
1.8
1.5
0.49
1.92
0.44
4.74
0.07
13.59
4.0
2.0
0.58
6.62
0.40
23.36
0.02
145.51
16.7
2.5
0.58
5.45
0.41
19.92
0.01
209.88
13.5
3.0
0.53
4.67
0.43
17.29
0.04
79.55
12.8
Table S2. Fitted parameters of the decay curve of the PL, measured for MAPbBr3-xClx and MAPbBr3-xIx in toluene, using three-exponential decay function. The average decay time 〈τ〉 was calculated using the equation, 〈τ〉 = Σi fiτi, where fi is the fraction of component i and τi is its decay time.
MAPbBr3-xClx
MAPbBr3-xIx
x
f1
τ1 (ns)
f2
τ2 (ns)
f3
τ3 (ns)
〈τ〉 (ns)
0
0.44
6.13
0.34
44.1
0.22
260.7
71.5
0.5
0.45
4.25
0.44
23.8
0.11
16.43
27.3
1.0
0.41
2.88
0.48
18.6
0.11
15.34
21.7
1.5
0.51
1.34
0.37
10.6
0.12
10.03
12.8
2.0
0.50
1.01
0.43
4.53
0.07
10.93
4.64
2.5
0.63
0.87
0.32
6.07
0.05
8.05
1.04
3.0
0.44
0.29
0.54
1.41
0.02
6.99
1.98
0.5
0.54
0.60
0.37
2.19
0.09
10.0
1.98
1.0
0.42
1.56
0.46
6.79
0.12
21.9
6.37
1.5
0.29
3.05
0.59
18.2
0.12
70.2
20.3
2.0
0.18
6.15
0.41
55.8
0.41
252.7
127.0
2.5
0.47
3.01
0.33
27.2
20.0
268.3
62.5
3.0
0.34
3.00
0.45
29.4
0.21
156.6
46.4
S5
Table S3. (a) Fitted parameters of the excitation photon energy (λ)- and intensity (I)-dependent decay curve of the PL, measured for MAPbBr3 and MAPbI3 in toluene, using three-exponential decay function. The average decay time 〈τ〉 was calculated using the equation, 〈τ〉 = Σi fiτi, where fi is the fraction of component i and τi is its decay time.
λ (nm)
I (µJ/cm2)
f1
τ1 (ns)
f2
τ2 (ns)
f3
τ3 (ns)
〈τ〉 (ns)
355
0.05
0.44
6.13
0.34
44.1
0.22
260.7
71.5
0.25
0.76
4.79
0.21
19.8
0.03
125.1
10.9
0.5
0.89
2.26
0.10
9.58
0.01
62.14
3.4
0.05
0.36
10.39
0.44
46.66
0.20
239.4
72.2
0.25
0.82
4.50
0.16
20.2
0.02
124.9
9.6
0.5
0.89
0.10
0.10
12.1
0.01
87.06
4.5
0.05
0.34
3.00
0.45
29.4
0.21
165.6
46.4
0.25
0.37
4.43
0.49
24.1
0.14
125.5
30.6
0.5
0.48
4.89
0.42
25.2
0.10
131.1
25.5
0.25
0.39
2.78
0.30
50.2
0.31
342.6
122.3
0.5
0.29
2.84
0.37
51.2
0.34
309.8
125.1
2.5
0.21
3.72
0.51
37.5
0.26
203.8
72.9
MAPbBr3
400
MAPbI3
355
710
(b) Fitted parameters of the decay curve of the PL, measured for MAPbCl3 in toluene, upon excitation of 400 nm (0.05 µJ/cm2), and MAPbBr3-xIx in toluene, upon excitation of 710 nm (0.25 µJ/cm2). x
f1
τ1 (ns)
f2
τ2 (ns)
f3
τ3 (ns)
〈τ〉 (ns)
MAPbBr3-xClx
3
0.70
0.59
0.24
2.63
0.06
13.03
1.8
MAPbBr3-xIx
1.8
0.28
23.35
0.48
63.57
0.24
273.43
102.7
2.0
0.34
10.83
0.37
67.36
0.29
440.30
156.3
2.5
0.21
5.61
0.42
57.55
0.37
298.89
135.9
3.0
0.39
2.78
0.30
50.16
0.31
342.63
122.3
S6
Table S4. (a) Fitted parameters of the size (d = diameter) -dependent decay curve of the PL, measured for MAPbBr3 in toluene (355 nm excitation, 0.05 µJ/cm2), using three-exponential decay function. The average decay time 〈τ〉 was calculated using the equation, 〈τ〉 = Σi fiτi, where fi is the fraction of component i and τi is its decay time.
