Efficient and stable DSSC sensitizers based on substituted dihydroindolo[2,3-b]carbazole donors with high molar extinction coefficients

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Shengyun Cai, Guojian Tian, Xin Li, Jianhua Su and He Tian……...…… Page 1– Page 10

Efficient and stable DSSC sensitizers based on substituted dihydroindolo[2,3-b]carbazole donor with high molar extinction

coefficients

Four new substituted dihydro-indolo[2,3-b]carbazole donor based organic dyes containing thiophene (or benzothiadiazole)

or thieno[3,2-b]thiophene were synthesized and successfully applied in dye-sensitized solar cells. It was found that these

dyes could achieve high molar extinction coefficients and the DSSCs based on these dyes displayed good performance and

high photo-stabilty.

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Efficient and stable DSSC sensitizers based on substituted

dihydroindolo[2,3-b]carbazole donor with high molar extinction

coefficients

Shengyun Cai,^aGuojian Tian,^aXin Li,^aJianhua Su^aand He Tian^a*

5

Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX

DOI: 10.1039/b000000x

Four novel metalꢀfree organic sensitizers based on 5,7ꢀdihexylꢀ6,12ꢀdiphenylꢀ5,7ꢀdihydroindolo[2,3ꢀ

b]carbazole (DDC) donor have been synthesized. Their optical/electrochemical properties, dyeꢀsensitized

solar cell (DSSCs) performances and photoꢀstability upon successive irradiation for 30 min have been

10 investigated. The optical data indicates that all these dyes showed a high molar extinction coefficient (5.6

ꢀ 6.3 × 10⁴M^ꢀ1cm^ꢀ1). Under standard global AM 1.5 solar light condition, the DDC4 sensitized cell gave

a short circuit photocurrent density (J_sc) of 14.81 mA cm^ꢀ2, an open circuit voltage (V_oc) of 0.688 V, and a

fill factor (FF) of 0.69, corresponding to an overall efficiency (η) of 7.03%. The benzothiadiazole units

and thieno[3,2ꢀb]thiophene (TT) in the π spacer were found to increase the photoꢀstability of the

15 corresponding dyes and these dyes based on this donor are promising candidates for the further

application in DSSCs.

here, we report a new donor 5,7ꢀdihexylꢀ6,12ꢀdiphenylꢀ5,7ꢀ

dihydroindolo[2,3ꢀb]carbazole (DDC) with easier preparation and

purification process. The considerations are as follows: 1)

carbazole is an excellent donor which has very strong electron

⁵⁰donating ability.⁷The new donor DDC contains two fused

carbazole units and can be expected to have stronger donating

ability; 2) the two fused carbazole units consists of a large πꢀ

plane, which could desirably delocalize the generated cation as

well as reinforce the photoꢀstability of the corresponding dyes.⁸

55 The effective conjugation of these two fused carbazole units

could be expected to contribute to a high molar extinction

coefficient; 3) the two alkyl chains attached on the two nitrogen

atoms will efficiently improve the solubility in common organic

solvents; 4) with the coefficient of both the free rotation of two

60 phenyl rings connected to the indolo[3, 2ꢀb]carbazole core and

the nonlinear structure of this donor, a controlled aggregation on

TiO₂could be anticipated; 5) the synthesis and purification of this

new donor by our methodology (In the synthesis part) is very

easy. As to the πꢀspacer, benzothiadiazole can stabilize the

65 chargeꢀseparated excitedꢀstate,⁹therefore, high photoꢀstability of

dyes could be accessible.¹⁰In addition, as an electronꢀ

withdrawing group in the πꢀspacer part, benzothiadiazole could

result in the striking redꢀshift of absorption spectrum of the

corresponding dyes.⁹Thieno[3,2ꢀb]thiophene (TT) is an excellent

70 πꢀspacer, it has been reported that the TT compound offers better

πꢀconjugation and smaller geometric relaxation energy upon

oxidation.¹¹However, as far as we know, the photoꢀstability of

dyes containing TT moiety as πꢀspacer has not been reported,

therefore the investigation on photoꢀstability of TT containing

75 dyes seems interesting. Based on the above considerations, four

new dyes based on DDC donor (Scheme 1), containing

Introduction

With the depletion of fossil energy, the energy problems are

more and more needed to be confronted with and solved day by

²⁰day.¹Among several promising candidates, dyeꢀsensitized solar

cells (DSSCs) based on Ruꢀcomplex dyes have been reported

with lightꢀtoꢀelectricity efficiency (η) as high as 11.5 %.²

However, Ruꢀcomplex dyes are not suitable for costꢀeffective and

environmentally friendly photovoltaic systems since they contain

²⁵the noble metal ruthenium which may limit their widespread

application in DSSCs.³Compared with metal complexes, organic

dyes have the advantages of environmental friendliness, higher

structural flexibility, lower cost, easier preparation and

purification, etc.⁴Most organic dyes are composed of a donorꢀπꢀ

30 acceptor (DꢀπꢀA) dipolar structure due to its effective photoꢀ

induced intramolecular charge transfer characteristics.⁵

The molar extinction coefficient of sensitizers in the visible

light region (ε) is an important factor that influences the DSSCs

efficiency. Generally, a high ε means a good light harvesting

35 ability, thus it will contribute to a large shortꢀcircuit current

density (J_sc).^5eThe photoꢀstability of dyes is also an important

factor and it will pose a great influence on the longꢀterm stability

of DSSCs.⁶As to be promisingly applied in the future DSSCs, a

donor should help the corresponding dyes to produce a high ε in

40 order to harvest photoelectrons as many as possible. Besides, the

donor should be able to stabilize the oxidized dyes upon light

irradiation in order to reinforce the photoꢀstability of dyes.⁶In

addition, the synthesis and purification of the donor should be

easy. However, as far as we know, donors based on the above

45 factors in DSSCs were seldom designed. Considering this point,

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benzothiadiazole (or thiophene) and TT (or thiophene) as πꢀ

The synthetic route to the four dyes DDC1-DDC4 containing

spacer, 2ꢀcyanoacetic acid as acceptor, were designed and 15 DDC moiety and reference dye CBZ with carbazole moiety were

synthesized. In order to investigate whether the two fused

carbazole units from the donor is good for the DSSCs

performance and stability of dyes upon light irradiation, CBZ

with Nꢀalkyl carbazole unit donor, was also synthesized as the

reference dye.

depicted in Scheme 2. The intermediate 1 was obtained from the

condensation reaction of 1 Hꢀindole and benzaldehyde under the

5

catalysis of iodine in CH₃CN, which employed the procedure

12a

previously reported by Mohit L. Deb.

However, the products

20 obtained were identified as not the reported product DDCX, but

the product (compound 1 in Scheme 2) exhibiting a different

configuration where two nitrogen atoms connected with the

central sixꢀmembered ring are in ex situ for each other. Moreover,

the central sixꢀmembered ring was not aromatized. The real

²⁵structure was identified as 1 which was directly characterized by

NMR and indirectly by DDC which was further characterized by

Xꢀray crystallography (Fig. 1). The DDC were synthesized by the

alkylation of 1, followed by the oxidation reaction by DDQ. The

synthesis of DDC was very simple with high yields and the

³⁰purification did not necessarily employ the column

chromatography, suggesting that its synthesis could be carried out

in mass production. The bromination of DDC gave the key

intermediate DDC-Br. The intermediates B1, B2 were

synthesized according to our previous work.^9bB3 and B4 were

35 obtained by repeated bromination and Suzuki Coupling reaction

and the starting material 3 was synthesized by four step reactions

according to previous report.^12bThe final products were obtained

via Suzuki coupling of DDC-Br with B1ꢀB4, followed by the

condensation with cyanoacetic acid in the presence of a catalytic

⁴⁰amount of piperidine in THF. The procedure to synthesis

reference dye CBZ from easily obtained intermediate 8 was very

similar to that of DDC1. The purification of intermediates was

performed by flash column chromatography and subsequent

HPLC. All the intermediates and target dyes were characterized

⁴⁵by standard spectroscopic methods including ¹H NMR, ¹³C NMR

and HRMS. Clearly, except the intermediates 1 and 2 which are

not very stable in solution, all the intermediates are fairly stable.

NC

S

DDC1

COOH

bridge=

bridge

N

DDC2

DDC3

N

S

DDC1. DDC2, DDC3, DDC4

N

S

DDC4

NC

S

COOH

CBZ

N

Scheme 1 Molecular structures of dyes (DDC1ꢀDDC4 and CBZ).

Fig. 1 Crystal structure of DDC (CCDC 933739).

50 Optical properties

UV/Vis absorption spectra of the five dyes in a diluted solution of

THF (1 ×10^ꢀ5M) are shown in Fig. 2(a) and their absorption data

are listed in Table 1. In the visible light region, the dyes DDC1-

DDC4 all exhibit three absorption bands: the major and broad

55 absorption band is located at 440ꢀ650 nm with the maximum

absorption at 453, 522, 464, 522 nm, respectively, which is

ascribed to the charge transfer (CT) transition between the donor

10

Scheme 2 Synthetic route to dyes DDC1ꢀDDC4 and CBZ.

