Insight into Electron-Donating Ancillary Ligands in Ruthenium

Apr 13, 2017 - Insight into Electron-Donating Ancillary Ligands in Ruthenium Terpyridyl Complexes Configuration on Performances of Dye-Sensitized Sola...
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Insight into Electron-Donating Ancillary Ligands in Ruthenium Terpyridyl Complexes Configuration on Performances of DyeSensitized Solar Cells Wang-Chao Chen,†,‡ Fan-Tai Kong,*,† Rahim Ghadari,§ Zhao-Qian Li,† Xue-Peng Liu,†,‡ Ting Yu,†,‡ Yin Huang,†,‡ Yang Huang,† Tasawar Hayat,∥ and Song-Yuan Dai*,†,∥,⊥ †

Key Laboratory of Novel Thin Film Solar Cells, Institute of Applied Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, 230088, People’s Republic of China ‡ University of Science and Technology of China, Hefei, 230026, People’s Republic of China ∥ NAAM Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia ⊥ Beijing Key Laboratory of Novel Thin Film Solar Cells, North China Electric Power University, Beijing, 102206, People’s Republic of China § Computational Chemistry Laboratory, Department of Organic and Biochemistry, Faculty of Chemistry, University of Tabriz, 5166616471 Tabriz, Iran S Supporting Information *

ABSTRACT: Three heteroleptic ruthenium terpyridyl complexes, RC-T51, RC-T52, and RC-T53, with efficient electrondonating ancillary ligands were molecularly designed, synthesized and applied as sensitizers for dye-sensitized solar cell. With the replacement of labile isothiocyanates (NCS) ligand by electron-donating ancillary ligands, all the RC dyes exhibited superior optical properties and suitable electrochemical characteristics. The lowest excited-state decay dynamic analysis for RC dyes were carried out by timeresolved photoluminescence measurements. Among the RC dyes, the solar cell sensitized by RC-T53 achieved the best short-circuit current density of 14.20 mA cm−2 and power conversion efficiency of 6.17%. Compared with N749, DFT calculations, and transient absorbance decay kinetics rationalized the relatively inferior performances of RC dyes which were ascribed to the improper delocalization of the HOMO energy level and the inefficient dye generation process. Substituting the labile NCS ligand by electron-donating ancillary ligand bearing bidentate structure, the devices based on RC dyes exhibited excellent stability in the accelerated tests (60 °C for 1000 h) in combination with low volatility electrolyte.

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competitor for high performance DSSC application.6,9,10 The benchmark ruthenium(II) terpyridyl-based dye known as black dye (N749)7 has exhibited a remarkable power conversion efficiency exceeding 10%.11 In general, the molecule modification based on N749 or its analogues mainly focused on two aspects. (i) Improving the light-harvesting ability in the short wavelength region: Although the absorption spectra of some ruthenium terpyridyl sensitizers12,13 have been extended to near-infrared regions, the performance are still limited by the inferior molar extinction coefficient, especially in the short wavelength region. (ii) Replacing the labile NCS ligand by stable ligand bearing chelating structure: Considering the presence of three NCS

INTRODUCTION The sensitization of semiconductors is the foundation of numerous photoelectron-chemistry processes related to solar energy application such as dye-sensitized solar cells (DSSCs) and some photocatalytic devices.1,2 In DSSC, dye sensitizers with broad absorption range, superior light-harvesting ability, and excellent stability play an important role to obtain excellent performance. In recent years, a large amount of dye sensitizers, from organic molecule sensitizer3,4 to zinc porphyrin,5 have been designed and developed, whereas, ruthenium complexes sensitizers6−8 remain the most widely applied and intensively investigated. Comparing with the conventional ruthenium(II) complexes bipyridyl-based sensitizers, for example, N719, ruthenium(II) terpyridyl complexes sensitizers can address more efficient panchromatic sensitization of TiO2 semiconductors extending to the long wavelength region, which enable this category of ruthenium(II) complexes a promising © XXXX American Chemical Society

Received: February 12, 2017 Revised: April 5, 2017 Published: April 13, 2017 A

DOI: 10.1021/acs.jpcc.7b01381 J. Phys. Chem. C XXXX, XXX, XXX−XXX

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Figure 1. Chemical structures of dyes N749, RC-T51, RC-T52, and RC-T53.

