Novel dye sensitizers of main chain polymeric metal complexes based on complexes of 2-(2′-pyridyl)benzimidazole derivative with Zn(II), Co(II): Synthesis, characterization, and photovoltaic performance for dye-sensitized solar cells

Article abstract of DOI:10.1007/s13738-014-0539-y

In this paper, four novel D-π-A polymeric metal complex as dye sensitizers for dye-sensitized solar cell, which have Poly(p-phenylenevinylene) or carbazole derivative used as an electron donor, thiophene derivatives used as π-bridge and 2-(2′-pyridyl)benzimidazole derivative metal (Zn, Co) complex used as an electron acceptor (A) were synthesized and characterized. They have been determined and studied by FT-IR, TGA, DSC, GPC, elemental analysis, UV-vis absorption spectroscopy, photoluminescence spectroscopy, cyclic voltammetry, J-V curves and IPCE plots. The results show that four novel polymeric metal complex exhibited good photovoltaic property and thermal stability. The DSSC fabricated by P1, P2, P3 and P4 exhibit good device performance with a power conversion efficiency of up to 2.15, 2.27, 2.30 and 2.41 % (under simulated air mass 1.5 G irradiation) respectively, indicating the polymeric metal complexes are promising in the development of DSSC.

Full text of DOI:10.1007/s13738-014-0539-y

J IRAN CHEM SOC
DOI 10.1007/s13738-014-0539-y
ORIGINAL PAPER
Novel dye sensitizers of main chain polymeric metal complexes
based on complexes of 2‑(2′‑pyridyl)benzimidazole derivative
with Zn(II), Co(II): synthesis, characterization, and photovoltaic
performance for dye‑sensitized solar cells
Dahai Peng · Wei Zhang · Guipeng Tang · Jun Zhou ·
Jiaomei Hu · Qiufang Xie · Chaofan Zhong
Received: 11 January 2014 / Accepted: 27 June 2014
©
Iranian Chemical Society 2014
Abstract In this paper, four novel D–π–A polymeric
metal complex as dye sensitizers for dye-sensitized solar
cell, which have Poly(p-phenylenevinylene) or carbazole
derivative used as an electron donor, thiophene derivatives
used as π-bridge and 2-(2′-pyridyl)benzimidazole deriva-
tive metal (Zn, Co) complex used as an electron acceptor
[2], dye-sensitized solar cells (DSSC) are one of the most
promising power sources for a new generation of solar
cells due to their energy-saving, versatile and environmen-
tal friendly nature. Among the key components of a DSSC,
the sensitizer always plays as one of the most crucial ele-
ments since it exerts a significant influence on the power
conversion efficiency (PCE) as well as the device stability.
To date, the new method raises DSSC power conversion
efficiency up to a record of 15 %, exceeding conventional,
amorphous silicon-based solar cells [3].
There are various types of dyes which can be divided
into metal-organic dyes [4–7], porphyrin dyes [8, 9], nat-
ural dyes and metal-free organic dyes [10–12] So far, Ru
complexes dyes such as N3 [13], N719 [14], and black dye
[15] as the most typical dyes have been used widely in the
DSSC and the power conversion efficiencies of these Ru
complexes dyes are up to over 11 % under air mass (AM)
1.5 illumination [16]. However, Ru complexes dyes met
with some problems such as limited resources and dif-
ficult purification. Organic dyes as the promising alterna-
tive to Ru complexes dyes have been studied extensively
due to their many advantages, diversity of molecular struc-
tures, high-molar extinction coefficient, low cost and envi-
ronmental friendliness. Moreover, compared with small
organic molecule, polymeric organic dyes show several
advantages such as tunable band gaps and large absorption
coefficients owing to its long conjugated chain, etc.
(A) were synthesized and characterized. They have been
determined and studied by FT-IR, TGA, DSC, GPC, ele-
mental analysis, UV–vis absorption spectroscopy, photolu-
minescence spectroscopy, cyclic voltammetry, J–V curves
and IPCE plots. The results show that four novel polymeric
metal complex exhibited good photovoltaic property and
thermal stability. The DSSC fabricated by P1, P2, P3 and
P4 exhibit good device performance with a power conver-
sion efficiency of up to 2.15, 2.27, 2.30 and 2.41 % (under
simulated air mass 1.5 G irradiation) respectively, indicat-
ing the polymeric metal complexes are promising in the
development of DSSC.