Results and discussion

Synthesis

2

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and the acceptor,¹³the high intensity of this band is wellꢀ

correlated with the large value of oscillator strength (Table 1); the

benefits the electrolyte diffusion in the film and reduces the

recombination possibility of the light induced charges during

other two narrower absorption bands which are not completely ³⁰transportation.¹⁴As to the CT bands for these dyes, three points

separated off are located at 350ꢀ440 nm and the maximum

absorption are almost located at the same positions around 402

and 421 nm, respectively, which may be resulted from the

localized aromatic π—π* transitions.¹³The intensity of π—π*

were noteworthy: 1) the introduction of TT unit instead of

thiophene unit did not surely result in obvious red shifted

absorption bands, such as DDC4 compared to DDC2; 2) as

expected, the benzo[c][1,2,5]thiadiazole unit results in obvious

5

transitions is higher than that of the chargeꢀtransfer transitions. ³⁵red shifted, the reason of which were discussed in previous

The reference dye CBZ displays only one absorption band at

report;¹⁰3) The dyes possessing electron withdrawing groups,

i.e., DDC4 and DDC2 displayed slightly lower values of molar

extinction coefficients of CT band compared to the others, i.e.,

DDC1 and DDC3, the similar situation was reported before. ¹⁰

The absorption spectra of DDC1–DDC4 and CBZ on thin

transparent films (8 ꢁm thick) after 12 h adsorption in THF

solution are shown in Fig. 2(b) and the absorption data are listed

in Table 1. It could be seen that in 350ꢀ440 nm region, the

absorption peaks for DDC1–DDC4 and CBZ on the TiO₂films

⁴⁵are located at almost the same positions as that from the solution

spectra. However, in 440ꢀ700 nm region, the absorption peaks for

DDC2–DDC4 and CBZ on the TiO₂films are located at 517,

458, 514 and 436 nm, correspondingly blueꢀshifted by 5, 6, 8 and

25 nm, respectively, from the solution, while the absorption peak

⁵⁰for DDC1 is redꢀshifted by 14 nm. Such blue shift and red shift

have been reported in many other organic dyes on TiO₂

electrodes.¹⁵

¹⁰350ꢀ650 nm with the maximum absorption at 461 nm which is

slightly redꢀshifted compared to CT band of DDC1. For the dyes

DDC1ꢀDDC4, the corresponding maximum molar extinction

coefficients for CT band are quite high, they are 6.31×10⁴,

5.63×10⁴, 5.97×10⁴and 5.95×10⁴M^ꢀ1cm^ꢀ1, respectively, which

¹⁵exhibit striking enhancement compared to that for the dye CBZ

(3.61×10⁴M^ꢀ1cm^ꢀ1). The maximum molar extinction coefficients

for the two absorption bands of DDC1ꢀDDC4 at 350ꢀ440 nm are

also very high, reaching up around 5×10⁴and 7×10⁴M^ꢀ1cm^ꢀ1.

40

1.5

(a)

DDC1

DDC2

DDC3

DDC4

1.0

CBZ

Electrochemical properties

Fig. S2 depicts the typical cyclic voltammogram of DDC1–

55 DDC4 and CBZ, measured with five sensitizers attached to a 8

ꢁm nanocrystalline TiO₂film deposited on conducting FTO glass

0.5

in CH₃CN containing 0.1

M TBAPF₆as the supporting

electrolyte with a 0.1V s^ꢀ1scan rate and the results are listed in

Table 1. Each new donor containing dyes (DDC1ꢀDDC4)

⁶⁰displayed two major semiꢀreversible waves: the lower voltage

one is ascribed to the oxidation of the donor, while the higher one

could be ascribed to the oxidation of the oligothiophene and

benzothiadiazole moieties (π spacer).¹⁶The carbazole donor

based dye (CBZ) presented only a wave which is derived from

⁶⁵the oxidation of carbazole moiety (donor). The HOMO level

energies decreased slightly in the order of CBZ (1.45) > DDC2

(0.91) > DDC3 (0.86) >DDC4 (0.85) ≈ DDC1 (0.85) (the values

are ones vs. NHE), thus the HOMO levels of these dyes were

sufficiently lower than that of electrolyte pair I^－/I₃^－(ca. 0.40 V),

70 which ensured a smooth electron flow from the electrolyte to the

dyes. It is noteworthy that the HOMO levels of the new donor

based dyes DDC1ꢀDDC4 were much higher than that of CBZ

based on carbazole donor, suggesting that the donating ability of

the new donor was much stronger than that of carbazole donor.

75 The LUMO levels were estimated by the values of E_oxand the E_0–

0.0

300

400

500

600

700

Wavelength/nm

(b)

1.0

0.8

0.6

0.4

0.2

0.0

DDC1

DDC2

DDC3

DDC4

CBZ

band gaps, which were estimated at the intersection of

400

500

600

700

0

absorption and emission spectra. A trend appeared as CBZ (–

0.69) > DDC2 (–1.00) > DDC4 (–1.09) > DDC1 (–1.16) ≈

DDC3 (–1.16). All these levels were considerably higher than the

80 conductive band level of TiO₂(ca. –0.5 V), indicating that the

excitedꢀstate electrons injection of all five dyes are guaranteed to

be efficient.

Wavelength/nm

20

Fig. 2 (a) UVꢀVis absorption spectra of DDC1ꢀDDC4 and CBZ in THF

(1×10^ꢀ5M); (b) absorption spectra of DDC1ꢀDDC4 and CBZ adsorbed on

TiO₂film.

The high molar extinction coefficients for DDC1ꢀDDC4

25 indicated that these dyes have good light harvesting ability. A

correspondingly thinner nanocrystalline film was allowed so as to

avoid the decrease in the film’s mechanical strength. This also

Computational analysis

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Table 1 Optical and electrochemical of DDC1-DDC4 and CBZ.

d

Dye

Calculated

energy

f ^a

λ_max^b/nm

λ_max^c/nm on TiO₂

E_0ꢀ0

E_HOMO^e(V)

E_LUMO^f(V)

(ε^g/10⁴M^ꢀ1cm^ꢀ1)

(eV, nm)

2.80, 443^h

2.60, 477

2.76, 449

2.55, 486

2.91, 425

DDC1

DDC2

DDC3

DDC4

CBZ

1.76

1.20

2.04

1.51

1.48

404 (5.77), 426 (7.87), 453 (6.31)

402 (6.08), 421 (7.34), 522 (5.63)

403 (5.09), 427 (6.85), 464 (5.97)

401 (5.77), 421 (7.02), 522 (5.95)

461 (3.61)

402, 427, 467

401, 420, 517

403, 427, 458

401, 422, 514

436

2.01

1.91

2.02

1.94

2.14

0.85

0.91

0.86

0.85

1.45

ꢀ1.16

ꢀ1.00

ꢀ1.16

ꢀ1.09

ꢀ0.69

^aOscillator strengths at CT bands calculated by DFT/B3LYP; ^bAbsorption maximum in THF solution; ^cAbsorption maximum on TiO₂film; ^dE_0ꢀ0: 0 _ 0

e

transition energy measured at the intersection of absorption and emission spectra; HOMOs were measured in CH₃CN containing 0.1 M (nꢀC₄H₉)₄NPF₆

with a scan rate of 100 mV s^ꢀ1(working electrode: Pt; reference electrode: SCE); calibrated with ferrocene/ferrocenium (Fc/Fc+) as an external reference.

f

Counter electrode: Pt wire. E_LUMOwas calculated by E_ox– E_0–0

;

^gAbsorption coefficient; ^hWavelength of the calculated oscillator strength in vacuo.

To gain deep insight into the electronic distribution of the frontier

and other closeꢀlying orbitals as well as the geometrical

configuration of these dyes, density functional theory (DFT)

calculations were carried out. In the calculations, the long alkyl

chains in these compounds were replaced by ethyl groups to save

computational time while preserving their steric effect. The

45 DSSCs performance

5

10 hybrid B3LYP functional¹⁷and the Ahlrichs split valence SVP

18

basis set was employed to optimize molecular geometries of

the dyes and to compute their frontier molecular orbitals, using

the ORCA program package.¹⁹Subsequent timeꢀdependent DFT

(TDDFT) calculations were performed to gain information of the

15 lowest singlet excited states of the sensitizer dyes, using the

20

Coulombꢀattenuated CAMꢀB3LYP

functional and the SVP

basis set implemented in Gaussian 09 program package.

The charge distribution in the frontier molecular orbitals is

depicted in Fig. S1. As shown in the graphs, in the above four

²⁰sensitizers, the HOMO level is localized mostly at indolo[3,2,ꢀ

b]carbazole moiety (D), while the LUMO is localized mostly at

oligothiophene units (π) and the anchoring cyanoacrylic acid (A)

group. The electron distributions of both D and A are heavily

coupled with the orbitals in the central bridge (π) and the

²⁵desirable shift of electron density from D to A once upon photo

excitation is obvious, suggesting that the electron transfer from

the donor part to the acceptor units would be efficient once upon

photoexcitation. The calculated oscillator strength (f) is shown in

Table 1. The f values for the lowest energy transitions, the CT

30 transitions, are all very high, ranging from 1.20 to 2.04. The

results are roughly consistent with the absorptivity measured in

solutions except for DDC2.

