carbazole Derivatives-Sensitized Solar Cells - American Chemical

Article pubs.acs.org/JPCC

Indolo[3,2,1-jk]carbazole Derivatives-Sensitized Solar Cells: Effect of π‑Bridges on the Performance of Cells Chunhua Luo,†,‡,‡ Weixin Bi,†,‡ Shiming Deng,∥ Jian Zhang,† Shiyou Chen,† Bo Li,† Qiancai Liu,∥ Hui Peng,*,†,§ and Junhao Chu†,‡ †

Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200241, China National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics of the Chinese Academy of Sciences, Shanghai 200083, China § Polymer Electronic Research Centre, The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand ∥ Chemistry Department, East China Normal University, Shanghai 200241, China ‡

S Supporting Information *

ABSTRACT: Four organic dyes based on indolo[3,2,1-jk]carbazole (IC-1, IC-2, IC-3, and IC-4) with different π-bridges (benzene ring and thiophene ring) are used for dye-sensitized solar cells (DSSCs) to investigate the effect of π-bridge on their photovoltaic performance. The introduction of thiophene ring as π-bridge (the dye IC-2) greatly improves the cell performance compared to benzene ring. The increasing conjugation length of the molecules decreases the performance of DSSCs. The best performance of DSSC based on IC-2 is obtained with a Voc of 0.66 V and a conversion efficiency of 3.68%. The poor performance of DSSCs based on IC-1 and IC-3 which contains only benzene ring as the π-bridge can be attributed to poor spectral coverage and higher electron charge transfer resistance as evaluated from EIS studies. groups,9,10 triphenylamines,11,12 indoline,13,14 carbazole,15−17 phenothiazine,18−20 porphyrin,21,22 ullazine23 and phthalocyanine,24,25 have been successfully reported. Cyanoacrylic acid is often chosen as the electron acceptor unit not only because of its strong electron-withdrawing ability, but also because it provides a strong binding to the semiconductor surface which facilitates the electron injection.26,27 The choice of π-bridge is one of the key issues for the design of highly efficient D−π−A dyes. For example, Liu et al. illustrated that different π-bridges resulted in different electron recombination and thus affected the cell performances by introducing 3,4-ethyldioxythiophene (EDOT), 3-hexylthiophene, and thiophene to the parent structure of TH305 as π-bridges.28 Tian et al. also reported that small structure changes in π-bridge unit could cause significant differences in the redox potential of the resulting dyes.29 Recently, there has been much interest in the chemical synthesis and characterization of indolocarbazole derivatives due to their high thermostability, good fluorescence quantum yield, and strong electron donor ability.30−33 For example, indolo[3,2-b]carbazole has been successfully used as highly efficient electroluminescent material,34 building organic thin-

1. INTRODUCTION Dye-sensitized solar cells (DSSCs) have been widely investigated due to their easy and inexpensive fabrication procedure, as well as reasonably good power conversion efficiency.1 DSSCs show great potential as a replacement for silicon-based solar cells. Traditional DSSCs consist of a photoanode, which is made up of a wide band gap semiconductor with adsorbed dye molecules as sensitizers, an electrolyte, and a conductive substrate coated with a catalyst as cathode. Among these components, the dye sensitizers play a key role in the performance of cells. Since the breakthrough of DSSCs in 1991,1 Ru based metal complexes have been widely used as efficient sensitizers, such as N3, N719, and Z907.2,3 The power conversion efficiencies of DSSCs based on these complexes reach more than 10% under AM1.5-simulated solar light (100 mW cm−2).2,3 However, the rareness and cost of ruthenium metal limit the potentially wide application of Ru based metal complexes. Therefore, more and more researchers are focusing on metal-free organic dyes which have much stronger light-harvesting ability due to high molar extinction coefficients and are more suitable for low-cost and environment friendly applications.4−6 In general, the design of highly efficient organic dyes involves a donor connected to an electron acceptor through a π-bridge (D−π−A) which allows fine-tuning of optical and electrochemical properties.5,7,8 For donor units, dialkylaminophenyl © XXXX American Chemical Society

Received: April 8, 2014 Revised: June 2, 2014

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dx.doi.org/10.1021/jp503455m | J. Phys. Chem. C XXXX, XXX, XXX−XXX

The Journal of Physical Chemistry C

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Figure 1. Synthetic route of indolo[3,2,1-jk]carbazole derivatives.

