Effect of structural manipulation in hetero-tri-aryl amine donor-based D-A′-π-A sensitizers in dye-sensitized solar cells

Article abstract of DOI:10.1039/c7nj04620k

The role of hetero-atom manipulation/hetero-aryl group insertion in the triarylamine to obtain hetero triarylamine as a donor in highly efficient photosensitizers was investigated to study the structure-efficiency relationship in dye-sensitized solar cells (DSSCs). A newly synthesized sensitizer was explored containing N-phenyl-N-(pyridin-2-yl) pyridine-2-amine (DPPA) and N-(pyridin-2-yl)-N-(thiophen-2-yl) pyridine-2-amine (DPTA) as the donor along with a strong electron-withdrawing cyano group (-CN) as the auxiliary acceptor group and cyanoacetic acid and rhodamine-3-acetic acid as anchoring groups. The triphenylamine donor was manipulated for the first time with the insertion of a nitrogen atom in the aryl ring for DSSCs. These hetero-aryl-based sensitizers showed a significant improvement in the photophysical as well as photovoltaic performance. The replacement of cyanoacetic acid by rhodanine-3-acetic acid as an anchoring unit resulted in a significant red-shift in absorption as well as emission maxima. The methylene group in rhodanine-3-acetic acid interrupted the LUMO delocalization on the anchoring group in sensitizers DP3 and DP4, as shown by DFT calculations. The presence of cyanoacetic acid in sensitizers DP1 and DP2 showed effective charge transfer from HOMO to LUMO and efficient electron injection from LUMO to the conduction band of the TiO₂ semiconductor. The sensitizer DP2 showed a maximum efficiency of 4.7%, a short-circuit current J_sc = 11.78 mA cm^-2, an open-circuit voltage V_oc = 0.608 V and a fill factor FF = 0.62. The enhanced efficiency of sensitizer DP2 was attributed to the presence of the strong electron-withdrawing cyanoacetic acid anchoring group and the presence of the thiophene linker at the N-aryl core.

Full text of DOI:10.1039/c7nj04620k

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ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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ARTICLE
Effect of Structural Manipulation in Hetero-tri-aryl Amine Donor
Based D-A’-π-A sensitizers in Dye Sensitized Solar Cells
Dinesh S. Patil,a Keval K. Sonigara,b Manoj M. Jadhav, a Kiran C. Avhad, a Suryapratap Sharma, a
Saurabh S. Soni,b,* Nagaiyan Sekara,*
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
The role of hetero-atom manipulation/hetero aryl group insertion in the triarylamine to have hetero triarylamine as a
donor in highly efficient photosensitizers is focused to investigate the structure-efficiency relationship in the dye sensitized
solar cell (DSSCs). Newly synthesized sensitizer contains N-phenyl-N-(pyridin-2-yl) pyridine-2-amine (DPPA) and N-(pyridin-
2-yl)-N-(thiophen-2-yl) pyridine-2-amine (DPTA) as donor along with strong electron withdrawing cyano group (–CN) as
auxiliary acceptor group while cyanoacetic acid and rhodamine-3-acetic acid are explored as anchoring groups.
Triphenylamine donor is manipulated first time with the insertion of the nitrogen atom in aryl ring for DSSCs. These hetero
aryls based sensitizer reflects significant improvement in photophysical as well as photovoltaic performance. The
replacement of cyanoacetic acid by rhodanine-3-acetic acid as an anchoring unit results in a significant red shift in
absorption and emission maxima. The methylene group in rhodanine-3-acetic acid interrupts the LUMO delocalization on
anchoring group in sensitizers DP3 and DP4, as shown by DFT calculations. The presence of cyanoacetic acid in sensitizers
DP1 and DP2 shows effective charge transfer from HOMO to LUMO and efficient electron injection from LUMO to the
conduction band of the TiO2 semiconductor. The sensitizer DP2 shows a maximum efficiency of 4.7%, short circuit current
Jsc=11.78 mA.cm-2, open circuit voltage Voc=0.608 V and fill factor FF=0.62. The enhanced efficiency of sensitizer DP2 has
been attributed to the presence of strong electron withdrawing cyanoacetic acid anchoring group & presence of thiophene
linker at N-aryl core.
www.rsc.org/
13
easy synthesis and purification process
, economic
15
Introduction
desirability 14, high molar extinction coefficient and ease in
optimizing photophysical properties by structural modification.
The efficient metal-free organic sensitizers have donor-π-
acceptor (D-π-A) structure and modification of every part
Dye Sensitized Solar Cells (DSSCs) have gained significant
importance in the past two decades due to the world demand
for clean, renewable, environmental friendly and freely
1
2
plays
a
significant role in altering the photovoltaic
available energy sources . Grätzel and co-workers in 1991
performance 16. The photophysical, electrochemical and
photovoltaic properties can be fined tuned by changing the
donor part, π-linker or acceptor 17. The different types of
donating groups used in D-π-A type sensitizer includes
reported the first dye sensitized solar cell based on ruthenium
complex since then DSSCs research has gained revolutionary
momentum 3–6. Several metals based sensitizers have been
synthesized in recent years and they have remarkable light to
electricity conversion efficiencies 7–10. However, tedious
synthetic protocol, high metal cost, and environmental burden
restricts their commercial exploration 11. Therefore, metal free
sensitizers are preferred in place of organometallic compounds
12. The metal-free organic sensitizers have an advantage due to
18
19
20
21
coumarin
,
merocyanine
,
cyanine
,
indole
,
,
triphenylamine 22, thiophene 23, carbazole 24, phenothiazine
25
26
julolidine
and phenoxazine 27. These donor units are
attached with the acceptor units using various π-linkers which
show moderate to high efficiencies 26–30. Among these donors
triphenyl amine based sensitizers have shown improved
performance over the years 31. The various strategies have
been employed to boost the donating capacities of triphenyl
amine by utilizing two donor ( D-D32 2D), two donor-pi system
attached new donor {(D-π)2-D} 33, donor-pi-donor (D-π-D),
auxiliary donor systems. The utilization pyridine based
triphenyl amine based donor remains unexplored in DSSCs. In
this paper we are reporting four novel molecules (DP1-DP4)
based on N-phenyl-N-(pyridin-2-yl) pyridine-2-amine (DPPA)
and N-(pyridin-2-yl)-N-(thiophen-2-yl) pyridine-2-amine (DPTA)
as donor group for their potential application in DSSCs
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(Scheme 1). We have used phenyl and thiophene as a pi- linker from DPPA and DPTA donor group to cyanoacetic acid
and cyano acetic acid and rhodanine-3-acetic acid as acceptor. acceptor group via thiophene π-bridge. DP3 and DP4 also show
Thiophene π-linker shows better performance over phenyl two absorption peaks in the range of 310-650 nm.
group as it has less delocalization of electron cloud over the
ring and electron density is available for charge transfer which
shows desirable polarizability, tuneable electrochemical and
spectroscopic properties 34,35. It plays significant role in
electron conduction and affects the absorption and emission
maxima of the sensitizers 36. DP1 and DP2 were compared with
their reported analogues to have established impact of donor
manipulation on photophysical and photovoltaic properties 35
.