The geometrical configuration of these dyes is shown in Fig. 3.

In the ground state, all these dyes are not totally planar. The

³⁵dihedron angles between the indolo[3,2,ꢀb]carbazole moiety and

the two phenyl rings connected to the central core of the donor

were near to 90^o, suggesting that these two phenyl rings may help

to suppress dye aggregation when dyes are loaded on TiO₂films.

For DDC1ꢀDDC4, those possessing withdrawing groupsꢀ

40 benzothiadiazole units are obviously twisted more between the

donor part and benzothiadizole units compared to the others, i. e.

such as DDC2 and DDC1, this phenomenon was reported by

some previous articles.²¹

Fig. 3 Dihedral angles between the neighbouring units.

To investigate the light harvesting ability of DDC1–DDC4 and

CBZ, DSSCs based on dyeꢀsensitized TiO₂(12 ꢁm) films and the

50 electrolyte in the experimental section were fabricated and the

performances were measured. Fig. 4(a) shows the action spectra

of incident photonꢀtoꢀcurrent conversion efficiency (IPCE) for

DSSCs with these dyes when CH₃CN (AV): DMF (v/v 3:1) was

used as the solvent for dye loading. The IPCE exceeds 60 % in

55 the range 360—570 nm for DDC1, 390—430 and 510—540 nm

for DDC2, 350—610 nm for DDC4 and 395—510 nm for CBZ,

with the highest value of 74.8 % at 470 nm for DDC1, 61.6 % at

420 nm for DDC2, 77.2 % at 430 nm for DDC4 and 66.0 % at

440 nm for CBZ, respectively. However, the highest value of

60 IPCE for DDC3 was only 58.9 % at 410 nm. Among these five

dyes, it could be easily seen that the IPCE for DDC3 displayed

poorest performance with low IPCE values and narrow IPCE

spectra, while the IPCE for DDC4 exhibited the best performance

with high IPCE values at broad spectra region, indicating that

65 DDC4 sensitized TiO₂electrode would generate a higher

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conversion yield compared to other four dyes. Except for DDC3,

the IPCE performances of the dyes based on the new donor all

displayed better than that of CBZ based on carbazole donor. One

electrode. Moreover, the electrolyte could also pose influence on

the IPCE values. Fig. 4(b) presents the photocurrent–voltage (J–

V) plots of DSSCs based on these dyes, along with that of CBZ

explanation is that the molar extinction coefficients of the dyes ³⁰for comparison. The detailed parameters, i.e., short circuit current

5

based on the new donor were much higher than that of CBZ

based on carbazole donor. Generally, a high molar extinction

coefficient means a good light harvesting ability, suggests that it

would be helpful to convert light to electricity more efficiently,²²

(J_sc), openꢀcircuit photovoltage (V_oc), fill factor (FF), and

solarꢀtoꢀ electricity conversion efficiency (η) measured under AM

1.5 solar light (100 mW cm^ꢀ2) are summarized in Table 2. When

the mixture solvents AV: DMF (v/v 3:1) were used as the solvent

thus that the high molar extinction coefficients would facilitate ³⁵for dye baths, the DSSCs based on DDC1–DDC4 and CBZ

¹⁰the new donor based dyes to display good IPCE perormance.

exhibited inferior conversion efficiency of 6.09%, 5.55%, 4.11%,

6.40% and 4.90%. The larger J_scof the DDC1 sensitized solar

cell as compared with that of the solar cell based on CBZ

demonstrates the beneficial influence of the high molar extinction

⁴⁰coefficients of DDC1 in solution. The superior performance of

DDC1 sensitized solar cell presented an advantage of the new

donor. The lower J_scof the DDC2 sensitized solar cell as

compared with that of DDC1 could be ascribed to the much

lower IPCE values although DDC2 had broad IPCE spectra. The

⁴⁵DDC3 sensitized DSSCs performed very poor with low J_scand

V_oc. The low J_scmay be resulted from the low electron injection

yield from LUMO levels into TiO₂conduction band. The low V_oc

implied that there were severe charge recombination between the

electrolytes and the oxidized dyes. Among these five dyes, the

⁵⁰DDC4 based DSSCs gave the best performance, with J_scof 13.96

mA cm^ꢀ2, an V_ocof 0.674 V, and a FF of 0.68, corresponding to

an overall conversion efficiency (η) of 6.40%. The large J_sccould

be attributed to the high IPCE values and the broad IPCE spectra.

However, V_ocof DDC4 sensitized solar cell was not high and one

⁵⁵possible reason is because of the existence of benzothiadiazole,

which were reported for many times previously.²³The low V_ocof

DDC2 was also consistent with this observation. Based on that

DDC1 and DDC4 sensitized solar cells displayed better

performance among the five dyes, the two dyes based DSSCs

⁶⁰with dye loading in CHCl₃: EtOH (v/v 1:3) were fabricated and

the performances were measured. The reason why the mixture

solvents CHCl₃: EtOH (v/v 1:3) were chosen as the dye baths

solvents was based on the consideration that many dyes based

DSSCs fabricated with dye baths in these mixture solvents

⁶⁵performed much better compared with other solvents.^9b

80

(a)

60

40

DDC1 AV:DMF(3:1)

DDC2 AV:DMF(3:1)

DDC3 AV:DMF(3:1)

DDC4 AV:DMF(3:1)

CBZ AV:DMF(3:1)

20

DDC1 CHCl₃:EtOH(1:3)

DDC4 CHCl₃:EtOH(1:3)

0

300

400

500

600

700

800

Wavelength/nm

15

(b)

10

5

DDC1 AV: DMF(3:1)

DDC2 AV: DMF(3:1)

DDC3 AV: DMF(3:1)

DDC4 AV: DMF(3:1)

CBZ AV: DMF(3:1)

DDC1 CHCl₃: EtOH (1:3)

DDC4 CHCl₃: EtOH (1:3)

0

Fig. 2 The performances of DSSCs based on DDC1ꢀDDC4 and CBZ.

Dye

Solvents

J_sc/mAcm^ꢀ2

11.95

11.57

9.40

V_oc/V FF (%)

η

(%)

-5

DDC1

DDC2

DDC3

DDC4

CBZ

AV: DMF (v/v 3:1)

CHCl₃: EtOH (v/v 1:3)

0.768

0.707

0.644

0.674

0.713

0.754

0.688

66

68

67

69

6.09

5.55

4.11

6.40

4.90

6.24

7.03

0.0

0.2

0.4

0.6

0.8

Voltage/V

Fig. 4 The performances of DSSCs sensitized by DDC1ꢀDDC4 and CBZ:

(a) IPCE spectra for DSSCs based on DDC1ꢀDDC4 and CBZ with dye

15 baths in CH₃CN (AV): DMF (v/v 3:1) or CHCl₃: EtOH (v/v 1:3); (b) IꢀV

curves for DSSCs based on DDC1ꢀDDC4 and CBZ with dye baths in

AV: DMF (v/v 3:1) or CHCl₃: EtOH (v/v 1:3) upon AM 1.5 solar light

irradiation and IꢀV curves for DSSCs based on DDC1ꢀDDC4 and CBZ

with dye baths in AV: DMF (v/v 3:1) under dark condition.

13.96

10.28

12.28

14.81

DDC1

DDC4

As shown in Table 2, the photovoltaic performance for DSSCS

70 based on DDC1 and DDC4 both exhibited better when CHCl₃:

EtOH (v/v 1:3) were used as the solvents for dye loading

compared with using AV: DMF (v/v 3:1) as the solvents for dye

loading. The reason why the two dyes performed well in CHCl₃:

EtOH (v/v 1:3) was very complicated including that the

⁷⁵diversified interactions among the dyes, solvents, electrolytes and

semiconductor surface could alter the optical and chemical

20

Note: 1) the order of the IPCE spectrum of the new four dyes

based cells DDC4 > DDC1 > DDC2 > DDC3 was consistent

with the order of the dye loading amount in practical devices

(Table 1S); 2) compared to the absorption spectra of sensitized

films, the IPCE spectra were broadened significantly. This

²⁵phenomenon could be ascribed to the scattering effect of the large

particles in the film and the reflective effect of the Pt counter

This journal is © The Royal Society of Chemistry [year]

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Journal of Materials Chemistry A

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DOI: 10.1039/C3TA11748K

properties of dyes and semiconductor. Also, the solvent effect

TiO₂/dye/electrolyte interface. It is related to the charge

recombination rate, generally, a smaller R_recindicates a faster

charge recombination and therefore a larger dark current (Shown

could pose an influence on the adsorbed amount of dyes on TiO₂

films.²⁴Noted that DDC4 based DSSCs fabricated with dye baths

in CHCl₃: EtOH (v/v 1:3) exhibited a very good performance with ³⁰in Fig. 4(b). The radius of the biggest semicircle R_recvalues

5

η enhanced up to 7.03 % with J_scof 14.81 mA cm^ꢀ2, V_ocof 0.69 V

and the FF of 0.69. The good performance of DDC4 sensitized

solar cell suggests that DDC4 is a promising candidate for

application in DSSCs.

decreased in the order of DDC1

>

DDC2

> CBZ

>DDC3≈DDC4. The result appears to be roughly consistent with

the increase of V_ocin the DSSCs based on DDC1–DDC4 and

CBZ. In Bode phase plots, the peak position of the middle

³⁵frequency is related to the electron lifetime and a shift to low

Electrochemical impedance spectroscopy

frequency corresponds to a longer

according to the Fig. 5(b), the order of the corresponding electron

lifetimes DDC1>DDC2≈CBZ>DDC4>DDC3 further

electron lifeꢀtime. Thus,

10

(a)

200

approximately support the order of the V_ocof DSSCs based on

40 these dyes.