film transistor,31 and within copolymers for photovoltaic applications.32,33 Indolo[3,2,1-jk]carbazoles, a special kind of indolo-carbazole positional isomers with an indolo- and a carbazole ring fused in a strained model, show quite interesting properties such as high thermostability, good fluorescence quantum yield, and strong electron donor ability, which led them to be promising components for charge transporting materials and conducting thin-film materials.30,35,36 However, there are seldom reports related to their applications in DSSCs. In this work, we report the application of four indolo[3,2,1jk]carbazole derivatives which contains different π-bridges as dye sensitizers. Their optical and physical properties were characterized by UV−vis and emission spectroscopy, and density functional theory (DFT) calculation. The effect of πbridges on the cell performance was investigated by electrochemical impedance spectroscopy which is a useful tool to get insight into the charge transport process in DSSCs.

electrode was then washed with ethanol and water, and annealed for 30 min at 500 °C. All DSSCs were assembled under the same conditions. The dye solution (0.5 mM) was first prepared in 5 mL of dichloromethane. The TiO2 film electrode was immersed in the dye solution under darkness at room temperature. After 48 h, the electrode was taken out and washed by dichloromethane and ethanol to wipe off unabsorbed dye molecules from the surface of the TiO2 film. Then the dye-adsorbed TiO2 film electrodes were assembled with the Pt-coated FTO counter electrode by using Surly film. The prepared electrolyte was injected through the hole drilled in the counter electrode. After that, the hole was sealed by using the Surly film. 2.4. Measurement. The absorption spectra of the dyes were measured by using a UV−vis spectrometer (TU-1901, Puxi Beijing) in dichloromethane solution. The emission spectra were recorded on a PerkinElmer LS55 fluorescence spectrometer. A solar simulator (SUN 2000, ABET technologies) was used to provide the standard light source (AM1.5G). The current− voltage (I−V) curves of the cells were recorded with an electrochemical workstation (CHI660D, Shanghai Chenhua). Electrochemical impedance spectra (EIS) of the cells were measured by using CHI660D electrochemical workstation. The TiO2 film electrode was used as the working electrode and a Ptcoated FTO electrode was used as both the auxiliary electrode and the reference electrode. The EIS were recorded in a frequency range from 1 Hz to 100 kHz under dark or AM1.5 illumination conditions by applying corresponding open circuit potential (Voc). The oscillation potential amplitude was set to 10 mV.

2. EXPERIMENTAL SECTION 2.1. Materials. TiO2 particles (P25, Degussa, Germany), and Pt-coated FTO counter electrode with a drilled hole were purchased from Heptachroma Ltd., China. The electrolyte solution was prepared by dissolving lithium iodide (0.1 M), iodine (0.05 M), and 4-tert-butylpyridine (0.5 M) in acetonitrile. The other chemicals were obtained from local companies and used without further purification. 2.2. Synthesis of Indolo[3,2,1-jk]carbazole Derivatives. The synthetic route of indolo[3,2,1-jk]carbazole derivatives (IC-1, IC-2, IC-3, and IC-4) is shown in Figure 1. Indolo[3,2,1-jk]carbazole was synthesized according to the procedure of the previous work.37 The details of synthesis are given in the Supporting Information (SI). 2.3. Fabrication of DSSCs. The TiO2 film electrodes were prepared according to the literature procedure.38 In brief, TiO2 was dispersed in terpineol to form a paste. The obtained paste was coated on the FTO conducting glass (10 Ω/square) by screen printing and then dried at 125 °C. This procedure was repeated six times. The prepared TiO2 electrode (area 6 × 6 mm; thickness of TiO2 film ∼12 μm) was sintered at 500 °C for 30 min in air, followed by a further treatment with 40 mM TiCl4 aqueous solution for 30 min at 70 °C. The TiO2

3. RESULTS AND DISCUSSION To better understand the optical properties of the prepared indolo[3,2,1-jk]carbazole derivatives, ab initio calculations based on the density functional theory were performed with the generalized gradient approximation (GGA) to the exchange-correlation functional. First the geometry of the molecules was relaxed and then the electronic structure was calculated. The wave functions of the HOMO and LUMO are shown in Figure 2. It can be seen that the HOMOs of IC-1 and IC-3, whose π-bridges are benzene ring, are mainly distributed B



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The absorption and emission spectra of the dyes (IC-1, IC-2, IC-3, and IC-4) were recorded in dichloromethane solution, as shown in Figure 3 and summarized in Table 1. In solution state, Table 1. Adsorption, Emission, and Electrochemical Properties of IC-1, IC-2, IC-3, and IC-4 adsorption

electrochemical properties

dye

λabs,π−π* (nm)

λabs,EnT (nm)

λabs,TiO2 (nm)

λem (nm)

E(S+/S)a (V)

E0−0b (eV)

E(S+/S*)c (V)