MAPbBr3
d (nm)
f1
τ1 (ns)
f2
τ2 (ns)
f3
τ3 (ns)
〈τ〉 (ns)
80
0.44
6.13
0.34
44.4
0.22
260.7
71.5
20
0.35
6.69
0.53
29.52
0.12
120.51
32.4
10
0.58
7.32
0.41
19.1
0.01
108.51
13.5
5
0.49
6.01
0.49
6.01
0.02
21.14
6.4
(b) Fitted parameters of the PL decay curves, measured for MAPbBr3-xClx and MAPbBr3-xIx NCs (size=10 nm) in toluene.
MAPbBr3-xClx
MAPbBr3-xIx
x
f1
τ1 (ns)
f2
τ2 (ns)
f3
τ3 (ns)
〈τ〉 (ns)
0
0.58
7.32
0.41
19.10
0.01
108.51
13.5
1.0
0.53
5.39
0.46
14.98
0.01
141.36
10.6
2.0
0.52
6.44
0.47
14.53
0.01
159.86
10.7
3.0
0.39
2.39
0.47
10.70
0.14
35.09
10.9
1.0
0.30
2.44
0.46
7.68
0.24
16.16
8.1
2.0
0.38
9.98
0.60
24.63
0.02
121.64
20.8
3.0
0.29
13.95
0.66
32.29
0.05
116.54
30.8
S7
Table S5. Summary of characteristics of previous MAPbI3 photodetectors.
a
Ref 32
Devices Film
λ (nm)a 633 laser
Intensity 0.07-6.78 µW
33
Film
365 780
0.05-4.5 mW/cm2
34
MAPbI3/TiO2
0.5 mW/cm2
35
MAPbI3/graphene
AM1.5 (100 mW/cm2 Xe lamp) 400-980 laser
36
ITO/MAPbI3/Mo O3/Ag
Xe lamp
10-7-10 mW/cm2
Ipb 40 nA at 1.0 kV/cm (area: L = 5-50 µm; W = 100 µm) 0.8 µA at 3 V (365 nm under 0.21 mW/cm2) 10 nA at 4 V (under 0.5 mW/cm2)
Sc --
Rd 5 mA/W
Ge
--
3.49 0.0367
1.19×103 5.84
--
0.49 (µA/W)
1.5 mA at 0.2 V (under 1 µW) (Idark = 3 mA)
--
180
1-2000 µW
10-5-1000 µA
--
5×104
299 (350 nm) 203 (530 nm) 242 (740 nm)
c
Wavelength; b Photocurrent; S = Photosensitivity = (Ilight- I0(=dark))/I0 = ∆I/I0, where ∆I is photocurrent;
d
R (A/W) = Responsitivity = ∆I/P, where ∆I = Ilight - I0(=dark) = photocurrent, P = light intensity (W); e G = Gain = number of electrons detected per incident photon = R (hν/q); hν = photon energy, q = electron charge. [References] 32. Horváth, E.; Spina, M.; Szekrényes, Z.; Kamarás, K.; Gaal, R.; Gachet, D.; Forró, L. Nanowires of Methylammonium Lead Iodide (CH3NH3PbI3) Prepared by Low Temperature Solution-Mediated Crystallization. Nano Lett. 2014, 14, 6761-6766. 33. Hu, X.; Zhang, X.; Liang, L.; Bao, J.; Li, S.; Yang, W.; Xie, Y. High-Performance Flexible Broadban d Photodetector Based on Organolead Halide Perovskite. Adv. Funct. Mater. 2014, 24, 7373-7380. 34. Xia, H. R.; Li, J.; Sun, W. T.; Peng, L. M. Organohalide Lead Perovskite Based Photodetectors with Much Enhanced Performance. Chem. Commun. 2014, 50, 13695. 35. Lee, Y.; Kwon, J.; Hwang, E.; Ra, C. H.; Yoo, W. J.; Ahn, J. H.; Park, J. H.; Cho, J. H. HighPerformance Perovskite–Graphene Hybrid Photodetector. Adv. Mater. 2015, 27, 41-46. 36. Dong, R.; Fang, Y.; Chae, J.; Dai, J.; Xiao, Z.; Dong, Q.; Yuan, Y.; Centrone, A.; Zeng, X. C.; Huang, J. High-Gain and Low-Driving-Voltage Photodetectors Based on Organolead Triiodide Perovskites. Adv. Mater. 2015, 27, 1912-1918.