Scheme 1. Synthesis Route for RC-T51, RC-T52, and RC-T53 Sensitizers

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EXPERIMENTAL SECTION Synthesis. The synthetic protocol of the RC-T51, RC-T52, and RC-T53 sensitizers is given in Scheme 1. All ancillary bipyridine ligands were gained from the 4,4′-dibromo-2,2′bipyridine and aromatic boric acid or boric acid ester using typical Suzuki coupling reaction in good yield. The RC dye sensitizers were carefully synthesized according to the classical one-pot method, then purified through the Sephadex LH-20 column chromatography. Finally, the pure product was separated at pH 2.5 with hexafluorophosphoric acid. The intact preparation procedure and identification for RC dye sensitizers with NMR and ESI-MS or MALDI-TOFMS are prudently accounted in the Supporting Information. Materials and Equipment. All organic reagents used in this work were purchased form Sigma-Aldrich or Alfa Aesar. The solvents and inorganic reagents were AR grade. 1H NMR were measured with Bruker Advance 400 spectrometer. Mass spectra were carried on Exactive GC Orbitrap MS Spectrometer. The UV−vis spectra were obtained by Thermo Scientific Evolution 260 Bio. Cyclic voltammetry (CV) were tested on CHI-660E with a scan rate of 50 mV s−1. In a typical threeelectrode electrochemical cell, the glassy carbon (GC) electrode was employed as the working electrode. Platinum wire and saturated calomel electrode (SCE) were applied as the counter electrode and reference electrode, respectively. Timeresolved photoluminescence (TRPL) was obtained on PTI QM400 and LaserStrobe. The J−V characteristics were obtained by Newport 3A grade solar simulator under AM 1.5G irradiation (100 mW cm−2) on the solar cells with the active surface area of 0.25 cm2 defined by a square black tape mask.

groups in this kind of dyes, which not only increases the isomerizations coproduct, but also give rise to a decomposition of the ruthenium complex resulting from the labile NCS group, the number of NCS ligand in ruthenium complexes sensitizers should be reduced even vanished urgently.14 Replacing two labile NCS group by an ancillary ligand with high delocalization electron-donating antennas is an advisible strategy to develop more efficient and stable ruthenium terpyridyl complexes sensitizers while maintaining favorable electrochemical characteristics.10,14,15 Furthermore, the electron-donating antennas on ancillary ligand may potentially stretch the distance between the TiO2 surface and excited-state dye cation, and thus retarding the interfacial recombination process.16 With the purpose of exploring the further insight into the evolution of ruthenium terpyridyl sensitizers, a series of ruthenium terpyridyl complexes (RC-T51, RC-T52, and RCT53) modified with three different electron-donating ancillary bipyridine ligands were molecularly synthesized and employed as dye sensitizers for DSSCs (see Figure 1). In accordance with the electron-donating capacity and conjugated length of the ancillary ligand sequence, different electron donor antenna (methoxyphenyl, phenylcarbazol, and methoxy-triphenylamine) is introduced on the ancillary bipyridine ligand of RC-T51, RCT52, and RC-T53, respectively. All these dyes contain the 4,4′,4″-tricarboxylic-2,2′:6′,2″-terpyridine ligand acting as an anchoring ligand for effective bonding. The only existed NCS group can adjusts the properties of the ruthenium metal center by destabilizing the ruthenium metal t2g orbital. The photophysical and electrochemical features of these RC dyes were characterized carefully. The photovoltaic features of fabricated solar cells sensitized by the new RC dye sensitizers were performed and compared with N749 sensitizer.17−19 B

DOI: 10.1021/acs.jpcc.7b01381 J. Phys. Chem. C XXXX, XXX, XXX−XXX

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Figure 2. (a) Electronic absorption spectra of RC dye sensitizers in DMF solution and (b) electronic absorption spectra of RC dye sensitizers adsorbed on the transparent TiO2 microspheres thin film (thickness: ca. 8 μm).

Fabrication of Dye-Sensitized Solar Cells (DSSCs). A 20 nm sized TiO2 nanoparticles (Dyesol) film (4 μm) was printed on and afterward coated by TiO2 microspheres (14 μm). In flowed air, the photoanode films were sintered at 450 °C for 30 min. Afterward, the TiO2 photoanode films were immersed in acetonitrile/tert-butanol mixed solvent, which contained 300 μM dye for 24 h. Covering a drop of 5 mM H2PtCl6 solution, the counter electrode was obtained. The internal space was filled with a liquid electrolyte by using a pipet. The electrolyte solution consisted of 1 M 1,3-dimethyl-imidazolium iodide (DMII), 40 mM LiI, 50 mM I2, 0.5 M TBP, and 0.1 M guanidinium thiocyanate (GuNCS) in a solvent mixture of 85% acetonitrile with 15% valeronitrile by volume. The sensitized square area were masked by black tape with 0.25 cm2 aperture.