IC-1 IC-2 IC-3 IC-4 SD144

376 382 379 376 379

395 435 396 404 463

430 500 440 475 465

522 476 553 576 619

1.03 0.90 0.93 0.97 1.17

2.77 2.47 2.70 2.61 2.3

−1.74 −1.57 −1.77 −1.64 −1.13

a The oxidation potentials of the dyes were measured in CH2Cl2 with 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) as electrolyte (working electrode: glassy carbon; reference electrode: Ag/AgCl; counter electrode: Pt; calibrated with ferrocene/ferrocenium (Fc/Fc+) as an internal reference and converted to NHE by addition of +0.67 V). bE0−0 is estimated from the absorption thresholds in dichloromethane. cCalculated from E(S+/S*) is estimated by subtracting E(0−0) from (E(S+/S).

Figure 2. LUMO and HOMO wave functions of the molecules IC-1, IC-2, IC-3 and IC-4.

over the indolo[3,2,1-jk]carbazole unit. But in the case of IC-2 and IC-4, whose π-bridges contain the thiophene ring, the HOMOs are distributed over the indolo[3,2,1-jk]carbazole unit and the π-bridge. The LUMOs of all dyes are mainly distributed over the anchoring group, cyanoacrylic acid, which favors electron injection from the excited state of the dyes to the semiconductor conduction band when bound to the TiO2 surface. Additionally, due to the fuse of indolo- and a carbazole ring in a strained model, the molecular structures of these four dyes are nonplanar which would result in the reduced dye aggregation when they are adsorbed on the TiO2 surface.

IC-1 shows an absorption band at 376 nm with a shoulder around 394 nm (Figure 3A). The shorter wavelength band is assigned to the localized aromatic π−π* transition and the longer one is corresponding to intramolecular charge transfer absorption. When a thiophene ring was used as π-bridge (the dye IC-2), the absorption bands were largely red-shifted

Figure 3. Absorption spectra of indolo[3,2,1-jk]carbazole derivatives in dichloromethane (A) and on TiO2 film (C). Emission spectra of indolo[3,2,1-jk]carbazole derivatives in dichloromethane (B) and on TiO2 film (D). C



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Table 1. It is clear that the E(S+/S) values of the dyes are all more positive than the redox potential of iodide/triiodide redox couple (0.4 V vs NHE), indicating that the oxidized dyes formed after electron injection into the conduction bands of TiO2 could thermodynamically accept electrons from the iodide ions and regenerate. The excited state oxidation potential (E(S+/S*)) was determined by E(S+/S) − E0−0, where E0−0 is the zero−zero transition energy estimated from the absorption curves of the dyes. The E(S+/S*) values of these four dyes are in the range of −1.57 to −1.77 V (vs NHE), which are more negative than the conduction band edge of TiO2 (∼ −0.5 V vs NHE). This provides ample thermodynamic driving force for electron injection from the excited dye into the conduction band of TiO2. Compared to IC-2, the E(S+/S*) values of IC-1, IC-3 and IC-4 are clearly lifted up by the benzene ring as πbridge, which makes the absorption spectra blue shift and results in worse photon harvesting efficiency. For comparison, the E(S+/S) and E(S+/S*) of the dye SD1 which contains a commonly used donor unit triphenylamine and a thiophene ring as π-bridge, are also given in Table 1 (the molecular structure of SD1 is given in the SI).44 IC-2 shows a decrease of 270 mV in E(S+/S) when compared to SD1, which implies a stronger electron-donating strength. Moreover, IC-2 has a larger energy gap (Egap) between the E(S+/S*) and the conductive band level of TiO2 (−0.5 V vs NHE). The increased Egap could yield a higher open-circuit voltage and improve the photovoltaic conversion efficiency. These results indicate that indolo[3,2,1-jk]carbazole shows some advantages over triphenylamine as a donor unit in the design of D−π−A structured dye sensitizers. The photovoltaic characteristics of DSSCs by using these dyes as sensitizers were measured under standard AM 1.5G illumination (100 mW/cm2). The losses of light reflection and absorption by the conducting glass were not corrected. The obtained photocurrent−voltage (I−V) plots are shown in Figure 5. The photovoltaic characteristic parameters of short-