S8
Table S6. Number of atoms (N), cell size, and stoichiometry in a primitive cell for various configurations of MAPbBr3–xClx and MAPbBr3–xIx.
MAPbBr3-xClx
x 0 1 2
MAPbBr3-xIx
3 1
2
3
*
Structure C TS TE-aa TE-ae TE-aa TE-ae C TS-ae (1) TS-aa TS-ae (2) TS-ee TS-ae (3) TE-ae TE-aa TS-ae (1) TS-ae (3) TS-aa S T -ae (2) TS-ee TE-ae TE-aa TS C
N 12 48 12 96 12 96 48 48 48 48 48 48 96 12 48 48 48 48 48 96 12 48 12
Cell size 1×1×1 1×1×1 1×1×1 2×2×2 1×1×1 2×2×2 1×1×1 1×1×1 1×1×1 1×1×1 1×1×1 1×1×1 2×2×2 1×1×1 1×1×1 1×1×1 1×1×1 1×1×1 1×1×1 2×2×2 1×1×1 1×1×1 1×1×1
Stoichiometry* MAPbBr3 (MAPb)4Br12 MAPbBr2Cl (MAPb)8Br16Cl8 MAPbBrCl2 (MAPb)8Br8Cl16 MAPbCl3 (MAPb)4Br8I4 (MAPb)4Br8I4 (MAPb)4Br8I4 (MAPb)4Br8I4 (MAPb)4Br8I4 (MAPb)8Br16I8 MAPbBr2I (MAPb)4Br4I8 (MAPb)4Br4I8 (MAPb)4Br4I8 (MAPb)4Br4I8 (MAPb)4Br4I8 (MAPb)8Br8I16 MAPbBrI2 (MAPb)4I12 MAPbI3
Stoichiometry of atoms in each primitive cell. Primitive cells are derived from more than one primitive cells of
MAPbX3 depending upon the system. For example, the primitive cells of TS configurations of MAPbBr3-xIx basically consisted of
2 × 2 × 2 primitive cells of MAPbBr3, by substituting appropriate number of Br
atoms with I atoms.
S9
III. Supporting Figures Figure S1. (a) XRD pattern of MAPbBr3−xClx NCs over the full 2θ range, where x = 0, 0.5, 1, 1.5, 2, 2.5, and 3, synthesized by the exchange reaction of MAPbBr3. (b) (200)C and (c) (210)C peaks in a magnified scale. The peaks of the MAPbCl3 and MAPbBr3 were indexed using the references: a = 5.675 Å for C-phase MAPbCl3; a = 5.90 Å for C-phase MAPbBr3. As x increases, the peaks shift from those of MAPbBr3 to those of MAPbCl3. The (200)C and (210)C peaks were well fitted to a Voigt function. We determined the particle size (d) using the Scherrer equation; d = 0.9λ/βcosθ, where β is the full-width at half-maximum, and θ is the Bragg angle.
