Copolymers of ionic liquids with polymeric or metallocomplex chromophores for quasi-solid-state DSSC applications

Article abstract of DOI:10.1039/c5ra27374a

The development of copolymers based on ionic liquid vinyl monomers of the imidazole family combined with polymerizable chromophoric units is presented herein. For this end, ruthenium complexes bearing polymerizable vinyl groups or ω-end vinyl rr-poly(3-alkyl thiophene) were prepared and copolymerized with the ionic liquid monomers under free radical polymerization conditions, affording chromophore/polyelectrolyte combinations. Homopolymer ionic liquids were also synthesized to select the optimum conditions for the copolymers thereafter. All the monomers and polymers were characterized for their optical properties, and were also structurally characterized using various complementary techniques. Selected copolymers and homopolymers were tested in quasi-solid-state sensitized solar cells based on titania and regioregular poly(3-hexyl thiophene) acting as a hole-transporting semiconducting polymer. The ionic liquid, which is miscible with the hole-conductor and can be deposited with the latter, provides a functionality that, in some cases, supports an increase in open-circuit voltage, thus increasing cell efficiency.

Full text of DOI:10.1039/c5ra27374a

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A. K. Andreopoulou, C. Anastasopoulos, D. Raptis, G. Sfyri, J. K. Kallitsis and P. Lianos, RSC Adv., 2016,
DOI: 10.1039/C5RA27374A.
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Copolymers of Ionic Liquids with Polymeric or Metallocomplex
Chromophores for Quasi-Solid State DSSC Applications
Panagiotis Giannopoulos,a Aikaterini K. Andreopoulou,a,b* Charalampos Anastasopoulos,a Dimitrios
Raptisb,c, Georgia Sfyrib,d, Joannis K. Kallitsis,a,b Panagiotis Lianosb,c
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a Department of Chemistry, University of Patras, University Campus, RioꢀPatras, GR26504, Greece
b Foundation for Research and Technology Hellas / Institute of Chemical Engineering Sciences (FORTH/ICEꢀ
HT), Platani Str., Patras, GR26504, Greece
c Department of Chemical Engineering, University of Patras, 26504 Patras, Greece.
d Department of Physics, University of Patras, 26504 Patras, Greece
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Abstract: The development of copolymers based on ionic liquid vinylꢀmonomers of the imidazole family,
which are combined with polymerizable chormophoric units, is presented herein. Thus, ruthenium complexes
bearing polymerizable vinyl groups or ωꢀend vinyl rrꢀpoly(3ꢀalkyl thiophene) were prepared and
copolymerized with the ionic liquid monomers under free radical polymerization conditions affording
chromophore/polyelectrolyte combinations. Homopolymer ionic liquids were also synthesized in order to
select the optimum conditions for the copolymers thereafter. All monomers and polymers were characterized
for their optical properties and were also structurally characterized using various complementary techniques.
Selected copolymers and homopolymers were tested in quasiꢀsolidꢀstate sensitized solar cells based on titania
and regioregular poly(3ꢀhexyl thiophene) acting as holeꢀtransporting semiconducting polymer. The ionic
liquid, which is miscible with the holeꢀconductor and can be deposited with the latter, provides a functionality
that, in some cases, supports the increase of openꢀcircuit voltage thus increasing cell efficiency.
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[1]

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Introduction
Research is focusing over the last years in the replacement of siliconꢀ based photovoltaic devices. This is
mainly due to their high cost of production and the limited range of applicable materials, something that
turned the interest to organic photovoltaic devices (OPVs), where the active layers of the device mainly
consist of organic materials1. OPVs show some advantages regarding the cost and environmental issues
despite their lower efficiency in comparison to inorganic light converters that are currently commercially
available. One technology that has shown increased conversion efficiency among OPVs is dyeꢀsensitized solar
cells (DSSCs)2.
In a typical DSSC, an inorganic semiconductor, usually TiO23,4,5,6 or ZnO7,8, acts as an electron acceptor and
transporter. The semiconductor also supports the sensitizer, i.e. a material that absorbs visible light and injects
the photogenerated electron into the conduction band of the supporting (acceptor) semiconductor. In DSSCs, a
dye plays the role of sensitizer. The dye must have anchoring groups to form stable bonds with the
semiconductor's surface. Such anchoring groups are mainly carboxylic, although other anchors have been
suggested, such as the perfluorophenyl group, which was recently reported by our group9,10. The remaining
functional components of a DSSC are a counter electrode, carrying usually Pt nanoparticles as catalyst,
although various attempts have been reported aiming to the replacement of Pt mainly with carbon hybrids11,
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and an electrolyte12,13,14
.
The electrolyte in DSSCs is very important, because it provides the required ionic conductivity and helps dye
regeneration with charge transfer reactions with the dye molecules. Liquid electrolytes present a major
drawback in the use of DSSCs due to solvent evaporation and the reduction of device lifetime and
performance, especially when the device is not perfectly sealed15. Thus, the replacement of typical solvents (or
solvent mixtures) with solid or quasi solid electrolytes is a very interesting and active field of research16.
Commonly ionic liquids, pꢀtype holeꢀtransport organic semiconductors, plastic crystals and polymer gel
electrolytes have been used instead of the typical liquid ones. This kind of electrolytes show long term
stability, although in many cases the efficiency remained lower when compared with typical
DSSCs17,18,19,20,21,22,23,2425
.
ILs are widely studied organic salts, that have gained much attention for a wide range of applications in
various chemical and industrial fields. This is attributed to their unique properties, such as high ionic
conductivity, good thermal, chemical and electrochemical stability and low vapor pressure26,27. Due to these
properties, ILs are commonly used as solvents for organic synthesis or catalysis (green solvents) and
polymerization processes, such as free radical polymerization28,29 and atom transfer radical polymerization
(ATRP)30,31. Their use is also extended into other applications, such as lithium batteries32,33,34, light emitting
devices35 and electrochemical capacitors36. Various IL chemical structures have been reported employing for
example imidazolium or pyrrolidinium moieties as cations and hexafluorophosphate or tetrafluoroborate as
anions. In the field of DSSCs, imidazoliumꢀbased ionic liquids37,38,39, or more recently electrolytes based on
these ionic liquids40,41 have been studied.
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Polymerizable ionic liquid monomers and their respective polymers (PILs) are recently considered as a
specific field in polymer science. These polymeric ionic liquids show increased thermal stability combined
with interesting electrochemical properties. One of the most studied imidazolium based PIL is poly[1ꢀ(4ꢀ
vinylbenzyl)ꢀ3ꢀbutyl imidazolium tetrafluoroborate] (PVBT) which remains stable up to 300 °C42, is highly
polar, is soluble in solvents such as N,Nꢀdimethylformamide (DMF), dimethylsulfoxide (DMSO) or
acetonitrile because of its ionic nature, and at the same time is hydrophobic. Polymeric ionic liquids (PILs) are
identified as exotic polyelectrolytes for various applications, like in dyeꢀsensitized solar cells (DSSCs) in
which they could effectively replace liquid electrolytes used up to now43,44,45,46. Although a lot of progress has
been reported in this field, with recent works aiming to the formation of ILꢀbased hybrids47,48, the use of ILꢀ
based polymer gels has only resulted to a few successful works28,49 and even less with the employment of
copolymers50. Despite that, research is focusing on this topic, since ILs can overcome solvent electrolyte
leakage, whereas the combination of an IL based electrolyte with a dye could improve cell stability without
sacrificing the overall efficiency of the cell51.