Scheme 1. Chemical structure of DP sensitizers
Results and discussion
Design and Synthesis of sensitizers
Scheme 2 and 3 explain the synthetic approach for the four
sensitizers: DP1- DP4. The compound 1 was synthesized by the
nucleophilic substitution reaction of 2-amino pyridine with 2-
bromo pyridine. The nucleophilic substitution reaction
between compound 1 and 4-bromo benzaldehyde and 5-
bromo-thiophene-2-carboxaldehyde gives 2a and 2b
respectively. The condensation of intermediates 2a and 2b
with thiophene acetonitrile gives intermediates 3a and 3b, the
Rieche formylation of 3a and 3b gives intermediates 4a and 4b.
Knoevenagel condensation of intermediates 4a and 4b with
cyanoacetic acid in the presence of piperidine resulted in the
sensitizer DP1 (72% yield) and DP2 (76% yield) and with
rhodamine-3-acetic acid in the presence of ammonium acetate
resulted in the sensitizer DP3 (81% yield) and DP4 (84% yield)
as final products.
Fig. 1. (a) UV Visible of DP dyes recorded in DMF (2 × 10-6M), (b) UV-Visible reflectance
spectra of dye coated TiO2
The first absorption peak near 395 nm is very prominent which
occurs due to aromatic π-π* electronic transition and second
broad peak lies in the range of 430 to 650 nm is due to the
37
intramolecular charge transfer (ICT)
from DPPA and DPTA
Photophysical properties
(donor group) to rhodanine-3-acetic acid (acceptor group) via
thiophene π-bridge. The sensitizers DP1 and DP3 are having
same donor group and thiophene π-bridge but DP3 shows red
shifted maxima. This red shift in maxima is due to rhodanine-3-
acetic acid anchoring group manipulated as compared with
DP1 having cyanoacetic acid. The red shift in DP3 in
comparison with DP1 suggest that rhodanine-3-acetic acid is
having better electron withdrawing capacity in comparison
with cyano acetic acid which lowers the LUMO level of dye
thus reducing the band gap. This is further proved by cyclic
voltammetry data and DFT calculations. A similar trend has
The UV-visible spectra of DP1-DP4 were recorded in N, N-
dimethyl formamide (2 × 10-6 M) and the corresponding
spectra are replicated in Fig. 1(a). The absorption maxima and
molar extinction coefficient data in DMF for all sensitizers is
given in Table 1. The sensitizers DP1 and DP2 show two
absorption peaks in DMF. The first weak absorption peak lies
in the range of 330-360 nm due to aromatic π-π* electron
transition and second broad peak in the range of 370-600 nm
22
broad peak is due to intramolecular charge transfer (ICT)
2 | J. Name., 2012, 00, 1-3
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Table 1
been observed between DP2 and DP4 having same donor
group and thiophene π-bridge. DP4 have highest absorbance
maxima value at 534 nm which is due to the presence of the
thiophene π-bridge with the strong electron withdrawing
cyano (CN) group which act as electron trap and rhodanine-3-
acetic acid as an anchoring group. The sensitizer DP2 has
comparatively high molar extinction coefficient value due to
the presence of thiophene ring with CN group (act as electron
trap) in π-bridge and universal famous anchoring group
cyanoacetic acid which suggest good light harvesting capacity.
The molar extinction coefficients values of DP1, DP2, DP3, and
DP4 are 63,479, 72,512, 54,562 and 58,313 M-1 cm-1
respectively. Same trends were observed when we have
measured UV-Visible reflectance spectra of dye loaded TiO2
films (Fig. 1 (b)). Here, the observed broadening of spectra is
compared with the spectra recorded in the solvent along with
the red shift in the absorbance, confirms the anchoring of
sensitizers on the nanocrystalline porous titania. DP3 and DP4
show red shift of 70 nm and 65 nm respectively and seems
large broadening spectra indicates the poor charge transfer
due to the rhodanine-3-acetic acid as anchoring group.
Whereas, DP1 and DP2 show a lower broadening of spectra
and large red shift of 82 nm and 81 nm for DP1 and DP2
respectively. This higher red shift indicates good charge
transfer from donor to acceptor due to cyanoacrylic acid as
strong acceptor as anchoring group and same is responsible
for higher absorbance coefficient profile of DP1 and DP2 on
TiO2 surface.
a
Sensiti
zer
λmax
λmax
Ɛmax
Onset
vs.
BG
HOM
Od
LUMOe
(V)
(M-
1cm-1)
a
b
c
Ag/Ag
Cl (V)
0.238
(V)
(eV)
DP1
DP2
DP3
DP4
426
482
468
534
508
563
538
599
63479
72512
54562
58313
2.4
7
0.88
1.13
1.02
1.07
-1.60
-1.03
-1.24
-0.88
0.507
0.391
0.437
2.1
7
2.2
6
1.9
5
a Measured in DMF, bMeasured from solid UV reflectance c Measured from λonset
,
d
All potentials were obtained from CV. BG = Band gap, Potential measured vs.
Fc/Fc+ was converted to the NHE by the addition of +0.63 V. Calculated from
d
LUMO = HOMO – Eg.
Electrochemical properties
The cyclic voltammetry (Fig. 3a) was used for the investigation
of electrochemical properties of these four sensitizers to
obtain the HOMO and LUMO energy level position of the
sensitizers (Table 1). Under the application of the positive
potential, CV showed two quasi-reversible oxidation waves
which correspond to oxidation–reduction process. These two
peaks were observed at 0.85 V and 1.25 V for DP2 versus
ferrocene/ferrocenium (Fc/Fc+) was attributed to the oxidation
of the π-conjugated backbone and donor, respectively.
Fig. 2. (a) CV curves in acetonitrile at a scan rate of 25 mV/s, (b) Frontier molecular
orbitals with the energy level diagram along with redox potentials of electrolyte
(HOMOs; bottom) and (LUMOs; top) of the DP sensitizers.
The well-defined first oxidation peak for DP2 compared to DP1
confirms better charge transformation between D and A in the
case of DPTA donor as compared to DPPA donor. The HOMO
and LUMO energy levels of these four sensitizers were figured
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out from the DFT calculations and CV data which are delocalization from donor to acceptor on excitation
summarized in Table 1
.
encourages the effective injection of electrons into the
The HOMO energy levels of DP1
,
DP2
,
DP3, and DP4 are 0.87, conduction band of TiO2 through the carboxyl anchoring
1.14, 1.02 and 1.07 V vs. the NHE (normal hydrogen electrode) group. The electronic distribution of HOMO and LUMO of all
respectively. These values are larger than the redox potential sensitizers at B3LYP/6-31G(d) level and their corresponding
-
of I-/I3 redox couple (0.4 V vs. the NHE) of the electrolyte. This energy gap is shown in Fig. S1
(
Table S1). The HOMO-LUMO
-
ensures a facile regeneration of the sensitizer by I-/I3 energy gap is high in the DP1 as compared with the other
electrolyte after electron injection. The LUMO energy levels of sensitizers and in the case of DP4, it is low as compared with
DP1, DP2, DP3, and DP4 are -1.60, -1.03, -1.24 and -0.88 V vs. other sensitizers and the same results obtained from the cyclic
NHE, respectively. The LUMO energy level of DP sensitizers is voltammetry. The optimized geometries of all four sensitizers
higher than the conduction band of TiO2 (0.5 V vs. NHE), which at B3LYP/6-31G(d) level shown in Fig. S2 in SI.
indicates the feasibility of smooth electron injection on TiO2 The calculated electronic vertical transition energy, oscillator
strengths (f), maximum absorption wavelength (λmax) and
upon photo-excitation.
nature of the transitions in various states are collected in Table
Computational study
2. From Table 2, the strongest absorption peaks for all dyes
mainly related to the transition from the HOMO to the LUMO.