Keywords Dye-sensitized solar cells · Polymeric metal
complex · Power conversion efficiency · 2-(2’-pyridyl)
benzimidazole · Carbazole · PPV
Introduction
Dye-sensitized solar cells (DSSC), also known as Grätzel
cells, were invented by Grätzel and O’Regan in 1991 [1].
In comparison with the traditional silicon-based solar cells
For the design of efficient molecular architectures, it is
crucial to determine the energy levels of the three compo-
nents of D–π–A sensitizers, as well as the location of the
relevant orbitals within the D–π–A complex. Carbazole is a
well-known electroluminescent and hole-transporting unit
due to the electron-donating capabilities associated with the
nitrogen in the carbazole. Wang and co-workers developed
some organic dyes containing an N-aryl carbazole moiety
D. Peng · W. Zhang · G. Tang · J. Zhou · J. Hu · Q. Xie ·
C. Zhong (*)
Key Laboratory of Environmentally Friendly Chemistry
and Applications of Ministry of Education, College of Chemistry,
Xiangtan University, Xiangtan 411105, Hunan, China
e-mail: zhongcf798@aliyun.com
1
3

J IRAN CHEM SOC
Scheme 1 Synthetic route of
the monomers and polymeric
metal complexes P1-P4
for DSSC and achieved a maximum conversion efficiency
of 8.3 % under AM 1.5 G and a maximum IPCE value of
metal-PBI as an acceptor (A), thiophene derivatives as a
π-conjugation linkage (π) and PPV or CZ as donor group
(D), which are shown in Scheme 1. Moreover, thermal
properties, optical properties and photovoltaic properties
of polymeric metal complexes are also investigated in this
paper.
7
5 % at 470 nm [17]. Bridge groups, as electron spacers
to connect the donor and acceptor, are not only to decide
light absorption regions of the DSSC but also influence the
electron injection from excited dyes to the TiO surface.
2
Thiophene and its derivatives have been successfully used
as a π-conjugated bridge in the molecular design of organic
dyes [18–20]. Benzimidazole and its derivatives are ubiqui-
tous in biology. They have the larger π-conjugated system
and the better electron donating property, it is significative
to design and synthesize the polymeric complexes contain-
ing benzimidazole for improving electrochemical proper-
ties and thermal stability [21].
Experimental section
Materials
3-Methylthiophene and carbazole were obtained
from Aldrich Chemical Co. and used as received.
1,4-bis(octyloxy)-2,5-divinylbenzene [22], N-octyl-3,6-di-
vinyl -carbazole [23] and 2-(2’-pyridyl)benzimidazole was
According to the above-mentioned points, we have
designed and synthesized four D–π–A dyes possessing a
1
3

J IRAN CHEM SOC
synthesized as previously reported [24]. N, N-dimethylfor-
Synthesis of L1 [26]
mamide was dried by distillation over CaH and methanol
2
was dried over molecular sieves and freshly distilled prior
to being used. The other materials were of common com-
mercial grade and used as received. All chemicals used
were of an analytical grade. Solvents were purified with
conventional methods.
Zn(CH COO) ·2H O (0.22 g, 1 mmol) was dissolved in
3
2
2
methanol (15 mL), and then PBI-Th (0.74 g, 2 mmol) in
THF (20 mL) were added to the solution. Then 1 mol L
-1
NaOH was added dropwise (under stirring) until the solu-
tion shows weakly acidic. After the solution was refluxed
for 6 h, the reaction system was allowed to cool to room
temperature. The precipitate was collected by filtration,
washed with dried ether many times and then dried in
vacuum at 60 ºC. A yellow solid (0.42 g, yield 80 %) was
Instruments and measurements
1
H NMR spectra were obtained in CDCl and recorded with
3
–
1
a Bruker ARX400 (400 MHz) Germany and using tetra-
methylsilane (0.00 ppm) as the internal reference. FT-IR
spectra were recorded using KBr pellets with a PerkinElmer
Spectrum One FT-IR spectrometer over the range 400–
obtained. FTIR (KBr; cm ): 3,095, 2,916 (aromatic and
vinylic C–H), 1,650 (C = N), 1,483 (C = C), 1,150 (C–
N–M), 510 (M–N). Anal. Calcd for [C H Br N O S Zn]:
3
8
30
2
6
4 2
C, 49.39; H, 3.27; Br, 17.30; N, 9.10; O, 6.93; S, 6.94; Zn,
7.08; found: C, 49.05; H, 3.46; N, 8.75.