transition. The lower-energy MLCT absorption bands arise at 520 nm for RC-T51, 526 nm for RC-T52, and 532 nm for RCT53. As shown in Figure 2a and Table 1, the molar extinction coefficients (ε) of the low-energy MLCT absorption bands are 14120, 21490, and 26270 M−1 cm−1 for RC-T51, RC-T52, and RC-T53, respectively, which are all higher than that of N749 (5810 M−1 cm−1). The better absorption performance for RC dye sensitizers compared to N749 uncover the positive impact from the incorporation of electron-donating moieties. The lower-energy MLCT bands of the RC dyes are hypsochromic compared with that of N749, which are ascribed to the reduced two NCS ligands. The sequence of these bands positions for the RC dye sensitizers is RC-T53 > RC-T52 > RC-T51. The above results are identical with the electron-donating capacity of the introduced electron-donating ancillary ligands. Figure 2b depicts the absorption spectra of RC dye sensitizers adsorbed on transparent TiO2 microspheres thin film (8 μm). All the immersed factors were consistent with the devices fabrication conditions. As shown in Figure 2b, we can see that the absorption spectra on the TiO2 microspheres thin films are apparently broader. The broadened low-energy MLCT bands are beneficial for light-harvesting, which can generated more substantial photocurrent. Comparing with those in DMF solution, a slightly hypochromatic shift of lowenergy MLCT bands to high energy indicates a destabilization in the energy levels of the RC dye sensitizers on the TiO2 microspheres films.20 The destabilization may be caused by the deprotonation of carboxylic moieties on terpyridine ligand during the molecule-assembly procedure or the interaction between carboxylic moieties and the TiO2 thin film surface.21 To evaluate the electrochemical characteristics and energy levels of RC dyes, the cyclic voltammetry measurements (CV) were carried out. As presented in Figure 3 and Table 1, we can see that the ground-oxidation potential (E0S+/S, HOMO energy level) of the RC sensitizer is 0.99, 0.86, and 0.80 V for RC-T51, RC-T52, and RC-T53, respectively, which is more positive than that of I−/I3− redox couple (0.4 V vs NHE).2 These relative results ensure efficient dye regeneration process. The HOMO energy level of the RC dyes decrease with the enhanced electron-donating ability from the different ancillary ligands. The excited-oxidation potentials (E0S+/S*, LUMO energy level) of the RC sensitizers are obtained from the difference between the HOMO and excitation transition energies (E0−0), which are estimated from the absorption thresholds of dye absorption spectra. The LUMO energy level of RC-T51, RC-T52, and RC-T53 are −1.01, −1.06, and −1.08 V, respectively. These values of LUMO energy level are more

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RESULTS AND DISCUSSION The UV−vis absorption spectra of RC dye sensitizers in N,Ndimethylformamide solution are displayed in Figure 2a, and the detailed absorption data are summarized in Table 1. All these Table 1. Photophysical and Electrochemical Features for RC Dyes and N749 sensitizer

λmaxa (nm; ε/M−1 cm−1)

E0S+/Sb (V)

E0−0c (eV)

E0S+/S*d (V)

RC-T51 RC-T52 RC-T53 N749

428 (16440); 520 (14120) 385 (43960); 526 (21490) 402 (42700); 532 (26270) 396 (8850); 549 (5810)e

0.99 0.86 0.80 0.89e

2.00 1.92 1.88 1.70e

−1.01 −1.06 −1.08 −0.81e

Recorded in DMF (2 × 10−5 M) . bMeasured in 0.1 M TBAP/DMF, GC working and Pt counter electrodes and SCE as the reference electrode, scan rate = 100 mV s−1, all potentials measured vs SCE were converted to normal hydrogen electrode (NHE) by addition of 630 mV. cEstimated from the absorption threshold of the absorption spectra in solvent. dCalculated from E0S+/S − E0−0. eAccording to ref 10. a

ruthenium complexes featured three absorption bands in DMF solutions. In general, the absorption spectra of these dyes possess three bands caused by intraligand π−π* charge transfer transitions (ILCT) and metal-to-ligand charge transfer transitions (MLCT).6,10 In the UV region between 300 and 350 nm, the absorption bands of RC dye sensitizers are dominated by ILCT transition of the 4,4′,4″-tricarboxylic2,2′:6′,2″-terpyridine anchoring ligand. The absorption bands around 400 nm should be assigned to the mixture of ILCT transition of the terpyridine ligand and high energy MLCT C

