A fluorine-induced high-performance narrow bandgap polymer based on thiadiazolo[3,4-: C] pyridine for photovoltaic applications

Article abstract of DOI:10.1039/c6ta04059d

Thiadiazolo[3,4-c]pyridine (PT) has great potential in the construction of high-performance narrow bandgap (NBG) photovoltaic polymers. But to date the best power conversion efficiencies (PCEs) for PT-containing polymers are only around 6%. Herein, we report two PT-containing NBG polymers PDTPT-2T and PDTPT-2TF based on 2,2′-bithiophene (2T) and 3,3′-difluoro-2,2′-bithiophene (2TF), respectively. The effects of a fluorine substituent on optoelectronic properties are thoroughly investigated. The film absorption onset of PDTPT-2TF is 855 nm, bathochromic-shifted by 24 nm in comparison with that (831 nm) of PDTPT-2T. The lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels of PDTPT-2TF are down-shifted by 0.15 and 0.11 eV relative to those of PDTPT-2T, respectively. X-ray diffraction (XRD) patterns indicate that a more ordered structure is formed in the solid film of PDTPT-2TF. Furthermore, the miscibility between the polymer and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) is significantly improved through the introduction of fluorine. Consequently, PDTPT-2TF exhibits a high PCE of 8.01%, while PDTPT-2T only shows a maximum PCE of 2.65%. The efficiency of 8.01% is the highest one for PT-containing polymers, and more importantly, it is achieved without any processing additives or post-treatments. This work indicates that PT would have great potential as a building block to construct high-performance photovoltaic polymers.

Full text of DOI:10.1039/c6ta04059d

View Article Online
View Journal
Journal of
Materials Chemistry A
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: J. Wang, X. Bao,
D. Ding, M. Qiu, Z. Du, J. Wang, J. Liu, M. Sun and R. Yang, J. Mater. Chem. A, 2016, DOI:
10.1039/C6TA04059D.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/materialsA

Please do not adjust margins
Journal of Materials Chemistry A
Page 1 of 10
View Article Online
DOI: 10.1039/C6TA04059D
Journal of Materials Chemistry A
ARTICLE
Fluorine-induced high-performance narrow bandgap polymer
based on thiadiazolo[3,4-c]pyridine for photovoltaic application†
Received 00th January 20xx,
Accepted 00th January 20xx
Jiuxing Wang,a,b Xichang Bao,*,a Dakang Ding,a,c Meng Qiu,a Zurong Du,a,b Junyi Wang,a,b Jie Liu,*,a
Mingliang Sunc and Renqiang Yang*,a,d
DOI: 10.1039/x0xx00000x
Thiadiazolo[3,4-c]pyridine (PT) has great potential in constructing high-performance narrow bandgap (NBG) photovoltaic
polymers. But to date the best power conversion efficiencies (PCEs) for PT-containing polymers are only around 6%. Herein
we report two PT-containing NBG polymers PDTPT-2T and PDTPT-2TF based on 2,2'-bithiophene (2T) and 3,3'-difluoro-
2,2'-bithiophene (2TF), respectively. The effects of fluorine substituent on optoelectronic properties are thoroughly
investigated. The film absorption onset of PDTPT-2TF is 855 nm, bathochromic-shifted by 24 nm in comparison with that
(831 nm) of PDTPT-2T. The lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO)
energy levels of PDTPT-2TF are down-shifted by 0.15 and 0.11 eV relative to those of PDTPT-2T, respectively. X-ray
diffraction (XRD) patterns indicate that more ordered structure is formed in the solid film of PDTPT-2TF. Furthermore, the
miscibility between polymer and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) is significantly improved through the
introduction of fluorine. Consequently, PDTPT-2TF exhibits a high PCE of 8.01% while PDTPT-2T only shows a maximum
PCE of 2.65%. The efficiency of 8.01% is the highest one for PT-containing polymers, and more importantly, it is achieved
without any processing additives or post-treatments. This work indicates that PT would have great potential as building
block to construct high-performance photovoltaic polymers.
www.rsc.org/
NBG polymers usually need complex morphology engineering
and interfacial modifications during device fabrications, which
may limit their further applications.6,20-22,27 Therefore, it’s
necessary to develop novel high-performance NBG polymers
with easy device processing methods and simple device
structures.