Moreover, one can find that the maximum absorption
wavelength of DP2 to DP4 is remarkably red-shifted in DMF
solution compared to DP1 and DP3 and the increased order is
Geometries of the sensitizers at their ground state were
38
optimized by using the DFT global hybrid function B3LYP
.
The basis set 6-31G (d) was used for all the atoms. The B3LYP
is a combination of Becke’s three parameter exchange
functional
DP1
< DP3 < DP2 < DP4. At the same time, the extent of the
red-shift of DP3 and DP4 is larger, which can be explained by
the difference of electronegativity for S atom and the better
electron delocalization allowed by the sulphur atom in relation
to the other atom. However, the red shift in sensitizer DP2 and
DP4 as compared with DP1 and DP3 due to the thiophene
(sulphur) ring present in DP2 and DP4. All sensitizers having D-
A’-π-A configuration could be better as compared to the D-π-A
structure. As a result, the calculated spectral data confirms
that the introduction of the additional acceptor in D-A’-π-A
system could be favourable for the long wavelength light-
harvesting, and can be beneficial for enhanced photo-to-
electric conversion efficiency of related solar cell as compared
to D-π-A system 46
.
Fig. 3. The highest occupied molecular orbitals (HOMO) and lowest unoccupied
molecular orbitals (LUMO) of all sensitizers. They were obtained at the B3LYP/6-31G(d)
level in a vacuum.
The LHE is one of the significant parameter related to the
intensity of the absorption spectra of the sensitizer and is
calculated using the following equation (1), LHE = 1–10-f
where f is the oscillator strength of the sensitizers. For an
efficient photocurrent conversion, the value LHE of the
sensitizers should be high. The LHE values were calculated for
various bands of all sensitizers are shown in Table S2. The LHE
of the sensitizers increases with an increase in red shift was
observed in the Table S2. The maximum value of LHE around
0.984 by TD-B3LYP is observed for DP4. Generally, all
sensitizers show LHE nearer to the unity, notably the DP2 show
more power conversion efficiency compared to other
sensitizers.
39
(B3) with the nonlocal correlation functional by Lee, Yang,
and Parr (LYP) 40. The first excited singlet states were
optimized using TD-DFT B3LYP/6-31G(d) basis set. Frequency
computations were also carried out on the optimized
geometry of the low-lying vibronically relaxed first excited
state of molecules 41. The polarizable continuum model (PCM)
42,43
was used for optimization in a solvent (DMF). The
Gaussian 09 program was used for DFT and TD-DFT
computations 44. Generally, the molecules which have both n –
π* and π - π* states (D-π-A system), global hybrids such as
B3LYP will generally provide an accurate estimate45 and hence
we preferred TD-DFT B3LYP method to perform the
calculation.
Photovoltaic performance
The frontier molecular orbital diagram (FMO) of all the
sensitizers are shown in Fig. 2, which shows that the electron
density was uniformly distributed on the donor group in
HOMO. On excitation electron cloud shifted towards the
anchoring group at LUMO level, resulting in more effective
intramolecular charge separation observed in sensitizers DP1
and DP2 as compared to the DP3 and DP4. The charge
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DP3 and DP4 is originated from the lower molar extinction
coefficient and the week acceptor/anchoring group rhodanine-
3-acetic acid, due to this the decrement in Jsc value reflected in
the device performance. Individually, between the DP2 and
DP1, keeping similar anchoring groups and the changing in
donor portion from phenyl to thiophene group provides the
hike in increasing molar absorption coefficient and λmax
absorbance, which make DP2 more efficient in photovoltaic
performance. A similar trend was observed in the DP3 and DP4
moieties. Correlating DP2 and DP4, the effect of different
anchoring groups reveals the performance difference between
the different capacity of charge injection into TiO2 in Jsc as well
as Voc values. The DP3 based DSSC showed Jsc of 4.11 mAcm-2,
Voc of 0.589 V with a fill factor of 0.59. Visible difference in Voc
parameters between DP1/DP2 to DP3/DP4 is related to
negative shifting of TiO2 conduction band after anchoring of
sensitizer 47, the here strong cyanoacrylic acid group made a
more negative shift of TiO2 conduction band and results higher
Voc compare to rhodanine-3-acetic acid.The photocurrent
characteristics of the fabricated DSSCs are estimated from the
incident photon-to-current conversion efficiency (IPCE) values
measured at short-circuiting against the wavelength.
Table 2 Photovoltaic performance of DP based sensitizers.
Sensitizers
DP1
Jsc(mA/cm2)
8.40 ± 0.20
11.78 ± 0.20
4.11 ± 0.20
5.80 ± 0.20
Voc (V)
FF
η (%)
0.624± 0.03
0.608± 0.03
0.589± 0.03
0.575± 0.03
0.66 ± 0.05
0.62 ± 0.05
0.59 ± 0.05
0.65 ± 0.05
3.5 ± 0.3
4.7 ± 0.3
1.5 ± 0.3
2.2 ± 0.3
DP2
DP3
DP4
Fig. 4. I−V curves of the DSSCs, (a) with 1sun illumination and (b) without illumination
Jsc: short-circuit current, Voc: open circuit voltage, ff: fill factor and PCE (%): power
in dark condition.
conversion efficiency.
Fig. 4a shows the current–voltage characteristics of DSSCs
fabricated with these dyes (DP1 to DP4) as sensitizers under
standard global AM 1.5 solar light conditions at 1 Sun
illumination whereas Fig. 4b shows I-V characteristics in dark
condition, which confirm the absence of dark reactions as all
the devices give zero current density. The detailed parameters
of short-circuit current density (Jsc), open-circuit voltage (Voc),
fill factor (FF), and photovoltaic conversion efficiency (ƞ) are
summarized in Table 3.
All sensitizers show high fill factors (FF) between 59% and 66%.
Fig. S2 (SI) represents the IPCE spectra of the fabricated DSSCs
exhibiting the highest values
∼80−82% for DP2 and other
sensitizers showing a broad plateau in the wavelength range of
400−700 nm. The trend in IPCE spectra of the fabricated DSSCs
was observed in the order DP3
< DP4 < DP1 < DP2. This
ensures a saturated light absorption by all the sensitizers DP1,
DP2, DP3 and DP4, which is in good agreement with the UV−vis
absorption spectra. It was important to note that the DP2
show higher value of photon to current conversion efficiency,
higher IPCE spectra value, higher molar extension coefficient,
and higher Jsc value.
The short-circuit current Jsc is correlated with a molar
extinction coefficient of the sensitizers, hence the sensitizers
with higher molar extinction coefficient yields the higher short-
circuit current. The molar extinction coefficient of DP2 is
highest among all other DP series hence shows highest Jsc
=
Electrochemical Impedance Spectroscopy and Tafel
Characterization
11.78 mA/cm2. The low Voc = 0.608 V of DP2 in comparison
with DP1 is attributed due to low LUMO level with respect to
DP1. The trend in photon light to current conversion efficiency
To get more understanding of power conversion of DSSC
devices based on different sensitizers, we have investigated
the interfacial charge transfer process within DSSCs using the
Electrochemical Impedance Spectroscopy (EIS) technique 48. As
shown in Fig. 5 EIS showed two semicircles in the Nyquist plots
for all sensitizers.
was observed in the order DP3
< DP4 < DP1 < DP2. DP2 shows
highest 4.7 % light to current conversion efficiency (Table 3)
.