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state lifetime of RC-T51, RC-T52, and RC-T53 is 39, 41, and 47 ns, respectively. When the dyes were used in the complete DSSC, the electron injection process always happened in fs-ps time range.24,25 The faster decay rate of the excited state lifetime of the excited-dye molecule is awaited to result the more efficient electron injection, shorter charge recombination time, and a decrease in kinetic redundancy.24,26 Durrant and coworkers27 found that the optimum DSSC performance could be obtained by adjusting the charge separation dynamics just fast enough to compete with the excited state decay rate. According to TRPL results, the decay rate of excited dyes in the complete DSSC was in the following order: RC-T53 > RC-T52 > RCT51. This order is well agreement with the performance of solar cells sensitized by RC dyes discussed in the following paper. The photovoltaic characteristics of solar cells sensitized by RC dyes are presented in Figure 5. The characteristic photovoltaic parameters, short circuit photocurrent density (JSC), open circuit voltage (VOC), fill factor (FF), and power conversion efficiency (η) are illustrated in Table 2. As shown in

Figure 3. Schematic representation of the ground/excited states energy levels of RC dye sensitizers.

negative than the conduction-band potential of TiO2 (−0.5 V vs NHE),2 confirming a sufficient electron injection from the excited state of the dyes into TiO2. What’s more, all RC sensitizers’ LUMO levels are higher than that of N749. The phenomena can be explained by the nature of the electrondonating system through the incorporation of different electron-donating ancillary ligands.20,22 Time-correlated photoluminescence (TRPL) measurements10,23 were employed to explore the luminescence decay properties of RC dyes in DMF solution and DSSC device. Figure 4 displays the luminescence decay properties of the RC

Table 2. Photovoltaic Performance of DSSCs Based on RC and N749 Sensitizers sensitizer

JSC (mA cm−2)

VOC (V)

FF

η (%)

dye loading (10−7 mol cm−2)

RC-T51 RC-T52 RC-T53 N749

12.03 13.57 14.20 15.49

0.645 0.611 0.630 0.710

0.69 0.70 0.69 0.70

5.35 5.80 6.17 7.69

1.41 1.19 1.33 1.55

Figure 5a, the devices based on RC-T51 (with methoxyphenylsubstituted ancillary bipyridine ligand) exhibit a JSC of 12.03 mA cm−2, a VOC of 0.645 V, and a η of 5.35%. With phenylcarbazol substituted bipyridyl ligand for the RC-T52 dye, the solar cell obtain a better JSC of 13.57 mA cm−2 and a VOC of 0.611 V, leading to a PCE value of 5.80%. The photovoltaic parameters of RC-T53 device are 14.20 mA cm−2 and 0.630 V, yielding a best PCE value of 6.17%. To assess the substantial photocurrent of the RC dye sensitizers, the typical photocurrent action spectra plotted as a function of wavelength along with RC-T51, RC-T52, and RCT53 are given in Figure 5b. The DSSC devices with RC dyes as sensitizer obtain the IPCE value around 50% from 410 to 570 nm. Comparing with other two dyes, the RC-T53 dye sensitizer gives better sensitization of TiO2 thin film extended to the whole visible region. The order of JSC values is consist with the relative electron-donating ability of the ancillary ligands. This

Figure 4. Excited state decay behavior of RC dye sensitizers.

dyes. All the dye solution was excited by a pulse laser (450 nm) and monitored at 760 nm. According to Figure 4, the excited

Figure 5. (a) Current density−voltage characterization for DSSC devices. (b) IPCE spectra of DSSCs sensitized by RC dye sensitizers. D

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Figure 6. HOMO-1, HOMO, LUMO, and LUMO+1 orbitals of RC sensitizers. Positive and negative lobes are presented by orange and purple colors, respectively, with an isosurface value of 0.02 Å−3.

Figure 7. Transient absorbance spectra of (a) RC-T53 and (b) N749 dye cation (S+) on TiO2 thin films in AN/VN (acetonitrile/valeronitrile) and the electrolyte with redox species.

