1

Indium tin oxide as a semiconductor material in efficient p-type dye-

sensitized solar cells Ze Yu,1,8 Ishanie R. Perera,2, 8 Torben Daeneke, 3,4 Satoshi Makuta,4 Yasuhiro Tachibana,4,5 Jacek J.

Jasieniak,1 Amaresh Mishra,6 Peter Bäuerle,6 Leone Spiccia*,2 and Udo Bach*1,3,7

1 Department of Materials Science and Engineering, Monash University, Victoria, 3800, Australia.

2 School of Chemistry, Monash University, Victoria, 3800, Australia.

3 Commonwealth Scientific and Industrial Research Organization, Materials Science and Engineering, Flexible Electronic Theme, Clayton, South, Victoria, 3169, Australia.

4 School of Engineering, RMIT University, Melbourne, Victoria, 3001, Australia.

5 Japan Science and Technology Agency, (JST), PRESTO 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan.

6 Institute of Organic Chemistry II and Advanced Materials, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany.

7 Melbourne Centre for Nanofabrication, 151 Wellington Road, Clayton, Victoria, 3168, Australia.

8 These authors contributed equally to this work.

*Correspondence to: Udo Bach, Email: Udo.Bach@monash.edu, Phone: +61 3 990 56264;

Leone Spiccia, Email leone.spiccia@monash.edu, Phone: +61 3 9905 4526

FAX: +61 3 9905 4597

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Table S1: Data for X-ray photoelectron spectroscopy

Device optimization summary

Figure S1. The dependence of device efficiency measured under simulated one sun irradiation

(1000 W m−2, AM1.5) on film thickness of the mesoporous ITO layer. Devices consist of

[Fe(acac)3]0/− based electrolyte in conjunction with PMI-8T-TPA.

Temperature (°C) Annealing time (min) In/Sn In+Sn/O

400 30 7.40 0.67

400 120 7.25 0.67

600 30 7.69 0.67

600 120 7.70 0.67

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Figure S2. The dependence of device efficiency measured under simulated one sun irradiation

(1000 W m−2, AM1.5) on film thickness of the mesoporous NiO layer. Devices consist of

[Fe(acac)3]0/− based electrolyte in conjunction with PMI-8T-TPA.

Figure S3: I–V curves measured at simulated one sun (1000 W m−2) and under dark conditions

for p-DSCs based on [Co(en)3]3+/2+ electrolyte sensitized with the PMI-6T-TPA dye on ITO or

NiO.

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Figure S4. I–V curves measured at simulated one sun (1000 W m−2) and under dark conditions

for p-DSCs based on [Co(en)3]3+/2+ electrolyte sensitized with the PMI-8T-TPA dye on ITO or

NiO.

Figure S5: IPCE spectra recorded under low light conditions (equivalent <2% sun) of p-DSCs

based on [Co(en)3]3+/2+ electrolyte sensitized with the dyes PMI–6T–TPA or PMI–8T–TPA on

ITO or NiO.

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Figure S6: I–V curves mesaured under dark and at 100% sun for devices with [Fe(acac)3]0/−

redox mediator in conjunction with PMI-8T-TPA in the presence and absence of ITO blocking

layer (BL) at the working electrode.

Figure S7: I–V curves measured at 10% Sun and 100% Sun for devices with I3−/I−,

[Co(en)3]3+/2+ and [Fe(acac)3]

0/− redox mediators in conjunction with PMI-8T-TPA.

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Table S2. Detailed photovoltaic parameters measured under 0.1 sun irradiation (1.5AM, 100

W m−2) of the devices prepared with the I3−/I−, [Co(en)3]

3+/2+, [Fe(acac)3]0/− based electrolytes

and PMI-8T-TPA sensitizer in the presence and the absence of the blocking layer (BL) at the

WE.

Electrolytes I3−/I− [Co(en)3]3+/2+ [Fe(acac)3]0/−

No BL With BL No BL With BL No BL With BL

VOC (mV) 259±2 252±18 614±5 690±8 492±68 604±22

JSC (mA cm−2) 0.38±0.01 0.42±0.01 0.36±0.01 0.30±0.02 0.54±0.01 0.69±0.01

FF 0.54±0.02 0.51±0.13 0.62±0.01 0.57±0.02 0.39±0.07 0.45±0.05

η (%) 0.54±0.01 0.54±0.15 1.40±0.02 1.15±0.04 1.05±0.35 1.86±0.25

The average values are from data measured on three or more devices. In some cases, a blocking layer (BL) of ITO was

introduced prior to screen printing the mesoporous ITO film using 25 mM of InCl3 and 2 mM of SnCl4·5H2O in 20% ethanol

in water (the pH of the solution was adjusted to 0.5). The working electrode consisted of FTO coated glass with a ~3.5 µm

thick mesoporous ITO layer. The counter electrode consisted of a thin Pt layer on FTO coated glass produced by pyrolysis of