Stability of the sensitizers

150

The stability of dyes is an essentially important factor considering

the practical application in DSSCs, because the stability of dyes

will greatly influence the lifetime of the corresponding DSSCs.

⁴⁵To evaluate the photoꢀstability of these dyes, the methodology by

Katoh and coworkers were employed.⁶Sensitizers adsorbed on 8

ꢁm TiO₂films without redox electrolyte were successively

irradiated upon AM 1.5 solar light for 30 min. Fig. 6 shows the

absorption curves of dyes DDC1–DDC4 and CBZ upon light

⁵⁰irradiation of AM 1.5 solar light (30 min). Obviously, sensitizers

based on the new donor are stable enough without any distinct

absorption peak shift and the variations of absorbance in CT

bands before and after irradiation are very small. Nevertheless,

the maximum absorbance variations in CT bands for

⁵⁵benzothiadiazoleꢀincorporated DDC2 and DDC4 before and after

irradiation is smaller than that for oligothiopheneꢀcontaining

DDC1 and DDC3, suggesting that the benzothiadiazoleꢀ

containing DDC2 and DDC4 are more stable than that DDC1 and

DDC3. This phenomenon is well consistent with the similar

⁶⁰situation reported before.¹⁰What’s more, from the comparison of

DDC1 and DDC3, it could be observed that the introduction of

TT instead of thiophene could increase the photoꢀstability of the

corresponding dyes. The comparison of DDC2 and DDC4

showed the same phenomenon. Finally, incorporating

⁶⁵benzothiadiazole unit and TT unit as πꢀspacer, both of which are

helpful to stabilize the oxidized dyes upon light irradiation,

DDC4 displayed the best photoꢀstability with very small

absorption variations in CT band. It is noteworthy that the

percentage of the maximum absorbance variations in CT bands

70 for CBZ based on carbazole donor is much larger than that for

the new donor based DDC1 which has the similar structure (9.0%

for CBZ, 4.1% for DDC1), indicating that the new donor are

much more capable of stabilizing oxidized state of dyes than that

the carbazole donor. The good photoꢀstability of dyes DDC2ꢀ

75 DDC4 further supports this viewpoint.

DDC1

DDC2

DDC3

DDC4

CBZ

100

50

0

100

200

300

400

500

Z^//ohm

60

50

40

30

20

10

0

(b)

DDC1

DDC2

DDC3

DDC4

CBZ

10^-1

10⁰

10¹

10²

10³

10⁴

10⁵

Frequence/Hz

Fig. 5 Impedance spectra of DSSCs based on DDC1ꢀDDC4 and CBZ

with dye baths in AV: DMF (v/v 3:1) measure at bias ꢀ0.70 V in the dark.

15 (a) Nyquist plots; and (b) bode phase plots.

To further clarify the dyes effect on the V_ocin the DSSCs

sensitized by these dyes, electrochemical impedance

spectroscopy (EIS) of the DSSCs made with these sensitizers was

performed. The Nyquist plots of the DSSCs based on the seven

20 dyes under a forward bias of ꢀ0.70V in the dark with a frequency

range of 0.1 Hz to 100 kHz are shown in Fig. 5(a). The Bode

phase was also shown in Fig. 5(b). Two semicircles were

observed in the Nyquist plots. The smaller semicircle at high

frequency is assigned to the redox chargeꢀtransfer response at the

25 Pt/electrolyte interface. The large one at the intermediate

frequency represents the electronꢀtransfer impedance at the

To investigate the temperature effects on the physics of the

dyes, absorption curves of dyes on TiO₂films which were kept

for 30 min at different temperatures (25^oC, 40^oC, 50^oC and 60^oC)

were measured. As shown in Fig. 4S, dyes on TiO₂films at these

80 four temperatures were fairly thermoꢀstable with the percentage

of the maximum absorbance variations in CT bands no more than

1.5 % before and after heating.

6

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DOI: 10.1039/C3TA11748K

Conclusions

2.5

DDC2

1.40

1.36

1.32

In summary, four dyes (DDC1ꢀDDC4) based on the new donor

with two fused carbazole units, containing benzothiadiazole (or

thiophene) and TT (or thiophene) as πꢀspacer, 2ꢀcyanoacetic acid

as acceptor, were successfully synthesized and demonstrated as

efficient sensitizers for DSSCs. The results showed that the

synthesis and purification of this new donor with two fused

carbazole units were simple. The large and effective conjugation

of the new donor contributed to a high molar extinction

¹⁰coefficient of the corresponding dyes which is in favour of the

dyes harvesting more photoelectrons. The comparison between

DDC1 and CBZ, no matter from the J_scor from the V_oc, both

suggested that the donor has some advantages over carbazole

donor for the corresponding DSSCs. Derived from the broad

¹⁵absorption spectrum and efficient electron injection into the

conduction band of TiO₂, DDC4 with the large J_sc, exhibited the

best performance overall efficiency of 7.03 % among these dyes

(J_scof 14.81 mA cm^ꢀ2, V_ocof 0.69 V and FF of 0.69). As to the

photoꢀstability of these dyes, the new donor facilitated the

²⁰corresponding dyes to stabilize the oxidized state once upon the

light irradiation. To the πꢀspacer, the introduction of

benzothiadiazole unit was once again proved to increase the

photoꢀstability of the corresponding dyes in this system. Most

importantly, the influence of the introduction of TT unit in πꢀ

²⁵spacer on the photoꢀstability of the corresponding dyes has firstly

been examined and in this system, the introduction of TT could

strikingly reinforce the photoꢀstability of the corresponding dyes.

2.0

1.5

1.0

0.5

0.0

5

500

510

520

530

Wavelength/nm

0 min

5

15

30

ꢀ

A_max=0.037,

ꢀ

A_max/A=2.7%

500

400

600

700

Wavelength/nm

30

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

DDC3

2.45

2.40

2.35

2.30

0 min

5

15

30

450

460

470

ꢀ

A_max=0.056,

Wavelength/nm

ꢀ

A_max/A=2.3%

400

500

600

700

2.0

DDC1

Wavelength/nm

1.38

2.25

1.36

DDC4

1.6

3

2

1

0

2.20

2.15

2.10

1.34

1.2

1.32

0 min

450

460

470

0.8

0.4

0.0

5

Wavelength/nm

0 min

5

15

30

500

510

520

530

15

Wavelength/nm

30

ꢀ

A_max=0.057,

A_max/A=4.1%

ꢀ

A_max=0.031,

A_max/A=1.4%

ꢀ

400

500

600

700

Wavelength/nm

400

500

600

700

Wavelength/nm

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Journal of Materials Chemistry A

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DOI: 10.1039/C3TA11748K

solution. The supporting electrolyte was 0.1M TBAPF₆in AV.

The scan rate was 100 mV s^ꢀ1. The potential of the reference

electrode was calibrated by ferrocene and all the potential data in

⁴⁵this paper are relative to normal hydrogen electrode (NHE). The

electrochemical impedance spectroscopy (EIS) measurements of

all the DSSCs were carried out under dark using a Zahner IM6e

CBZ

3.0

2.5

2.0

1.5

1.0

0.5

0.0

2.8

2.7

2.6

2.5

Impedance Analyzer (ZAHNERꢀElektrik GmbH

& CoKG,

0 min

5

15

30

Kronach, Germany). The spectra were scanned in a frequency

⁵⁰range of 0.1ꢀ10⁵Hz with applied potential set at open circuit of

the corresponding DSSCs. The alternate current amplitude was

set at 10 mV.

425 430 435 440 445 450

Wavelength/nm

ꢀ

A

=0.25,

max

/A=9.0%

Measurements:

Photovoltaic measurements were performed by an AM 1.5 solar

55 simulator A 300 W xenon lamp (Model No. 91160, Oriel) was

used as the light source. The work curves of the cell were

obtained under the following conditions: 1) the power of the

simulated light was calibrated to 100 mW cm^ꢀ2by a reference Si

solar cell; 2) Cell active area was tested with a mask of 0.25 cm^ꢀ2

60 was used to cover around the cell active area. The photocurrent

action spectra were obtained through an IPCE test system with a

model SR830 DSP Lock. A 7IL/PX150 xenon lamp was used as

the light source and the IPCE spectra were recorded on a

7ISW301 spectrometer.

400

500

600

700

Wavelength/nm

Fig. 6 Absorption curves of dyes DDC1ꢀDDC4 and CBZ on 8 ꢁm TiO₂

films upon light irradiation of AM 1.5 solar light (30 min) at ambient

temperature; ꢂA_max: the maximum absorbance variations in CT bands

before and after irradiation (30 min); A: the maximum absorbance in CT

bands before irradiation; ꢂA_max/A: the percentage of the maximum

absorbance variations in CT bands upon light irradiation (30 min).