compared with those of IC-1. The spectral coverage of IC-2 was from the UV until ∼510 nm, which is favorable for the performance of DSSCs as more photons could be harvested. IC-3 contains two benzene rings as π-bridge, but the main absorption band has only a red-shift of 3 nm compared to that of IC-1. When both benzene ring and thiophene ring were used as π-bridge (IC-4), the spectral coverage was also greatly improved compared to that of IC-1. These results illustrate that thiophene ring is much better than benzene ring as π-bridge in terms of improving the spectral coverage in the visible light range due to its lower stabilization energy which ensures more efficient electronic communication between the indolocarbazole donor and the cyanoacrylic acid acceptor. Figure 3B represents the emission spectra of the dyes in dichloromethane measured upon an excitation wavelength of 370 nm. It can be seen that the increase the conjugation lengths caused the red shift of emission wavelength. For the dye IC-4, the emission peak was split into two which were located at 478 and 578 nm, respectively. The emission spectra of all four dyes are partly overlapped with their adsorption spectra, thus intermolecular energy transfer (EnT) process could occur in these dyes, which will have a positive effect on improving the performance.39,40 When the dyes are attached to TiO2 surface, the absorption spectra of these dyes are broadened and adsorption peaks are red-shifted more or less as compared to that in solutions (Figure 3C). Similar broadening and red shifts have been reported in thiazole melocyanines41 and indoline dyes42 on TiO2 electrodes,42,43 which are ascribed to the interaction between neighboring dyes and the formation of J-aggregate on the TiO2 electrode.43 Figure 3D gives the corresponding emission spectra. After adsorbed on the TiO2 electrode, the fluorescence of these dyes is greatly quenched, indicating efficient electron transfer between the excited dyes and TiO2. To estimate the energetics of electron transfer from the excited dyes to the conduction band of TiO2, the cyclic voltammetry was performed at a potential scan rate of 100 mV/ s by using 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) as electrolyte. The results are represented in Figure 4. It can be found that the introduction of the thiophene ring (IC-2) or increase of the conjugation length (IC-3 and IC-4) made the molecules easy to be oxidized. The ground-state oxidation potential (E(S+/S)) measured by using ferrocene/ ferrocenium (Fc/Fc+) as an internal reference are listed in

Figure 5. Photocurrent density vs voltage (I−V) curves of DSSCs built using the prepared dyes as sensitizers under irradiation of AM 1.5 simulated solar light (100 mW cm−2).

circuit currents density (Isc), open-circuit potential (Voc), fill factor (FF), and photovoltaic conversion efficiency (η) are listed in Table 2. It can be seen that DSSC based on IC-1 showed the highest Voc compared to the other three dyes due to its more negative LUMO level. The short-circuit current of IC-2 was the highest which was attributed to its much broader absorption spectrum. Although the absorption spectrum of IC3 which contains two benzene rings as π-bridge was similar to

Figure 4. Cyclic voltammograms of indolo[3,2,1-jk]carbazole derivatives measured in CH2Cl2 with 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) as electrolyte at a scan rate of 100 mV/s. D



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better understand the EIS results, an equivalent circuit shown in Figure 6B as an inserted picture was used to fit the experimental data.46 It is composed of a series of two Randlestype circuits to characterize the electrode interfaces (TiO2/dye/ electrolyte and electrolyte/Pt/FTO) and a further series resistance Rs. RT is the electron transfer resistance between the TiO2 film and electrolyte and RCE is the resistance of electron transport in the counter electrode. Considering the porosity of interfaces, the constant phase element (CPE) was used instead of the capacitance. The fitting results are summarized in Table 3. It can be found from Table 3 that

Table 2. Photovoltaic Performance of DSSCs Based on IC-1, IC-2, IC-3, and IC-4 at AM 1.5G Illumination DSSC

Isc (mA·cm−2)

Voc (V)

fill factor (FF %)

efficiency (η %)

IC-1 IC-2 IC-3 IC-4

7.05 9.78 4.04 7.57

0.69 0.66 0.62 0.64

52.65 56.64 63.85 52.82

2.56 3.68 1.59 2.55

that of IC-1, the short-circuit current of IC-3 was much lower than that of IC-1. Considering IC-1 and IC-3 have similar driving force for electron injection, the observed lower Isc of IC3 is probably due to the aggregation of IC-3 on the TiO2 film caused by enhanced π−π stacking interaction. The photovoltaic conversion efficiencies of DSSCs based on these four dyes are in the order of IC-2 > IC-1 > IC-4 > IC-3. The highest photovoltaic conversion efficiency of DSSC based on IC-2 reaches 3.68%. These results mentioned above clearly illustrate that the thiophene ring shows great advantages over benzene ring as the π-bridge. To further analyze the different photovoltaic properties of the prepared dyes, electrical impedance spectroscopy (EIS) was employed to characterize the fabricated DSSCs since this technique has been a useful tool to estimate electron recombination resistance and to know the dye regeneration efficiency.45,46 Figure 6 gives the Nyquist plots DSSCs based on these four dyes under illuminated and dark conditions. Generally, all the spectra of DSSCs exhibit two semicircles, which are assigned to charge transfers at the Pt counter electrode (high frequency domain) and the TiO2/dye/electrolyte interface (low frequency domain), respectively.45,46 To