Introduction
Polymer solar cells (PSCs) have generated significant interest
due to their potential in fabrication of large-scale flexible
devices through low-cost solution processing techniques.1-4
During the last decade, remarkable progress has been made in
enhancing the power conversion efficiency (PCE) of the PSCs,
such as development of high-performance polymer donors,4-14
incorporation of efficient interfacial materials,15-17 and
advancement of device architectures.18,19 Despite plenty of
high-performance polymer donors having been reported, only
a limited number of them are narrow bandgap (NBG, < 1.50 eV)
polymers.6,20-23 Compared with large and medium bandgap
polymers, NBG polymers have strong and broad absorption in
near-infrared region, which makes them an important
component for constructing multicomponent and tandem
solar cells.21,24-26 However, most reported high-performance
An effective strategy to design NBG polymer is to
incorporate alternating electron-rich and electron-deficient
moieties along the backbone of the conjugated polymer.1,28,29
Compared with the widely used acceptor unit benzothiadiazole
(BT), thiadiazolo[3,4-c]pyridine (PT) has a stronger electron-
withdrawing ability.30-32 Polymers containing PT usually have
broader absorption spectra extending into near-infrared
region.31,33-35 In 2010, Zhou et al. reported a series of polymers
containing alkylthienyl-flanked PT (DTPT).32 Compared with
their BT counterparts, the PT-containing polymers showed
smaller bandgaps and decreased lowest unoccupied molecular
orbital (LUMO) and highest occupied molecular orbital (HOMO)
energy levels. The best-performing PSC gave an impressive PCE
of 6.32%. In 2013, Heeney and coworkers synthesized three
polymers based on benzo[d][1,2,3]triazole (BTz), 5,6-
a. CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and
Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, China. E-
mail: baoxc@qibebt.ac.cn; liu_jie@qibebt.ac.cn; yangrq@qibebt.ac.cn
b. University of Chinese Academy of Sciences, Beijing 100049, China.
c. Institute of Material Science and Engineering, Ocean University of China, Qingdao
266100, China.
difluorobenzo[c][1,2,5]thiadiazole
(ffBT),
and
PT,
respectively.36 The PT-containing polymer exhibited the
smallest bandgap and the largest short-circuit current density
(Jsc = 19.6 mA/cm2), in comparison with the BTz-containing
polymer (Jsc = 6.17 mA/cm2) and the ffBT-containing polymer
(Jsc = 5.74 mA/cm2). As a result, the polymer containing PT
showed the highest PCE of 6.6% among the three polymers.
d. State Key Laboratory of Luminescent Materials and Devices, South China
University of Technology, Guangzhou 510641, China.
†
Electronic Supplementary Information (ESI) available: [TGA plots, temperature-
dependent absorption spectra of PDTPT-2TF, HOMO and LUMO distributions, hole
mobility measurements, photovoltaic performance of PDTPT-2T with additive,
TEM images, 1H NMR and 13C NMR spectra]. See DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry A
Page 2 of 10
ARTICLE
Journal Name
View Article Online
DOI: 10.1039/C6TA04059D
Scheme 1 Chemical structures and synthetic routes of DTffBT-OD, PDTPT-2T and PDTPT-2TF.
Previous studies indicate that PT should be a promising unit
for constructing high-performance NBG polymers. However, to
the best of our knowledge, none of the reported PCEs of PT-
containing polymers is over 7%, implying that there is still
considerable
room
to
improve
the
photovoltaic
performance.32,36-43 Therefore, it is necessary and meaningful
to further investigate the structure-property relationships of
PT-containing polymers. Incorporating fluorine into polymer
chains is usually an effective strategy to improve their
photovoltaic properties. Polymers containing fluorinated units,
such as ffBT,4,5 3-fluorothieno[3,4-b]thiophene (TTF),7 and 3,3'-
difluoro-2,2'-bithiophene (2TF),5 have realized very high PCEs.