(b) MAPbBr3
(c)
(210)C
(200)C
(311)
(220)
(300)
(112)
(210)
(200)
(100)
(a)
(110)
The size is ca. 60–100 nm, which is consistent with the size of square plates.
x=0
Intensity (arb. units)
x = 0.5 x = 1.0 x = 1.5 x = 2.0 x = 2.5
40
50 30
31
Degree (2θ)
S10
(210)C
MAPbCl3
(200)C
(300)
(220)
30
(112)
20
(210)
(200)
10
(110)
(100)
x = 3.0
34
35
Figure S2. Survey-scan XPS of (a) MAPbBr3−xClx and (b) MAPbBr3−xIx, where x = 0, 0.5, 1, 1.5, 2, 2.5, and 3, synthesized by the exchange reaction of MAPbBr3. The x value was determined using Pb 4f, Br 3d, Cl 2p, and I 3d peaks, and correlated well with the x
Intensity (arb. units)
x = 2.5
Br 3d I 4d
Pb 4f
x = 2.5
x=2
x=2
x = 1.5
x = 1.5
x=1
x=1
x = 0.5
x = 0.5
x=0
x=0
600
C 1s
x=3
N 1s
I 3d
(b) Br 3d
Cl 2p
C 1s
x=3
N 1s
(a)
Pb 4f
values determined by the XRD peak position.
500
400
300
200
100
0
600
500
400
300
200
100
Binding Energy (eV)
(a) MAPbBr3-xClx
3.0
2.5
(b) MAPbBr3-xIx
2.5
x = I (XPS)
x = Cl (XPS)
3.0
2.0 1.5 1.0
2.0 1.5 1.0
0.5
0.5
0.0
0.0 0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.0
0.5
1.0
1.5
2.0
x = I (XRD)
x = Cl (XRD)
S11
2.5
3.0
0
Figure S3. EDX spectra of MAPbBr3−xClx (x = 0.5, 1, 1.5, and 2.0) and MAPbBr3−xIx (x = 0.5, 1, and 2). The corresponding scanning TEM (STEM) images are shown in the inset. The composition was calculated using the Pb L shell, Cl K shell, Br K, and I L shell peaks. The STEM and EDX mapping of MAPbBr3 using the Pb L shell, Br K shell, and C K shell peak shows the homogeneous composition distribution over the NCs.
2
4
6
8
10 12
Energy (keV)
8
2
2
4
6
8
4
6
8
2
4
6
8
10 12
Energy (keV)
Energy (keV)
S12
0
2
Pb L Br K
Br L
Cu K
Pb M Cl K
Pb : Br : I = 1 : 1 : 2
10 12 0
Pb : Br : Cl = 1 : 1 : 2
Pb L Br K 10 12
Energy (keV)
Pb M IL
0
Cu K
Br L Pb M Cl K
10 12 0
Pb L Br K
6
Pb : Br : I = 1 : 2 : 1 Br L
Cu K Pb L Br K
IL
Br L
Pb M
Pb : Br : I = 1 : 2.5 : 0.5
0
4
Energy (keV)
Cu K
2
Cu K Pb L Br K
Br L Pb M Cl K
Pb L Br K
10 12 0
IL
8
Br L
6
Energy (keV)
Pb M
4
Pb : Br : Cl = 1 : 1.5 : 1.5
Pb L Br K
2
Pb : Br : Cl = 1 : 2 : 1
Cu K
0
Cu K
Cl K
Br L
Pb M
Pb : Br : Cl = 1 : 2.5 : 0.5
4
6
8
10 12
Energy (keV)
Figure S4. UV–visible absorption and PL spectra of (a) MAPbBr3−xClx and (b) MAPbBr3−xIx NCs in toluene under low excitation power (10 µW) of 355 nm. The
Intensity (arb. units)
concentration was adjusted to have an absorbance (A) = 0.5 at the absorption peak.
(a)
(b) MAPbBr3-xClx
MAPbBr3-xIx
MAPbBr3-xIx
MAPbBr3-xClx
400
500
600
700
400
800
Wavelength (nm)
500
600
700
800
Wavelength (nm)
Figure S5. PL decay curves of (a) MAPbBr3−xClx and (b) MAPbBr3−xIx in toluene, upon excitation at 355 nm with the lowest excitation intensity (0.05 µJ/cm2). The fitting parameters are summarized in Table S2.