H2PtCl6. The [Co(en)3]3+/2+ electrolyte contained 0.30 M [Co(en)3](BF4)2 (prepared in situ using 0.30 M Co(BF4)2·6H2O and

1.67 M 1,2-diaminoethane), 0.07 M [Co(en)3](BF4)3 and 0.10 M LiTFSI in acetonitrile. The I3−/I− electrolyte contained 0.03

M I2, 0.50 M tBP, 0.60 M 1-butyl-3-methylimidazolium iodide and 0.10 M guanidium thiocyanate in acetonitrile. The

[Fe(acac)3]0/− electrolyte contained 0.10 M Bu4N[Fe(acac)3], 0.05 M Fe(acac)3, 0.25 M tBP, 0.05 M LiTFSI and 0.01 M

chenodeoxycholic acid in acetonitrile.

Figure S8: I–V curves measured at simulated one Sun (1000 W m−2) for devices based on I3−/I−

electrolyte in conjunction with PMI-8T-TPA or MK2 sensitized on ITO.

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Table S3: Detailed photovoltaic parameters of the devices prepared with the I3−/I− based

electrolyte in conjunction with PMI-8T-TPA or MK2 sensitizer measured at 100% Sun.

ITO

Sensitizer MK2 PMI-8T-TPA

VOC (mV) -7±8 321±1

JSC (mA cm−2) -0.03±0.01 3.55±0.01

FF 0.07±0.14 0.56±0.01

η (%) 0.00±0.00 0.65±0.01

The average values were taken from not less than three devices. Within the devices the working electrode was made up of a ~3.5 µm thickness

ITO layer or ~3.1 µm thickness In2O3 layer and the counter electrode was made up of thermally decomposed Pt. The I3−/I− electrolyte contained

0.03 M I2, 0.50 M tBP, 0.60 M 1-butyl-3-methylimidazolium iodide and 0.10 M guanidium thiocyanate in acetonitrile.

Figure S9: Normalized UV-Vis spectra of the dyes PMI-6T-TPA and PMI-8T-TPA in

dichloromethane.

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Figure S10: Absorption spectra of 1 μm thick bare and PMI-8T-TPA sensitized ITO and NiO

films.

Figure S11: Calculated light harvesting efficiencies of ITO (4.1 μm thick) and NiO (3.1 μm

thick) films sensitized by dyes, PMI-6T-TPA and PMI-8T-TPA.

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Figure S12: Calculated APCE spectra of p-DSCs based on ITO and NiO sensitized with dyes

PMI-6T-TPA and PMI-8T-TPA.

Figure S13: Calculated APCE spectra of [Fe(acac)3]0/−, I3

−/I−, and [Co(en)3]3+/2+ mediated p-

DSCs based on ITO sensitized with PMI-8T-TPA.

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Figure 14: I–V curve measured at simulated one Sun (1000 W m−2) for p-DSCs based on

[Co(en)3]3+/2+ electrolyte sensitized with PMI–8T–TPA on antimony-doped tin oxide (ATO).

Inset represents the detailed photovoltaic parameters of the devices.

Table S4: Bimolecular dye regeneration rate constants (kreg) and observed rate constant (kobs)

for dye anion oxidation measured for [Fe(acac)3]0/−, I3

−/I−, and [Co(en)3]3+/2+ based

electrolytes.

Electrolyte I3−/I− [Co(en)3]3+/2+ [Fe(acac)3]0/−

kreg (108 M−1 s−1) 0.13 N/A 1.36

kobs (105 s−1) 0.55 11.6 0.59

The following equations were used in calculating the parameters described in the Table S4:

∆𝐎𝐃(𝒕) = 𝚫 𝐎𝐃(𝒕=𝟎)𝒆−(

𝒕

𝝉𝒘𝒘)𝜷

(1)

𝚪 (𝟏

𝜷) = ∫ 𝒖

𝟏

𝜷−𝟏

𝒆−𝒖𝒅𝒖∞

𝟎 (2)

𝝉𝒐𝒃𝒔 = 𝝉𝒘𝒘/𝜷 𝚪 (𝟏/𝜷) (3)

𝒌𝒐𝒃𝒔 = 𝟏

𝝉𝒐𝒃𝒔 (4)

