transport materials for perovskite solar cells · Ortho substituted 1,3,5-Triphenylbenzene hole...
Transcript of transport materials for perovskite solar cells · Ortho substituted 1,3,5-Triphenylbenzene hole...
Ortho substituted 1,3,5-Triphenylbenzene hole transport materials for perovskite solar cells
Michal Maciejczyka, Ruihao Chenb, Alasdair Browna, Nanfeng Zhengb* and Neil Robertsona*
a School of Chemistry and EaStCHEM, University of Edinburgh, King’s Buildings, David Brewster Road, Edinburgh, Scotland EH93FJ, UK. E-mail: [email protected]
b State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, 422 Siming South Road, Xiamen, Fujian 361005, P. R. China, Email: [email protected]
Table of contentsExperimental Section ...............................................................................................................................2
General methods ..................................................................................................................................2
Electrochemistry ..................................................................................................................................2
UV-Visible Spectroscopy ....................................................................................................................4
Thermal Analysis .................................................................................................................................4
Powder X-Ray Diffraction...................................................................................................................6
Cost analysis ........................................................................................................................................7
Synthesis ..............................................................................................................................................7
Solubility..............................................................................................................................................9
Device performance.............................................................................................................................9
NMR Spectra .........................................................................................................................................12
Electronic Supplementary Material (ESI) for Journal of Materials Chemistry C.This journal is © The Royal Society of Chemistry 2019
Experimental Section
General methods Elemental analyses were carried out by Stephen Boyer of the Science Centre, London Metropolitan
University using a Carlo Erba CE1108 Elemental Analyser. NMR spectroscopy was conducted using
Bruker (400, 500 or 600 MHz) spectrometers. 1H and 13C NMR spectra were all recorded in deuterated
dichloromethane. Mass spectra were recorded with Xevo QTOF (Waters) high resolution, accurate mass
tandem mass spectrometer equipped with Atmospheric Solids Analysis Probe (ASAP) and Bruker
MicroToF 2. All spectra were recorded using electrospray ionisation (ESI).
FTO glass substrates were sequentially washed in ultrasonic baths of detergent, acetone, distilled water
and ethanol for 10 min, respectively. Then, The FTO was calcined at 500 oC for 0.5 h. The ZnO layer
was firstly deposited on the FTO. The precursor solution of magnesium acetate tetrahydrate (169 mg)
and 8 mg ethanolamine (EA) in 2.3 mL of anhydrous ethanol was spin-coated on pre-treated ZnO
substrate. The substrate was then annealed at 450 oC for 30 min to obtain the ZnO-MgO-EA (NH3)+
ETL. A 150 nm thick layer of mesoporous-TiO2 was deposited on the ZnO-MgO-EA (NH3)+ substrate
by spin-coating of the TiO2 paste (Dyesol DSL 18NR-T) with ethanol (1:5, mass ratio), which was
followed by annealing at 450 for 30 min. The CH3NH3PbI3 perovskite layers were fabricated by reacting
mesoporous PbI2 (m-PbI2) with CH3NH3I. A mixture of 461 mg of PbI2 and 70 mg of dimethyl sulfoxide
(DMSO) dissolved in 600 mg of N,N-Dimethylformamide (DMF) was spin-coated on the as-prepared
substrate at 3,000 rpm for 25 s. The films were annealed at 70 °C for 15 min to obtain the m-PbI2 film.
After cooling to room temperature, the m-PbI2 film was immersed into the solution of CH3NH3I in
isopropanol for 45 s, and then was washed by isopropanol to remove the excess I- rich ionic compound.
After the preparation of perovskite layer, different hole transport layers were coated via solution process
at 4,000 rpm for 30 s, with the additives containing Li-TFSI/acetonitrile and TBP. Finally, an 80-nm
thick Au counter electrode was deposited via thermal evaporation under reduced pressure of 4 × 10−7
Torr. The active area was 0.10 cm2.
ElectrochemistryAll cyclic voltammetry measurements were carried out in freshly distilled CH2Cl2 using 0.3 M
[TBA][PF6] electrolyte in a three-electrode system, with each solution being purged with N2 prior to
measurement. The working electrode was a Pt disk (0.2 mm). The reference electrode was Ag/AgCl
and the counter electrode was a Pt rod. All measurements were made at room temperature using a
mAUTOLAB Type III potentiostat, driven by the electrochemical software GPES. Cyclic voltammetry
(CV) measurements used scan rates of 0.05 V s-1. Square wave voltammetry (SWV) was carried out at
a step potential of 0.004 V, square wave amplitude of 0.025 V, and a square wave frequency of 25 Hz.