DP1 shows second highest photocurrent efficiency was 3.5 %
and highest Voc was 0.624 V owing to the lowest λmax value, but
it has beneficial properties like DP2. The lower performance of
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The smaller (higher frequency from 103 to 105 Hz) and larger Here, the higher electron lifetime τr indicates the lower
semi-circles (lower frequency from 1 to 102 Hz) in the Nyquist recombination of an electron from TiO2 to the electrolyte and
plots are related to charge transfer at the counter it results in the higher Jsc value 50. Based on said phenomenon
electrode/electrolyte interface and the TiO2/dye/electrolyte the trend is in good agreement with the variation tendency of
interface respectively. Third, the slightly visible arc is related to Jsc observed in the J–V curves.
iodide diffusion in the electrolyte, it is very moderate due to To support the phenomena observed from the EIS
51
use of liquid electrolyte 49. First small arcs were almost similar characteristics, Tafel polarization technique is used to study
in all the sensitizers which are due to the use of the same better understanding of the recombination kinetics of
counter electrode and electrolyte components. In the EIS electrolyte and electrode component of the solar cells (Fig. 6).
measurement, the curves were fitted using an equivalent Tafel analysis tells in brief on the interfacial charge transfer of
circuit model (Inset of Fig. 5) and the obtained parameters are electrolyte redox couple at the catalyst platinum electrode and
shown in Table 4. The recombination resistance of the DP2 oxidation/reduction reaction exhibit at the semiconductor
device was higher than that of the other devices according to electrolyte interface which can be understood by the help of
the value derived from curve fitting in Z-view software. The Buttler-Volmer equation 52. The nature of Tafel plots looks very
trend observed for the recombination resistance are DP3 < similar and it indicates the similar smooth catalytic reaction at
DP4 < DP1 < DP2.
the counter electrode and electrolyte interface. Tafel
measurement data was fitted using corrview software and the
exchange current density was estimated for all devices.
-2
140
120
100
DP1
DP2
DP3
DP4
-3
-4
-5
80
(a)
-6
DP1
60
40
20
0
DP2
DP3
DP4
-7
-8
-9
-10
0
50
100
150
200
250
300
350
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8
Z', Ohm
Potential, V
Fig. 5. EIS spectra of all devices in dark condition at -0.65 V DC forward bias. Inset of
figure shows the equivalent circuit for fitting the Nyquist plot.
Fig. 6 Tafel polarization curve of DSSCs taken in dark.
Table 3 DSSC parameters Rpt, Rrec, tn and j0 extracted from EIS measurements and Tafel
Order of exchange current density well supports the
recombination resistance extracted from the EIS spectra and
while the well proved obtained I-V performance of the DSSC
performed with these dyes.
polarization study
a
a
a
b
b
b
Na
Rsa
Rpt
Rct
C a
τr
βa
βc
j0
me
(Ω)
(Ω)
(Ω)
(µF)
(ms)
(mV)
(mV)
(A/cm2)
DP
1
26.
82
13.
19
164
7.22
8.92
3.05
4.34
1.86 108.5
2.53 118.6
0.27 98.36
0.56 106.0
212.1
3.01 ×
10-6
Experimental
DP
2
24.
97
29.
69
284
140
129
244.2
203.0
217.0
3.07 ×
10-6
Materials and Methods
DP
3
23.
04
16.
05
1.12 ×
10-6
All chemicals and synthetic reagents required for synthesis are
procured from S. D. Fine Chemicals. 3-methoxy propionitrile
(MNP), Guanidinium thiocyanate (GSCN), 4-tert butyl pyridine
(TBP), Iodine, 1-butyl-3-methylimidazolium iodide were
purchased from Sigma-Aldrich and TCI chemicals. FTO
substrates (7Ω/cm2) and hot melt tape were purchased from
Solaronix Inc, Switzerland. 0.25 mm silica gel 60 F254
percolated plates on alumina is used for monitoring the
DP
4
23.
02
11.
24
1.76 ×
10-6
a Values estimated by fitting the Nyquist plot. b Estimated from Tafel polarization
curves.
DP3 and DP4 show lowest recombination resistance as
compared to the other device. DP1 show the second highest
value of recombination resistance. Electron lifetime (τr)
calculated for all the four devices is of the following order: DP2
(2.53 ms) > DP1 (1.86 ms) > DP4 (0.56 ms) > DP3 (0.27 ms).
1
reaction progress, which was visualized with UV light. H-NMR
and 13C-NMR spectra were recorded on Agilent technology
500-MHz instrument by using TMS as an internal standard. The
6 | J. Name., 2012, 00, 1-3
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UV-visible absorption spectra of the compounds were pressures and 200 0C temperature. After completion of the
recorded on a Perkin-Elmer Lambda- 25 spectrometers. The reaction (monitored by TLC), the reaction mixture was cooled
solid UV-visible reflectance of dye loaded TiO2 performed using to room temperature and poured into ice water. The crude
Ocean optics spectrometer analyzing with spectra suite product was extracted with ethyl acetate and the organic layer
software. Cyclic Voltammetry (CV) was performed with (CH was washed with water and dried over anhydrous sodium
instruments model 660E) electrochemical workstation with sulphate. After removing the solvent under reduced pressure,
three standard electrochemical cells. Dye solution prepared in the residue was purified by column chromatography using
acetonitrile and platinum disc was used as
electrode, Ag/Ag+ electrode as the reference and Pt wire as (48% yield).
counter electrode. 0.1
tetrabutylammonium 1H NMR (500 MHz, CDCl3) δppm 9.92 (s, 1H), 8.39 (dd, J = 5.1,
a working ethyl acetate/hexane (40:60) to afford the light yellow solid 2a
M
hexafluorophosphate (TBAPF6) dissolved in acetonitrile solvent 2.0 Hz, 2H), 7.83 (d, J = 8.5 Hz, 2H), 7.65 (td, J = 7.8, 2.0 Hz,
is used as supporting electrolyte. CV curves were calibrated by 2H), 7.23 (d, J = 8.6 Hz, 2H), 7.07 – 7.04 (m, 4H).
using ferrocene as the standard. The photocurrent density- 13C NMR (125 MHz, CDCl3) δppm 190.92, 157.50, 150.70,
voltage (J-V) characteristics of the fabricated DSSCs were 149.11, 138.13, 131.13, 124.70, 119.70, 118.37.
measured by using Keithly-2450 digital source meter
controlled by a computer scan rate of 10 mVs-1. A solar
5-(Di(pyridin-2-yl) amino) thiophene-2-carbaldehyde (2b)
simulator (PET 80AAA, USA) 300 W xenon lamp, connected
with an AM 1.5 G filter to serve as the light source, give In 50ml sealed tube 5-bromo thiophene-2-carboxaldehyde
100mW/cm2 at the surface of the test cell to remove (0.84 mmol) and compound 1 (0.7 mmol) were dissolved in
ultraviolet and infrared radiation. While Electrochemical and DMF (15ml), then added K2CO3 (0.84 mmol) and Cu(I)I (0.14
Impedance measurements were carried out using SOLARTRON mmol) in the reaction mixture. The sealed tube was kept for
electrochemical analyzer (Solartron 1287
+
1260). The heating at 1500C for 16 hours. After completion of the reaction
impedance of the DSSC was measured by sweeping low (monitored by TLC), the reaction mixture was cooled to room
amplitude AC signal (10 mV) having a frequency ranging from temperature and poured into ice water. The crude product
120 kHz to 0.1 Hz. During the measurement, cells were held in was extracted with ethyl acetate and the organic layer washed
dark under the application of -0.70
V DC bias. Tafel with water and dried over anhydrous sodium sulphate. After
polarization curves were obtained by sweeping potential from removing the solvent under reduced pressure, the residue was
-0.7 to 0.7 to the DSSC in dark and resulting data were fitted in purified by column chromatography using eluent ethyl
Buttler-Volmer equation.
acetate/hexane (40:60) to afford the light yellow solid 2b (43%
yield).