donating ancillary ligands. The calculated HOMO-1, HOMO, LUMO, and LUMO+1 orbitals of RC sensitizers employing DFT calculations are displayed in Figure 6. The DFT calculations are performed using the with a Gaussian 09 program package at B3LYP energy functional and DGDZVP basis set. As same as N749, the LUMO and LUMO+1 orbitals of RC sensitizers are localized on the terpyridine ligands containing carboxylic groups. It is well-known that the delocalization of the HOMO energy level of N749 mainly exists on the three NCS ligand and extends into the terpyridyl scaffolding.10,31 For RC-T51 and RC-T52, however, the HOMO-1 and HOMO orbitals are mainly delocalized on the only existing NCS ligand and with minimal portion on the electron-donating ancillary ligands. Further, in the case of RCT53, the HOMO-1 and HOMO orbitals are mainly delocalized on the methoxy-triphenylamine bipyridyl ancillary ligand and with few parts on the NCS ligand. It has been demonstrated

indicate that the introduction of electron-donating ancillary ligands can apparently influence the capacity to generate more photocurrent of ruthenium dyes. Owing to the possibly serious electron recombination process occurring at the dyed-TiO2 film/electrolyte interface from the bulk electron-donating ancillary ligands of RC dyes, all RC dyes show attenuated VOC values.28 The RC-T52 record the lowest value among the three RC dye sensitizers.29 The serious charge recombination may be induced by the poor dye coverage on TiO2 thin film surface with resulting void spaces which could be speculated from the dye loading amount values (collected in Table 2).30 Under the similar fabrication conditions, the DSSC based on the benchmark N749 dye exhibited a JSC, VOC, and FF of 15.49 mA cm−2, 0.710 V, 0.70, respectively, corresponding to a PCE of 7.69%. The inferior performance of RC dyes can be explained in two aspects: (i) the change in the delocalization of the HOMO energy level inducing by the introduced electronE

DOI: 10.1021/acs.jpcc.7b01381 J. Phys. Chem. C XXXX, XXX, XXX−XXX

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The Journal of Physical Chemistry C that holding the HOMO energy level delocalized on the NCS ligand can generates more efficient electron transport and charge separation.31 Compared to N749, these changes in the delocalization of the HOMO-1 and HOMO energy level seriously worsen the charge transfer and separation in RC dyes, which should be ascribed to the lower efficiency of RC dyes compared with that of N749. (ii) The ruthenium dyes’ regeneration, in general, is dominated by a formation of dye cation/iodide intermediate species between oxidized dye and redox species in the electrolyte.32 The key for the formation of dye cation/iodide intermediate species is the binding of iodide species to the S atom in the NCS ligands.33 Whereas, the NCSless characteristic of RC dyes inhibit the formation of dye cation/iodide intermediate species even the efficient dye regeneration process. To further survey the dye regeneration dynamics of the RC and N749 dyes, we employed the transient absorption spectra (TAS) to investigate the dynamics of the photoexcited-state dye with dissociative electrons in the TiO2 conduction band or redox species in the electrolyte (EL).26,34 The representative TAS decay dynamics of the RC-T53 excited-state dye molecule on TiO2 films in inactive mixture (AN/VN, acetonitrile/valeronitrile) or redox species in EL are presented in Figure 7a. In the AN/VN mixture solution, the decay of absorption signals are ascribed to the charge transfer from TiO2 conduction band to the oxidized dye cation S+.34 The decay of absorption signals are well fitted to the exponential decay equation OD (Δt) = A0 + A1e−Δt/τ, featuring a fitted lifetime (τ0) of 24.22 μs. In the presence of EL containing I−/I3− redox species, the S+ can be regenerated not only by the injected electrons in the TiO2 conduction band but also by the I−/I3− redox species in the EL. As shown in the Figure 7a, the decay absorption signals in EL is significantly accelerated, and the fitted lifetime (τ1) of the dye regeneration process is 6.72 μs. The branching ratio of τ0 and τ1 is 3.60, indicating that only 72.2% of S+ can be regenerated. Whereas in the case of N749 (shown in Figure 7b), the corresponding fitted lifetime τ0 and τ1 are 17.91 and 1.37 μs, in the inactive mixture and EL, respectively. The branching ratio of τ0 and τ1 is over 13, indicating that more than 92.3% of S+ can be regenerated favorably. The facts demonstrate that the ineffective dye regeneration in the RC dye sensitized device, associated with the dye’s NCS-less characteristic, should be criticized for the poor performances compared with N749. A low-volatility electrolyte (1 M DMII, 0.15 M I2, 0.5 M Nbutylbenzimidazole and 0.1 M GuNCS in methoxypropionitrile) based DSSCs were resorted to evaluate the stability of the RC sensitizers. During the stability testing, all the three RC sensitizers showed similar performance. The emblematic photovoltaic parameters fluctuations of RC-T53 based solar cells are given in Figure 8. The original photovoltaic parameters of RC-T53 based solar cells (JSC, VOC, and PCE) are 13.2 mA cm−2, 0.55 V, and 5.08%, respectively. Throughout the test period, these parameters fluctuated slightly from the original values. The fact demonstrates the excellent stability for RC dye sensitizers.