𝒌𝒓𝒆𝒈 =𝑘𝑜𝑏𝑠−𝑘𝑟𝑒𝑐2

[𝑂𝑥] (5)

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τww = characteristic stretched lifetime, β = stretch parameter, = gamma function, ΔOD(t) = measured

change in optical density, ΔOD(t=0) = initial change in optical density, τobs = weighted average lifetime

of the stretched exponential, = variable of integration and krec2 = recombination between injected

electrons and dye+ (This is measured on a device containing an inert electrolyte without the redox

couple).1

Synthesis of dye PMI-8T-TPA:

Figure S15: Synthesis of D-A triad PMI-8T-TPA.

5-([N-(2,6-Diisopropylphenyl)]-9-perylenyl-3,4-dicarboximide)-4 ,3, 3’’, 3’’’, 3’’’’, 3’’’’’, 3’’’’’’,

3’’’’’’’-octahexyl-2, 2’:5’, 2’’:5’’, 2’’’:5’’’, 2’’’’:5’’’’, 2’’’’’:5’’’’’, 2’’’’’’:5’’’’’’, 2’’’’’’’-

octithiophene (4). To a solution of 370 mg (0.23 mmol) PMI-6T-I 2 in 3 mL degassed 1,2-

dimethoxyethane (DME) a solution of 159 mg (0.35 mmol) 3 in 2 mL degassed DME and 13.3 mg

(11.5 µmol) tetrakis(triphenylphosphine) palladium(0) was added. The mixture was degassed in

vacuum and purged with argon again before 288 µL (576 µmol) of 2M aqueous potassium phosphate

was added. The mixture was heated to 90 °C for 14 h and then poured on 1 M HCl and extracted with

dichloromethane (DCM). The organic phase was washed with dilute HCl, water and sat. aqueous

NaHCO3 solution and dried over Na2SO4. The residue was first purified by column chromatography

(SiO2) eluting with DCM to remove unreacted bithiophene and other impurities.

The major fraction was purified on a HPLC column (Nucleosil-NO2, 5 µm, Macherey & Nagel) using

hexane-dichloromethane (1:1 v/v) to furnish product 4 as a red solid 0.36 g in 87% yield. M.p. 66-67 °C; 1H-NMR (400 MHz, CDCl3): = 8.61 (d, 3J = 8.0 Hz, 2H, Pery-2H,5H), 8.40 (d, 3J = 8.0 Hz, 1H, Pery-

1H), 8.39 (d, 3J = 8.0 Hz, 1H, Pery-6H), 8.36 (d, 3J = 8.2 Hz, 2H, Pery-12H,7H), 7.99 (d, 3J = 8.5 Hz,

1H, Pery-10H), 7.66 (d, 3J = 7.7 Hz, 1H, Pery-8H), 7.60 (t, 3J = 8.0 Hz, 1H, Pery-11H), 7.47 (t, 3J =

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7.7 Hz, 1H, Ph-4H), 7.35 (d, 3J = 7.8 Hz, 2H, Ph-3H,5H), 7.17 (s, 1H, Th-3H), 7.12 (d, 3J = 7.8 Hz, 1H,

Th-5H’’’’’’’), 7.03 (s, 1H, Th-4H’), 7.00 (s, 1H, Th-4H’’), 6.99 (s, 1H, Th-4H’’’), 6.98 (s, 1H, Th-

4H’’’’), 6.96 (s, 1H, Th-4H’’’’’), 6.94 (s, 1H, Th-4H’’’’’’), 6.91 (d, 3J = 5.2 Hz, 1H, Th-4H’’’’’’’), 2.90-

2.75 (m, 16H, Ph-CH(CH3)2, Th-’-’’’’’’’-CH2), 2.46 (t, 3J = 7.5 Hz, 2H, Th--CH2-), 1.80-1.53 (m,

16H, -CH2-), 1.50-1.10 (m, 48H, -CH2-), 1.22 (d, 3J = 6.8 Hz, 12H, Ph-CH(CH3)2), 0.95-0.85 (m, 21H,

Th’-Th’’’’’’’CH3), 0.78 (t, 3J = 6.9 Hz, 3H, Th-CH3); MS (MALDI-TOF) m/z = 1810 (M+), calc.

1809.78; Elemental analysis calcd. (%) for C114H139NO2S8: C 75.57, H 7.73, N 0.77; found: C 75.65, H

7.79, N 0.85.