Synthesis
1H NMR (500 MHz, DMSO) δppm 9.73 (s, 1H), 8.60 (dd, J = 4.9,
1.7 Hz, 2H), 7.91 (td, J = 7.8, 1.9 Hz, 2H), 7.68 (d, J = 4.4 Hz,
1H), 7.36 (dd, J = 7.3, 4.9 Hz, 2H), 6.97 (d, J = 8.2 Hz, 2H), 6.02
Di(pyridin-2-yl) amine (1)
2-Amino pyridine (5.31 mmol) and 2-bromo pyridine (6.37 (d, J = 4.4 Hz, 1H).
mmol) in toluene (50ml) were added to a round bottom flask 13C NMR (125 MHz, DMSO) δppm 184.06, 154.83, 153.92,
equipped with a condenser. NaH (5.31 mmol) added slowly to 149.20, 140.12, 137.31, 133.44, 121.67, 118.08, 114.02.
the reaction mixture. In addition, the reaction mixture was
heated under reflux condition for 24 h. The reaction was (E)-3-(4-(Di(pyridin-2-yl) amino) phenyl)-2-(thiophen-2-yl)
monitored using TLC (eluent: 40% ethyl acetate in hexane). acrylonitrile (3a)
After completion of the reaction, the reaction mass was
In 50ml round bottom flask, 2 to 3 drops of piperidine were
poured into water. The organic layer was separated and
added to a solution of the compound 2a (0.29 mmol) and
washed, several times with water and then dried over
thiophene acetonitrile (0.34 mmol) in ethanol (12 ml). The
anhydrous sodium sulfate. The dried organic layer was
reaction mixture was refluxed for 6 h. After completion of the
evaporated on a rotary evaporator. The resulting residue was
reaction (monitored by TLC), the reaction mixture was cooled
purified
by
column
chromatography
using
ethyl
to room temperature and poured into ice water. The crude
product was extracted with ethyl acetate and the organic layer
washed with water and dried over anhydrous sodium sulphate.
After removing the solvent under reduced pressure, the
residue purified by column chromatography using eluent ethyl
acetate/hexane (40:60) to afford the yellow solid 3a (84%
yield).
acetate/hexane (40:60), thereby affording the desired product
as a white solid 1 (Yield: 51%).
1H NMR (500 MHz, CDCl3) δppm 8.28 (ddd, J = 5.0, 1.8, 0.8 Hz,
2H), 8.01 (s, 1H), 7.62 – 7.55 (m, 4H), 6.86 – 6.83 (m, 2H).
13C NMR (125 MHz, CDCl3) δppm 154.10, 147.74, 137.72,
116.33, 111.67.
1H NMR (500 MHz, CDCl3) δppm 8.37 (d, J = 4.7 Hz, 1H), 8.35 (d,
J = 4.8 Hz, 1H), 7.84 (d, J = 8.6 Hz, 1H), 7.63 (d, J = 8.1 Hz, 1H),
7.59 (d, J = 9.9 Hz, 1H), 7.39 – 7.31 (m, 2H), 7.29 (d, J = 6.7 Hz,
2H), 7.23 (d, J = 8.4 Hz, 1H), 7.20 (d, J = 8.6 Hz, 1H), 7.05 (d, J =
7.6 Hz, 2H), 7.03 – 6.97 (m, 3H).
4-(Di(pyridin-2-yl) amino) benzaldehyde (2a)
The compound 1 (0.7 mmol) and p-bromo benzaldehyde (0.84
mmol) was dissolved in DMF (12 ml) then subsequent added
K2CO3 (0.84 mmol) and Cu(I) (0.14 mmol) in a 20ml microwave
vial, and irradiation of microwave for 55 minutes with 10 bar
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(12 ml) at 0°C. TiCl4 (0.52 mmol) was then added dropwise to
the above solution. The reaction mixture was stirred at room
temperature for 0.5 h. After completion of the reaction
(monitored by TLC), the reaction mixture was poured into cold
(E)-3-(5-(Di(pyridin-2-yl) amino) thiophen-2-yl)-2-(thiophen-2-yl)
acrylonitrile (3b)
This was prepared as described in the preparation of 3a. The dilute HCl solution. The crude product was extracted into
residue of the 3b was purified by column chromatography dichloromethane and the organic layer was washed with water
using eluent ethyl acetate/hexane (40:60) to afford orange and dried over anhydrous sodium sulphate. After removing the
solid 3b (81% yield).
solvent under reduced pressure, the residue was purified by
1H NMR (500 MHz, CDCl3) δ 8.47 (dd, J = 4.9, 1.3 Hz, 2H), 7.69 – column chromatography using eluent ethyl acetate/hexane
7.65 (m, 2H), 7.40 (d, J = 4.2 Hz, 1H), 7.36 (s, 1H), 7.26 (d, J = (40:60) to afford the orange solid 4a (83% yield).
3.5 Hz, 1H), 7.23 (dd, J = 5.1, 0.9 Hz, 1H), 7.09 (dd, J = 7.2, 5.0 1H NMR (500 MHz, CDCl3) δppm 9.89 (s, 1H), 8.39 (dd, J = 4.9,
Hz, 2H), 7.04 – 6.99 (m, 3H), 6.48 (d, J = 4.2 Hz, 1H).
1.9 Hz, 2H), 7.89 (d, J = 8.7 Hz, 2H), 7.72 (d, J = 4.0 Hz, 1H), 7.66
13C NMR (126 MHz, CDCl3) δ 155.91, 151.55, 148.75, 139.34, – 7.63 (m, 2H), 7.50 (s, 1H), 7.44 (d, J = 3.9 Hz, 1H), 7.22 – 7.20
138.33, 132.90, 131.43, 131.37, 128.10, 125.99, 125.19, (m, 2H), 7.08 – 7.04 (m, 4H).
119.89, 119.32, 117.53, 117.05, 100.18.
13C NMR (126 MHz, CDCl3) δppm 182.46, 157.45, 149.09,
148.95, 148.57, 148.19, 142.72, 142.36, 138.05, 136.87,
131.16, 130.88, 128.28, 127.13, 125.14, 119.56, 118.22,
116.37, 103.19.