(a) MAPbBr3-xClx
0
PL Intensity (arb. units)
10
0 0.5 1 1.5 2 2.5 3
(b) MAPbBr3-xIx
0
10
-1
10
-2
10
0 0.5 1 1.5 2 2.5 3
-1
10
-2
10
0
100
200
300
400
500
Decay Time (ns)
0
100
200
300
Decay Time (ns)
S13
400
500
Figure S6. PL decay curves of MAPbBr3 upon excitation at (a) 355 nm (0.05, 0.25, and 2.5 µJ/cm2) and (b) 400 nm (0.05, 0.25, and 0.5 µJ/cm2) in toluene; MAPbI3 upon excitation at (c) 355 nm (0.05, 0.25, and 2.5 µJ/cm2) and (d) 710 nm (0.25, 0.5 and 2.5 µJ/cm2) in toluene. The fitting parameters are summarized in Table S3. As the laser intensity increases, the decay time decreases. We used the lowest intensity 0.05 µJ/cm2 for 355 nm and 400 nm, and 0.25 µJ/cm2 for 710 nm to study the compositiondependence of the PL decay time.
(a) MAPbBr3 (at 355 nm)
Intensity (arb. units)
0
-1
10
(b) MAPbBr3 (at 400 nm)
10
2
0.05 µJ/cm 2 0.25 µJ/cm 2 0.5 µJ/cm
Intensity (arb. units)
0
10
-2
10
-3
10
-4
10
-1
10
-2
10
-3
10
-4
0
100
200
300
400
10
500
0
100
Time (ns)
300
400
500
Intensity (arb. units)
10
-2
10
-3
10
2
(d) MAPbI3 (at 710 nm)
10
2
0.05 µJ/cm 2 0.25 µJ/cm 2 0.5 µJ/cm
-1
200
Time (ns)
0
(c) MAPbI3 (at 355 nm)
0
10
Intensity (arb. units)
2
0.05 µJ/cm 2 0.25 µJ/cm 2 0.5 µJ/cm
0.25 µJ/cm 2 0.5 µJ/cm 2 2.5 µJ/cm
-1
10
-2
10
-3
10
-4
10
0
100
200
300
400
500
0
100
200
300
Time (ns)
Time (ns)
S14
400
500
Figure S7. PL decay curves of (a) MAPbBr3 and MAPbCl3 in toluene, upon excitation at 400 nm (0.05 µJ/cm2); (b) MAPbBr3−xIx in toluene, upon excitation at 710 nm (0.25 µJ/cm2). (c) Average value of decay time (〈τ〉 in ns) versus composition (x), MAPbBr3−xClx and MAPbBr3−xIx. The fitting parameters are summarized in Table S3. The MAPbBr3 and MAPbCl3 have 〈τ〉 = 72.2 ns and 1.8 ns, respectively, showing a decrease with increasing x. The 〈τ〉 of MAPbBr3−xIx series is 102.7, 156.3, 135.9, and 122.3 ns for x = 1.8, 2, 2.5, and 3, respectively, which shows an increase-to-decrease with increasing x. The maximum value is obtained for x = 2. Both MAPbBr3−xClx and MAPbBr3−xIx series exhibit similar
0
10
(a)
(b)
at 400 nm
at 710 nm
0
10
MAPbBr3
-1
10
-1
10 -2
10
MAPbCl3
3.0 2.5 2.0 1.8
MAPbBr3-xIx -2
10
-3
10
0
100
200
300
400
500
0
100
Time (ns) 150
(ns)
PL Intensity (arb. units)
composition dependence of 〈τ〉 for two different photon energies.