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An optimum concept for such organic solventꢀfree quasiꢀsolidꢀstate DSSCs, could be the simultaneous
incorporation of chromophores and ILs that should broaden absorption and ion transfer in the final device.
These facts urged us to investigate the use of PILs as electrolytes in DSSC applications and compare them
with copolymers based on ILs and suitable dyes. Both organic dyes and metallocomplexes have been
employed, in order to compare the applicability of organic versus organometallic dyes, even though the
drawbacks of ruthenium (or other metal) containing dyes, such as toxicity and availability, should be also
taken into consideration. Therefore, in the present study, we employed two polymerizable vinylꢀILs, namely
1ꢀ(4ꢀvinylbenzyl)ꢀ3ꢀmethyl imidazolium tetrafluoroborate (VBMImT) 52 and 1ꢀvinylꢀ3ꢀhexylꢀimidazolium
bromide (VHImBr) 53 and polymerizable dye (macro)molecules, a low molecular weight ωꢀend vinyl
terminated regioregular poly (3ꢀalkylthiophene)54 and a vinylphenylꢀbipyridine ruthenium complex with two
bipyridines as coꢀligands55, in order to prepare homopolymer and copolymer PILs. Polymerizations were
carried out in various conditions in order to achieve the best yields for the homopolymers, but also as a first
test regarding the forthcoming copolymerizations. Through this route, the homopolymers PVBMImT and
PVHImBr were synthesized, followed by the synthesis of copolymers based in the ionic liquids combined
with the ωꢀend vinylꢀpoly(3ꢀoctylꢀthiophene) or the (vinylphenylꢀbipyridine)ꢀRu(II)ꢀdi(bipyridine) complex.
Both homopolymer and copolymer PILs were structurally characterized and also their optical properties were
evaluated. Such materials were then employed in the fabrication of solar cells and the testing of their
performance.
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Experimental Section
Materials
ωꢀend vinylꢀpoly(3ꢀoctylthiophene) (vinylꢀP3OT)54 and Ru(bpy)2(styrylbpy)55 were prepared according to
literature. The synthetic procedures of the ionic liquid monomers VBMImT52 and VHImBr53 are given in the
Supporting Information.
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All solvents and reagents were purchased from Sigma Aldrich, Alfa Aesar or Acros Organics and were used
without further purification unless otherwise stated. All reactions were carried out under argon atmosphere.
Tetrahydrofuran (THF) was dried and distilled just before use over sodium wire in the presence of
benzophenone. Acetonitrile (MeCN) was dried and distilled over calcium hydride (CaH2). 2,2′ꢀAzobis(2ꢀ
methylpropionitrile) (AIBN) was recrystallized using methanol (MeOH).
Dye sensitizer N719 was obtained from Solaronix, conductive polymer PEDOT:PSS (Baytron P) from
H.C.Starck, regioregular poly(3ꢀhexyl thiophene) from Rieke Metals and silver ink (5007E) from DuPont.
Characterization methods
1H NMR spectra were recorded on a Bruker Advance DPX 400.13 MHz spectrometer, using MeOHꢀd1,
DMSOꢀd6 or CDCl3 as solvents containing TMS as internal standard.
Thermogravimetric analysis (TGA) was carried out on about 8 mg samples contained in alumina crucibles in a
Labsys TM TG apparatus of Setaram under nitrogen and at a heating rate of 10 oC minꢀ1.
IR spectra were recorded on an ALPHAꢀP diamond ATR spectrometer of Bruker Optics GmbH.
Mass spectra were recorded on a Waters Acquity ESIꢀMS system with a Waters 2966 Photodiode Array
detector coupled to a Waters Micromass ZQ mass spectrometer. A singleꢀquadrupole Quattro micro mass
spectrometer (ACQUITY SQ Detector) equipped with an electrospray ionization (ESI) interface was used for
analytical detection. ESIꢀMS was operated in positive mode under the following operating parameters:
o
o
capillary voltage, 3.5 kV; cone voltage, 30 V; source temperature, 80 C; desolvation temperature, 300 C;
desolvation gas (nitrogen), 5500 L/h; cone gas (nitrogen), 50 L/h. All data were acquired and processed using
Masslynx 4.1 software (Waters Corp., MA, Milford, USA).
Size exclusion chromatography (SEC) measurements were carried out at 25 °C with a flow rate of 1 mL/min,
using a polymer lab chromatographer equipped with two Ultra Styragel linear columns (104 Å, 500 Å) and a
UV detector. Polystyrene standards were used for the calibration and the eluent was CHCl3.
UVꢀVis spectra were recorded using a Hitachi Uꢀ1800 spectrophotometer. Photoluminescence (PL) spectra
were recorded using a Perkin–Elmer LS45 luminescence spectrometer, after excitation at the UVꢀVis
absorption maxima.
For solar cell characterization, illumination of the samples was made with a PECCELL PECꢀL01
35
Solar Simulator set at 100 mW/cm2. J−V characteristic curves were recorded under ambient
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conditions with a Keithley 2601 source meter that was controlled by Keithley computer software
(LabTracer).
Transmission electron microscopy (TEM) measurements were performed on a JEOL JEM2100 operating at
200 kV. Sample preparation for TEM examination involved the preparation of dilute solutions of the samples
in CHCl3. A drop of the solution was placed on 3 mm carbon coated copper grids (Electron Microscopy
Sciences) and the samples were dried in air for 2 days.
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Synthetic Procedures
Synthesis of homopolymers PVBMImT and PVHImBr
Polymerizations of the above monomers were carried out in dry MeCN, under inert atmosphere. MeCN was
used as solvent, using different solvents and monomer/initiator ratios, as shown in Table 1. Specifically, using
the optimum procedure's conditions, 1.155 mmol (1.5 eq) of using monomer (either VBMImT or VHImBr)
and 0.077 mmol AIBN (0.1 eq), were dissolved in 2 mL MeCN, under inert atmosphere and heated at reflux
for 24 h. The formed polymer was precipitated with diethyl ether at 0 oC and dried in a vacuum oven at 60 oC
overnight.
Synthesis of copolymer poly(P3OTꢀcoꢀVBMImT)
VinylꢀP3OT nꢀhexane fraction (40 mg) and VBMImT (320 mg) were dissolved in a dry MeCN/Chloroform
mixture (10 mL, 1/1:v/v) (with the addition of 0.2 mL oDCB in order to fully dissolve vP3OT) in a round
bottom flask, equipped with a stirring bar and a reflux condenser under inert atmosphere. AIBN (10.8 mg) was
then added, the system was degassed again and heated at reflux for 48 h. The solvents were removed after
heating at 60 oC. The forming copolymer was washed consecutively with ethyl acetate (EtOAc) and MeCN in
order to remove unreacted species. The reddish solid, was filtrated and dried under vacuum overnight.