But to date fluorinated polymers containing PT unit haven’t
been reported. In this work, we firstly applied fluorine in PT-
containing polymer and thoroughly studied the effects of
fluorine substituent on its optoelectronic properties. A new
acceptor moiety, namely DTPT-OD (Scheme 1), was designed
by introducing a long branched alkyl chain onto the 4-position
of the flanking thiophene ring of DTPT to improve the solubility
and molecular weight of the polymers.32 As shown in Fig. 1,
DTPT-OD exhibits obviously bathochromic-shifted and broader
absorption profile in comparison with DTffBT-OD (one of the
most efficient moieties for constructing photovoltaic polymers,
Scheme 1), indicating a distinct advantage of DTPT-OD as
building block. To make a comparative study, 2TF and 2,2'-
bithiophene (2T) were chosen as the electron-rich units,
respectively. Thus, two new polymers comprising DTPT-OD and
2T (named PDTPT-2T) or 2TF (named PDTPT-2TF) were
synthesized. The two polymers showed noticeably different
Fig. 1 Normalized absorption spectra of DTPT-OD and DTffBT-OD in CHCl3
solution.
optoelectronic properties. The incorporation of fluorine
significantly improved the photovoltaic performance. PDTPT-
2TF exhibited a high PCE of 8.01% while PDTPT-2T only showed
a maximum PCE of 2.65%.
Results and discussion
Synthesis and characterization
Scheme 1 describes the synthetic routes of PDTPT-2T and
PDTPT-2TF. Detailed synthetic procedures can be found in the
Experimental section. The polymers were synthesized through
Stille coupling reaction. In both cases, polymerization was
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 10
Journal of Materials Chemistry A
Please do not adjust margins
Journal Name
ARTICLE
rapid and the reacting solution became gel within two hours.
Both polymers had a good solubility in o-dichlorobenzene (DCB)
at heated temperature. The molecular weights of PDTPT-2T
and PDTPT-2TF were measured by gel permeation
chromatography (GPC). The number-average molecular weight
(Mn) of PDTPT-2T is 47 kDa with a polydispersity index (PDI) of
1.67, and the Mn of PDTPT-2TF is 77 kDa with a PDI of 2.01.
Thermogravimetric analysis (TGA) was performed to analyze
the thermal stability of PDTPT-2T and PDTPT-2TF. As shown in
Fig. S1 (Supplementary Information), PDTPT-2T and PDTPT-2TF
exhibited similar thermal decomposition temperatures (Td, 5%
View Article Online
DOI: 10.1039/C6TA04059D
o
o
weight loss) of 425 C and 427 C, respectively. Both polymers
can meet the requirements of thermal stability for
photovoltaic application.
Optical properties
Normalized UV-vis absorption spectra of PDTPT-2T and PDTPT-
2TF in dilute DCB solution and as solid films are depicted in Fig.
2a. Detailed optical parameters are summarized in Table 1.
Both polymers showed very broad absorption extending into
near-infrared region. The optical properties of the two
polymers differ greatly. PDTPT-2T exhibited two absorption
peaks both in solution and as solid film. From solution to film,
Fig. 2 (a) Normalized absorption spectra of PDTPT-2T and PDTPT-2TF in DCB
solution and as solid films at room temperature. (b) Absorption coefficients of
PDTPT-2T and PDTPT-2TF films.
the main peak in long-wavelength had
a noticeable
bathochromic-shift of 48 nm. PDTPT-2T showed no shoulder
peak indicating no intense aggregations formed in solution or
film. Compared with PDTPT-2T, PDTPT-2TF exhibited obviously
bathochromic-shifted and broader absorption with a strong
shoulder peak both in dilute solution and as solid film. The
emergence of a strong shoulder peak suggests the existing of
intense aggregations in PDTPT-2TF. With the increase of the
temperature, the shoulder peak was gradually weakened and
finally disappeared due to the disaggregation of the aggregates
(Fig. S2).9,44 The absorption spectrum of PDTPT-2TF showed no
obvious bathochromic-shift from solution to film state at room
temperature, which was quite different from that of PDTPT-2T.