(E)-3-(4-(Di(pyridin-2-yl) amino) phenyl)-2-(5-formylthiophen-2-yl)
acrylonitrile (4a)
(E)-3-(5-(Di(pyridin-2-yl) amino) thiophen-2-yl)-2-(5-
formylthiophen-2-yl) acrylonitrile (4b)
The dichloromethyl methyl ether (0.52 mmol) was added to a
solution of the compound 3a (0.17 mmol) in dichloromethane
N
N
N
a
b
c
N
N
N
+
and
N
NH2
N
Br
N
N
H
N
S
1
O
O
2b
2a
N
N
N
N
S
N
N
N
S
N
N
N
N
N
N
d
e
S
S
and
and
2a and 2b
S
N
N
N
N
S
S
3b
3a
O
O
4b
4a
Scheme 2. Synthesis of intermediat: (a) NaH, toluene, reflux (b) 4-bromo-benzaldehyde, K2CO3, Cu(I), microwave. (c) 5-bromo-thiophene-2-carboxaldehyde, K2CO3,
Cu(I), seal tube. (d) thiophene acetonitrile, piperidine, ethanol, reflux. (e) TiCl4, dichloromethyl methyl ether, DCM, R.T.
This was prepared as described in the preparation of 4a. The 1H NMR (500 MHz, CDCl3) δppm 9.83 (s, 1H), 8.55 (dd, J = 4.9,
residue of the 4b was purified by column chromatography 1.3 Hz, 2H), 7.74 – 7.70 (m, 2H), 7.67 (d, J = 4.0 Hz, 1H), 7.54 (s,
using eluent ethyl acetate/hexane (40:60) to afford red solid 1H), 7.49 (d, J = 4.4 Hz, 1H), 7.30 (d, J = 4.0 Hz, 1H), 7.18 (ddd, J
4b (78% yield).
8 | J. Name., 2012, 00, 1-3
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= 7.3, 4.9, 0.6 Hz, 2H), 6.95 (d, J = 8.2 Hz, 2H), 6.29 (d, J = 4.4 131.40, 128.70, 127.16, 125.42, 120.11, 118.50, 117.23,
Hz, 1H).
116.80, 102.23, 100.52.
13C NMR (126 MHz, CDCl3) δppm 182.27, 154.82, 153.59, Elemental Analysis- Calculated: C, 68.20; H, 3.60; N, 14.73; O,
149.40, 148.90, 141.61, 138.71, 137.30, 136.33, 133.55, 6.73; S, 6.74.
129.34, 125.78, 120.57, 117.38, 117.10, 116.67, 97.47.
Found: C, 68.23; H, 3.59; N, 14.75.
(E)-2-Cyano-3-(5-((E)-1-cyano-2-(4-(di(pyridin-2-yl) amino) phenyl)
vinyl) thiophen-2-yl) acrylic acid (DP1)
(E)-2-Cyano-3-(5-((E)-1-cyano-2-(5-(di(pyridin-2-yl) amino)
thiophen-2-yl) vinyl) thiophen-2-yl) acrylic acid (DP2)
Two to three drops of piperidine were added to a solution of This was prepared as described in the preparation of DP1. The
the compound 4a (0.0526 mmol) and cyanoacetic acid (0.105 residue was purified by solvent treatment (wash with diethyl
mmol) in acetonitrile (5 ml). The reaction mixture was refluxed ether) to afford compound DP2 as dark red solid (76% yield).
for 3.5 hrs. After completion of the reaction (monitored by 1H NMR (500 MHz, DMSO) δppm 8.52 (d, J = 3.8 Hz, 2H), 7.99 (d,
TLC), the reaction mixture was cooled to room temperature J = 8.1 Hz, 2H), 7.91 – 7.86 (m, 2H), 7.63 (dd, J = 19.5, 4.1 Hz,
and poured into water. The product filtered washed with 2H), 7.35 (d, J = 3.9 Hz, 1H), 7.31 (dd, J = 6.9, 5.2 Hz, 2H), 7.01
water then purified by solvent treatment (wash with diethyl (d, J = 8.2 Hz, 2H), 6.23 (d, J = 4.2 Hz, 1H).
ether) to afford compound DP1 as a red solid (72% yield).
13C NMR (125 MHz, DMSO) δppm 162.76, 154.58, 152.57,
1H NMR (500 MHz, DMSO) δppm 8.49 (s, 1H), 8.31 (dd, J = 4.8, 149.10, 143.98, 139.86, 136.95, 136.53, 136.41, 135.18,
1.3 Hz, 2H), 8.00 (d, J = 4.0 Hz, 2H), 7.96 (d, J = 8.8 Hz, 2H), 7.77 129.35, 125.42, 121.35, 119.70, 118.00, 117.89, 116.40, 96.35.
– 7.74 (m, 2H), 7.64 (d, J = 4.0 Hz, 1H), 7.17 – 7.12 (m, 4H), 7.04 Elemental Analysis- Calculated: C, 62.36; H, 3.14; N, 14.54; O,
(d, J = 8.3 Hz, 2H).
6.64; S, 13.32.
13C NMR (125 MHz, DMSO) δppm 163.73, 157.46, 149.05, Found: C, 62.39; H, 3.13; N, 14.56.
148.37, 147.63, 146.33, 143.60, 141.00, 138.86, 136.00,
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N
N
N
S
N
N
N
S
N
N
N
S
N
N
N
S
and
and
f
N
N
N
N
S
S
N
O
O
OH
4b
HO
DP2
O
N
4a
O
DP1
N
N
N
N
S
N
N
N
N
S
N
N
N
N
S
S
and
and
g
N
N
N
N
S
S
S
O
S
O
4b
S
O
4a
O
O
N
N
S
O
OH
OH
DP4
DP3
Scheme 3. Synthesis of DP sensitizers: (f) cyanoacetic acid, acetonitrile, ammonium acetate, reflux. (g) rhodanine-N-acetic acid, ammonium acetate, acetic acid,
reflux.
with diethyl ether) to afford compound DP3 as a red solid (81
2-((Z)-5-((5-((E)-1-Cyano-2-(4-(di(pyridin-2-yl) amino) phenyl) vinyl)
% yield).
1H NMR (500 MHz, DMSO) δppm 8.31 (d, J = 4.5 Hz, 2H), 8.17 (s,
thiophen-2-yl) methylene)-4-oxo-2-thioxothiazolidin-3-yl) acetic
acid (DP3)
1H), 8.01 (s, 1H), 7.96 (d, J = 8.7 Hz, 2H), 7.82 (d, J = 4.1 Hz,
Ammonium acetate (0.0477 mmol) was added to a solution of
1H), 7.78 – 7.74 (m, 2H), 7.59 (d, J = 3.9 Hz, 1H), 7.18 – 7.12 (m,
compound 4a (0.0477 mmol) and rhodanine-3-acetic acid
4H), 7.04 (d, J = 8.2 Hz, 2H), 4.72 (s, 2H).
13C NMR (125 MHz, DMSO) δppm 192.14, 167.69, 166.41,
(0.0572 mmol) in acetic acid (6 ml). The reaction mixture was
refluxed for 2.5 hrs. After completion of the reaction
157.48, 149.04, 148.20, 147.29, 142.51, 138.85, 137.82,
(monitored by TLC), the reaction mixture was cooled to room
131.26, 128.91, 128.32, 126.60, 125.53, 120.52, 120.18,
temperature and poured into water. The product filtered
120.07, 118.46, 117.12, 102.42, 45.73
washed with water then purified by solvent treatment (wash
Elemental Analysis- Calculated: C, 59.88; H, 3.29; N, 12.04; O,
8.25; S,16.53.