Synthesis of copolymer poly(P3OTꢀcoꢀVHImBr)
The copolymerization of vinylꢀP3OT (40 mg) with VHImBr (320 mg) was carried out using analogous
conditions to the as described before poly(P3OTꢀcoꢀVBMT) (Polymer 1) with a slight modification. Instead of
the MeCN/chloroform mixture, only chloroform was used (again with the addition of 0.2 mL oDCB) since the
VHImBr monomer is also soluble in chloroform.
Synthesis of copolymer poly(RuꢀcoꢀVBMImT)
Ru(bpy)2(styrylbpy)55 (61 mg, 0.06 mmol) and VBMImT (100 mg, 0.35 mmol) were dissolved in 3 mL of dry
MeCN, under inert atmosphere. Afterwards, 5.2 mg (0.03 mmol) AIBN were added and the system was
heated at reflux for 48 h. The solution was cooled to RT, filtered and thoroughly washed with MeCN. The
remaining solid was dried under vacuum overnight and used without further purification.
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Fabrication of quasi-solid-state DSSCs
The cells studied in the present work were quasiꢀsolidꢀstate DSSCs with a layer structure obeying the
following configuration: (1) a layer of mesoscopic titania sensitized with a standard dye sensitizer; (2) a mixed
layer composed of a blend of the hole transporting polymer P3HT (Poly(3ꢀhexylthiopheneꢀ2,5ꢀdiyl) with
polymeric ionic liquid at various proportions; and (3) a top layer of conductive PEDOT:PSS plus silver
conduct electrodes making the counter electrode. Such cells were fabricated as follows. FTOꢀcoated glass
substrates were cut in pieces of dimensions 1 cm × 3 cm. One third of the conductive layer was removed using
zinc powder and hydrochloric acid. Then they were washed with detergent, rinsed with distilled water and
subsequently with ethanol in an ultrasonic bath, finally dried under air stream. A thin layer of compact titania
was first sprayed over the patterned FTO electrode using 0.2 mol Lꢀ1 diisopropoxytitanium
bis(acetylacetonate) solution in ethanol and then it was heated at 500 °C for 1 h. On this thin bottom layer, a
titania paste made of P25 nanoparticles was applied by screen printing. 90 mesh screen was used. The film
was heated again up to 500 °C for 20 min. Then, the film was treated with a 0.04 mol L−1 aqueous solution of
TiCl4 for 30 min at 70 °C, followed by heating up to 500 °C for 20 min. This final titania film was about 10
µm thick, as determined by its profile using SEM. As soon as the final film was taken out of the oven, it was
dipped in a 0.5 mmol L−1 N719 solution in ethanol containing 5 mmol L−1 chenodeoxycholic acid and was left
overnight. The film was then heavily coloured with attached dye. It was rinsed with ethanol and dried in a N2
stream. The presence of chenodeoxycholic acid is a recent common practice56,57 and it was beneficial also in
the present case. Next step of cell fabrication was the deposition of the mixture of the hole transporting P3HT
with polymeric ionic liquid. The mixture was prepared by making 20 mg/mL solutions in chloroform using
various proportions of the two materials. Optimal results were obtained by mixing 18 mg of P3HT with 2 mg
of polymeric ionic liquid. Both homopolymer and copolymer ionic liquids were tried. This layer was
deposited by spinꢀcoating at 3000 rpm for 1 min and it was dried in an oven for 15 min at 100 °C. Then a
layer of PEDOT:PSS was deposited by spin coating the commercial solution at 1500 rpm, which was annealed
in an oven for 15 min at 150 °C. Finally, silver electrodes were painted on the top with a brush using a mask.
The electrodes were rapidly annealed (30 s) at 130 °C. Their size was 1 mm x 10 mm.
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Results and Discussion
Synthesis of the vinyl monomer ILs
The first step of this work was the synthesis of IL polymerizable monomers. We used two different starting
materials, 1ꢀvinyl imidazole and 1ꢀmethyl imidazole, in order to synthesize two, different type of ionic liquid
monomers. As a result we obtained two monomers, 1ꢀ(4ꢀvinylbenzyl)ꢀ3ꢀmethyl imidazolium tetrafluoroborate
(VBMImT)52 (after ion exchange between chloride and tetrafluoroborate) and 1ꢀvinylꢀ3ꢀhexylꢀimidazolium
bromide (VHImBr)53.
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Scheme 1: Synthetic procedures for the monomer VBMImT and for the homopolymer PVBMImT.
Scheme 2: Synthetic procedures for the monomer VHImBr and for the homopolymer PVHImBr.
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The first part of Schemes 1 and 2 show the synthetic procedures for the preparation of the ionic liquid
monomers VBMImT and VHImBr respectively.
1
The successful formation of the desired monomers was confirmed by H NMR (Figures S1a, S2a) and ESIꢀ
MS (Figure S3). The assignment of the NMR peaks, to the monomers' protons show the absence of any
byproducts. This is also proven by the mass spectra, which show the M+ ion mass as the ESIꢀMS instrument
has been tuned in positive ion mode. In the case of VBMImT, an intense m/z of 117.38 [M+] and 118.39
[M+H+] can be observed, besides the one at 199.32 [M+] and 200.33 [M+H+] attributed to the product. This
peak is due to the fragment that occurs when the methylimidazolium unit has been cleaved from VBMImT. IR
spectroscopy of the monomers was also carried out as shown in Figures S4a and S4b for the two monomers,
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respectively, and in comparison to the starting materials in each case. In both ionic liquid monomers,
characteristic bands from the presence of the imidazolium unit can be observed. More specifically, the
symmetric C=C stretching vibration around 1565ꢀ1570 cmꢀ1, the aromatic CꢀH stretch (3050ꢀ3100 cmꢀ1), the
C=N stretch (1630ꢀ1650 cmꢀ1), the CꢀN stretch (1160ꢀ1170 cmꢀ1) and the inꢀplane CꢀC vibrations of the
imidazolium ring (around 1580 cmꢀ1) exist in both products. On the other hand, the VBMImT monomer
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ꢀ
presents two peaks at 760 cmꢀ1 and 1150 cmꢀ1, respectively, due to the BF4 anion. The VHImBr monomer
shows an aliphatic CꢀH peak around 2850 cmꢀ1 because of the hexyl chain and a broad peak at 3300 – 3500
cmꢀ1, due to the hydration of the ionic liquid58,59,60,61
.