One possible explanation might be that PDTPT-2TF has already
formed intense aggregations in dilute solution, which is
verified in Fig. S2. The onset wavelength (λonset) of film
polymer induced to obviously enhanced intermolecular
interactions, bathochromic-shifted and broader absorption,
and noticeably increased absorption coefficient, which are
conducive to harvesting more light.1,8,45
Molecular energy levels
The HOMO energy levels of PDTPT-2T and PDTPT-2TF were
estimated by cyclic volt ammetry (CV). Fig. 3 shows the cyclic
voltammograms and energy level diagram of the two polymers.
HOMO energy level was calculated from the equation EHOMO = -
e(4.8 + Eox - E1/2,(Fc/Fc+)), where Eox is the onset oxidation
potential of the polymer and E1/2,(Fc/Fc+) is the half-wave
potential of the ferrocene/ferrocenium (Fc/Fc+) redox couple.7
The value of E1/2,(Fc/Fc+) was calibrated to be 0.40 V vs saturated
calomel electrode (SCE). The Eox values obtained from the
cyclic voltammograms were 0.83 and 0.94 V for PDTPT-2T and
PDTPT-2TF, respectively. Thus the corresponding HOMO
energy levels were -5.23 and -5.34 eV for PDTPT-2T and
PDTPT-2TF, respectively. As it was difficult to record the
accurate reduction potentials of the polymers, their LUMO
energy levels were determined by HOMO and Egopt, using the
equation ELUMO = EHOMO + Egopt. The LUMO energy levels were -
3.74 and -3.89 eV for PDTPT-2T and PDTPT-2TF,
spectrum was 831 nm for PDTPT-2T and 855 nm for PDTPT-2TF.
opt
According to the equation Eg
= 1240/λonset, the optical
bandgap (Egopt) values were calculated to be 1.49 and 1.45 eV
for PDTPT-2T and PDTPT-2TF, respectively. Incorporating
fluorine onto 2T reduces the Egopt of the resulting polymer. The
maximum film absorption coefficients were 5.47 × 104 and
8.50 × 104 cm-1 for PDTPT-2T and PDTPT-2TF, respectively,
indicating that PDTPT-2TF has a stronger ability of harvesting
light (Fig. 2b). From the optical features of the two polymers, it
can be concluded that the incorporation of fluorine into the
Table 1 Optical and energy level parameters of PDTPT-2T and PDTPT-2TF
λmax (nm)
λonset (nm)
Film
Absorption
coefficient (cm-1)
opt
Eg (eV)a
HOMO (eV)b
LUMO (eV)c
Polymer
Solution
Film
PDTPT-2T
435, 690
831
855
1.49
5.47 × 104
-5.23
-3.74
425, 642
PDTPT-2TF
455, 700, 765
457, 705, 770
1.45
8.50 × 104
-5.34
-3.89
opt
aCalculated from the absorption onset of the polymer film. bMeasured by cyclic voltammetry. cCalculated from the equation ELUMO = EHOMO + Eg
.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry A
Page 4 of 10
ARTICLE
Journal Name
View Article Online
DOI: 10.1039/C6TA04059D
Fig. 4 Molecule models and backbone dihedral angles of optimized geometries
obtained by DFT calculations.