5

Experimental section

Materials and Reagents:

65 Fabrication of DSSCs

10 Optically transparent FTO conducting glass (Fꢀdoped SnO,

transmission > 90% in the visible, sheet resistance 15ꢃ square^ꢀ1,

Geao Science and Educational Co. Ltd. of China) was washed

with detergent, redistilled water, ethanol, choloroform and

acetone successively under supersonication for 30 min each

¹⁵before use. Titania pastes of TiꢀNanoxide T/SP and TiꢀNanoxide

300 were obtained from Geao Science and Educational Co. Ltd.

of China. Reagent grade LiI, I₂(purity > 99.999%), TiCl₄,

acetonitrile (AV), 1,2ꢀdimethylꢀ3ꢀpropylimidazolium iodide

To a wellꢀcleaned FTO conducting glass, thin TiO₂films (12 ꢁm)

consisting of a transparent layer (TiꢀNanoxide T/SP) and a 4 ꢁm

scattering layer (TiꢀNanoxide 300 ) were coated using a screen

printing technique ¹⁸, followed by calcinated at 500^oC under an

⁷⁰air flow in muffle for 30 min. After cooling down to the ambient

temperature, the obtained films were immersed in 0.05 M

o

aqueous TiCl₄solution for 30 min at 75 C, then washed with

redistilled water and anhydrous ethanol consecutively, followed

o

by annealed at 450 C for 30 min. After cooling down, the

(DMPII),

Tetraꢀnꢀbutylammonium

hexafluorophosphate

75 obtained films were immersed into the dye solution (0.1 M in the

required solvents) for 12 h. After dyes loaded on the films, the

working electrodes were rinsed with chloroform and anhydrous

ethanol respectively. The Ptꢀcounter electrodes were made by

depositing ~100 nm thick Pt on the conductive surface and two

80 holes (0.8ꢀmm diameter) were drilled by Drillꢀpress. The working

and Ptꢀcounter electrodes were assemble into a sandwich type

solar cell and sealed with a hotꢀmelt gasket of 25ꢁm thickness.

The electrolyte was injected into the cell from the holes and the

fabrication of the solar cells was finally finished by sealing the

85 holes using a UVꢀmelt gum. The electrolytes was composed of

0.1 M lithium iodide, 0.6 M 1,2ꢀdimethylꢀ3ꢀ propylimidazolium

iodide (DMPII), 0.05 M I₂, 0.5 M 4ꢀtertbutylpyridine (4ꢀTBP) in

acetonitrile (AV) as a liquid electrolyte.

²⁰(TBAPF₆), 4ꢀtertꢀbutylpyridine (TBP), chloroform, N, Nꢀ

dimethylformamide (DMF), ethanol (C₂H₅OH), 2.4 M BuLi

solution in hexane and the reaction catalyst Pd(PPh₃)₄were used

as received without further purification from commercial sources.

Acetonitrile with HPLC purity was purchased from SK

²⁵Chemicals. THF was preꢀdried over sodium and distilled under

argon atmosphere from sodium benzophenone ketyl immediately

prior to use. All other chemicals were used as received without

further purification.

Instruments and Characterization

30 The new compounds were characterized by ¹H NMR (400 MHz),

¹³C NMR (100 MHz) and Mass. NMR spectra were obtained on a

Brucker AM 400 spectrometer and Mass spectra were recorded

on an ESI mass spectrometer. Elemental analyses were measured

by German elementar vario EL III. The UVꢀVis absorption

35 spectra of the dyes solutions and dyeꢀloaded films were measured

Synthesis:

90

5'-(5,11-dihexyl-6,12-diphenyl-5,11-dihydroindolo[3,2-

b]carbazol-2-yl)-[2,2'-bithiophene]-5-carbaldehyde (DDB1)

In a dry flask, 1.6 M nꢀBuLi in hexane (2.4 ml, 3.85 mmol) was

added dropwise to a solution of compound 3 (1.0 g, 2.57 mmol)

with

a Varian Cary 500 spectrophotometer. The cyclic

voltammograms of dyes were obtained from a Versastat II

electrochemical workstation (Princeton applied research). The

conventional three electrode configuration was employed with a

40 dyeꢀloaded film as working electrode, a Pt wire counter electrode,

and a regular calomel reference electrode in saturated KCl

o

in THF at ꢀ78 C under a N₂atmosphere. After stirring for 1.5 h

95 at this temperature, triisopropyl borate (1.5 ml, 6.43 mmol) was

added dropwise and the mixture was allowed to warm to r.t

followed by stirring for 2 h. Then compound B1 (701 mg, 2.57

8

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mmol), K₂CO₃(1.38 g, 10 mmol), Pd(PPh₃)₄(50 mg, 0.05

44.51, 44.38, 31.36, 31.35, 28.72, 28.65, 26.27, 26.26, 22.47,

mmol), water (5mL), and THF (15mL) was added and the 60 22.45, 13.91. HRMS (m/z): [M + H]⁺calcd for C₅₃H₄₈N₂OS₃,

mixture was warmed to reflux after the flask was recharged with

N₂. After refluxing for 4h, the mixture was allowed to cool down

to r.t. and then washed with water. The organic layer was dried

over anhydrous Na₂SO₄and the solvent was removed by using a

824.2929; found, 824.2927.

5-(7-(5,11-dihexyl-6,12-diphenyl-5,11-dihydroindolo[3,2-

b]carbazol-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thieno[3,2-

b]thiophene-2-carbaldehyde (DDB4)

5

rotary evaporator. The crude materials was purified by silica gel 65 ¹H NMR (400 MHz, CDCl₃), δ: 10.00 (s, 1H), 8.50 (s, 1H), 8.11

column chromatography using a petroleum and dichloromethane

– 8.06 (m, 1H), 7.99 (s, 1H), 7.93 (s, 1H), 7.75 (s, 2H), 7.69 (s,

2H), 7.67 – 7.62 (m, 5H), 7.57 (t, J = 7.2 Hz, 1H), 7.48 – 7.39 (m,

2H), 7.37 – 7.32 (m, 1H), 7.28 (d, J = 6.6 Hz, 1H), 7.22 (d, J =

1.6 Hz, 1H), 6.84 (t, J = 7.4 Hz, 1H), 6.54 (d, J = 7.9 Hz, 1H),

mixture as the eluent to obtain the desired product as an orange

1

¹⁰solid 1.54 g, 20%. H NMR (400 MHz, DMSOꢀd₆), δ: 9.90 (s,

1H), 8.03 (t, J = 4.7 Hz, 1H), 7.85 – 7.78 (m, 3H), 7.76 – 7.68 (m,

8H), 7.53 (dd, J = 6.7, 3.0 Hz, 1H), 7.51 – 7.43 (m, 3H), 7.37 – ⁷⁰3.89 – 3.80 (m, 4H), 1.56 – 1.48 (m, 4H), 1.24 – 1.19 (m, 4H),

7.28 (m, 1H), 7.09 (t, J = 4.7 Hz, 1H), 6.78 (t, J = 7.6 Hz, 1H),

6.54 (d, J = 1.7 Hz, 1H), 6.37 (d, J = 7.8 Hz, 1H), 3.96 – 3.87 (m,

¹⁵2H), 3.85 – 3.76 (m, 2H), 1.53 – 1.37 (m, 4H), 1.19 (dd, J = 14.6,

7.3 Hz, 4H), 1.12 – 1.04 (m, 4H), 0.87 – 0.80 (m, 10H). ¹³C NMR

1.13 (d, J = 7.3 Hz, 4H), 0.86 (q, J = 7.2 Hz, 10H). ¹³C NMR

(126 MHz, CDCl₃), δ: 183.02, 153.95, 152.47, 148.09, 146.64,

145.11, 142.73, 142.44, 138.82, 138.77, 138.56, 135.56, 132.65,

132.55, 130.49, 130.45, 129.03, 128.91, 128.86, 128.16, 128.02,

(126 MHz, CDCl₃), δ: 183.00, 149.21, 148.66, 143.16, 143.09, ⁷⁵127.09, 126.58, 126.29, 126.24, 125.35, 123.80, 123.64, 123.40,

141.50, 139.40, 139.20, 138.19, 133.61, 133.36, 133.09, 131.14,

129.89, 129.65, 129.05, 128.91, 127.88, 126.15, 124.14, 123.93,

²⁰123.86, 123.75, 123.70, 123.53, 123.13, 123.03, 122.69, 120.49,

118.98, 118.72, 118.67, 109.21, 108.92, 45.24, 45.11, 32.09,

29.46, 29.40, 27.00, 23.20, 14.65. HRMS (m/z): [M + H]⁺calcd

for C₅₁H₄₉N₂OS₂, 769.3286; found, 769.3287.

122.84, 122.83, 122.55, 122.37, 119.74, 118.26, 118.03, 117.94,

108.24, 108.20, 44.55, 44.39, 31.37, 31.35, 29.59, 28.72, 28.63,

26.26, 22.45, 22.44, 13.90, 13.88. HRMS (m/z): [M + H]⁺calcd

for C₅₅H₄₉N₄OS₃, 877.3069; found, 877.3063.