Ferrocene was used as the internal standard in each measurement.
Figure S1. Cyclic voltammograms at different scan rates for TPB(2-MeOTAD) (left) and TPB(2-TPTZ) (right).
0.2 0.4 0.6 0.8 1.0 1.2-3x10-6
-2x10-6
-1x10-6
0
1x10-6
2x10-6
3x10-6
4x10-6
5x10-6
Curr
ent /
A
Voltage vs Ag/AgCl / V
0.02V 0.03V 0.04V 0.05V 0.06V
0.4 0.6 0.8 1.0 1.2 1.4-3x10-6
-2x10-6
-1x10-6
0
1x10-6
2x10-6
3x10-6
Curr
ent /
A
Voltage vs Ag/AgCl / V
0.03V 0.04V 0.05V 0.06V 0.07V 0.08V
0.10 0.15 0.20 0.25 0.30-4x10-6
-2x10-6
0
2x10-6
4x10-6
6x10-6
R2 = 0.989
Ipa IpcCu
rren
t / A
(Scan Rate)1/2 / (V/s)1/2
R2 = 0.999
0.15 0.20 0.25 0.30-3x10-6
-2x10-6
-1x10-6
0
1x10-6
2x10-6
3x10-6
4x10-6
Ipa Ipc
Curr
ent /
A
(Scan Rate)1/2 / (V/s)1/2
R2 = 0.999
R2 = 0.999
Figure S2. Plots of peak anodic (Ipa) and cathodic (Ipc) currents against the square root of the scan rate for TPB(2-MeOTAD) (left) and TPB(2-TPTZ) (right).
Table S1. Half wave potentials for each oxidation peak from cyclic voltammetry measurements.
Material E1/2 (1) / V E1/2 (2) / V E1/2 (3) / V E1/2 (4) / VTPB(2-MeOTAD) 0.19 0.29 0.36 0.99ǂ
TPB(2-TPTZ) 0.24 0.33 0.44 1.11ǂ
ǂChemically irreversible
UV-Visible SpectroscopyUV-visible absorption spectra were recorded in solution using a Jasco V-670 UV/vis/NIR
spectrophotometer controlled with SpectraManager software. All samples were measured at a
concentration of 2 × 10-5 M in dichloromethane, at room temperature in a 1 cm cell.
Thermal AnalysisDifferential scanning calorimetry (DSC) and Thermal Gravimetric Analysis were performed on
NETZSCH STA 449F1 at scan rates of 20 and 10 K min-1 under nitrogen atmosphere in DSC/TG
aluminium pan. The measurement range was 25 °C to 350 °C.
Figure S3. Full cyclic voltammograms for TPB(2-MeOTAD) (left) and TPB(2-TPTZ) (right).
-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0-8x10-6
-6x10-6
-4x10-6
-2x10-6
0
2x10-6
4x10-6
6x10-6
8x10-6
1x10-5
1x10-5Cu
rren
t / A
Voltage vs Ag/AgCl / V-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
-2x10-5
-1x10-5
-5x10-6
0
5x10-6
1x10-5
2x10-5
2x10-5
3x10-5
Curr
ent /
A
Voltage vs Ag/AgCl / V
Figure S4. Differential Scanning Calorimetry for TPB(2-MeOTAD), measured at 20 K min-1.
Figure S5. Thermal Gravimetric Analysis of TPB(2-MeOTAD), measured at 10 K min-1.
Figure S6. Differential Scanning Calorimetry for TPB(2-TPTZ), measured at 25 K min-1.
Figure S5. Thermal Gravimetric Analysis of TPB(2-TPTZ), measured at 10 K min-1.
Powder X-Ray DiffractionPowder diffraction was performed on a Bruker Discover D8 with CuKa1/2 source and a scintillation
detector.
Cost analysisWe conducted simplified cost analysis of the studied materials. We did not included
workup/purification steps as this is highly variable and can be optimized to reduce final cost of the step.
Especially typically used solvents like dichloromethane/chloroform or method of purification like
column chromatograph, constituting significant percentage of the final cost, on the large scale would
be substituted by appropriate solvent choice and more cost efficient purification method like
crystallization.
Table S2. Materials quantities and cost for the synthesis of TPB(2-TBr).
Chemical name Weight reagent (g/g)
Price of Chemical ($/g)
Material Cost ($/g product)
Percentage of Step (%)
2′-Bromoacetophenone 1.134 0.96 1.09 66.2SiCl4 2.895 0.12 0.35 21.1Ethanol 6.919 0.03 0.21 12.6Total cost ($/g) 1.64
0 10 20 30 40 500
2x103
4x103
6x103
8x103
1x104
Inte
nsity
/ a
.u.