Figure 8. Characteristic parameter variations during stability test for the devices sensitized by RC-T53 with low-volatility electrolyte.

ancillary ligand significantly improved the photophysical, electrochemical properties of ruthenium terpyridyl complexes and the excellent stability of the dye molecule skeleton. During the RC dyes, the device sensitized by RC-T53 which contained the MeO-TPA electron-donating antenna achieved the best short circuit photocurrent density of 14.20 mA cm−2 and power conversion efficiency of 6.17% under simulated AM 1.5G one sun (100 mW cm−2). Compared with N749, the relatively inferior performance of RC dyes were ascribed to the improper delocalization of the HOMO energy level and the inefficient dye generation process. The molecule engineering strategy offers an alternative route for the construction of more efficient and stable ruthenium terpyridyl complexes sensitizers.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpcc.7b01381. Detailed synthetic route and characterization of synthesized ligands and sensitizers (PDF).

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. Tel.: +86 55165593222. *E-mail: [email protected]. Tel.: +86 1061772268. ORCID

Fan-Tai Kong: 0000-0002-9548-6781 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We would like to express our gratitude for the financial support from the National Basic Research Program of China (No. 2015CB932200), CAS-Iranian Vice Presidency for Science and Technology Joint Research Project (No. 116134KYSB20160130), and Natural Science Foundation of Anhui Province (No. 1508085SMF224).

CONCLUSIONS We report a study on the synthesis, characterization of three ruthenium terpyridyl complex sensitizers incorporating efficient electron-donating ancillary ligands, coded as RC-T51, RC-T52, and RC-T53, and their application in dye-sensitized solar cells. The replacement of labile NCS by strong electron-donor F

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Dyes for Highly Efficient Dye-Sensitized Solar Cells. J. Phys. Chem. C 2015, 119, 21852−21859. (19) Liu, S. D.; Ren, Y. K.; Zhou, Z.; Chen, W. C.; Li, Z. Q.; Guo, F. L.; Dai, S. Y. Synthesis of TiO2 Microspheres Building on the Etherification and its Application for High Efficiency Solar Cells. J. Power Sources 2016, 329, 225−231. (20) Chen, W. C.; Kong, F. T.; Li, Z. Q.; Pan, J. H.; Liu, X. P.; Guo, F. L.; Zhou, L.; Huang, Y.; Yu, T.; Dai, S. Y. Superior Light-Harvesting Heteroleptic Ruthenium (II) Complexes with Electron-Donating Antennas for High Performance Dye-Sensitized Solar Cells. ACS Appl. Mater. Interfaces 2016, 8, 19410−19417. (21) Nazeeruddin, M. K.; Humphry-Baker, R.; Liska, P.; Grätzel, M. Investigation of Sensitizer Adsorption and the Influence of Protons on Current and Voltage of a Dye-Sensitized Nanocrystalline TiO2 Solar Cell. J. Phys. Chem. B 2003, 107, 8981−8987. (22) El-Shafei, A.; Hussain, M.; Islam, A.; Han, L. Structure-Property Relationship of Hetero-Aromatic Electron-Donor Antennas of