5-([N-(2,6-Diisopropylphenyl)]-9-perylenyl-3,4-dicarboximide)-4, 3, 3’’, 3’’’, 3’’’’, 3’’’’’, 3’’’’’’,

3’’’’’’’-octahexyl-5’’’’’’’-iodo-2, 2’:5’, 2’’:5’’, 2’’’:5’’’, 2’’’’:5’’’’, 2’’’’’:5’’’’’, 2’’’’’’:5’’’’’’,

2’’’’’’’-octithiophene (5). To a solution of 263 mg (0.147 mmol) PMI-8T 4 in 5 mL dry

dichloromethane was added 65.7 mg (0.153 mmol) mercury caproate and stirred at r.t. for 25 hr under

exclusion of light in which a clear solution is formed. Then 40.3 mg (0.16 mmol) iodine, dissolved in 1

mL dichloromethane was added. The mixture is stirred at r.t. for 8 h and then filtered over a short pad

of basic alumina. The solvent was removed and the crude product was purified by column

chromatography on silica using dichloromethane as eluent to furnish product 5 as a dark red solid in a

yield of 95% (270 mg). 1H-NMR (400 MHz, CDCl3): = 8.61 (d, 3J = 8.0 Hz, 2H, Pery-2H,5H), 8.40

(d, 3J = 8.0 Hz, 2H, Pery-1H,6H), 8.36 (d, 3J = 8.2 Hz, 2H, Pery-12H,7H), 7.99 (d, 3J = 8.5 Hz, 1H,

Pery-10H), 7.66 (d, 3J = 7.7 Hz, 1H, Pery-8H), 7.60 (t, 3J = 8.0 Hz, 1H, Pery-11H), 7.47 (t, 3J = 7.7 Hz,

1H, Ph-4H), 7.35 (d, 3J = 7.8 Hz, 2H, Ph-3H,5H), 7.18 (s, 1H, Th-3H), 7.04 (s, 2H, Th-4H’,H’’), 7.00

(s, 1H, Th-4H’’’), 6.99 (s, 1H, Th-4H’’’’), 6.98 (s, 1H, Th-4H’’’’’), 6.96 (s, 1H, Th-4H’’’’’’), 6.87 (s,

1H, Th-4H’’’’’’’), 2.90-2.65 (m, 16H, Ph-CH(CH3)2, Th-’-’’’’’’’-CH2), 2.71 (t, 3J = 7.8 Hz, 2H, Th-

-CH2-), 1.80-1.53 (m, 16H, -CH2-), 1.50-1.10 (m, 48H, -CH2-), 1.22 (d, 3J = 6.8 Hz, 12H, Ph-

CH(CH3)2), 0.95-0.82 (m, 21H, Th’-Th’’’’’’’CH3), 0.78 (t, 3J = 6.9 Hz, 3H, Th-CH3); HR MS (MALDI-

TOF) m/z = 1935.75652 (M+), calc. 1935.75381.

Di-tert-butyl-4,4'-[(4-{5’’’’’’’-([N-(2,6-diisopropylphenyl)]-9-perylenyl-3,4-dicarboxyimide)-3, 4’,

4’’, 4’’’, 4’’’’, 4’’’’’, 4’’’’’’, 4’’’’’’’-octahexyl-2, 2’:5’, 2’’:5’’, 2’’’:5’’’, 2’’’’:5’’’’, 2’’’’’:5’’’’’,

2’’’’’’:5’’’’’’, 2’’’’’’’-octithien-5-yl}phenyl)imino]dibenzoate (7). To a solution of 209 mg (0.11

mmol) PMI-8T-I 5 and 80.8 mg (0.14 mmol) boronic ester 6 in 3 mL degassed 1,2-dimethoxyethane

0.22 mL (0.44 mmol) 2 molar aqueous potassium phosphate solution was added. After degassing in a

flow of argon 2.8 mg (2.7 µmol) Pd2(dba)3•CHCl3 and 1.6 mg (5.4 µmol) [HPtBu3]PF6 were added and

the mixture stirred for 25 h at room temperature under argon. The dark mixture was poured on 10 mL

water and extracted with dichloromethane three times. The combined organic phases were dried over

MgSO4 and the solid residue after evaporation of solvent was purified by column chromatography (flash

SiO2) using dichloromethane. Product 7 was isolated in 179 mg (73 %) as dark red solid. 1H-NMR (400

MHz, CDCl3): = 8.70 (d, 3J = 8.0 Hz, 2H, Pery-2H), 8.69 (d, 3J = 8.0 Hz, 2H, Pery-5H), 8.58-8.50