10 | J. Name., 2012, 00, 1-3
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Found: C, 59.89; H, 3.28; N, 12.05.
amine (DPPA) and N-(pyridin-2-yl)-N-(thiophen-2-yl) pyridine-
2-amine (DPTA) groups acting as electron donor. All the
sensitizers have thiophene acetonitrile π- conjugation systems
which are attached to cyanoacetic acid and rhodanine-3-acetic
acid as anchoring groups. Their structural, electrochemical,
optical properties were performed, and device fabrication
2-((Z)-5-((5-((E)-1-Cyano-2-(5-(di(pyridin-2-yl) amino) thiophen-2-
yl) vinyl) thiophen-2-yl) methylene)-4-oxo-2-thioxothiazolidin-3-yl)
acetic acid (DP4)
This was prepared as described in the preparation of DP3. The studies were carried out to evaluate the manipulation effect. It
residue was purified by solvent treatment (wash with diethyl is important to note that the absorption maximum values were
ether) to afford compound DP4 as a dark blue solid (84% red shifted in the order DP1 < DP3 < DP2 < DP4. The thiophene
yield).
acetonitrile linker in all above sensitizers but DP4 had higher
1H NMR (500 MHz, DMSO) δppm 8.55 (dd, J = 4.9, 1.1 Hz, 2H), absorption maxima due to the presence of DPTA donor group
8.11 (d, J = 3.1 Hz, 2H), 7.90 (td, J = 8.1, 1.9 Hz, 2H), 7.76 (d, J = and rhodamine-3-acetic acid. The sensitizer (DP2) comprising
4.2 Hz, 1H), 7.62 (d, J = 4.5 Hz, 1H), 7.40 (d, J = 4.0 Hz, 1H), 7.36 of DPTA donor group with thiophene acetonitrile as a π-spacer
– 7.32 (m, 2H), 7.00 (d, J = 8.2 Hz, 2H), 6.17 (d, J = 4.4 Hz, 1H), and cyanoacetic acid as an acceptor group shows good
4.70 (s, 2H).
efficiency as compared with other sensitizers having same or
13C NMR (126 MHz, DMSO) δppm 192.06, 167.73, 166.35, different donors with same or different acceptor like
154.19, 153.22, 149.14, 148.61, 140.00, 138.33, 137.27, rhodanine-3-acetic acid. The significant trend in molar
136.47, 135.63, 128.99, 126.81, 126.61, 121.59, 119.20, extinction coefficient was observed in the order DP3 < DP4 <
118.01, 117.79, 115.73, 95.56, 45.67. DP1 < DP2, the sensitizer DP2 had a higher value of molar
Elemental Analysis- Calculated: C, 55.18; H, 2.92; N, 11.92; O, extinction coefficient than the other sensitizers due to DPTA
8.17; S, 21.82.
donor group and cyanoacetic acid anchoring group. It is
concluded that, the DP2 is superior sensitizer for photovoltaic
performance than the other DP sensitizers.
Found: C, 55.19; H, 2.91; N, 11.93.
Fabrication and measurement of DSSC
DSSC were fabricated as per our previously reported method 53
using sandwich type configuration of photoelectrode and
counter electrode. FTO coated glass substrate was cleaned
with the soap solution, water, and ethanol followed by 10 min
sonication in every step. Using this cleaned substrate,
photoelectrode was made from the commercial TiO2
nanocrystalline semiconductor (P25, Sigma Aldrich). A thin film
of the TiO2 particles was deposited through screen printing
from the TiO2 paste containing ethyl cellulose and α-terpineol.
The electrodes were calcined in a tubular furnace at 450 °C for
25 minutes and then soaked in the 10 mM dye solution. Dye
soaking of the photoelectrode was carried out in a glove box
filled with nitrogen under very low light level for 24 h. Counter
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
One of the author, Dinesh Patil is thankful to UGC-SAP, India
for Junior and Senior Research Fellowship. Authors thank to
DST-CERI, New Delhi (DST/TM/CERI/C285(C) for the financial
assistant. SSS and KKS are also thankful to UGC, New Delhi for
funding under CPEPA program (Phase II).
electrodes were fabricated by spin coating of 50 mM H2PtCl6 Notes and references
solution in isopropanol onto pre-drilled FTO substrate followed
1
B. Pashaei, H. Shahroosvand, M. Graetzel and M. K.
by sintering at 450 ºC for 15 min. Dye coated photoelectrode
and Pt counter electrode were sealed together using hot melt
sealing tape upon application of heat. Electrolyte solution
comprises of the 0.5 M 1-butyl-3-methylimidazolium iodide,
0.05 M I2, 0.5 M TBP, 0.5M GSCN in 3-methoxy propionitrile,
was inserted through the predrilled holes onto the counter
electrode. Holes were sealed using epoxy adhesive and cover
glass. DSSC were stored in dark at room temperature for 12
hours prior to measurements. The active area of the DSSC was
set to 0.16 cm2 and was maintained constant using the same
screen for coating. The thickness of the TiO2 nanocrystalline
Nazeeruddin, Chem. Rev., 2016, 116, 9485–9564.
B. O’Regan and M. Grätzel, Nature, 1991, 353, 737–740.
Z. L. Wang and W. Wu, Angew. Chem. Int. Ed. Engl., 2012,
51, 11700–21.
2
3
4
5
M. G. Tzel, Acc. Chem. Res., , DOI:10.1021/ar900141y.
K. Ladomenou, V. Nikolaou, G. Charalambidis and a G.
Coutsolelos, Dalt. Trans., 2016, 45, 1111–1126.
D. Wei, Int. J. Mol. Sci., 2010, 11, 1103–1113.
F.-T. Kong, S.-Y. Dai and K.-J. Wang, Adv. Optoelectron.,
2007, 2007, 1–13.
6
7
8
M. Grätzel, J. Photochem. Photobiol. C Photochem. Rev.,
2003, 4, 145–153.
layer was 12 ꢀm.
9
A. Hagfeldt, G. Boschloo, L. Sun, L. Kloo and H. Pettersson,
Chem. Rev., 2010, 110, 6595–6663.
Conclusions
10
C. Pavan Kumar, V. Anusha, K. Narayanaswamy, K.
Bhanuprakash, A. Islam, L. Han, S. P. Singh and M.
Chandrasekharam, Inorganica Chim. Acta, 2015, 435, 46–
Manipulation in novel metal-free organic sensitizers DP1, DP2,
DP3, and DP4 having N-phenyl-N-(pyridin-2-yl) pyridine-2-
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52.
Journal Name
Acta Part A Mol. Biomol. Spectrosc., 2017, 174, 7–16.
S. Huang, Y. Hsu, Y. Yen, H. H. Chou, T. Lin, C. Chang, C.
11
12
13
14
15
16
17
K. S. V Gupta, S. P. Singh, A. Islam, L. Han and C. M.,
Electrochim. Acta, 2015, 174, 581–587.
35
Hsu, C. Tsai, D. Yin and J. T. Lin, J. Phys. Chem. C, 2008,
19739–19747.
A. Mishra, M. K. R. Fischer and P. Bäuerle, Angew. Chem.
Int. Ed. Engl., 2009, 48, 2474–99.
36
37
38
W. Wu, J. Yang, J. Hua, J. Tang, L. Zhang, Y. Long and H.
Tian, J. Mater. Chem., 2010, 20, 1772.
Y. Cui, Y. Wu, X. Lu, X. Zhang, G. Zhou, F. B. Miapeh, W. Zhu
and Z. S. Wang, Chem. Mater., 2011, 23, 4394–4401.