80

5'-(9-hexyl-9H-carbazol-3-yl)-[2,2'-bithiophene]-5-

carbaldehyde (CBA)

Compound DDB2ꢀDDB5 were synthesized by the same

25 procedure as described for C1

¹H NMR (500 MHz, CDCl₃), δ: 9.81 (s, 1 H), 8.27 (s, 1 H), 8.09

(d, J =7.7 Hz, 1 H), 7.67 (dd, J =8.5, 1.5 Hz, 1 H), 7.63 (d, 1 H, J

= 3.9 Hz), 7.44 (dd, J =9.3, 5.7 Hz, 1 H), 7.37 (d, J =2.6 Hz, 1 H),

5-(7-(5,11-dihexyl-6,12-diphenyl-5,11-dihydroindolo[3,2-

b]carbazol-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thiophene-2-

carbaldehyde (DDB2)

⁸⁵7.35 (d, J =3.0 Hz, 1 H), 7.32 (d, J =3.8 Hz, 1 H), 7.25 (d, J =3.8

Hz, 1 H), 7.22 (d, J =4.0 Hz, 2 H), 4.26 (t, J =7.2 Hz, 2 H), 1.83

(dt, J =15.1, 7.5 Hz, 2 H), 1.34 (ddd, J =10.4, 7.7, 4.6 Hz, 2 H),

1.26 – 1.17 (4 H, m), 0.84 – 0.78 (3 H, m). ¹³C NMR (126 MHz,

CDCl₃), δ: 182.24, 147.89, 147.61, 141.02, 140.89, 140.33,

¹H NMR (400 MHz, CDCl₃), δ: 9.99 (s, 1H), 8.22 (d, J = 4.0 Hz,

30 1H), 8.08 (dd, J = 8.6, 1.7 Hz, 1H), 8.00 (d, J = 7.5 Hz, 1H), 7.86

(d, J = 4.0 Hz, 1H), 7.77 – 7.73 (m, 2H), 7.71 (dd, J = 6.5, 3.0

Hz, 2H), 7.67 – 7.61 (m, 5H), 7.57 (d, J = 7.4 Hz, 1H), 7.45 (d, J ⁹⁰137.33, 133.64, 127.19, 126.11, 124.48, 123.87, 123.44, 123.28,

= 7.6 Hz, 1H), 7.41 (d, J = 8.6 Hz, 1H), 7.34 (s, 1H), 7.29 (s, 1H),

7.23 (d, J = 1.6 Hz, 1H), 6.83 (s, 1H), 6.54 (d, J = 7.8 Hz, 1H),

³⁵3.88 – 3.80 (m, 4H), 1.23 (dd, J = 14.6, 7.4 Hz, 4H), 1.18 – 1.09

(m, 4H), 0.94 – 0.82 (m, 10H). ¹³C NMR (100 MHz, CDCl₃), δ:

122.88, 122.59, 120.45, 119.19, 117.72, 109.04, 108.92, 43.15,

31.46, 28.85, 26.85, 22.43, 13.88. HRMS (m/z): [M + H]⁺calcd

for C₂₇H₂₆NOS₂, 444.1456; found, 444.1459.

(E)-2-cyano-3-(5'-(5,11-dihexyl-6,12-diphenyl-5,11-

183.06, 154.01, 152.70, 149.40, 142.98, 142.84, 142.47, 138.86, 95 dihydroindolo[3,2-b]carbazol-2-yl)-[2,2'-bithiophen]-5-

138.61, 136.94, 136.25, 132.68, 132.57, 130.54, 130.52, 129.17,

129.03, 128.28, 128.17, 127.76, 127.51, 126.72, 126.37, 126.28,

⁴⁰125.46, 123.76, 123.49, 123.28, 122.88, 122.61, 122.46, 118.33,

118.12, 118.01, 108.38, 108.29, 44.64, 44.47, 31.47, 28.82,

yl)acrylic acid (DDC1)

A mixture of DDB1 (384mg, 0.5mmol), 2ꢀcyanoacetic acid

(160mg, 2 mmol ) and 2 drops of piperidine in 20ml THF was

refluxed for 4h under N₂atmosphere. After cooled to r.t. , the

28.74, 26.37, 22.57, 14.04. HRMS (m/z): [M + H]⁺calcd for 100 solvent was removed in vacuo. The residual was dissolved in 200

C₅₃H₄₉N₄OS₂, 821.3348; found, 821.3344.

5-(5-(5,11-dihexyl-6,12-diphenyl-5,11-dihydroindolo[3,2-

45 b]carbazol-2-yl)thiophen-2-yl)thieno[3,2-b]thiophene-2-

carbaldehyde (DDB3)

ml dichloromethane and washed with redistilled water for 3

times. The combined organic layer was dried over anhydrous

MgSO₄and then filtered. The filtrate was concentrated using

rotary evaporator. The crude product was chromatographed on

¹H NMR (400 MHz, CDCl₃), δ: 9.95 (s, 1H), 7.89 (s, 1H), 7.74 105 silica gel and firstly using pure dichloromethane as the eluent to

(s, 5H), 7.69 (dd, J = 6.7, 3.1 Hz, 2H), 7.65 (d, J = 2.3 Hz, 3H),

7.61 – 7.57 (m, 1H), 7.35 (s, 2H), 7.27 (s, 2H), 7.21 (d, J = 3.7

50 Hz, 1H), 6.87 (d, J = 3.8 Hz, 1H), 6.83 (dd, J = 9.7, 5.5 Hz, 1H),

6.71 (d, J = 1.5 Hz, 1H), 6.53 (d, J = 7.7 Hz, 1H), 3.88 (dd, J =

exclude the impurities and then using THF and methanol mixture

(1:1) as the eluent to obtain the pure product as a red solid (382

mg, 90%). H NMR (400 MHz, DMSOꢀd₆), δ: 8.26 (d, J = 1.2

1

Hz, 1H), 7.88 – 7.82 (m, 1H), 7.81 – 7.75 (m, 3H), 7.73 – 7.64

16.1, 7.0 Hz, 2H), 3.80 (dt, J = 9.1, 6.5 Hz, 2H), 1.55 – 1.48 (m, ¹¹⁰(m, 8H), 7.43 (t, J = 7.0 Hz, 4H), 7.32 (t, J = 7.7 Hz, 1H), 7.05 (d,

4H), 1.22 (s, 4H), 1.16 – 1.09 (m, 4H), 0.86 (t, J = 7.2 Hz, 10H).

¹³C NMR (126 MHz, CDCl₃), δ: 182.74, 147.74, 146.78, 146.40,

55 144.12, 142.44, 142.31, 138.70, 138.48, 137.07, 133.45, 132.65,

132.36, 130.42, 129.13, 128.91, 128.86, 128.29, 128.17, 126.36,

J = 3.8 Hz, 1H), 6.78 (t, J = 7.6 Hz, 1H), 6.53 (d, J = 1.3 Hz, 1H),

6.36 (d, J = 8.0 Hz, 1H), 3.95 – 3.84 (m, 2H), 3.81 – 3.71 (m,

2H), 1.50 – 1.36 (m, 4H), 1.16 (dd, J = 9.2, 5.2 Hz, 4H), 1.11 –

1.02 (m, 4H), 0.88 – 0.79 (m, 10H). ¹³C NMR (126 MHz, THFꢀ

125.41, 123.41, 123.29, 123.02, 122.96, 122.81, 122.40, 122.31, 115 d₈), δ: 141.43, 141.22, 137.67, 131.92, 131.42, 131.12, 129.36,

121.82, 119.68, 118.24, 117.98, 117.94, 114.71, 108.48, 108.18,

129.21, 128.03, 127.63, 127.30, 126.80, 125.50, 123.96, 122.29,

Journal Name, [year], [vol], 00–00 | 9

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Journal of Materials Chemistry A

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DOI: 10.1039/C3TA11748K

122.25, 121.90, 121.77, 121.49, 121.18, 121.03, 120.66, 118.36,

942.2970; found, 942.2983. Anal. Calcd for C₅₈H₄₉N₅O₂S₃: C,

117.05, 116.97, 116.46, 107.23, 106.87, 42.96, 42.86, 30.24, 60 73.78; H, 5.23; N, 7.42. Found: C, 73.53; H, 5.47; N, 7.14.

30.14, 27.51, 27.37, 25.00, 23.63, 21.26, 12.15. HRMS (m/z): [M

ꢀ H]⁺calcd for C₅₄H₄₈N₃O₂S₂, 834.3188; found, 834.3195. Anal.

Calcd for C₅₄H₄₉N₃O₂S₂: C, 77.57; H, 5.91; N, 5.03. Found: C,

77.31; H, 6.01; N, 4.78.