Preparation of homopolymers and copolymers
For the synthesis of the homopolymers PVBMImT and PVHImBr (as shown in Scheme 1 and 2,
respectively), a number of different conditions were tested (Table 1) by varying the monomer to initiator ratio
and the solvent used. Successful polymerizations were obtained using the conditions of entries 3, 5 and 6 of
Table 1. As it can be seen from the data of Table 1, best results were obtained when MeCN and/or CHCl3
1
were used as solvents. After purification, the formed homopolymers were characterized via H NMR
spectroscopy (Figure S1b and S2b) and via ATR spectroscopy (the respective ATR spectra are given in
Figures 2a and 2b in comparison to the respective copolymers with vinylꢀP3OT as will be described below).
1
From the H NMR characterization of the homopolymers (Figure S1b for PVBMImT and Figure S2b for
PVHImBr) compared to their respective monomers (Figures S1a and S2a, respectively), no monomer
residues can be observed since the vinyl protons (located at 5.2, 5.6 and 6.8 ppm) have disappeared
completely and broad peaks are formed proving the polymeric nature of the final purified products.
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Table 1: Polymerization conditions used for the preparation of homopolymers PVBMImT and PVHImBr, and
for the copolymers poly(P3OTꢀcoꢀVBMImT), poly(P3OTꢀcoꢀVHImBr) and poly(RuꢀcoꢀVBMImT).
a/a
Monomer
Solvent
Homopolymers
Monomer/AIBN ratio
VBMImT
VBMImT
VBMImT
VHImBr
VHImBr
VHImBr
DMF
DMSO
20/1
15/1
15/1
20/1
15/1
15/1
1
2
3
4
5
6
MeCN (dry)
DMF
CHCl3
MeCN (dry)
Copolymers
MeCN (dry)/
CHCl3
VBMImT/vꢀP3OT
VHImBr/vꢀP3OT
15/1
1
CHCl3
15/1
11/1
2
3
VBMImT/Ru(bpy)2(styrylbpy) MeCN (dry)
5
After the successful formation of the homopolymers, respective copolymers based on the ionic liquid vinyl
monomers and vinyl functionalized dye molecules, either a ωꢀend vinylꢀpolythiophene macromonomer
(Schemes 3) or a ruthenium complex (Scheme 4) were formed.
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Scheme 3: Synthesis of polythiophene – ionic liquid random copolymers poly(P3OTꢀcoꢀVBMImT) and
poly(P3OTꢀcoꢀVHImBr).
(a)
(b)
poly(P3OT-co-VHImBr)
poly(P3OT-co-VBMImT
)
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6
5
4
3
2
1
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7
6
5
4
3
2
1
Chemical Shift (ppm)
Chemical Shift (ppm)
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Figure 1: 1H NMR of poly(P3OTꢀcoꢀVBMImT) (a) and poly(P3OTꢀcoꢀVHImBr) (b) in CDCl3.
1
For the polythiophene containing copolymers of Scheme 3, their H NMR characterization (Figures 1a and
1b), using CDCl3, revealed the disappearance of the vinyl groups (located at 5.2, 5.6 and 6.8 ppm) which
demonstrates the full conversion of the monomers to polymers. The conversion of the ionic liquid monomers
was further confirmed by ATR spectroscopy (Figure 2). The existence of a small peak at 2900 cmꢀ1 in
PVBMImT but not in VBMImT is due to the conversion of vinyl groups (CH2=CH bond) to the polymeric
chain (CH2ꢀCH bond). This alternation could not be observed among the VHImBr and the PVHImBr, because
VHImBr bears an alkyl hexyl chain which absorbs in the same region. After the copolymerization of the IL
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vinyl monomers with vinylꢀP3OT, the specific peak is more intense, because of the thiophene's octyl chain.
Vibrations from the imidazolium group can be observed at 1040 and 1140 cmꢀ1 due to the CꢀN bond and near
1550 cmꢀ1 due to C=N59,62. Furthermore, bands appearing in the area 700 – 900 cmꢀ1 can also be ascribed to
contributions from ring bending modes of the imidazolium cation63.
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(a)
(b)
VHImBr
PVHImBr
vP3OT
VBMImT
PVBMImT
vP3OT
poly(P3OT-co-VHImBr)
poly(P3OT-co-VBMImT)
4000 3500 3000 2500 2000 1500 1000 500
4000 3500 3000 2500 2000 1500 1000 500
-1
-1
Wavenumbers (cm )
Wavenumbers (cm )
Figure 2: ATR spectra of poly(P3OTꢀcoꢀVBMImT) (a) and poly(P3OTꢀcoꢀVHImBr) (b) in comparison to the
starting materials and the respective homopolymers.
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Efforts were also done for the characterization of the copolymers via GPC. However, due to the ionic nature
and the nitrogen containing heterocycles of the polymeric ionic liquid blocks the molecular weights were
substantially underestimated leading to even lower molecular weights than the initial vinyl polythiopene
macromonomer. In particular, for the poly(P3OTꢀcoꢀVBMImT) copolymer an Mn=6.500 was found while for
the copolymer poly(P3OTꢀcoꢀVHImBr)] its Mn was in the range of 4.800 which are significantly lower than
the initial vinylꢀP3OT macromonomer’s Mn of 21.000.
The polythiopheneꢀionic liquid copolymers were also characterized by thermogravimetric analysis (TGA).
Specifically, as seen in Figure S5, both copolymers show increased thermal stability when compared to the
ionic liquid monomers and homopolymers, that are almost completely degraded around 450 oC (VBMImT and
o
PVBMImT) and 350 C (VHImBr and PVHImBr). On the other hand, vinylꢀP3OT is thermally stable until
500 oC leading to copolymers of higher degradation temperatures.
Regarding the optical properties of the synthesized compounds, UVꢀVis absorption and PL emission spectra
were carried out in solution. VinylꢀP3OT and the corresponding copolymers poly(P3OTꢀcoꢀVBMImT) and
poly(P3OTꢀcoꢀVHImBr) were dissolved in CHCl3. VHImBr is also soluble in chloroform, in contrast with the
other monomeric ionic liquid, VBMImT, for which acetonitrile was used instead. Finally, both homopolymers
were dissolved in MeOH. The two copolymers have similar behaviors in their absorption spectra presenting a
broad peak around 450 nm. As can be seen in Figure 3, this peak is slightly shifted to lower wavelength in the
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copolymers’ cases in comparison to the pure vinylꢀP3OT. The intense peak at 280 nm in poly(P3OTꢀcoꢀ
VBMImT) is attributed to VBMImT and is shifted around 25 nm in comparison to the monomeric VBMImT.
Figure 4 shows the PL spectra of the copolymers versus the vinylꢀP3OT macromonomer in chloroform
solutions, after excitation at the P3OT absorption maximum. The PL spectra of the respective ionic liquid
homopolymers are given in the inset of Figure 4. For both the copolymers emissions due to the P3OT blocks
are detected at 564 nm, slightly blue shifted compared to the net vinylꢀP3OT which emits at 570 nm.
5
VHImBr
PVHImBr
P3OT
(a)
(b)
VBMT
PVBMT
P3OT
poly(P3OT-co-VHImBr)
poly(P3OT-co-VBMImT)
300
400
Wavelength (nm)
500
600
300
400
500
600
Wavelength (nm)
Figure 3: UVꢀVis spectra of poly(P3OTꢀcoꢀVBMImT) (a) and poly(P3OTꢀcoꢀVHImBr) (b) in comparison to
10
the starting materials and the respective homopolymers.