(m, 4H, Pery-1H,6H,7H,12H), 8.02 (d, 3J = 8.4 Hz, 1H, Pery-8H), 7.89 (d, 3J = 8.6 Hz, 4H, (tBu)OOC-

Ph-2H,6H), 7.72 (d, 3J = 7.8 Hz, 1H, Pery-10H), 7.68 (t, 3J = 8.0 Hz, 1H, Pery-11H), 7.52 (d, 3J = 8.6

Hz, 2H, TPA-Ph-3H,5H), 7.49 (t, 3J = 7.7 Hz, 1H, Ph-4H), 7.36 (d, 3J = 7.8 Hz, 2H, Ph-3H,5H), 7.16

(s, 1H, Th-3H), 7.12-7.09 (m, 8H, Th’-4H, Th’’’’’’’-4H, TPA-Ph-2H,6H, (tBu)OOC-Ph-3H,5H), 7.02

(s, 1H, Th-4H’’), 7.00 (s, 1H, Th-4H’’’), 6.99 (s, 1H, Th-4H’’’’), 6.98 (s, 2H, Th-4H’’’’’,4H’’’’’’), 2.89-

2.72 (m, 15H, Ph-CH(CH3)2, Th-’-’’’’’’’-CH2), 2.46 (t, 3J = 7.5 Hz, 2H, Th--CH2-), 1.80-1.65 (m,

16H, -CH2-), 1.59 (s, 18H, C(CH3)3), 1.50-1.28 (m, 32H, -CH2-), 1.25-1.10 (m, 16H, -CH2-), 1.19 (d, 3J = 6.8 Hz, 12H, Ph-CH(CH3)2), 0.95-0.85 (m, 21H, Th’-Th’’’’’’’CH3), 0.78 (t, 3J = 6.9 Hz, 3H, Th-

CH3); HR MS (MALDI-TOF) m/z = 2253.06936 (M+), calc. 2253.06626.

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4,4'-[(4-{5’’’’’’’-([N-(2,6-diisopropylphenyl)]-9-perylenyl-3,4-dicarboxy-imide)-3, 4’, 4’’, 4’’’,

4’’’’, 4’’’’’, 4’’’’’’, 4’’’’’’’-octahexyl-2, 2’:5’, 2’’:5’’, 2’’’:5’’’, 2’’’’:5’’’’, 2’’’’’:5’’’’’, 2’’’’’’:5’’’’’’,

2’’’’’’’-octithien-5-yl}phenyl)imino]dibenzoic acid (1). 125 mg (0.055 mmol) 7 was treated

with a mixture of 2 mL dry dichloromethane and 0.4 mL trifluoroacetic acid at room temperature under

argon. After stirring for 10 hr. the solvent was evaporated and the product precipitated from

dichloromethane solution with n-hexane. The dicarboxylic acid 1 was isolated in 117 mg (99%) yield. 1H-NMR (400 MHz, CDCl3): = 8.70-8.68 (d, 3J = 8.0 Hz, 2H, Pery-2H,5H), 8.58-8.50 (m, 4H, Pery-

1H,6H,7H,12H), 8.10-8,00 (m, 5H, HOOC-Ph-2H,6H, Pery-8H), 7.72 (d, 3J = 7.8 Hz, 1H, Pery-10H),

7.68 (t, 3J = 8.0 Hz, 1H, Pery-11H), 7.60 (d, 3J = 8.6 Hz, 2H, TPA-Ph-3H,5H), 7.49 (t, 3J = 7.7 Hz, 1H,

Ph-4H), 7.36 (d, 3J = 7.8 Hz, 2H, Ph-3H,5H), 7.20-7.15 (m, 8H, HOOC-Ph-3H,5H, TPA-Ph-2H,6H,

Th-3H, Th’’’’’’’-4H), 7.04-6.97 (m, 6H, Th’-Th’’’’’’’-4H), 2.89-2.72 (m, 15H, Ph-CH(CH3)2, Th-’-

’’’’’’’-CH2), 2.46 (t, 3J = 7.5 Hz, 2H, Th--CH2-), 1.80-1.60 (m, 16H, -CH2-), 1.50-1.30 (m, 32H, -

CH2-), 1.25-1.10 (m, 16H, -CH2-), 1.19 (d, 3J = 6.8 Hz, 12H, Ph-CH(CH3)2), 0.95-0.85 (m, 21H, Th’-

Th’’’’’’’CH3), 0.78 (t, 3J = 6.9 Hz, 3H, Th-CH3); HR MS (MALDI-TOF) m/z = 2140.93382 (M+), calc.

2140.94106.