Table 3. Fitted EIS Parameters Values of Dye-Sensitized Solar Cells Rs (Ω)

RCE (Ω)

RT (Ω)

DSSCs

dark

light

dark

light

dark

light

IC-1 IC-2 IC-3 IC-4

34.30 41.14 33.31 37.67

34.31 41.06 33.31 37.52

17.20 15.21 15.69 16.21

12.45 10.01 11.55 11.81

82.76 54.70 105.10 71.57

27.61 14.26 40.11 19.34

the values of RCE were almost the same for these four dyes under the same measurement conditions (illumination or dark). This is because of the same counter electrode materials and same electrolyte used. No matter under light or dark conditions, the values of RT of these four dyes are in the order of IC-3 > IC-1> IC-4 > IC-2. Clearly higher RT values were obtained for the dyes containing benzene ring as π-bridge. The introduction of thiophene ring as π-bridge largely

Figure 6. Nyquist plots of DSSCs based on (A) IC-1, (B) IC-2, (C) IC-3 and (D) IC-4 at VOC under AM 1.5G illumination (100 mW cm−2) (●) and in dark (▲). The symbols are the experimental data and the solid lines are the fitting results. Inset: equivalent circuit proposed to fit the EIS data. E



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(2013CB922302), and China Postdoctoral Science Foundation (2012M510897), PCSIRT and NCET.

decreases the electron transfer resistance. For IC-2, the value of RT was 14.26 Ω under light condition, whereas the RT value of IC-1 was 27.61 Ω. The decrease of RT value would result in the better performance, i.e., photoregeneration is more efficient. The fitting data of EIS agreed well with the cell efficiency shown in Figure 5 and Table 2.

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4. CONCLUSIONS Four metal-free organic dyes containing indolo[3,2,1-jk]carbazole as electron donor unit and different π-bridges (benzene ring and thiophene ring) were investigated to unravel the effect of π-bridge on their performance activities as solar dyes. The molecular orbital calculations illustrate that the electrons of these four dyes can be separated at the ground state and at the excited state efficiently. The introduction of thiophene ring as π-bridge (dye IC-2) greatly improved the spectral coverage in the visible light range, which is favorable for the performance of DSSCs. Electrochemical studies revealed the location of the E(S+/S) and E(S+/S*) of the dyes to be appropriate for the regeneration of excited dye by iodide/ triiodide redox couple and for electron injection from excited dye to TiO2 conduction band. The comparison with the dye SD1 indicates that indolo[3,2,1-jk]carbazole shows some advantages over triphenylamine as a donor unit in the design of D−π−A structured dye sensitizers. The photovoltaic performance of DSSCs based on these four dyes illustrates that these dyes are capable of producing significant amounts of photocurrent and photovoltage. The DSSC based on IC-2 shows the best performance with a Voc of 0.66 V and a power conversion efficiency of 3.68%. The poor performance of DSSCs based on IC-1 and IC-3 which contains only benzene rings as π-bridge could be attributed to two reasons: poor spectral coverage and higher electron charge transfer resistance as evaluated from EIS studies. The present work demonstrates that the π-bridges have significant effect on the photovoltaic performance of indolo[3,2,1-jk]carbazole based dyes in solar cells. Considering the relatively low conversion efficiency of 3.68%, further work needs to be carried out, including broadening of absorption spectra and tuning energy levels by introducing other π-bridge units such as EDOT and 3hexylthiophene.

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ASSOCIATED CONTENT

S Supporting Information *

Additional information on the synthesis route of the dyes. This material is available free of charge via the Internet at http:// pubs.acs.org.