Polypyridyl Ru (II) Complexes for High Efficiency Dye-Sensitized Solar Cells. Prog. Photovoltaics 2014, 22, 958−969. (23) Chen, W. C.; Kong, F. T.; Liu, X. P.; Guo, F. L.; Zhou, L.; Ding, Y.; Li, Z. Q.; Dai, S. Y. Effect of Electron-Donor Ancillary Ligands on the Heteroleptic Ruthenium Complexes: Synthesis, Characterization, and Application in High-Performance Dye-Sensitized Solar Cells. Phys. Chem. Chem. Phys. 2016, 18, 11213−11219. (24) Haque, S. A.; Palomares, E.; Cho, B. M.; Green, A. N.; Hirata, N.; Klug, D. R.; Durrant, J. R. Charge Separation versus Recombination in Dye-Sensitized Nanocrystalline Solar Cells: the Minimization of Kinetic Redundancy. J. Am. Chem. Soc. 2005, 127, 3456−3462. (25) Barnes, P. R.; Miettunen, K.; Li, X.; Anderson, A. Y.; Bessho, T.; Grätzel, M.; O’Regan, B. C. Interpretation of Optoelectronic Transient and Charge Extraction Measurements in Dye-Sensitized Solar Cells. Adv. Mater. 2013, 25, 1881−1922. (26) Antila, L. J.; Myllyperkiö, P.; Mustalahti, S.; Lehtivuori, H.; Korppi-Tommola, J. Injection and Ultrafast Regeneration in DyeSensitized Solar Cells. J. Phys. Chem. C 2014, 118, 7772−7780. (27) Koops, S. E.; Durrant, J. R. Transient Emission Studies of Electron Injection in Dye Sensitised Solar Cells. Inorg. Chim. Acta 2008, 361, 663−670. (28) Singh, S. P.; Gupta, K. S. V.; Chandrasekharam, M.; Islam, A.; Han, L.; Yoshikawa, S.; Haga, M. A.; Roy, M. S.; Sharma, G. D. 2, 6-Bis (1-methylbenzimidazol-2-yl) pyridine: A New Ancillary Ligand for Efficient Thiocyanate-Free Ruthenium Sensitizer in Dye-Sensitized Solar Cell Applications. ACS Appl. Mater. Interfaces 2013, 5, 11623− 11630. (29) Daeneke, T.; Mozer, A. J.; Kwon, T. H.; Duffy, N. W.; Holmes, A. B.; Bach, U.; Spiccia, L. Dye Regeneration and Charge Recombination in Dye-Sensitized Solar Cells with Ferrocene Derivatives as Redox Mediators. Energy Environ. Sci. 2012, 5, 7090− 7099. (30) Abrahamsson, M.; Johansson, P. G.; Ardo, S.; Kopecky, A.; Galoppini, E.; Meyer, G. J. Decreased Interfacial Charge Recombination Rate Constants with N3-Type Sensitizers. J. Phys. Chem. Lett. 2010, 1, 1725−1728. (31) Koyyada, G.; CH, P. K.; Salvatori, P.; Marotta, G.; Lobello, M. G.; Bizzarri, O.; Angelis, F. De; Malapaka, C. New Terpyridine-Based Ruthenium Complexes for Dye Sensitized Solar Cells Applications. Inorg. Chim. Acta 2016, 442, 158−166. (32) Clifford, J. N.; Palomares, E.; Nazeeruddin, M. K.; Grätzel, M.; Durrant, J. R. Dye Dependent Regeneration Dynamics in Dye Sensitized Nanocrystalline Solar Cells: Evidence for the Formation of a Ruthenium Bipyridyl Cation/Iodide Intermediate. J. Phys. Chem. C 2007, 111, 6561−6567. (33) Lobello, M. G.; Fantacci, S.; De Angelis, F. Computational Spectroscopy Characterization of the Species Involved in Dye Oxidation and Regeneration Processes in Dye-Sensitized Solar Cells. J. Phys. Chem. C 2011, 115, 18863−18872. (34) Chen, W. C.; Kong, F. T.; Ghadari, R.; Li, Z. Q.; Guo, F. L.; Liu, X. P.; Huang, Y.; Yu, T.; Hayat, T.; Dai, S. Y. Unravelling the