PVBMImT
vP3OT
PVHImBr
poly
(
P3OT-co-VBMImT
)
poly
(
P3OT-co-VHImBr
)
250 300 350 400 450 500 550
Wavelength (nm)
500
550
600
650
700
Wavelength (nm)
Figure 4: PL spectra of poly(P3OTꢀcoꢀVBMImT and poly(P3OTꢀcoꢀVHImBr) in comparison to vinylꢀP3OT
after excitation at 450 nm. The inset shows the initial monomers’ PL spectra, VBMImT in MeOH and
VHImBr in MeCN, after excitation at 220 and 250 nm, respectively.
15
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Scheme 4 presents the copolymerization reaction of the Ru(bpy)2(styrylbpy) monomer55 with the monomeric
VBMImT. Since, both the ruthenium complex and the monomeric ionic liquid are soluble in acetonitrile,
MeCN was used as the polymerization solvent while the IL/initiator ratio was 11/1 (Table 1).
5
Scheme 4: Synthesis of the copolymer poly(RuꢀcoꢀVBMImT).
poly(Ru-co-VBMImT)
10
9
8
7
6
5
4
3
2
1
Chemical Shift (ppm)
Figure 5: 1H NMR of poly(RuꢀcoꢀVBMImT) in DMSOꢀd6.
1
10
15
The structural characterization of the copolymer was carried out using H NMR and ATR spectroscopies
(Figures 5 and S6a). Thermogravimetric analysis of poly(RuꢀcoꢀVBMImT) showed increased thermal
stability in comparison to the ionic liquid monomer and homopolymer (Figure S6b), which is attributed to the
increased thermal stability of the ruthenium complex monomer.
UVꢀVis and PL spectroscopies of acetonitrile solutions of the Ru(bpy)2(styrylbpy) and of the copolymer
poly(RuꢀcoꢀVBMImT) were employed for their optical properties evaluation as shown in Figure 6,
respectively. In the absorption spectra of the poly(RuꢀcoꢀVBMImT), no significant alternation was observed
in comparison to the monomer complex Ru(bpy)2(styrylbpy) in the region above 260 nm (Figure 6a). On the
other hand, the copolymer showed an intense peak around 210 nm, which does not exist in the monomeric
ruthenium complex, and is attributed to VBMImT. At 320 nm both the monomeric complex and the
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copolymer show an absorption due to the πꢀπ* LC (ligandꢀcentered) transitions of 2,2′ꢀbipyridine, and also an
absorption at around 450 nm, which is characteristic of the dꢀπ* MLCT (metal to ligand charge transfer) of the
Ru(bpy)2(styrylbpy) complexes.55 The photoluminescence examination in solution of both the copolymer
poly(RuꢀcoꢀVBMImT) and of the monomer complex Ru(bpy)2(styrylbpy) showed a broad peak around 600
nm, after excitation at 450 nm, due to the ruthenium complex’s dꢀπ* MLCT absorption band (Figure 6b).
5
Ru(bpy) (styrylbpy)
2
poly(Ru-co-VBMImT)
(a)
(b)
VBMT
PVBMT
Ru(bpy)2(styrylbpy)
polu(Ru-co-VBMImT)
500
550
600
650
700
750
800
200
300
400
500
600
Wavelength (nm)
Wavelength (nm)
Figure 6: UVꢀVis spectra (a) and PL spectra (b) after excitation at 450 nm of VBMImT, PVBMImT,
Ru(bpy)2(styrylbpy) and poly(RuꢀcoꢀVBMImT), in MeCN solutions.
10
15
20
25
Quasiꢀsolidꢀstate DSSC fabrication and testing
Quasiꢀsolidꢀstate DSSCs were constructed in a layer structure using a standard mesoporous titania film
sensitized by the most frequently employed Ruꢀbased dye N719. We used P3HT as hole collecting and
transfer layer and a combination of PEDOT:PSS with silver electrodes as counter electrode. The novelty of
the present work was the introduction of a small quantity of polymeric ionic liquid into the hole transporting
layer. It has been previously reported that ionic content in the hole transporting layer may modify its
electronic properties and subsequently affect the efficiency of solid state sensitized solar cells64,65,66. This was
also verified by the presently studied cells. The term quasiꢀsolidꢀstate DSSC has been used in the present work
to underline the fact that the P3HT/polymeric ionic liquid blend can no more be considered as a purely solid
material.
A few different polymeric ionic liquids have been employed and tested in quasiꢀsolidꢀstate DSSC
configuration. Figure 7 and Table 2 show currentꢀvoltage data for the studied cells. It must first be underlined
that cells showed an acceptable performance when the polymeric ionic liquid content was relatively low. Thus
optimized data were obtained when the P3HT/polymeric ionic liquid ratio was 9:1 w/w. On the other hand,
most polymeric ionic liquids did not show any substantial influence to the cell performance compared to pure
P3HT. However, one of the prepared samples did demonstrate a marked improvement of cell efficiency.
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Indeed, as seen in Figure 7 and Table 2, introduction of PVHImBr resulted in about 30% improvement of
efficiency. This increase was due to the large increase of the openꢀcircuit voltage of the cell and the
improvement of the fill factor despite the fact that a substantial decrease of the current density was caused by
the introduction of the ionic liquid. The decrease of the current is most probably due to the fact that the above
cells function by hole collection and transfer through the holeꢀconducting P3HT. The interference of the ionic
agent most probably disrupts some of the holeꢀtransporting channels. On the contrary, the presence of the
ionic agent establishes a potential gradient that results in openꢀcircuit voltage increase. Such a voltage increase
was also observed in a previous publication treating a solid state quantum dot sensitized solar cell where a tiny
quantity of Na2S was added as an ionic agent66. Even though, current dropped in the present case, voltage
increase had a marked beneficial effect on cell performance. The advantage of the presently introduced
materials is that they can be mixed with P3HT eliminating solubility problems.
5
10
18
16
1
14
12
4
10
3
8
2
6
4
2
0
0,0
0,1
0,2
0,3
0,4
0,5
0,6
Voltage (Volts)
Figure 7: J−V curves for solar cells made of photoanodes bearing a nanocrystalline titania film on FTO
electrode sensitized by N719 dye and on the top P3HT mixed with 10% w/w of a polymeric poly ionic liquid:
(1) no ionic liquid, 2) P3HT and poly(P3OTꢀcoꢀVHImBr), (3) P3HT and PVBImT, (4) P3HT and PVHImBr.
15
Table 2: Current voltage characteristics of the cells. Data extracted from Figure 13.