-1
4
,000 cm . Gel permeation chromatography (GPC) analy-
ses were measured by a WATER 2414 system equipped
with a set of HT , HT and HT , l-styrayel columns with
Synthesis of L2
3
4
5
THF as eluent and polystyrene as standard. Thermogravi-
metric analyses (TGA), differential scanning calorimetry
In the same manner as described for L1, L2 affords a light
brown solid (Yield: 91 %). Anal. Calcd for C H Br N
6
(DSC) and elemental analysis were performed on Shimadzu
3
8
30
2
TGA-7 Instrument, Perkin-Elmer DSC-7 thermal analyzer
and Perkin-Elmer 2400 II instrument, respectively. UV–
visible spectra of all the polymers were taken on a Lambda
O S Co: C, 49.74; H, 3.30; Br, 17.42; Co, 6.42; N, 9.16;
4 2
O, 6.97; S, 6.99. Found: C, 49.23; H, 3.16; N, 9.24. FTIR
–
1
(KBr, cm ): 3,068, 2,903 (aromatic and vinylic C–H),
1,663 (C = N), 1,475 (C = C), 1,116 (C–N–M), 504
(M–N).
25 spectrophotometer. Photoluminescent spectra (PL) were
taken on a Perkin-Elmer LS55 luminescence spectrom-
eter with a xenon lamp as the light source. Cyclic voltam-
metry (CV) was conducted on a CHI630C electrochemical
workstation using a three electrode system, in a [Bu N]BF
Synthesis of Polymeric metal complex P1
4
4
(
0.1 M) DMF solution at a scan rate of 100 mV/s. The
The polymeric metal complex P1 was synthesized using
the Heck coupling method, according to the literature
[27]. A flask was charged with a mixture of metal com-
plex L1 (0.173 g, 0.315 mmol), 1,4-bis(octyloxy)-2,5-di-
working electrode was a glassy carbon electrode, the auxil-
iary electrode was a platinum wire electrode and a saturated
calomel electrode (SCE) was used as reference electrode.
vinylbenzene (0.122 g, 0.315 mmol), Pd(OAc) (0.0024 g,
2
Synthesis
0.012 mmol), triethylamine (3 mL), 3-o-tolyl phospine
(0.0220 g, 0.072 mmol) and DMF (8 mL). Then the flask
Synthesis of 2‑Bromo‑5‑[2‑(2′‑pyridyl)benzimidazolyl]‑3‑m
was pumped into a vacuum and purged with N . The mix-
2
ethylthiophene [25]
ture was heated at 90 ºC for 18 h under N . After that, it was
2
cooled to room temperature and filtered, then the filtrate
was poured into ethanol. The yellow precipitate was filtered
and washed with cold ethanol. The crude product was puri-
fied by dissolving in DMF and precipitating into ethanol to
afford a light yellow solid (Yield: 0.184 g, 53 %). FT-IR
(PBI-Th).
A mixture of 2, 5-dibromo-3-methylthiophene (1.27 g,
5
.0 mmol), 2-(2′-pyridyl)benzimidazole (0.99 g, 5.0 mmol),
CuI (0.081 g, 0.43 mmol), 1,10-phenanthroline (0.16 g,
.88 mmol) and K CO (1.38 g, 8.9 mmol) was suspended
–
1
0
(KBr, cm ): 3,075, 2,930, 2,851, 1,658 (C = N), 1,052 (C–
2
3
in 3.0 mL of DMF. The mixture was refluxed for 24 h and
then cooled to room temperature. The resulting brown
sticky residue was extracted with CH Cl (50 mL × 4), and
N–M), 475 (N–M). Anal. Calcd for [C H N O S Zn]: C,
6
4
70
6
6 2
67.24; H, 6.50; N, 7.13; O, 8.14; S, 5.44; Zn, 5.55. Found:
C, 66.57; H, 6.32; N, 7.02. Mn = 7.8 kg/mol, PDI = 1.49.