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REFERENCES

(1) O’Regan, B.; Graetzel, M. A Low-Cost, High-Efficiency Solar Cell Based on Dye-Sensitized Colloidal Titanium Dioxide Films. Nature 1991, 353, 737−40. (2) Nazeeruddin, M. K.; Kay, A.; Rodicio, I.; Humphry-Baker, R.; Mueller, E.; Liska, P.; Vlachopoulos, N.; Graetzel, M. Conversion of Light to Electricity by Cis-X2bis(2,2′-Bipyridyl-4,4′-Dicarboxylate)Ruthenium(II) Charge-Transfer Sensitizers (X = Cl−, Br−, I−, Cn−, and Scn−) on Nanocrystalline Titanium Dioxide Electrodes. J. Am. Chem. Soc. 1993, 115, 6382−6390. (3) Nazeeruddin, M. K.; Pechy, P.; Gratzel, M. Efficient Panchromatic Sensitization of Nanocrystalline TiO2 Films by a Black Dye Based on Atrithiocyanato−Ruthenium Complex. Chem. Commun. 1997, 1705−1706. (4) Kloo, L. On the Early Development of Organic Dyes for DyeSensitized Solar Cells. Chem. Commun. 2013, 49, 6580−6583. (5) Kim, B.-G.; Chung, K.; Kim, J. Molecular Design Principle of AllOrganic Dyes for Dye-Sensitized Solar Cells. Chem.−Eur. J. 2013, 19, 5220−5230. (6) Liang, M.; Chen, J. Arylamine Organic Dyes for Dye-Sensitized Solar Cells. Chem. Soc. Rev. 2013, 42, 3453−3488. (7) Guo, F.; He, J.; Qu, S.; Li, J.; Zhang, Q.; Wu, W.; Hua, J. Structure-Property Relationship of Different Electron Donors: New Organic Sensitizers Based on Bithiazole Moiety for High Efficiency Dye-Sensitized Solar Cells. RSC Adv. 2013, 3, 15900−15908. (8) Liu, X.; Cao, Z.; Huang, H.; Liu, X.; Tan, Y.; Chen, H.; Pei, Y.; Tan, S. Novel D−D−Π-a Organic Dyes Based on Triphenylamine and Indole-Derivatives for High Performance Dye-Sensitized Solar Cells. J. Power Sources 2014, 248, 400−406. (9) Hara, K.; Kurashige, M.; Ito, S.; Shinpo, A.; Suga, S.; Sayama, K.; Arakawa, H. Novel Polyene Dyes for Highly Efficient Dye-Sensitized Solar Cells. Chem. Commun. 2003, 252−253. (10) Kitamura, T.; Ikeda, M.; Shigaki, K.; Inoue, T.; Anderson, N. A.; Ai, X.; Lian, T.; Yanagida, S. Phenyl-Conjugated Oligoene Sensitizers for TiO2 Solar Cells. Chem. Mater. 2004, 16, 1806−1812. (11) Xu, W.; Peng, B.; Chen, J.; Liang, M.; Cai, F. New Triphenylamine-Based Dyes for Dye-Sensitized Solar Cells. J. Phys. Chem. C 2008, 112, 874−880. (12) Hwang, S.; et al. A Highly Efficient Organic Sensitizer for DyeSensitized Solar Cells. Chem. Commun. 2007, 4887−4889. (13) Yang, J.; et al. Influence of the Donor Size in D−π−A Organic Dyes for Dye-Sensitized Solar Cells. J. Am. Chem. Soc. 2014, 136, 5722−5730. (14) Yum, J.-H.; Holcombe, T. W.; Kim, Y.; Rakstys, K.; Moehl, T.; Teuscher, J.; Delcamp, J. H.; Nazeeruddin, M. K.; Grätzel, M. BlueColoured Highly Efficient Dye-Sensitized Solar Cells by Implementing the Diketopyrrolopyrrole Chromophore. Sci. Rep. 2013, 3, No. 10.1038/srep02446. (15) Teng, C.; Yang, X.; Yuan, C.; Li, C.; Chen, R.; Tian, H.; Li, S.; Hagfeldt, A.; Sun, L. Two Novel Carbazole Dyes for Dye-Sensitized Solar Cells with Open-Circuit Voltages up to 1 V Based on Br−/Br3− Electrolytes. Org. Lett. 2009, 11, 5542−5545. (16) Wan, Z.; Jia, C.; Duan, Y.; Zhou, L.; Zhang, J.; Lin, Y.; Shi, Y. Influence of the Antennas in Starburst Triphenylamine-Based Organic Dye-Sensitized Solar Cells: Phenothiazine Versus Carbazole. RSC Adv. 2012, 2, 4507−4514. (17) Michaleviciute, A.; Degbia, M.; Tomkeviciene, A.; Schmaltz, B.; Gurskyte, E.; Grazulevicius, J. V.; Bouclé, J.; Tran-Van, F. Star-Shaped Carbazole Derivative Based Efficient Solid-State Dye Sensitized Solar Cell. J. Power Sources 2014, 253, 230−238. (18) Hart, A. S.; Chandra Bikram, K. C.; Subbaiyan, N. K.; Karr, P. A.; D’Souza, F. Phenothiazine-Sensitized Organic Solar Cells: Effect of Dye Anchor Group Positioning on the Cell Performance. ACS Appl. Mater. Interfaces 2012, 4, 5813−5820. (19) Wu, W.; Yang, J.; Hua, J.; Tang, J.; Zhang, L.; Long, Y.; Tian, H. Efficient and Stable Dye-Sensitized Solar Cells Based on Phenothia-

AUTHOR INFORMATION

Corresponding Author

*Tel.: +862154342726. Fax: +862154345119. E-mail:hpeng@ ee.ecnu.edu.cn. Author Contributions ‡

Authors C.L. and W.B. contributed equally.