Composition of the hole transporting/ionic liquid layer Voc (V) Jsc (mA/cm2) FF (%) η (%)
P3HT alone
17.0
7.0
35
30
33
42
2.5
0.9
1.1
3.2
0.42
0.42
0.29
0.55
1
2
3
4
P3HT/ poly(P3OTꢀcoꢀVHImBr)
P3HT/ PVBImT
11.2
14.1
P3HT/ PVHImBr
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Morphology characterization of the polymeric materials employed in DSSC testing
Having the results from the DSSC measurements in mind, and in an effort to clarify the unexpected better
performance of the net PIL homopolymer versus its copolymer with P3HT, we proceed with the morphology
evaluation of blends as those that were prepared and tested in the DSSC devices. The transmission electron
microscopy (TEM) images of the net P3HT, the 9:1 blend of P3HT/poly(P3OTꢀcoꢀVHImBr) and the 9:1 blend
of P3HT/PVHImBr, all casted from dilute CHCl3 solutions, are presented in the below Figure 8.
5
As can be seen in Figure 8a, the net P3HT formed uniform films that presented some degree of organization
into fibrillary structures due to the close packing and crystallization of the high molecular weight P3HT.1 The
casting procedure for the preparation of the TEM samples of course does not allow ordering to a great extend
but the method for preparing the P3HT film on the DSSC device which is accompanied by thermal treatment
should have a more prominent effect on the crystallization of the P3HT macromolecular chains.
On the contrary, the 9:1 blend of P3HT/poly(P3OTꢀcoꢀVHImBr) shown in Figure 8b did not present any
fibrillar morphological features. The insertion of even a small percentage of the poly(P3OTꢀcoꢀVHImBr)
copolymer to the P3HT matrix obviously led to the compatibilization of the P3HT and the PIL fractions and
moreover suppressed the crystallization ability of the net P3HT.
10
15
Surprisingly, the P3HT/PVHImBr 9:1 blend, Figure 8c, presented the same crystallization tendency of the
net P3HT (see Figure 8a) while some darker regions were observed. When looking deeper into those darker
regions we noticed that they consisted of dark spots of about 2 nm and up to 6 nm diameter (inset of Figure
8c). These higher contrast spots are attributed to the charged imidazolium cation and Br anion of the
PVHImBr ionic liquid hompolymer and more specifically to the high contrast of the Br atoms under the
electron beam.67 Therefore it can be concluded that the presence of the homopolymer PVHImBr did not
disturb the crystallization and ordering of the P3HT and that it was quite uniformly dispersed in selective
regions along the polythiophene matrix.
20
25
The above findings constitute an explanation of the better DSSC device performance of the P3HT/PVHImBr
blend over the P3HT/poly(P3OTꢀcoꢀVHImBr) one, since for P3HT it is known that charge transport is
promoted along its crystalline domains which are interconnected with amorphous regions.1
,68 Thus, the net
P3HT and the P3HT/PVHImBr blend, did work nicely in the DSSC devices whereas the P3HT/poly(P3OTꢀ
coꢀVHImBr) blend with no ordering into crystalline species did not show the analogous DSSC performance.
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Figure 8: TEM images of (a) P3HT scale bar 200 nm (inset scale bar 50 nm) (b) P3HT/poly(P3OTꢀcoꢀ
VHImBr) 9:1 scale bar 100 nm (inset scale bar 50 nm) and (c) P3HT/PVHImBr 9:1 scale bar 200 nm (inset
scale bar 20 nm).
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Conclusions
Polymeric ionic liquids based on the imidazole moiety and their respective copolymeric ionic liquids using
ωꢀ
end vinyl rrꢀpoly(3ꢀoctyl thiophene) or (vinylphenylꢀbipyridine)ꢀRu(II)ꢀdi(bipyridine) were prepared in this
present study. Aiming at materials that could eventually be employed in quasi solid state DSSC we prepared
these ionic liquid polymers and copolymers in order to aid the ionic character of the hole transporting layer of
the cell.
5
10
15
The homopolymer PILs and copolymer PILs with the thiophene or ruthenium based dyes were prepared via
radical polymerizations. Their adequate solubility in common organic solvents allows their processability and
introduction as an additive of the net organic hole transporting layer of the cell. Although further
improvements are of course necessary in order to increase the efficiency of the solid state DSSCs, the
methodology reported herein shows a promising route for the enhancement of the cells performance. Perhaps
the most important finding of this present work is that the presence of the PIL fraction into the hole
transporting P3HT layer does improve the device performance as long as it does not disturb the development
of crystalline domains that promote the necessary charge carrier transport.
Acknowledgements
This research has been coꢀfinanced by the European Union (European Social Fund–ESF) and Greek national
funds through the Operational Program "Education and Lifelong Learning" of the National Strategic
Reference Framework (NSRF)ꢀResearch Funding Program: THALES. Investing in knowledge society through
the European Social Fund. Project title: “Innovative materials for nanocrystalline solar cells” (MIS: 377756).
20
References
1
G. Dennler, M. C. Scharber and C. J. Brabec, Adv. Mater., 2009, 21, 1323–1338, (DOI:
10.1002/adma.200801283)
2 B. O'Regan and M. Grätzel, Nature, 1991, 353, 737–740, (DOI: 10.1038/353737a0)
3 J. Boucle and J. Ackermann, Polym. Int., 2012, 61, 355–373, (DOI: 10.1002/pi.3157)
4 J. Qu and C. Lai, J. Nanomater., 2013, 2013, 762730, (DOI: 10.1155/2013/762730)
5
H. C. Weerasinghe, F. Huang and Y.ꢀB. Cheng, Nano Energy, 2013, 2, 174–189, (DOI:
10.1016/j.nanoen.2012.10.004)
6 W. Mai, Z. Chai, J. Gu, J. Khan, Y. Yuan, L. Du, X. Yu and M. Wu, RSC Adv., 2015, 5, 88052ꢀ88058 (DOI:
10.1039/C5RA17294B)
7
Q. Zhang, C. S. Dandeneau, X. Zhou and G. Cao, Adv. Mater., 2009, 21, 4087–4108, (DOI:
10.1002/adma.200803827)
[18]

Page 19 of 23
RSC Advances
View Article Online
DOI: 10.1039/C5RA27374A
8 A. L. Briseno, T. W. Holcombe, A. I. Boukai, E. C. Garnett, S. W. Shelton, J. J. M. Frechet and P. Yang,
Nano Lett., 2010, 10, 334–340, (DOI: 10.1021/nl9036752)
9 P. Giannopoulos, A. Nikolakopoulou, A. K. Andreopoulou, L. Sygellou, J. K. Kallitsis, and P. Lianos, J.
Mater. Chem A, 2014, 2, 20748ꢀ20759 (DOI: 10.1039/C4TA04515G).