Fig. 3 (a) Electrochemical cyclic voltammograms and (b) energy level diagram of
PDTPT-2T and PDTPT-2TF.
respectively. Compared with PDTPT-2T, PDTPT-2TF exhibited
pronouncedly down-shifted HOMO and LUMO levels, which
should be attributed to the incorporation of electron-
withdrawing substituent fluorine. The lower-lying HOMO
energy level of PDTPT-2TF is favorable to realizing a higher
open-circuit voltage (Voc) in PSCs.46 The differences of LUMO
energy levels between the polymers and [6,6]-phenyl-C71-
butyric acid methyl ester (PC71BM) are sufficient to guarantee
efficient exciton separation at polymer/PC71BM interfaces.47
Theoretical calculations
Fig. 5 XRD patterns of PDTPT-2T and PDTPT-2TF films.
To obtain more information about the molecular
conformations and distributions of HOMO and LUMO of
PDTPT-2T and PDTPT-2TF, density functional theory (DFT)
calculations were performed in the gas phase using Gaussian
09 program at the B3LYP/6-31G (d,p) level. One repeat unit
with isobutyl side chains was chosen as the calculating model
to reduce the consumption. The optimized molecular
geometries were characterized as the minimum-energy
conformations by vibrational frequency analysis at the
B3LYP/6-31G (d,p) level. Molecule models and backbone
dihedral angles of the optimized geometries are shown in Fig.
4. All the optimized geometries of the four molecular models
show very small θ1 and θ2 values (< 3.5o), indicating that DTPT
unit has good planarity. This feature should benefit from C-
intramolecular interaction through F···S interaction.4 As shown
in Fig. S3, all of the four molecular models exhibit similar
HOMO and LUMO distributions: HOMO is distributed along the
whole backbone and LUMO is mainly localized on DTPT.
Therefore, it is safe to conclude that 2TF remains a donor
moiety despite the incorporation of two fluorine atoms.
X-ray diffraction (XRD) analysis
XRD was performed to get a better insight of the effects of
fluorine substituent on molecular ordering in solid film. As
shown in Fig. 5, neither as-cast nor thermal annealed films of
PDTPT-2T showed diffraction peaks, suggesting a more
amorphous stacking of PDTPT-2T solid film.36 In comparison, a
H
···N and N···S non-covalent interactions.4 The values of θ4
diffraction peak centered at ~
4.0o could be identified in the
are 15.85o and 18.78o for the non-fluorinated models DTPT-2T-
a and DTPT-2T-b, and 1.21o and 0.20o for the fluorinated
XRD patterns of PDTPT-2TF and the peak was strengthened
upon annealing, implying the existing of lamellar ordering in
PDTPT-2TF film. The corresponding interlamellar distance is
models
DTPT-2TF-a
and
DTPT-2TF-b,
respectively.
Incorporating fluorine onto 2T unit significantly reduces the
dihedral angle θ4, which should result from increased
~
2.2 nm. Accordingly, PDTPT-2TF exhibits more ordered
molecular arrays in film than PDTPT-2T. The amorphous solid
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 10
Journal of Materials Chemistry A
Please do not adjust margins
Journal Name
ARTICLE
structure of PDTPT-2T may result from the regio-random
nature of its backbone. The significantly enhanced non-
covalent interactions in PDTPT-2TF through C-H···F, F···S, F···F,
and C-F···πF interactions, evidenced by UV-vis absorption
spectra, are beneficial for forming a more ordered solid
structure.4,48-51
Table 2 Photovoltaic parameters of the PSCs based on PDTPT-2T and PDTPT-2TF under
View Article Online
AM 1.5G illumination (100 mW/cm2)
DOI: 10.1039/C6TA04059D
D/A
ratio
1:1.5
1:2
1:2.5
1:1.5
1:2
Jsc
(mA/cm2)
5.06
5.34
4.07
15.07
15.52
14.86
FF
(%)
PCEmax
Polymer
PDTPT-2T
Voc (V)
0.72
0.73
0.73
0.77
0.74
0.72
(PCEave)a (%)
2.45 (2.14)
2.65 (2.51)
2.02 (1.67)
7.58 (7.38)
8.01 (7.88)
7.51 (7.44)
67.14
67.91
68.05
65.29
69.73
70.01
Solar cell fabrication and performance
PDTPT-2TF
Single junction bulk heterojunction (BHJ) PSCs based on the
two polymers were fabricated to investigate the effects of
fluorine substituent on photovoltaic properties. The
configuration of the devices was a typical conventional
1:2.5
aThe average PCE value was from 5 devices.