Notes

The authors declare no competing financial interest

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ACKNOWLEDGMENTS This work was financially supported by National Natural Science Foundation of China (61306020, 61106087, 91233121), National Program on Key Basic Research project F



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zine Sensitizers with Thiophene Units. J. Mater. Chem. 2010, 20, 1772−1779. (20) Hua, Y.; Chang, S.; Wang, H.; Huang, D.; Zhao, J.; Chen, T.; Wong, W.-Y.; Wong, W.-K.; Zhu, X. New Phenothiazine-Based Dyes for Efficient Dye-Sensitized Solar Cells: Positioning Effect of a Donor Group on the Cell Performance. J. Power Sources 2013, 243, 253−259. (21) Subbaiyan, N. K.; Wijesinghe, C. A.; D’Souza, F. Supramolecular Solar Cells: Surface Modification of Nanocrystalline TiO2 with Coordinating Ligands to Immobilize Sensitizers and Dyads Via Metal-Ligand Coordination for Enhanced Photocurrent Generation. J. Am. Chem. Soc. 2009, 131, 14646−14647. (22) Parussulo, A. L. A.; Iglesias, B. A.; Toma, H. E.; Araki, K. Sevenfold Enhancement on Porphyrin Dye Efficiency by Coordination of Ruthenium Polypyridine Complexes. Chem. Commun. 2012, 48, 6939−6941. (23) Delcamp, J. H.; Yella, A.; Holcombe, T. W.; Nazeeruddin, M. K.; Grätzel, M. The Molecular Engineering of Organic Sensitizers for Solar-Cell Applications. Angew. Chem., Int. Ed. 2013, 52, 376−380. (24) Ragoussi, M.-E.; Cid, J.-J.; Yum, J.-H.; de la Torre, G.; Di Censo, D.; Graetzel, M.; Nazeeruddin, M. K.; Torres, T. Carboxyethynyl Anchoring Ligands: A Means to Improving the Efficiency of Phthalocyanine-Sensitized Solar Cells. Angew. Chem., Int. Ed. 2012, 51, 4375−4378 S4375/1-S4375/14. (25) Martinez-Diaz, M. V.; de la Torre, G.; Torres, T. Lighting Porphyrins and Phthalocyanines for Molecular Photovoltaics. Chem. Commun. 2010, 46, 7090−7108. (26) Srinivas, K.; Yesudas, K.; Bhanuprakash, K.; Rao, V. J.; Giribabu, L. A Combined Experimental and Computational Investigation of Anthracene Based Sensitizers for DSSC: Comparison of Cyanoacrylic and Malonic Acid Electron Withdrawing Groups Binding onto the TiO2 Anatase (101) Surface. J. Phys. Chem. C 2009, 113, 20117− 20126. (27) Hara, K.; Sato, T.; Katoh, R.; Furube, A.; Ohga, Y.; Shinpo, A.; Suga, S.; Sayama, K.; Sugihara, H.; Arakawa, H. Molecular Design of Coumarin Dyes for Efficient Dye-Sensitized Solar Cells. J. Phys. Chem. B 2002, 107, 597−606. (28) Liu, J.; Yang, X.; Zhao, J.; Sun, L. Tuning Band Structures of Dyes for Dye-Sensitized Solar Cells: Effect of Different π-Bridges on the Performance of Cells. RSC Adv. 2013, 3, 15734−15743. (29) Tian, H.; Yang, X.; Chen, R.; Zhang, R.; Hagfeldt, A.; Sun, L. Effect of Different Dye Baths and Dye-Structures on the Performance of Dye-Sensitized Solar Cells Based on Triphenylamine Dyes. J. Phys. Chem. C 2008, 112, 11023−11033. (30) Henry, J. B.; Wharton, S. I.; Wood, E. R.; McNab, H.; Mount, A. R. Specific Indolo[3,2,1-Jk]Carbazole Conducting Thin-Film Materials Production by Selective Substitution. J. Phys. Chem. A 2011, 115, 5435−5442. (31) Wu, Y.; Li, Y.; Gardner, S.; Ong, B. S. Indolo[3,2-B]CarbazoleBased Thin-Film Transistors with High Mobility and Stability. J. Am. Chem. Soc. 2004, 127, 614−618. (32) Zhou, E.; Yamakawa, S.; Zhang, Y.; Tajima, K.; Yang, C.; Hashimoto, K. Indolo[3,2-B]Carbazole-Based Alternating DonorAcceptor Copolymers: Synthesis, Properties and Photovoltaic Application. J. Mater. Chem. 2009, 19, 7730−7737. (33) Tsai, J.-H.; Chueh, C.-C.; Lai, M.-H.; Wang, C.-F.; Chen, W.-C.; Ko, B.-T.; Ting, C. Synthesis of New Indolocarbazole-Acceptor Alternating Conjugated Copolymers and Their Applications to Thin Film Transistors and Photovoltaic Cells. Macromolecules 2009, 42, 1897−1905. (34) Zhao, H.-P.; Wang, F.-Z.; Yuan, C.-X.; Tao, X.-T.; Sun, J.-L.; Zou, D.-C.; Jiang, M.-H. Indolo[3,2-B]Carbazole: Promising Building Block for Highly Efficient Electroluminescent Materials. Org. Electron. 2009, 10, 925−931. (35) Niebel, C.; Lokshin, V.; Ben-Asuly, A.; Marine, W.; Karapetyan, A.; Khodorkovsky, V. Dibenzo[2,3:5,6]Pyrrolizino[1,7-Bc]Indolo[1,2,3-Lm]Carbazole: A New Electron Donor. New J. Chem. 2010, 34, 1243−1246. (36) Wharton, S. I.; Henry, J. B.; McNab, H.; Mount, A. R. The Production and Characterisation of Novel Conducting Redox-Active