Angle / 20 10 20 30 40 50
0
2x103
4x103
6x103
8x103
1x104
Inte
nsity
/ a
.u.
Angle / 2
TPB(2-MeOTAD) TPB(2-TPTZ)
Figure S8. Powder X-Ray Diffraction data for TPB(2-MeOTAD) and TPB(2-TPTZ).
Table S3. Materials quantities and cost for the synthesis of TPB(2-MeOTAD).
Chemical name Weight reagent (g/g)
Price of Chemical ($/g)
Material Cost ($/g product)
Percentage of Step (%)
TPBBr 0.758 1.64 1.24 9.6Dimethoxydiphenylamine 1.288 8.6 11.08 85.3Pd(OAc)2 0.011 19.45 0.21 1.6P(t-Bu)3HBF4 0.015 6.72 0.10 0.8Toluene 10.404 0.03 0.31 2.4NaOt-Bu 0.682 0.05 0.03 0.3Total cost ($/g) 12.98
Table S4. Materials quantities and cost for the synthesis of TPB(2-TPTZ).
Chemical name Weight reagent (g/g)
Price of Chemical ($/g)
Material Cost ($/g product)
Percentage of Step (%)
TPBBr 1.214 1.64 1.99 64.4Phenothiazine 1.781 0.025 0.04 1.4Pd(OAc)2 0.01 19.45 0.19 6.3P(t-Bu)3HBF4 0.026 6.72 0.17 5.6Toluene 20.808 0.03 0.62 20.2NaOt-Bu 1.288 0.05 0.06 2.1Total cost ($/g) 3.09
For the cost-per-peak-Watt estimation we assumed 200 nm thick HTM layer and no loss of the hole
transporting material during processing, following method introduced by Osedach et al. and further
developed by Petrus et al.1,2,3 Assumed price for spiro-MeOTAD was 100 $/g while prices of TPB(2-
MeOTAD) and TPB(2-TPTZ) were taken from cost estimation shown in tables above showing 12.98
$/g and 3.09 $/g, respectively.
SynthesisAll preparations were carried out using standard Schlenk line and air-sensitive chemistry techniques
under nitrogen atmosphere. The starting material, 1,3,5-Tris(2-bromophenyl) benzene has been
prepared according to previously reported procedure.4 All other materials were purchased from
1 T. P. Osedach, T. L. Andrew and V. Bulović, Energy Environ. Sci., 2013, 6, 711.2 M. L. Petrus, M. T. Sirtl, A. C. Closs, T. Bein and P. Docampo, Mol. Syst. Des. Eng., 2018, 3, 734–740.3 M. L. Petrus, T. Bein, T. J. Dingemans and P. Docampo, J. Mater. Chem. A, 2015, 3, 12159–12162.4 1 D. Trawny, M. Quennet, N. Rades, D. Lentz, B. Paulus and H.-U. Reissig, European J. Org. Chem., 2015, 2015, 4667–4674.
commercial suppliers and used without further purification. Toluene was dried using a solvent
purification system. Column chromatography was carried out using Silica 60A (particle size 35-70 µm,
Fisher, UK) as the stationary phase, and TLC was performed on pre-coated silica gel plates (0.25 mm
thick, 60 F254, Merck, Germany) and observed under UV light.
1,3,5-Tris(2’-((N,N-di(4-methoxyphenyl)amino)phenyl)benzene (TPB(2-MeOTAD))
A mixture of 1,3,5-Tris(2-bromophenyl) benzene (0.50 g, 0.921 mmol), 4,4'-dimethoxydiphenylamine
(0.85 g, 3.707 mmol), palladium (II) acetate (0.007 g, 0.031 mmol), sodium tert-butoxide (0.45 g, 4.683
mmol) and tri-tert-butylphosphonium tetrafluoroborate (0.01 g, 0.034 mmol) was added to an oven-
dried Schlenk tube and dried under vacuum for 30 minutes. Dry toluene (12 mL) was added and the
mixture was stirred under nitrogen at 110 °C for 24 hours. The solution was diluted with
dichloromethane, filtered through Cellite, washed with acetone and concentrated on a rotary evaporator.
The residue was purified by column chromatography (SiO2, eluent: 5:1 acetone:hexane) then
precipitated from a solution of acetone into an excess of methanol. The precipitate was filtered off and
washed with methanol. The white solid was dried under vacuum for 2 hours. This reaction was
conducted twice to collect at least 1 g of material. The first and second reactions yielded 0.66 g (73%)
and 0.49 g (55%) respectively.