(c)
100
200
Time (ns) MAPbBr3-xIx 355 nm 710 nm MAPbBr3-xClx 355 nm 400 nm
50
0 0.0
300
0.5
1.0
1.5
2.0
X (Cl or I) S15
2.5
3.0
400
500
Figure S8. (a) PL decay curves of MAPbBr3 NCs having an average size of 5, 10, 20, and 80 nm, dispersed in toluene upon excitation at 355 nm (0.05 µJ/cm2). The fitting parameters are summarized in Table S4. (b) The average decay time (〈τ〉 in ns) is plotted as a function of size, showing that the average decay time increases with increasing the size. (c) HRTEM images of MAPbBr3 NCs shows the average size of 5, 10, and 20 nm. The synthesis method was described in the Experimental Section. 80 0
10
(a)
(b) 70 60
20 nm
-1
10
50
10 nm
(ns)
Intensity (arb. units)
80 nm
-2
10
5 nm
40 30
-3
10
20 10
-4
10
0 0
20
40
60
80
100
0
10
5 nm
30
40
50
60
70
80
90
Size (nm)
Time (ns)
(c)
20
10 nm
S16
20 nm
Figure S9. PL decay curves of (a) MAPbBr3−xClx and (b) MAPbBr3−xIx NCs (size = 10 nm) in toluene, upon excitation at 355 nm with the lowest excitation intensity (0.05 µJ/cm2). The fitting parameters are summarized in Table S4. Average value of decay time (〈τ〉 in ns) versus composition (x) for (c) MAPbBr3−xClx and (d) MAPbBr3−xIx NCs. The MAPbBr3 exhibits 〈τ〉 = 13.5 ns. The 〈τ〉 of MAPbBr3−xClx series decreases to 10.9 ns with increasing x to 3. The 〈τ〉 of MAPbBr3−xIx series is 8.1, 20.8, and 30.8 ns for x = 1, 2, and 3, respectively. It initially decreases (x = 1) and then increases with increasing x. Both series exhibit similar composition dependence of 〈τ〉 for two different size of
Intensity (arb. units)
nanoplates; 70 nm and 10 nm.
0
10
(a) MAPbBr3-xClx
0 1.0 2.0 3.0
-1
10
0
10
(b) MAPbBr3-xIx
-1
10
-2
10
-2
-3
10
-4
10
10
-3
10
-4
10
0
20
40
60
80
100
0
20
40
60
80
100
Time (ns)
Time (ns) 13
0 1.0 2.0 3.0
35
(c) MAPbBr3-xClx
30
(d) MAPbBr3-xIx
(ns)
25 12
20 15
11
10 5 0
1
2
3
0
X (Cl)
1
2
X (I)
S17
3
Figure S10. Photocurrents of MAPbBr3 and MAPbBrI2 films as a function of film thickness, at a bias voltage of 2 V under 365 nm (60 mW/cm2). SEM images shows the morphology and thickness (T) of the film.
Photo current (nA)
250 200
MAPbBr3
150 100
MAPbBrI2 50 0 3
6
9
12
15
18
21
24
Thickness (µm)
S18
27
Figure S11. Two different views (projected onto the a-b and a-c planes) of PBE-D2 structures for configurations (a) C- MAPbX3, (b) TE-ae, (c) TS-ae(1), (d) TS-aa, and (e) TS-ae(3). For example, in the TS-ae(1-3) configuration of MAPbBr2I, two Pb cations are coordinated with twelve anions (eight Br and four I), two of four I are located at axial sites, while other two I are located at equatorial sites. In the TS-aa configuration, all I are located at axial sites. Other configurations of the organic backbone are possible, but the corresponding band gap is quite different from the reference value.
(a) C-MAPbX3 a-b
a-c
S19
(b) TE-ae a-c
a-b
(c) TS-ae(1) a-b
a-c
(d) TS-aa S20
a-b
a-c
(e) TS-ae (3) a-b
a-c
S21
IV. Snapshots of Movie S1 (total time is 1 min, 30X of 30 min movie) Snapshots were taken for 0, 0.5, 1, 5, 15, and 30 min, for the exchange reaction of MAPbBr3 → MAPbI3; MAPbBr3 → MAPbCl3; MAPbCl3 → MAPbI3; MAPbCl3 → MAPbBr3. We prepared the MAPbBr3 film on ITO substrate (1 cm × 1 cm) with a thickness of 10 µm, and each piece was immersed in 0.1 M MAI and MACl dissolved IPA solution (5 mL). The time taken for the complete change into MAPbI3 and MAPbCl3 is about 5 min and 30 min, respectively. The MAPbCl3 film (prepared by the exchange reaction of MAPbBr3 → MAPbCl3) was immersed in 0.1 M MAI and MABr dissolved IPA solution to produce the MAPbI3 and MAPbBr3, respectively. The time takes about 1 min and 30 min, respectively.
S22