Oligomeric Thin Films from Electrooxidised Indolo[3,2,1-Jk]Carbazole. Chem.Eur. J. 2009, 15, 5482−5490. (37) Lv, J.; Liu, Q.; Tang, J.; Perdih, F.; Kranjc, K. A Facile Synthesis of Indolo[3,2,1-Jk]Carbazoles Via Palladium-Catalyzed Intramolecular Cyclization. Tetrahedron Lett. 2012, 53, 5248−5252. (38) Ito, S.; Chen, P.; Comte, P.; Nazeeruddin, M. K.; Liska, P.; Péchy, P.; Grätzel, M. Fabrication of Screen-Printing Pastes from TiO2 Powders for Dye-Sensitised Solar Cells. Prog. Photovoltaics Res. Appl. 2007, 15, 603−612. (39) Etgar, L.; et al. Enhancing the Efficiency of a Dye Sensitized Solar Cell Due to the Energy Transfer between CdSe Quantum Dots and a Designed Squaraine Dye. RSC Adv. 2012, 2, 2748−2752. (40) Ning, Z.; Tian, H. Triarylamine: A Promising Core Unit for Efficient Photovoltaic Materials. Chem. Commun. 2009, 5483−5495. (41) Sayama, K.; Hara, K.; Mori, N.; Satsuki, M.; Suga, S.; Tsukagoshi, S.; Abe, Y.; Sugihara, H.; Arakawa, H. Photosensitization of a Porous TiO2 Electrode with Merocyanine Dyes Containing a Carboxyl Group and a Long Alkyl Chain. Chem. Commun. 2000, 1173−1174. (42) Horiuchi, T.; Miura, H.; Uchida, S. Highly-Efficient Metal-Free Organic Dyes for Dye-Sensitized Solar Cells. Chem. Commun. 2003, 3036−3037. (43) Nüesch, F.; Moser, J. E.; Shklover, V.; Grätzel, M. Merocyanine Aggregation in Mesoporous Networks. J. Am. Chem. Soc. 1996, 118, 5420−5431. (44) Shen, P.; Liu, Y.; Huang, X.; Zhao, B.; Xiang, N.; Fei, J.; Liu, L.; Wang, X.; Huang, H.; Tan, S. Efficient Triphenylamine Dyes for Solar Cells: Effects of Alkyl-Substituents and Π-Conjugated Thiophene Unit. Dyes Pigm. 2009, 83, 187−197. (45) Wang, Q.; Moser, J.-E.; Grätzel, M. Electrochemical Impedance Spectroscopic Analysis of Dye-Sensitized Solar Cells. J. Phys. Chem. B 2005, 109, 14945−14953. (46) van de Lagemaat, J.; Park, N. G.; Frank, A. J. Influence of Electrical Potential Distribution, Charge Transport, and Recombination on the Photopotential and Photocurrent Conversion Efficiency of Dye-Sensitized Nanocrystalline TiO2 Solar Cells: A Study by Electrical Impedance and Optical Modulation Techniques. J. Phys. Chem. B 2000, 104, 2044−2052.

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carbazole Derivatives-Sensitized Solar Cells - American Chemical

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