10 P. Giannopoulos, C. Anastasopoulos, A. K. Andreopoulou, and J. K. Kallitsis, J. Surf. Interfac. Mater.,
2014, 2, 274ꢀ279 (DOI: 10.1166/jsim.2014.1061)
11 X. Chen, Q. Tang, B. He and H. Chen, RSC Adv., 2015, 5, 43402ꢀ43407 (DOI: 10.1039/C5RA05078B)
12 H. M. Upadhyaya, S. Senthilarasu, M.ꢀH. Hsu and D. K. Kumar, Sol. Energy Mater. Sol. Cells, 2013, 119,
291ꢀ295 (DOI:10.1016/j.solmat.2013.08.031)
13
K. Saranya, Md. Rameez and A. Subramania, Eur. Polym. J., 2015, 66, 207–227
(DOI:10.1016/j.eurpolymj.2015.01.049)
14 E. Stathatos, P. Lianos, S.M. Zakeeruddin, P. Liska and M. Grätzel, Chem. Mater., 2003, 15, 1825ꢀ1829
(DOI: 10.1021/cm0213568)
15
J. M. Pringle and V. Armel, Int. Rev. Phys. Chem., 2012, 30, 371ꢀ407, (DOI:
10.1080/0144235X.2011.638450)
16 J. Wu, Z. Lan, J. Lin, M. Huang, Y. Huang, L. Fan and G. Luo, Chem. Rev., 2015, 115, 2136–2173 (DOI:
10.1021/cr400675m)
17 S. Venkatesan, S.ꢀC. Su, W.ꢀN. Hung, IꢀP. Liu, H. Teng and Y.ꢀL. Lee, J. Power Sources, 2015, 298, 385ꢀ
390 (DOI: 10.1016/j.jpowsour.2015.07.062)
18 M. M. Rashad, A. E. Shalan, M. M. Moharam, A. M. Elseman, M. Rasly and M. LiraꢀCantu
, RSC Adv.,
2015, 5, 103095ꢀ103104 (DOI:10.1039/C5RA21822E)
19 A. Sacco, F. Bella, S. De La Pierre, M. Castellino, S. Bianco, R. Bongiovanni and C. F. Pirri, Chem. Phys.
Chem., 2015, 16, 960ꢀ969 (DOI: 10.1002/cphc.201402891)
20 F. Bella, A. Chiappone, J. R. Nair, G. Meligrana and C. Gerbaldi, Chemical Engineering Transactions,
2014, 41, 211ꢀ216 (DOI: 10.3303/CET1441036)
21 M. Gorlov and L. Kloo, Dalton Trans., 2008, 20, 2655ꢀ2666 (DOI: 10.1039/b716419j)
22
S. M. Zakeeruddin and M. Grätzel, Adv. Funct. Mater., 2009, 19, 2187ꢀ2202 (DOI:
10.1002/adfm.200900390)
23 M. Y. A. Rahman, A. Ahmad, A. A. Umar, R. Taslim, M. S. Suait and M. M. Salleh, Ionics, 2014, 20,
1201–1205 (DOI: 10.1007/s11581ꢀ014ꢀ1211ꢀ3)
24 C.ꢀP. Lee, T.ꢀC. Chu, L.ꢀY. Chang, J.ꢀJ. Lin and K.ꢀC. Ho, 2013, Ionic Liquids ꢀ New Aspects for the
Future (DOI: 10.5772/53647)
25 A. Apostolopoulou, A. Margalias and E. Stathatos, RSC Adv., 2015, 5, 58307ꢀ58315 (DOI:
10.1039/C5RA08744A)
26 M. Armand, F. Endres, D. R. MacFarlane, H. Ohno and B. Scrosati, Nat. Mater., 2009, 8, 621ꢀ629 (DOI:
10.1038/nmat2448)
[19]

RSC Advances
Page 20 of 23
View Article Online
DOI: 10.1039/C5RA27374A
27 J. V. Zamory, M. Bedu, S. Fantini, S. Passerini and E. Paillard, J. Power Sources, 2013, 240, 745ꢀ752 (DOI:
10.1016/j.jpowsour.2013.04.127)
28
J. Lu, F. Yan and J. Texter, Prog. Polym. Sci., 2009, 34, 431–448 (DOI:
10.1016/j.progpolymsci.2008.12.001)
29 H. Zhang, K. Hong and J. W. Mays, Macromolecules, 2002, 35, 5738–5741 (DOI: 10.1021/ma025518x)
30 T. Biedron and P. Kubisa, Polym. Int., 2003, 52, 1584–1588 (DOI: 10.1002/pi.1343)
31 S. Ding, M. Radosz and Y. Shen, Macromolecules, 2005, 38, 5921–5928 (DOI: 10.1021/ma050093a)
32 G. H. Lane, P. M. Bayley, B. R. Clare, A. S. Best, D. R. MacFarlane, M. Forsyth and A. F. Hollenkamp, J.
Phys. Chem. C, 2010, 114, 21775ꢀ21785 (DOI: 10.1021/jp1054809)
33
A. Lewandowski and A. SwiderskaꢀMocek, J. Power Sources 2009, 194, 601ꢀ609 (DOI:
10.1016/j.jpowsour.2009.06.089)
34 E. Paillard, Q. Zhou, W. A. Henderson, G. B. Appetecchi, M. Montanino and S. Passerini, J. Electrochem.
Soc., 2009, 156, A891ꢀ895 (DOI: 10.1149/1.3208048)
35 R. D. Costa, E. Orti, H. J. Bolink, S. Graber, C. E. Housecroft and E. C. Constable, Adv. Funct. Mater.,
2010, 20, 1511ꢀ1520 (DOI: 10.1002/adfm.201000043)
36 A. Balducci, W. A. Henderson, M. Mastragostino, S. Passerini, P. Simon and F. Soavi, Electrochim. Acta,
2005, 50, 2233ꢀ2237 (DOI:10.1016/j.electacta.2004.10.006)
37
P. Wang, S. M. Zakeeruddin, I. Exnar and M. Grätzel, Chem. Commun., 2002, 8, 2972ꢀ2973 (DOI:
10.1039/b209322g)
38 W. Kubo, S. Kambe, S. Nakade, T. Kitamura, K. Hanabusa, Y. Wada, S. Yanagida, J. Phys. Chem. B,
2003, 107, 4374ꢀ4381 (DOI: 10.1021/jp034248x)
39
D. Xu, H. Zhang, X. Chen and F. Yan, J. Mater. Chem. A, 2013, 1, 11933–11941 (DOI:
10.1039/c3ta12031g)
40
H. M. Ng, S. Ramesh, K. Ramesh, Electrochim. Acta, 2015, 175, 169ꢀ175
(DOI:10.1016/j.electacta.2015.01.076)
41 L. Chang, C. Lee, C. Li, M. Yeh, K. Ho and J. Lin, J. Mater. Chem. A, 2014, 2, 20814ꢀ20822 (DOI:
10.1039/C4TA05436A.)