(E)-2-cyano-3-(5'-(9-hexyl-9H-carbazol-3-yl)-[2,2'-

bithiophen]-5-yl)acrylic acid (CBZ)

5

¹H NMR (400 MHz, DMSOꢀd₆), δ: 8.58 (s, 1H), 8.50 (s, 1H),

8.29 (d, J = 7.8 Hz, 1H), 8.00 (d, J = 4.0 Hz, 1H), 7.85 (d, J = 8.2

⁶⁵Hz, 1H), 7.72 – 7.60 (m, 5H), 7.49 (t, J = 7.6 Hz, 1H), 7.24 (t, J =

7.5 Hz, 1H), 4.42 (t, J = 6.9 Hz, 2H), 1.82 – 1.73 (m, 2H), 1.25

(dt, J = 12.3, 6.7 Hz, 6H), 0.81 (t, J = 6.9 Hz, 3H). ¹³C NMR (126

MHz, DMSOꢀd₆), δ: 163.68, 147.29, 146.16, 146.09, 141.45,

140.57, 140.00, 133.47, 132.59, 128.35, 126.22, 124.33, 123.87,

(E)-2-cyano-3-(5-(7-(5,11-dihexyl-6,12-diphenyl-5,11-

dihydroindolo[3,2-b]carbazol-2-yl)benzo[c][1,2,5]thiadiazol-

4-yl)thiophen-2-yl)acrylic acid (DDC2)

10 ¹H NMR (400 MHz, DMSOꢀd₆), δ: 8.57 (s, 1H), 8.30 (t, J = 6.0

Hz, 2H), 8.12 (d, J = 4.0 Hz, 1H), 8.06 – 8.01 (m, 1H), 7.70 (d, J

= 12.6 Hz, 9H), 7.65 (dd, J = 8.1, 3.5 Hz, 1H), 7.61 – 7.54 (m, ⁷⁰123.82, 123.62, 122.69, 122.01, 120.76, 119.15, 117.54, 116.68,

2H), 7.43 (s, 1H), 7.31 (d, J = 7.5 Hz, 2H), 6.78 (t, J = 7.7 Hz,

1H), 6.37 (d, J = 7.9 Hz, 1H), 3.83 (d, J = 5.1 Hz, 4H), 1.50 –

¹⁵1.38 (m, 4H), 1.18 (dd, J = 16.5, 7.4 Hz, 4H), 1.09 (ddd, J = 12.3,

8.5, 5.9 Hz, 4H), 0.83 (dd, J = 15.9, 7.3 Hz, 10H). ¹³C NMR (126

MHz, THFꢀd₈), δ: 161.88, 152.66, 151.49, 147.46, 144.30,

141.79, 141.50, 137.84, 136.79, 135.19, 134.70, 131.47, 131.41,

129.41, 127.97, 127.69, 126.98, 126.86, 126.50, 126.29, 125.56,

²⁰125.24, 124.99, 123.91, 122.65, 122.23, 121.84, 121.68, 121.47,

121.03, 117.15, 117.11, 116.50, 114.49, 106.92, 43.11, 42.94,

30.26, 27.50, 27.41, 25.05, 23.63, 21.29, 12.17. HRMS (m/z): [M

ꢀ H]⁺calcd for C₅₆H₄₈N₅O₂S₂, 886.3249; found, 886.3251. Anal.

Calcd for C₅₆H₄₉N₅O₂S₂: C, 75.73; H, 5.56; N, 7.89. Found: C,

25 75.61; H, 5.90; N, 7.76.

Compound DDC3ꢀDDC5 were synthesized by the same

procedures as described above for DDC1 using corresponding

carbaldehyde (DDB3–DDB4)

(E)-2-cyano-3-(5-(5-(5,11-dihexyl-6,12-diphenyl-5,11-

³⁰dihydroindolo[3,2-b]carbazol-2-yl)thiophen-2-yl)thieno[3,2-

b]thiophen-2-yl)acrylic acid (DDC3)

109.87, 109.52, 42.37, 30.94, 28.47, 26.10, 21.98, 13.79. HRMS

(m/z): [M ꢀ H]⁺calcd for C₃₀H₂₅N₂O₂S₂, 509.1357; found,

509.1365. Anal. Calcd for C₃₀H₂₆N₂O₂S₂: C, 70.56; H, 5.13; N,

5.49. Found: C, 70.79; H, 5.17; N, 5.24.

75 Acknowledgements

This work was supported by NSFC/China (91233207) & National

Basic Research 973 Program.

Notes and references

^aKey Laboratory for Advanced Materials and Institute of Fine

80 Chemicals, East China University of Science & Technology, 130 Meilong

Road, Shanghai, 200237, PR China. Fax: 8621 64252756; Tel: 8621

64252756; Eꢀmail: tianhe@ecust.edu.cn

† Electronic Supplementary Information (ESI) available: (1) The frontier

orbital plots of the HOMO and LUMO of these dyes; (2) Cyclic

85 voltammograms of dyes attached on 8 ꢁm TiO₂films; (3) Crystal

structure of DDC; (4) Absorption curves of dyes on TiO₂films which

were kept for 30 min at different temperatures (25^oC, 40^oC, 50^oC and

60^oC); (5) Adsorbed amount of DDC1ꢀDDC4 and CBZ under the

following two conditions: The mixture solvents CH₃CN: DMF (v:v= 3:1)

90 were used as the solvents for dyeꢀloading; the TiO₂films are consisted of

8 ꢄm (T/SP); (6) Crystallography of DDC; (7) Synthetic procedure of

intermediate DDC-Br, 4-7 and B3-B4. See DOI: 10.1039/b000000x/

¹H NMR (400 MHz, DMSOꢀd₆), δ: 8.27 (s, 1H), 8.08 (s, 1H),

7.91 (s, 1H), 7.81 (t, J = 7.5 Hz, 2H), 7.77 – 7.67 (m, 9H), 7.45

(dd, J = 8.7, 2.9 Hz, 2H), 7.38 (d, J = 3.7 Hz, 1H), 7.33 (s, 1H),

³⁵7.08 (d, J = 3.8 Hz, 1H), 6.78 (s, 1H), 6.51 (d, J = 1.4 Hz, 1H),

6.37 (d, J = 8.1 Hz, 1H), 3.97 – 3.87 (m, 2H), 3.84 – 3.73 (m,

2H), 1.51 – 1.39 (m, 4H), 1.21 – 1.13 (m, 4H), 1.07 (dd, J = 9.6,

5.0 Hz, 4H), 0.88 – 0.80 (m, 10H). ¹³C NMR (126 MHz, THFꢀd₈),

δ: 145.82, 145.06, 143.69, 141.40, 141.04, 137.65, 136.92,

40 136.36, 132.77, 131.35, 131.06, 129.34, 129.21, 127.94, 127.60,

127.14, 126.76, 124.64, 123.96, 122.42, 122.16, 121.75, 121.55,

121.18, 121.02, 120.42, 118.21, 116.97, 116.92, 116.45, 113.42,

107.15, 106.86, 42.86, 30.24, 30.08, 28.44, 27.47, 27.34, 25.01,

24.96, 21.26, 12.17, 12.13. HRMS (m/z): [M ꢀ H]⁺calcd for

45 C₅₆H₄₈N₃O₂S₃, 890.2909; found, 890.2912. Anal. Calcd for

C₅₆H₄₉N₃O₂S₃: C, 75.39; H, 4.71; N, 5.54. Found: C, 75.54; H,

4.78; N, 5.39.

1

2

(a) B. O’Regan and M. Grätzel, Nature, 1991, 353, 737; (b) M.

Grätzel, Nature, 2000, 35, 3523.

95

100

105

110

115

120

(a) M. K. Nazeeruddin, A. Kay, I. Rodicio, R. HumphryꢀBaker, E.

Müller, P. Liska, N. Vlachopoulos and M. Grätzel, J. Am. Chem.

Soc., 1993, 115, 6382; (b) M. K. Nazeeruddin, P. Péchy, T.

Renouard, S. M. Zakeeruddin, R. HumphryꢀBaker, P. Comte, P.

Liska, L. Cevey, E. Costa, V. Shklover, L. Spiccia, G. B. Deacon,

C. A. Bignozzi and M. Grätzel, J. Am. Chem. Soc., 2001, 123, 1613;

(c) F. Gao, Y. Wang, D. Shi, J. Zhang, M. Wang, X. Jing, R.

HumphryꢀBaker, P. Wang, S. M. Zakeeruddin and M. Grätzel, J.

Am. Chem. Soc., 2008, 130, 10720; (d) C.ꢀY. Chen, M. Wang, J.ꢀY.

Li, N. Pootrakulchote, L. Albabaei, C.ꢀH. Ngocꢀle, J.ꢀD. Decoppet,

J.ꢀH. Tsai, C. Grätzel, C.ꢀG. Wu, S. M. Zakeeruddin and M. Grätzel,

ACS Nano, 2009, 3, 3103; (e) F. Sauvage, J.ꢀD. Decoppet, M.

Zhang, S. M. Zakeeruddin, P. Comte, M. Nazeeruddin, P. Wang and

M. Grätzel, J. Am. Chem. Soc., 2011, 133, 9304.

(E)-2-cyano-3-(5-(5-(5,11-dihexyl-6,12-diphenyl-5,11-

dihydroindolo[3,2-b]carbazol-2-yl)thiophen-2-yl)thieno[3,2-

50 b]thiophen-2-yl)acrylic acid (DDC4)

3

4

(a) A. Mishra, M. K. Fischer and P. Bäuerle, Angew. Chem., Int. Ed.,

2009, 48, 2474; (b) W. Q. Li, Y. Z. Wu, X. Li, Y. S. Xie and W. H.