REFERENCES

(1) Robertson, N. Optimizing Dyes for Dye-Sensitized Solar Cells. Angew. Chem., Int. Ed. 2006, 45, 2338−2345. (2) Hagfeldt, A.; Boschloo, G.; Sun, L.; Kloo, L.; Pettersson, H. Dye Sensitized Solar Cells. Chem. Rev. 2010, 110, 6595−6663. (3) Zhang, X.; Xu, Y.; Giordano, F.; Schreier, M.; Pellet, N.; Hu, Y.; Yi, C.; Robertson, N.; Hua, J.; Zakeeruddin, S. M.; et al. Molecular Engineering of Potent Sensitizers for Very Efficient Light Harvesting in Thin-Film Solid-State Dye-Sensitized Solar Cells. J. Am. Chem. Soc. 2016, 138, 10742−10745. (4) Li, L. L.; Diau, E. W. Porphyrin-Sensitized Solar Cells. Chem. Soc. Rev. 2013, 42, 291−304. (5) Spettel, K. E.; Damrauer, N. H. Exploiting Conformational Dynamics of Structurally Tuned Aryl-Substituted Terpyridyl Ruthenium(II) Complexes to Inhibit Charge Recombination in DyeSensitized Solar Cells. J. Phys. Chem. C 2016, 120, 10815−10829. (6) Huang, W. K.; Wu, H. P.; Lin, P. L.; Diau, E. W. G. Design and Characterization of Heteroleptic Ruthenium Complexes Containing Benzimidazole Ligands for Dye-Sensitized Solar Cells: The Effect of Thiophene and Alkyl Substituents on Photovoltaic Performance. J. Phys. Chem. C 2013, 117, 2059−2065. (7) Kono, T.; Masaki, N.; Nishikawa, M.; Tamura, R.; Matsuzaki, H.; Kimura, M.; Mori, S. Interfacial Charge Transfer in Dye-Sensitized Solar Cells Using SCN-Free Terpyridine Coordinated Ru Complex Dye and Co Complex Redox Couples. ACS Appl. Mater. Interfaces 2016, 8, 16677−16683. (8) Yin, J. F.; Velayudham, M.; Bhattacharya, D.; Lin, H. C.; Lu, K. L. Structure Optimization of Ruthenium Photosensitizers for Efficient Dye-Sensitized Solar Cells-a Goal toward a “Bright” Future. Coord. Chem. Rev. 2012, 256, 3008−3035. (9) Numata, Y.; Islam, A.; Sodeyama, K.; Chen, Z. H.; Tateyama, Y.; Han, L. Substitution Effects of Ru-Terpyridyl Complexes on Photovoltaic and Carrier Transport Properties in Dye-Sensitized Solar Cells. J. Mater. Chem. A 2013, 1, 11033−11042. (10) El-Sherbiny, D.; Cheema, H.; El-Essawy, F.; Abdel-Megied, A.; El-Shafei, A. Synthesis and Characterization of Novel Carbazole-Based Terpyridyl Photosensitizers for Dye-Sensitized Solar Cells (DSSCs). Dyes Pigm. 2015, 115, 81−87. (11) Han, L.; Islam, A.; Chen, H.; Malapaka, C.; Chiranjeevi, B.; Zhang, S.; Yang, X.; Yanagida, M. High-Efficiency Dye-Sensitized Solar Cell with a Novel Co-Adsorbent. Energy Environ. Sci. 2012, 5, 6057− 6060. (12) Wang, P.; Klein, C.; Humphry-Baker, R.; Zakeeruddin, S. M.; Grätzel, M. A High Molar Extinction Coefficient Sensitizer for Stable Dye-Sensitized Solar Cells. J. Am. Chem. Soc. 2005, 127, 808−809. (13) Dong, R.; Calzolari, A.; di Felice, R.; El-Shafei, A.; Hussain, M.; Buongiorno Nardelli, M. Optical Enhancement in Heteroleptic Ru (II) Polypyridyl Complexes Using Electron-Donor Ancillary Ligands. J. Phys. Chem. C 2014, 118, 8747−8755. (14) Wu, K. L.; Ku, W. P.; Clifford, J. N.; Palomares, E.; Ho, S. T.; Chi, Y.; Liu, S. H.; Chou, P. T.; Nazeeruddin, M. K.; Grätzel, M. Harnessing the Open-Circuit Voltage via a New Series of Ru (II) Sensitizers Bearing (iso-) Quinolinyl Pyrazolate Ancillaries. Energy Environ. Sci. 2013, 6, 859−870. (15) Yang, S. H.; Wu, K. L.; Chi, Y.; Cheng, Y. M.; Chou, P. T. Tris (thiocyanate) Ruthenium (II) Sensitizers with Functionalized Dicarboxyterpyridine for Dye-Sensitized Solar Cells. Angew. Chem., Int. Ed. 2011, 50, 8270−8274. (16) Cao, K.; Lu, J.; Cui, J.; Shen, Y.; Chen, W.; Alemu, G.; Wang, Z.; Yuan, H.; Xu, J.; Wang, M.; et al. Highly Efficient Light Harvesting Ruthenium Sensitizers for Dye-Sensitized Solar Cells Featuring Triphenylamine Donor Antennas. J. Mater. Chem. A 2014, 2, 4945− 4953. (17) Li, Z. Q.; Chen, W. C.; Guo, F. L.; Mo, L. E.; Hu, L. H.; Dai, S. Y. Mesoporous TiO2 Yolk-Shell Microspheres for Dye-Sensitized Solar Cells with a High Efficiency Exceeding 11%. Sci. Rep. 2015, 5, 14178. (18) Yang, Z.; Liu, C.; Shao, C.; Lin, C.; Liu, Y. First-Principles Screening and Design of Novel Triphenylamine-Based D-π-A Organic G

DOI: 10.1021/acs.jpcc.7b01381 J. Phys. Chem. C XXXX, XXX, XXX−XXX

Article

The Journal of Physical Chemistry C Structural-Electronic Impact of Arylamine Electron-Donating Antennas on the Performances of Efficient Ruthenium Sensitizers for DyeSensitized Solar Cells. J. Power Sources 2017, 346, 71−79.

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DOI: 10.1021/acs.jpcc.7b01381 J. Phys. Chem. C XXXX, XXX, XXX−XXX