structure
of
indium
tin
oxide
(ITO)/poly(3,4-
Voc of 0.77 V was achieved for 1:1.5 D/A ratio. The
improvement of the Voc may benefit from the lower-lying
HOMO energy level induced by fluorine substituent. The
maximum PCE for PDTPT-2TF was also obtained from 1:2 D/A
ratio. Compared with PDTPT-2T-based devices, the devices
based on PDTPT-2TF showed a significantly enhanced PCE of
8.01%, along with a slightly higher Voc of 0.74 V, a remarkably
enhanced Jsc of 15.52 mA/cm2, and a little higher FF of 69.73%.
This efficiency is the highest one for PT-containing polymers,
and more importantly, it was achieved without any processing
additives or post-treatments. The great improvement of
photovoltaic performance is mainly ascribed to the significant
enhancement of Jsc. The thicker active layer, higher absorption
coefficient, and broader and bathochromic-shifted absorption,
which are all beneficial for harvesting more light, should
partially contribute to the significant enhancement of the Jsc of
PDTPT-2TF-based devices.1,8,45 For 1:2.5 D/A ratio, the best-
performing device based on PDTPT-2TF showed a slightly
lower Voc (0.72 V) than that based on PDTPT-2T (0.73 V).
Besides the HOMO-LUMO difference between polymer and
PC71BM, other factors such as shunt resistance, energetic
disorder and morphology also play an important role in
affecting the Voc.8,52-55
ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS,
~
30 nm)/polymer:PC71BM/Ca (
~
10 nm)/Al (
~
100 nm). The
o
blend of polymer:PC71BM was stirred in DCB at 100 C for 2 h
before spin coating. In both cases, polymer concentration was
6 mg/mL. The optimized thickness of the active layer was
nm for PDTPT-2T and 123 nm for PDTPT-2TF.
Fig. depicts the current density-voltage (J-V)
~67
~
6
characteristics of the PSCs with different polymer/acceptor
(D/A) ratios. Detailed photovoltaic parameters of the devices
are provided in Table 2. The devices based on PDTPT-2T
showed very poor photovoltaic performance. The best-
performing device only gave a maximum PCE of 2.65%, with a
Voc of 0.73 V, a Jsc of 5.34 mA/cm2, and a fill factor (FF) of
67.91%. In striking contrast, PDTPT-2TF exhibited excellent
photovoltaic performance. The optimum PCEs of the devices
based on various D/A ratios were all exceeding 7.50%. A high
For comparison, photovoltaic parameters of the PSCs based
on PDTPT-2TF and other reported high-performance PT-
containing polymers are summarized in Table 3. PDTPT-2TF-
based devices exhibited dramatically enhanced FF and PCE in
comparison with other PT-containing polymers. To the best of
our knowledge, the highest PCE previously reported for PT-
containing polymers is only 6.7%, which is obviously lower
Table 3 Photovoltaic parameters of the PSCs based on PDTPT-2TF and other reported
high-performance PT-containing polymers
Jsc
(mA/cm2)
15.52
19.6
PCE
(%)
8.01
6.6
Polymer
PDTPT-2TF
PDTG-PT
Voc (V)
0.74
0.59
0.88
0.85
0.71
0.75
0.86
0.75
FF (%)
69.73
57
Reference
This work
36
43
32
32
32
41
42
PIPT-RG
13.9
55
6.7
PBnDT-DTPyT
PNDT-DTPyT
PQDT-DTPyT
PIPCP
12.78
14.16
13.49
13.4
58.2
61.7
55.1
53
6.32
6.20
5.57
6.13
5.11
PBPT-12
12.56
54.2
Fig. 6 J-V characteristics of the PSCs based on (a) PDTPT-2TF and (b) PDTPT-2T
with different polymer/PC71BM ratios.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry A
Page 6 of 10
ARTICLE
Journal Name
View Article Online
DOI: 10.1039/C6TA04059D
Fig. 7 EQE spectra of the PSCs based on PDTPT-2T and PDTPT-2TF.