2
2
the organic extracts were combined, dried over MgSO and
4
purified by column chromatography (1:1 THF/hexane) to
Synthesis of Polymeric metal complex P2
obtain the crude product of Brmt as yellow powder (0.74 g
1
yield 40.2 %). H NMR (400 MHz, CDCl ): 8.57(s, 1H),
8
7
With the similar synthetic method as P1, P2 affords solid
(0.174 g, 51 %). FT-IR (KBr, cm ): 3,067, 2,915, 2,841,
1,675 (C = N), 1,096 (C–N–M), 496 (N–M). Anal. Calcd
3
–
1
.19(d, 1H), 7.86(d, 2H), 7.75–7.82(t, 1H), 7.40(s, 1H),
.27(s, 2H), 6.78 (s, 1H), 2.23(s, 3H).
1
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J IRAN CHEM SOC
Fig. 1 1H NMR spectra of PBI-
Th in CDCl solution
3
for [C H N O S Co]: C, 67.61; H, 6.53; Co, 5.03; N,
6
4
70
6
6 2
7
.17; O, 8.19; S, 5.47. Found: C, 67.23; H, 6.75; N, 7.11.
Mn = 8.9 kg/mol, PDI = 1.63.
Synthesis of Polymeric metal complex P3
With the similar synthetic method as P1, P3 affords solid
–
1
(
1
0.195 g, 62 %). FT-IR (KBr, cm ): 3,086, 2,932, 2,854,
,695 (C = N), 1,054 (C–N–M), 492 (N–M). Anal. Calcd
for [C H N O S Zn]: C, 68.40; H, 5.65; N, 8.72; O,
6
2
48
7
4 2
5
.70; S, 5.71; Zn, 5.82. Found: C, 68.03; H, 5.35; N, 8.71.
Mn = 10.6 kg/mol, PDI = 1.54.
Synthesis of Polymeric metal complex P4
With the similar synthetic method as P1, P4 affords a yel-
Fig. 2 FT-IR spectra of L1, P1, P3
–
1
low solid (0.168 g, 48 %). FT-IR (KBr, cm ): 3,076, 2,952,
,844, 1,685 (C = N), 1,050 (C–N-M), 498 (N-M). Anal.
Calcd for [C H N O S Co]: C, 68.80; H, 5.68; Co, 5.27;
2
temperature. But they exhibit a poor solubility in the other
solvents, such as in methanol and chloroform.
6
2
48
7
4 2
N, 8.78; O, 5.73; S, 5.74. Found: C, 68.03; H, 5.75; N,
.71. Mn = 8.5 kg/mol, PDI = 1.51.
1
8
Figure 1 displays the H NMR spectrum of PBI-Th. In
1
the H NMR spectra of PBI-Th the proton signals at δ 8.57,
8
.19, 7.86, 7.75 ~ 7.82, 7.40, 7.27, 6.78, 2.23 can be easily
Results and discussion
assigned to each corresponding hydrogen.
The IR spectra of the metal complex (L1, L2) and the
target polymers (P1, P2, P3, P4) are shown in Figs. 2 and 3.
From Figs. 2 and 3, absorption peaks at 1,616 cm are due
Synthesis and characterization
–
1
The detailed synthetic routes of the four main chain pol-
ymeric metal complexes (P1, P2, P3, P4) are shown in
Scheme 1, which were synthesized by the Heck coupling
to C = N bond stretching vibration and 1,483 is the bond
–
1
stretching vibration of C = C, the peaks of 1,150 cm and
–
1
1,116 cm are due to C–N–M stretching vibration of metal
compound L1 and L2, respectively [29]. And then integrat-
ing with the results of elemental analysis, we can come up
[28]. The four as-synthesized polymers could be dis-
solved in common organic solvents such as DMF at room
1
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J IRAN CHEM SOC
Fig. 4 UV-vis absorption spectra of L1, L2 and polymeric metal
complexes P1-P4 in DMF solution
Fig. 3 FT-IR spectra of L2, P2, P4
with the metals Zn2+ and Co which have been success-
fully coordinated, namely, complexes L1 and L2 have been
successfully synthesized.
2+
the maximum absorptions of P1, P2, P3 and P4 are at
422, 425, 416 and 424 nm, respectively. P3 and P4 poly-
mers have very weak shoulder absorption peak in the band
520–550 nm due to the CZ of excellent electron-donating
ability in the polymer. The one which shows a better UV
absorption by comparing P2 with P4 as well as P1 with P3,
indicates that polymers containing metal––Co have better
absorption of light than polymers containing metal––Zn.
In UV–vis the maximum absorption peak of polymeric
metal complexes P1, P2, P3 and P4 has a red-shift on TiO2
film as shown in Fig. 5.