Zhu, Energy Environ. Sci., 2011, 4, 1830.

¹H NMR (400 MHz, DMSOꢀd₆), δ: 8.59 (s, 1H), 8.18 (d, J = 7.6

Hz, 2H), 8.10 (s, 1H), 8.04 (dd, J = 7.0, 2.9 Hz, 1H), 7.73 (d, J =

3.2 Hz, 9H), 7.67 – 7.62 (m, 1H), 7.60 (d, J = 7.4 Hz, 2H), 7.44

(d, J = 8.1 Hz, 1H), 7.31 (s, 2H), 6.78 (t, J = 7.5 Hz, 1H), 6.38 (d,

55 J = 7.9 Hz, 1H), 3.92 – 3.77 (m, 4H), 1.45 (m, 4H), 1.21 – 1.14

(m, 4H), 1.09 (d, J = 7.2 Hz, 4H), 0.88 – 0.79 (m, 10H). ¹³C

NMR (126 MHz, DMSOꢀd₆), δ: not sufficiently soluble to obtain

a spectrum. HRMS (m/z): [M ꢀ H]⁺calcd for C₅₈H₄₈N₅O₂S₃,

(a) H. N. Tian, X. C. Yang, R. K. Chen, Y. Z. Pan, L. Li, A. Hagfeldt

and L. C. Sun, Chem. Commun., 2007, 43, 3741; (b) W. J. Wu, J. B.

Yang, J. L. Hua, J. Tang, L. Zhang, Y. T. Long and H. Tian, J.

Mater. Chem., 2010, 20, 1772; (c) Y. Ooyama and Y. Harima, Eur.

J. Org. Chem., 2009, 18, 2903; (d) H. N. Tian, X. C. Yang, R. K.

Chen, Y. Z. Pan, L. Li, A. Hagfeldt and L. C. Sun, Chem. Commun.,

2007, 3741; (e) Z. S. Wang, Y. Cui, Y. Danꢀoh, C. Kasada, A.

Shinpo and K. Hara, J. Phys. Chem. C, 2007, 111, 7224; (f) K. Hara,

Z. S. Wang, T. Sato, A. Furube, R. Katoh, H. Sugihara, Y. Danꢀoh,

10 | Journal Name, [year], [vol], 00–00

Journal of Materials Chemistry A

Page 12 of 12

View Article Online

DOI: 10.1039/C3TA11748K

C. Kasada, A. Shinpo and S. Suga, J. Phys. Chem. B, 2005, 109,

15476; (g) Z. S. Wang, Y. Cui, K. Hara, Y. Danꢀoh, C. Kasada and

A. Shinpo, Adv. Mater., 2007, 19, 1138.

5

(a) S.ꢀY. Qu and H. Tian, Chem. Commun., 2012, 48, 3039; (b) K.

Hara, K. Sayama, Y. Ohga, A. Shinpo, S. Suga and H. Arakawa,

Chem. Commun., 2001, 37, 569; (c) Z.ꢀS. Wang, Y. Cui, K. Hara,

Y. Danꢀho, C. Kasada and A. Shinpo, Adv. Mater., 2007, 19, 1138;

(d) N. Cocherel, P. Leriche, E. Ripaud, N. GallegoꢀPlanas, P. Frere

and J. Roncali, New J. Chem., 2009, 33, 801; (e) J. Mao, N. He, Z.

Ning, Q. Zhang, F. Guo, L. Chen, W. Wu, J. L. Hua and H. Tian,

Angew. Chem. Int. Ed. 2012, 51, 9873.

5

10

15

20

6

7

R. Katoh, A. Furube, S. Mori, M. Miyashita, K. Sunahara, N.

Koumura and K. Hara, Energy Environ. Sci., 2009, 2, 542.

(a) M. J. Cho, S. S. Park, J. H. Kim and D. H. Choi, Synth. Met.,

2010, 160, 1754; (b) D. Cao, J. Peng, Y. P. Hong, X. M. Fang, L. Y.

Wang and H. Meier, Org. Lett., 2011, 13, 1610.

K. Do, D. Kim, N. Cho, S. Paek, K. Song and J. Ko, Org. Lett., 2012,

14, 222.

(a) P. Sonar, E. L. Williams, S. P. Singh and A. Dodabalapur, J.

Mater. Chem., 2011, 21, 1053; (b) S. Y. Cai, X. H. Hu, Z. Y. Zhang,

J. H. Su, X. Li, A. Islam, L. Y. Han and H. Tian, J. Mater. Chem. A,

2013, 1, 4763.

8

9

10 Y. Z. Wu, M. Marszalek, S. M. Zakeeruddin, Q. Zhang, H. Tian, M.

Grätzel and W. H. Zhu, Energy Environ. Sci., 2012, 5, 8261;

²⁵11 (a) X. B. Cheng, M. Liang, S. Y. Sun, Y. B. Shi, Z. J. Ma, Z. Sun and

S. Xue, Tetrahedron, 2012, 68, 5375; (b) X. L. Hao, M. Liang, X. B.

Cheng, X. Q. Pian, Z. Sun and S. Xue, Org. Lett., 2011, 13, 5424; (c)

N. Metri, X. Sallenave, C. Plesse, L. Beouch, P. –H. Aubert, F.

Goubard, C. Chevrot and G. Sini, J. Phys. Chem. C, 2012, 116,

30

3765.

12 (a) M. L. Deb, B. Baruah and P. J. Bhuyan, Synthesis, 2008, 2, 286;

(b) S. P. Mishra, A. K. Palai, A. Kumar, R. Srivastava, M. N.

Kamalasanan and M. Patri, Macromol. Chem. Phys., 2010, 211,

1890.

³⁵13 (a) J. S. Song, F. Zhang, C. H. Li, W. L. Liu, B. S. Li, Y. Huang and

Z. S. Bo, J. Phys. Chem. C, 2009, 113, 13391; (b) S. Hwang, J. H.

Lee, C. Park, H. Lee, C. Kim, C. Park, M. H. Lee, W. Lee, J. Park,

K. Kim, N. G. Park and C. Kim, Chem. Commun., 2007, 46, 4887.

14 J. Tang, W. J. Wu, J. L. Hua, X. Li and H. Tian, Energy. Environ.

40

Sci., 2009, 2, 982.

15 (a) J. X. He, W. J. Wu, J. L. Hua, Y. H. Jiang, S. Y. Qu, J. Li, Y. T.

Long and H. Tian, J. Mater. Chem., 2011, 21, 6054; (b) L. Wang, H.

Y. Wang, H. H. Fang, H. Wang, Z. Y. Yang, B. R. Gao, Q. D. Chen,

W. Han and H. B. Sun, Adv. Funct. Mater., 2012, 22, 2783.

⁴⁵16 (a) L. Y. Lin, C. ꢀH. Tsai, K. –T. Wong, T. –W. Huang, L. Hsieh, S.

–H. Liu, H. –W. Lin, C. –C. Wu, S. –H. Chou, S. –H. Chen and A. ꢀ

I.Tsai, J. Org. Chem., 2010, 75, 4778; (b) D. Sahu, H. Padhy, D.

Patra, J. –F. Yin, Y. –C. Hsu, J. –T. Lin, K. –L. Lu, K. –H. Wei and

H. –C. Lin, Tetrahedron, 2011, 67, 303.

⁵⁰17 P. J. Stephens, F. J. Devlin, C. F. Chabalowski and M. J. Frisch, J.

Phys. Chem., 1994, 98, 11623.

18 A. Schaefer, H. Horn and R. Ahlrichs, J. Chem. Phys., 1992, 97,

2571.

19 ORCA, An ab initio, DFT and semiempirical SCFꢀMO package,

55

60

65

version 2.9, http://www.thch.uniꢀbonn.de/tc/orca/

20 T. Yanai, D. Tew and N. Handy, Chem. Phys. Lett., 2004, 393, 51.

21 H. H. Chou, Y. C. Chen, H. J. Huang, T. H. Lee, J. T. Lin, C. Tsai

and K. Chen, J. Mater. Chem., 2012, 22, 10929.

22 A. Morandeira, I. LópezꢀDuarte, B. O’Regan, M. V. MartínezꢀDíaz,

A. Forneli, E. Palomares, T. Torres and J. R. Durrant, J. Mater.

Chem., 2009, 19, 5016;

23 Y. Z. Wu and W. H. Zhu, Chem. Soc. Rev., 2013, 42, 2039.

24 (a) N. Robertson, Angew. Chem., Int. Ed., 2006, 45, 2338; (b) H.

Ozawa, M. Awa, J. Ono, and H. Arakawa, Chem.–Asian J., 2012, 7,

156; (c) C. ꢀJ. Yang, Y. J. Chang, M. Watanabe, Y. ꢀS. Hon and T.

J. Chow, J. Mater. Chem., 2012, 22, 4040; (d) H. N. Tian, X. C.

Yang, R. K. Chen, R. Zhang, A. Hagfeldt and L. C. Sun, J. Phys.

Chem. C, 2008, 112, 11023.

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Article Doi

Efficient and stable DSSC sensitizers based on substituted dihydroindolo[2,3-b]carbazole donors with high molar extinction coefficients

DOI: 10.1039/c3ta11748k

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