than that (8.01%) for PDTPT-2TF.43 Most of the FF values for
other PT-containing polymers are below 60% while the FF for
PDTPT-2TF approached almost 70%, and more importantly, it
was achieved without any processing additives or post-
treatments. The Jsc (15.52 mA/cm2) for PDTPT-2TF is among
the highest ones for PT-containing polymers. From Table 3, it
seems that photovoltaic devices based on PT-containing
polymers with high Jsc values tend to exhibit low Voc. Next work
focusing on simultaneously enhancing the Voc and Jsc needs to
be done to further increase the PCE of PT-containing polymers.
The external quantum efficiencies (EQEs) of the best-
performing photovoltaic devices based on PDTPT-2T and
PDTPT-2TF were measured and the EQE curves are shown in
Fig. 7. The PDTPT-2TF-based device exhibited high EQE values (>
50%) in a very broad wavelength range from 365 to 775 nm,
more than two times higher than those of PDTPT-2T-based
device. The significant enhancement of EQE indicates
noticeably improved charge generation and collection in
PDTPT-2TF-based device. The Jsc values integrated from the
EQE curves are in good agreement with those obtained from
the J-V measurements.
Fig. 8 AFM and TEM images of polymer:PC71BM blends. AFM (a) height image, (b)
phase image, and (c) TEM image of PDTPT-2T:PC71BM. AFM (d) height image, (e)
phase image, and (f) TEM image of PDTPT-2TF:PC71BM. The size of the AFM
images is 5 μm × 5 μm.
heterogeneous surface with a root-mean-square (RMS) surface
roughness of 2.13 nm (Fig. 8a). In contrast, the surface of
PDTPT-2TF:PC71BM was smoother and much more
homogeneous (RMS = 1.37 nm, Fig. 8d). Previous reports have
demonstrated that smooth surface can help reduce leakage
current and contact resistance, thus facilitating to yield a high
PCE.56,57 The TEM image (Fig. 8c) of PDTPT-2T:PC71BM
suggested that the film was heterogeneous and large polymer-
rich and PC71BM-rich domains were formed in the film. It is
widely believed that: (i) The exciton diffusion length is limited
Hole mobilities of PDTPT-2T:PC71BM (1:2) and PDTPT-
2TF:PC71BM (1:2) films were measured by hole-only devices
using space-charge-limited current (SCLC) method. The
to be ~10 nm, and thus in large domains, inner excitons could
configuration
of
the
devices
is
hardly reach D/A interfaces before recombination;29,58,59 (ii)
Large phase separation would reduce the contact area of D/A
interfaces where excitons separated into free charges.29
Therefore, the large domains formed in the PDTPT-2T:PC71BM
film were detrimental to exciton diffusion and separation, thus
resulting in low Jsc values. In contrast, PDTPT-2TF showed a
good miscibility with PC71BM. A homogeneous nanoscale
phase separation with appropriate domain sizes can be
observed in TEM image (Fig. 8f). Therefore, efficient exciton
diffusion and separation could be guaranteed in the PDTPT-
2TF:PC71BM blend, facilitating to generate large Jsc values. This
could also explain why the active layer in PDTPT-2TF-based
devices was much thicker than that in PDTPT-2T-based devices.
The significant improvement of morphology should be
attributed to the incorporation of fluorine into the polymer,
which can improve the miscibility between the polymer and
ITO/PEDOT:PSS/polymer:PC71BM/MoO3/Al. Fig. S4 shows the
dark J-V plots of the hole-only devices. The PDTPT-2TF:PC71BM
film exhibited about one order of magnitude higher hole
mobility (5.63 × 10-4 cm2/V s) than PDTPT-2T:PC71BM (6.10 ×
10-5 cm2/V s). The higher hole mobility of PDTPT-2TF:PC71BM
should also contribute in part to the higher Jsc of PDTPT-2TF-
based devices.