The normalized photoluminescent (PL) spectra of P1, P2,
P3 and P4 in DMF solution are shown in Fig. 6 The excita-
tion wavelengths were set according to the absorption peak
of UV–vis spectrum and the corresponding optical data are
also listed in Table 2. It can be seen that the PL peaks of
them are at 471, 488, 467 and 475 nm, respectively, which
can be attributed to the π–π* transition of intra-ligand.
Gel permeation chromatography (GPC) study for all the
target polymers is shown in Table 1. The average molecular
weight of P1, P2, P3 and P4 is 7.8, 8.9, 10.6 and 8.5 kg/mol
and the units of them are 7, 8, 10 and 8, respectively. All
the PDI of polymeric metal complexes are relatively wide
(
P1, P2, P3, P4: 1.49, 1.63, 1.54 and 1.51, respectively).
The changes of the molecular weight also proved that the
copolymerization has taken place between the monomers,
which is a further evidence for the target polymers that
have been successfully synthesized.
Optical properties
The UV–vis and normalized PL spectra of the polymeric
metal complexes P1, P2, P3 and P4 (10 M in DMF solution
–5
and on TiO film) are shown in Figs. 4, 5 and 6, respectively,
2
and the corresponding data are summarized in Table 2.
The ligand L shows a UV–vis normalized absorption
peak located at about 370 nm, corresponding to the π–π*
electron transitions of the conjugated molecules. In Fig. 4,
Thermal stability
The thermal properties of the polymeric metal complexes
were investigated by differential scanning calorimetric
Table 1 Molecular weights and thermal properties of the polymeric metal complexes
a
3
a
3
b
o
c o
Polymer
M¯ n (× 10 )
M¯ w (× 10 )
PDI
N
T ( C)
T ( C)
g
d
P1
P2
P3
P4
7.8
8.9
11.6
14.5
16.3
12.8
1.49
1.63
1.54
1.51
7
173
167
194
205
335
329
373
352
8
10
8
10.6
8.5
a
Determined by gel permeation chromatography using polystyrene as standard
b
c
o
Determined by DSC with a heating rate of 20 C/min under nitrogen
The temperature at 5 % weight loss under nitrogen
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J IRAN CHEM SOC
P4 possess good thermal stability with 5 % weight loss at
temperatures (T ) of 335, 329, 373 and 352 ºC in nitrogen,
d
respectively. We could see that P1, P2, P3 and P4 have glass
transition temperature (T ) ranging from 167 to 105 ºC and
g
followed the order P4 > P3 > P1 > P2, which suggests that
polymeric metal complex containing CZ holds higher rigid-
ity than that containing PPV.
Electrochemical properties
The electrochemical behaviors of the polymers were inves-
tigated by cyclic voltammetry, which is one of the impor-
tant properties for organic materials used in solar cells. Fig-
ure 8 shows the cyclic voltammetry curves of P1, P2, P3
and P4. The lowest unoccupied molecular orbital (LUMO),
highest occupied molecular orbital (HOMO) energy levels
Fig. 5 UV-vis absorption spectra of polymeric metal complexes
P1-P4 on TiO film
2
and energy gap (E ) can be handled conveniently by equa-
g
tions as follows [30]:
HOMO = e(Eox + 4.40) (eV)
LUMO = −e(Ered + 4.40) (eV)
Eg = HOMO − LUMO
The units of Eox and Ered are measured through elec-
trochemical curve and the data obtained are listed in
Table 2. The reduction and oxidation potentials of P1
were measured to be Eox = 1.12 V and E = –1.01 V,
red
respectively. The energy value of the HOMO was calcu-
lated to be –5.52 eV and the energy value of the LUMO
was calculated to be –3.39 eV, so the energy band gap
was 2.13 eV. In the same way, we can get the related data
Fig. 6 PL spectra of the four polymeric metal complexes in DMF
solution
of other polymers. The E of the complexes follows the
g
order, P2 > P1 > P3 > P4, so P4 is more suitable for fab-
rication of optoelectronic devices than P1, P2 and P3,
(DSC) and thermo-gravimetric analysis (TGA) and the
because a relatively low E can absorb light efficiently, it
g
corresponding data are also reported in Table 1. The TGA
image which is present in Fig. 7 shows that P1, P2, P3 and
is very important to improve power conversion efficiency
[31].