42 H. Tang, S. Ding, Y. Shen and M. Radosz, J. Polym. Sci. Part A: Polym. Chem., 2004, 42, 5794ꢀ5801
(DOI: 10.1002/pola.20423)
43 B. Lin, T. Feng, F. Chu, S. Zhang, N. Yuan, G. Qiao and J. Ding, RSC Adv, 2015, 5, 57216ꢀ57222 (DOI:
10.1039/C5RA10702D)
44
P. Wang, B. Wenger, R. HumphryꢀBaker, J.ꢀE. Moser, J. Teuscher, W. Kantlehner, J. Mezger, E. V.
Stoyanov, S. M. Zakeeruddin, and M. Grätzel, J. Am. Chem. Soc., 2005, 127, 6850ꢀ685 (DOI:
10.1021/ja042232u)
45 D. Kuang, P. Wang, S. Ito, S. M. Zakeeruddin and M. Grätzel, J. Am. Chem. Soc., 2006, 128, 7732–7733
(DOI: 10.1021/ja061714y)
[20]

Page 21 of 23
RSC Advances
View Article Online
DOI: 10.1039/C5RA27374A
46 X. Chen, Q. Li, J. Zhao, L. Qiu, Y. Zhang, B. Sun and F. Yan, J. Power Sources, 2012, 207, 216–221
(DOI:10.1016/j.jpowsour.2012.01.143)
47 J.ꢀG. Chen, R. Vittal, M.ꢀH. Yeh, C.ꢀY. Chen, C.ꢀG. Wu and K.ꢀC. Ho, Electrochim. Acta, 2014, 130, 587–
593 (DOI: 10.1016/j.electacta.2014.03.061)
48 O. Fontaine, A. Touidjine, M. Maréchal, C. Bonhomme, F. Ribot, B. Geffroy, B. Jousselme, C. Sanchez and
C. LabertyꢀRobert, New J. Chem., 2014, 38, 2008ꢀ2015 (DOI: 10.1039/c3nj01272g)
49
M. S. Su’ait, M.Y.A. Rahman and A. Ahmad, Solar Energy, 2015, 115, 452–470 (DOI:
10.1016/j.solener.2015.02.043)
50 M. Yoshizawa, W. Ogihara and H. Ohno, Polym. Adv. Technol., 2002, 13, 589ꢀ594 (DOI: 10.1002/pat.261)
51
Y. Han, J. M. Pringle and Y.ꢀB. Cheng, Photochem. Photobiol., 2015, 91, 315ꢀ322 (DOI:
10.1111/php.12399)
52 W. S. Chi, J. K. Koh, S. H. Ahn, J.ꢀS. Shin, H. Ahn, D. Y. Ryu and J. H. Kim, Electrochem. Commun.,
2011, 13, 1349–1352 (DOI: 10.1016/j.elecom.2011.08.005)
53 R. Marcilla, J. A. Blazquez, J. Rodriguez, J. A. Pomposo and D. Mecerreyes, J. Polym. Sci. Part A: Polym.
Chem., 2004, 42, 208–212 (DOI: 10.1002/pola.11015)
54 R. S. Loewe, P. C. Ewbank, J. Liu, L. Zhai and R. D. McCullough, Macromolecules, 2001, 34, 4324–4333,
(DOI: 10.1021/ma001677)
55
E. K. Pefkianakis, N. P. Tzanetos, and J. K. Kallitsis, Chem. Mater., 2008, 20, 6254–6262 (DOI:
10.1021/cm800911y)
56 D. Joly, L. Pelleja, S. Narbey, F. Oswald, J. Chiron, J. N. Clifford, E. Palomares and R. Demadrille, Sci.
Rep., 2014, 4, 4033, 1ꢀ7 (DOI: 10.1038/srep04033)
57 C. V. Kumar, D. Raptis, E. N. Koukaras, L. Sygellou and P. Lianos, Org. Electron., 2015, 25, 66ꢀ73 (DOI:
10.1016/j.orgel.2015.06.009)
58 Y. Jeon, J. Sung, C. Seo, H. Lim, H. Cheong, M. Kang, B. Moon, Y. Ouchi, and D. Kim, J. Phys. Chem. B
2008, 112, 4735ꢀ4740 (DOI: 10.1021/jp7120752)
59 T. Moumene, El H. Belarbi, B. Haddad, D. Villemin, O. Abbas, B. Khelifa, S. Bresson, J. Mol. Struct. 2015,
1083, 179–186 (DOI: 10.1016/j.molstruc.2014.11.061)
60 S. J. L. P. Perez and S. D. Arco, J. Chin. Chem. Soc., 2014, 61, 935ꢀ939 (DOI: 10.1002/jccs.201300555)
61 F. Shi and Y. Deng, Spectrochim. Acta, Part A, 2005, 62, 239–244 (DOI: 10.1016/j.saa.2004.12.031)
62 K. Malek, Agnieszka Puc, G. Schroeder, V. I. Rybachenko and L. M. Proniewicz, Chem. Phys., 2006, 327,
439–451 (DOI:10.1016/j.chemphys.2006.05.021)
63 K. Noack, P. S. Schulz, N. Paape, J. Kiefer, P. Wasserscheid and A. Leipertz, Phys. Chem. Chem. Phys.,
2010, 12, 14153ꢀ14161 (DOI: 10.1039/c0cp00486c)
64
R. Zhu, C.ꢀY. Jiang, B. Liu and S. Ramakrishna, Adv. Mater., 2009, 21, 994ꢀ1000 (DOI:
10.1002/adma.200802388)
[21]

RSC Advances
Page 22 of 23
View Article Online
DOI: 10.1039/C5RA27374A
65 N. Balis, V. Dracopoulos, M. Antoniadou and P. Lianos, J. Photochem. Photobiol., A, 2010, 214, 69−73
(DOI: 10.1016/j.jphotochem.2010.06.010)
66 G. Sfyri, S. Sfaelou, K. S. Andrikopoulos, N. Balis, G. A. Voyiatzis and P. Lianos, J. Phys. Chem. C, 2014,
118, 16547ꢀ16551 (DOI: 10.1021/jp412134m)
67 M. Koebe, M. Drechsler, J. Weber and J. Yuan , Macromol. Rapid Commun
. 2012, 33, 646−651 (DOI:
10.1002/marc.201100836)
68 V. D. Mihailetchi, H. Xie, B. de Boer, L.M. Popescu, J. C. Hummelen, P.W. M. Blom and L. J. A. Koster,
Appl. Phys. Lett. 2006, 89, 012107 ( DOI: 10.1063/1.2212058)
[22]

View Article Online
DOI: 10.1039/C5RA27374A
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RSC Advances
Copolymers of Ionic Liquids with Polymeric or Metallocomplex
Chromophores for Quasi-Solid State DSSC Applications
Panagiotis Giannopoulos, Aikaterini K. Andreopoulou,* Charalampos Anastasopoulos,
Dimitrios Raptis, Georgia Sfyri, Joannis K. Kallitsis, Panagiotis Lianos
Table of Contents entry
Polymeric and copolymeric ionic liquids were prepared and tested in quasi solid DSSCs as additives of a P3HT
hole transporting layer. The blend’s morphology played a decisive role on the cell performance. The PIL/P3HT
blend retained the organization of P3HT increasing the cell’s performance due to the increased ionic nature of
the blend. Contrary, the P3HT/ poly(P3OT-co-VHImBr) blend showed reduced efficiency due to the disruption
of P3HT’s ordering.
P3HT/poly(P3OT-co-VHImBr)
TiO2/dye
P3HT/PVHImBr