Elemental Analysis (%). Calculated for C66H57N3O6: C 80.08, H 5.74, N 4.34. Found: C 80.13, H 5.74,
N 4.36.
1H NMR (500 MHz, Methylene Chloride-d2) δ 3.70 (s, 18H), 6.56 (d, 24H), 6.63 (s, 3H), 6.87 (d, J =
7.5 Hz, 3H), 7.10 (d, J = 7.8 Hz, 3H), 7.15 (t, J = 7.3 Hz, 3H), 7.27 (t, J = 7.9 Hz, 3H).
13C NMR (126 MHz, Methylene Chloride-d2) δ 53.0, 53.2, 53.4, 53.6, 53.8, 55.3, 113.9, 123.5, 124.5,
127.4, 128.3, 128.4, 131.9, 139.0, 140.6, 142.0, 145.7, 154.3.
MS (ESI): m/z (%) = 988.4 [(M + H)+, 100].
1,3,5-Tris(2’-(N-phenothiazylo)phenyl)benzene (TPB(2-TPTZ))
A mixture of 1,3,5-Tris(2-bromophenyl) benzene (0.50 g, 0.921 mmol), phenothiazine (0.80 g, 4.015
mmol), palladium (II) acetate (0.006 g, 0.027 mmol), sodium tert-butoxide (0.48 g, 4.995 mmol) and tri-
tert-butylphosphonium tetrafluoroborate (0.018 g, 0.062 mmol) was added to an oven-dried Schlenk
tube and dried under vacuum for 30 minutes. Dry toluene (12 mL) was added and the mixture was
stirred under nitrogen at 110 °C for 24 hours. The solution was diluted with dichloromethane, filtered
through Cellite, washed with acetone and concentrated on a rotary evaporator. The residue was purified
by column chromatography (SiO2, eluent: 85:10:5 petroleum ether (40-60):chloroform:diethyl ether)
then precipitated from a solution of acetone into an excess of methanol. The precipitate was filtered off
and washed with methanol. The white solid was dried under vacuum for 2 hours. This reaction was
repeated with the same proportions but on a 1.25 g scale to yield over 1 g of product. The first and
second reactions yielded 0.31 g (36%) and 1.03 g (50%) respectively.
Elemental Analysis (%). Calculated for C60H39N3S3: C 80.06, H 4.39, N 4.59; Found: C 80.11, H 4.30,
N 4.62.
1H NMR (500 MHz, Methylene Chloride-d2) δ 6.06 (d, J = 6.1 Hz, 6H), 6.68-6.74 (m, 12H), 6.88 (dd,
J = 6.9, 2.3 Hz, 6H), 7.34 (d, J = 8.2 Hz, 3H), 7.39 (t, J = 7.5 Hz, 3H), 7.51 (s, 3H), 7.51-7.55 (m, 6H).
13C NMR (126 MHz, Methylene Chloride-d2) δ 53.0, 53.2, 53.4, 53.6, 53.8, 115.7, 118.8, 122.1, 126.2,
126.9, 128.5, 128.8, 129.1, 132.9, 137.2, 137.4, 141.2, 143.8.
MS (ESI): m/z (%) = 897.2 [(M + H)+, 100].
SolubilityTable S5. Solubility of HTMs.
Material Chloroform Toluene Chlorobenzene
TPB(2-MeOTAD) >100 mg/ml >160 mg/ml >50 mg/ml
TPB(2-TPTZ) >260 mg/ml >50 mg/ml >110 mg/ml
Device performance
Figure S9. J–V curves and photovoltaic parameters of the devices with different concentration of TPB(2-MeOTAD) as HTM, recorded using from forward and reverse bias to short circuit.
Figure S10. Top-view SEM images of PSCs with TPB(2MeOTAD) as HTM with different concentration.
Figure S11. J–V curves and photovoltaic parameters of the devices with different concentration of TPB(2-TPTZ) as HTM, recorded using from forward and reverse bias to short circuit.
Figure S12. Top-view SEM images of PSCs with TPB(2MeOTAD) as HTM with different concentration.
Figure S12. J–V curves of the champion PSCs with TPB(2-MeOTAD) and TPB(2-TPTZ) HTMs recorded using from forward and reverse bias to short circuit.
Table S6. Photovoltaic parameters determined from J-V measurements of PSCs based on TPB(2-MeOTAD) and TPB(2-TPTZ) as HTMs.