Table 2 Optical and electrochemical properties of the polymeric metal complexes
d
e
Eox (V)g
Ered (V)g
Eg,EC/eV h
Polymer
λ
, λa,onset
λ
HOMO (eV)
LUMO (eV)
a,max
p,max
P1
P2
P3
P4
422,525
425,550
416,592
424,598
471
488
467
475
1.12
1.16
1.08
1.02
−1.01
−1.07
−0.97
−0.99
−5.52
−5.56
−5.48
−5.42
−3.39
−3.33
−3.43
−3.41
2.13
2.23
2.05
2.01
d
λa,max, λa,onset: The maxima and onset absorption from the UV–vis spectra in DMF solution
e
f
λ
p,max: The PL maxima in DMF solution
Eg,opt: Optical energy band gap calculated from the formula E = 1,240/λ
Values determined by cyclic voltammetry
(eV)
g
a,onset
g
h
Eg,EC: Electrochemical band gap estimated from HOMO and LUMO
1
3

J IRAN CHEM SOC
Table 3 Photovoltaic parameters of devices with sensitizers P1-P4 in
–
2
DSSCs at full sunlight (AM 1.5 G, 100 wM cm )
Polymer
Solvent
Jsc (mA/cm2)
Voc (V)
ff (%)
η (%)
P1
P2
P3
P4
DMF
DMF
DMF
DMF
4.32
4.25
4.22
4.19
0.75
0.77
0.82
0.82
66.4
69.5
67.3
70.2
2.15
2.27
2.30
2.41
o
Fig. 7 TGA curves of P1-P4 with a heating rate of 20 C/min under
nitrogen atmosphere
Fig. 10 Spectra of incident photon-to-current conversion efficiencies
IPCE) for DSSCs based on dyes (P1-P4)
(
Photovoltaic properties
Figure 9 displays the irradiation source for the photocurrent
density–voltage (J–V) measurement of the DSSC devices
based on the four polymeric metal complexes. Measurement
of DSSC merits such as corresponding open-circuit volt-
age (V ), short-circuit current density (J ), fill factor (ff),
oc
sc
Fig. 8 Cyclic voltammograms for P1-P4 in DMF/0.1 M [Bu N]BF
at 100 mV/s
4
4
and power conversion efficiency (η) are listed in Table 3. It
can be seen from the table that the V values of P1, P2, P3
oc
and P4 are 0.75, 0.77, 0.82 and 0.82, respectively. The cor-
responding ff values could be achieved a higher level about
2
7
0.2 %. However, the J values increased from 4.19 mA/cm
sc
2
for P4 to 4.32 mA/cm for P1. The power conversion effi-
ciency based on P4 reached 2.41 %, which is the highest of
the device based on those four polymeric metal complexes.
The low J is chalked up to the long distance between
sc
donor and acceptor, which leads to the low charge separa-
tion and transportation efficiency and it also can be seen
from the input photon to converted current efficiency
(IPCE) curves as shown in Fig. 10. The IPCE values of P1,
P2, P3 and P4 are only about 30 % at 425 nm, and are very
low compared with N719 which could be achieved to 80 %
at 425 nm [32]. As discussed in the UV–vis absorption
spectra section, those two groups of data are proportional
development and the IPCE value is decided by the absorp-
tion of light.
Fig. 9 J-V curves of DSSCs based on dyes (P1-P4) under the illumi-
nation of AM 1.5, 100 mW cm
–
2
1
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J IRAN CHEM SOC
Conclusion
9. C.Y. Lin, C.F. Lo, L. Luo et al., J. Phys. Chem. C113, 755 (2009)
1
0. D.W. Chang, S.J. Ko, Y.K. Jin et al., Macromol. Rapid Commun.
2, 180 (2011)
3
Four novel D–π–A polymeric metal complexes dyes com-
prising 2-(2′-pyridyl) benzimidazole derivative metal (Zn,
Co) complex as the electron acceptor, thiophene derivatives
as π-bridge and alkoxy benzene or carbazole derivative as
electron donor were designed, synthesized and used for the
fabrication of DSSC. The performance of the photovoltaic
devices depended on the strength of the electron-donating
group along the conjugated main. Among all of the dyes
studied, DSSC based on P4 demonstrated the best overall
light-to-electricity conversion efficiency of 2.41 % under
AM1.5 irradiation. The results show that these polymeric
metal complexes dyes are promising candidates in the
development of high-performance DSSC.
1
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