S. Yang, J. Liu, P. Zhou, K. Han and G. He, Chem. Phys. Lett.,
2011, 512, 66–69.
Z. Wan, C. Jia, J. Zhang, Y. Duan, Y. Lin and Y. Shi, J. Power
Sources, 2012, 199, 426–431.
O. Treutler and R. Ahlrichs, J. Chem. Phys., 1995, 102, 346–
354.
J. Wu, G. Li, L. Zhang, G. Zhou and Z. Wang, J. Mater. Chem.
A, 2016, 0, 1–14.
39
40
A. D. Becke, J. Chem. Phys., 1993, 98, 1372–1377.
C. Lee, W. Yang and R. G. Parr, Phys. Rev. B, 1988, 37, 785–
789.
Z. S. Wang, Y. Cui, Y. Dan-oh, C. Kasada, A. Shinpo and K.
Hara, J. Phys. Chem. C, 2007, 111, 7224–7230.
X. Zarate, F. Claveria-Cadiz, D. Arias-Olivares, A. Rodriguez-
Serrano, N. Inostroza and E. Schott, Phys. Chem. Chem.
Phys., 2016, 18, 24239–24251.
41
42
43
44
M. E. Casida, C. Jamorski, K. C. Casida and D. R. Salahub, J.
Chem. Phys., 1998, 108, 4439–4449.
M. Cossi, V. Barone, R. Cammi and J. Tomasi, Chem. Phys.
Lett., 1996, 255, 327–335.
18
19
K. Hara, K. Sayama, H. Arakawa, Y. Ohga, A. Shinpo and S.
Suga, Chem. Commun., 2001, 569–570.
J. Tomasi, B. Mennucci and R. Cammi, Chem. Rev., 2005,
105, 2999–3094.
K. Sayama, S. Tsukagoshi, K. Hara, Y. Ohga, A. Shinpou, Y.
Abe, S. Suga and H. Arakawa, J. Phys. Chem. B, 2002, 106,
1363–1371.
G. E. M. J. F. G. W. T. H. B. Schlegel, G. A. S. M. A. R. J. R. C.
G. S. V. B. B. Mennucci, J. P. H. N. M. C. X. L. H. P. H. A. F.
Izmaylov, J. B. G. Z. J. L. S. M. H. M. E. K. T. R. Fukuda, J. A.
H. M. I. T. N. Y. H. O. K. H. N. T. Vreven, K. N. M. J. J. E. P. F.
O. M. B. J. J. H. E. Brothers, J. K. V. N. S. R. K. J. N. K. R. A.
Rendell, J. E. C. B. S. S. I. J. T. M. C. N. R. J. M. M. M. Klene,
R. E. S. K. J. B. C. V. B. C. A. J. J. R. Gomperts, K. O. Y. A. J. A.
R. C. C. P. J. W. O. R. L. Martin, S. M. V. G. Z. G. A. V. P. S. J.
J. Dannenberg, and D. D. A. D. D. O. F. J. B. F. J. V. O. J.
Cioslowski and W. C. J. F. G. Inc., .
20
21
22
23
A. Ehret, L. Stuhl and M. T. Spitler, J. Phys. Chem. B, 2001,
105, 9960–9965.
D. D. Babu, S. R. Gachumale, S. Anandan and A. V. Adhikari,
Dye. Pigment., 2015, 112, 183–191.
L. Wang, P. Shen, Z. Cao, X. Liu, Y. Huang, C. Liu, P. Chen, B.
Zhao and S. Tan, J. Power Sources, 2014, 246, 831–839.
S. S. M. Fernandes, M. C. R. Castro, I. Mesquita, L. Andrade,
A. Mendes and M. M. M. Raposo, Dye. Pigment., 2017,
136, 46–53.
45
C. Adamo and D. Jacquemin, Chem. Soc. Rev., 2013, 42,
845–856.
24
25
S. S. Soni, K. B. Fadadu, J. V. Vaghasiya, B. G. Solanki, K. K.
Sonigara, A. Singh, D. Das and P. K. Iyer, J. Mater. Chem. A,
2015, 3, 21664–21671.
46
47
Y. Wu and W. Zhu, Chem. Soc. Rev., 2013, 42, 2039–2058.
E. Ronca, G. Marotta, M. Pastore and F. De Angelis, J. Phys.
Chem. C, 2014, 118, 16927–16940.
Y. Hua, S. Chang, H. Wang, D. Huang, J. Zhao, T. Chen, W. Y.
Wong, W. K. Wong and X. Zhu, J. Power Sources, 2013, 243, 48
J. Bisquert, J. Phys. Chem. B, 2002, 106, 325–333.
J. V. Vaghasiya, K. K. Sonigara, K. B. Fadadu and S. S. Soni,
Perspect. Sci., 2016, 8, 2–5.
253–259.
49
50
51
52
53
26
27
G. Wu, F. Kong, J. Li, W. Chen, C. Zhang, Q. Chen, X. Zhang
and S. Dai, Synth. Met., 2013, 180, 9–15.
H. Tan, C. Pan, G. Wang, Y. Wu, Y. Zhang, Y. Zou, G. Yu and
M. Zhang, Org. Electron. physics, Mater. Appl., 2013, 14,
2795–2801.
Y. Wu, X. Zhang, W. Li, Z. S. Wang, H. Tian and W. Zhu, Adv.
Energy Mater., 2012, 2, 149–156.
P. J. Cameron, L. M. Peter and S. Hore, J. Phys. Chem. B,
2005, 109, 930–936.
28
29
30
31
32
33
Z. S. Wang, Y. Cui, K. Hara, Y. Dan-Oh, C. Kasada and A.
Shinpo, Adv. Mater., 2007, 19, 1138–1141.
X. Chen, C. Jia, Z. Wan and X. Yao, Dye. Pigment., 2014,
104, 48–56.
J. N. Soderberg, A. C. Co, A. H. C. Sirk and V. I. Birss, J. Phys.
Chem. B, 2006, 110, 10401–10410.
R. L. Vekariya, K. K. Sonigara, K. B. Fadadu, J. V. Vaghasiya
and S. S. Soni, ACS Omega, 2016, 1, 14–18.
C. Teng, X. Yang, C. Yuan, C. Li, R. Chen, H. Tian, S. Li, A.
Hagfeldt and L. Sun, 2009, 11–14.
M. Liang and J. Chen, Arylamine organic dyes for dye-
sensitized solar cells, 2013, vol. 42.
Z. Ning, Q. Zhang, W. Wu, H. Pei, B. Liu and H. Tian, J. Org.
Chem., 2008, 73, 3791–3797.
T. Kaewpuang, N. Prachumrak, S. Namuangruk, S.
Jungsuttiwong, T. Sudyoadsuk, P. Pattanasattayavong and
V. Promarak, European J. Org. Chem., 2016, 2016, 2528–
2538.
34
C. Chitpakdee, S. Jungsuttiwong, T. Sudyoadsuk, V.
Promarak, N. Kungwan and S. Namuangruk, Spectrochim.
12 | J. Name., 2012, 00, 1-3
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New Journal of Chemistry
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DOI: 10.1039/C7NJ04620K
Table of Contents:
Insertion of heteroatom in triarylamine donor along with variation in anchoring groups finely
manipulate the photophysical and photovoltaic structure to property behaviour of DꢀA’ꢀπꢀA
sensitizers in DSSCs for better efficiency achievement.