Name JSC/mAcm-2 VOC/V FF/% η/% Rs/Ωcm-2
TPB(2-MeOTAD)-RS 19.32 0.97 64.54 12.14 9.10
TPB(2-MeOTAD)-FS 19.64 0.96 48.26 9.10 10.36
TPB(2-TPTZ)-RS 8.89 0.88 55.30 4.32 28.71
TPB(2-TPTZ)-FS 6.38 0.86 43.53 2.38 39.30
RS: reverse scan, FS: forward scan.
Figure S13. IPCE spectra and corresponding integrated JSC of the champion devices based on TPB(2-MeOTAD) and TPB(2-TPTZ) as HTMs. Obtained values are: 18.8 mAcm-2 for TPB(2-MeOTAD) and 7.2 mAcm-2 for TPB(2-TPTZ).
Figure S14. Devices performance statistics of 18 individual devices with TPB-2-MeOTAD and TPB(2-TPTZ) as HTM at FS and RS..
Figure S15. PCE evolution of encapsulated devices of TPB(2-MeOTAD), TPB(2-TPTZ) and Spiro-MeOTAD devices under dark storage in a dry box (25 °C, RH 30%).
Figure S16. Cross-sectional SEM images of the control PSCs with Spiro-MeOTAD as HTM.
Figure S17. J–V curves and photovoltaic parameters of the control PSCs with Spiro-MeOTAD as HTM, recorded using from forward and reverse bias to short circuit.
NMR SpectraTPB(2-MeOTAD)
6.456.506.556.606.656.706.756.806.856.906.957.007.057.107.157.207.257.30f1 (ppm)
-10000
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
100000
110000
120000
130000
140000
150000
A (d)7.10
B (t)7.27
C (t)7.15
D (d)6.87
E (s)6.63
F (d)6.56
22
.62
2.9
9
2.9
7
3.0
4
3.0
7
3.0
1
6.56
6.56
6.58
6.63
6.63
6.63
6.86
6.86
6.87
6.87
6.88
6.88
7.09
7.09
7.10
7.10
7.11
7.11
7.11
7.11
7.13
7.13
7.14
7.14
7.15
7.15
7.15
7.15
7.16
7.16
7.17
7.17
7.26
7.26
7.26
7.27
7.27
7.28
7.28
7.29
7.29
7.29
100105110115120125130135140145150155160165f1 (ppm)
-2000
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
22000
A (s)154.28
B (s)145.68
C (s)142.09
D (s)140.61
E (s)139.04
F (s)131.94
G (s)128.43
H (s)128.25
I (s)127.43
J (s)124.53
K (s)123.48
L (s)113.94
0.6
4
0.5
30
.17
0.1
50
.17
0.1
6
0.1
6
0.0
80
.08
0.2
0
0.0
9
0.1
7
113.
94
123.
48
124.
53
127.
4312
8.25
128.
43
131.
94
139.
0414
0.61
142.
09
145.
68
154.
28
TPB(2-TPTZ)
6.06.16.26.36.46.56.66.76.86.97.07.17.27.37.47.57.6f1 (ppm)
-100
100
300
500
700
900
1100
1300
1500
1700
1900
2100
2300
C (dd)6.88
D (m)6.71
E (d)6.06
F (m)7.53
G (s)7.51
H (t)7.39
I (d)7.34
5.7
8
12
.00
5.6
2
3.0
5
3.0
3
3.0
65
.82
6.04
6.05
6.06
6.07
6.07
6.08
6.68
6.68
6.69
6.70
6.70
6.71
6.71
6.72
6.72
6.73
6.74
6.87
6.87
6.88
6.88
6.89
7.33
7.34
7.34
7.35
7.35
7.37
7.38
7.39
7.39
7.40
7.41
7.51
7.51
7.52
7.52
7.53
7.53
7.53
7.54
7.54
7.55
4550556065707580859095100105110115120125130135140145150f1 (ppm)
-200
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
3200
3400
A (s)143.79
B (s)141.16
C (s)137.38
D (s)137.18
E (s)132.98
F (s)132.96
G (s)129.11
H (s)128.76
I (s)128.53
J (s)126.86
K (s)126.19
L (s)122.13
M (s)118.82
N (s)115.72
O (s)53.84
P (s)53.63
Q (s)53.41
R (s)53.19
S (s)52.98
0.4
50
.84
1.3
10
.84
0.4
6
0.2
90
.13
0.2
70
.29
0.3
00
.14
0.1
50
.14
0.1
00
.18
0.0
90
.08
0.0
70
.13
52.9
853
.19
53.4
153
.63
53.8
4
115.
72
118.
82
122.
13
126.
1912
6.86
128.
5312
8.76
129.
11
132.
9613
2.98
137.
1813
7.38
141.
16
143.
79