Morphology study
Active layer morphology plays an important role in affecting
the photovoltaic performance. To explore the effects of
fluorine substituent on the morphology of active layers, atomic
force microscopy (AFM) and transmission electron microscopy
(TEM) measurements were performed. AFM and TEM images
of the active layers of the best-performing devices are shown
in Fig. 8. The PDTPT-2T:PC71BM film showed a rough and
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 10
Journal of Materials Chemistry A
Please do not adjust margins
Journal Name
ARTICLE
fullerene through reducing the surface energy of the 1H NMR (600 MHz, CDCl3): δ 8.80 (s, 1H), 8.49 (s,Vi1ewH)A,rti7cl.e9O2nl(inse,
polymer.50,60,61
1H), 7.16 (s, 1H), 7.03 (s, 1H), 2.65-2.63 D(mOI,: 410H.1)0,319./7C36-T1A.074005(m9D,
2H), 1.36-1.25 (m, 64H), 0.88-0.86 (m, 12H). 13C NMR (150
MHz, CDCl3): δ 154.94, 148.11, 146.38, 143.97, 143.21, 141.16,
140.67, 136.03, 133.63, 129.88, 126.56, 122.85, 120.53, 38.94,
38.91, 35.14, 35.02, 33.38, 31.93, 30.05, 30.04, 29.71, 29.67,
29.37, 27.86, 26.85, 26.66, 22.69, 17.53, 14.11, 13.59.
Conclusions
In summary, incorporating fluorine into PT-containing polymer
is a very effective strategy to improve the photovoltaic
properties. Compared with PDTPT-2T, the fluorinated polymer
PDTPT-2TF exhibits obviously enhanced intermolecular
interactions, noticeably increased absorption coefficient,
broader and bathochromic-shifted absorption, pronouncedly
down-shifted LUMO and HOMO energy levels, more ordered
solid structure, and significantly improved miscibility with
PC71BM. These features are conducive to yielding better
photovoltaic properties. Conventional photovoltaic devices
based on PDTPT-2T only gave a maximum PCE of 2.65%, along
with a Voc of 0.73 V, a Jsc of 5.34 mA/cm2, and an FF of 67.91%
while those based on PDTPT-2TF exhibited a significantly
enhanced PCE of 8.01%, with a slightly higher Voc of 0.74 V, a
remarkably enhanced Jsc of 15.52 mA/cm2, and a little higher
FF of 69.73%. The efficiency of 8.01% is the highest one for PT-
containing polymers, and more importantly, it is achieved
without any processing additives or post-treatments. The easy
device processing method for PDTPT-2TF makes it very
competitive for potential applications in multicomponent and
tandem solar cells. This work indicates that PT would be a
promising building block to construct high performance
Synthesis of 4,7-bis(5-bromo-4-(2-octyldodecyl)thiophen-2-
yl)-[1,2,5]thiadiazolo[3,4-c]pyridine (4). To a mixture of
compound
3 (1.23 g, 1.43 mmol), CHCl3 (25 mL), and acetic
acid (5 mL), N-bromosuccinimide (0.56 g, 3.14 mmol) was
added in small portion at room temperature. The reaction was
monitored by TLC. After the completion of the reaction, the
mixture was poured into 50 mL of distilled water. Then 30 mL
of CHCl3 was added and the organic layer was washed with
distilled water (3×, 100 mL) and saturated NaHCO3 (1×, 100 mL)
sequentially. The solution was dried over anhydrous Na2SO4.
The solvent was removed by rotary evaporation and the crude
product was purified by silica gel column chromatography
using PE and DCM as the eluent to give compound
4 as a dark
red solid (1.18 g, 81% yield). 1H NMR (600 MHz, CDCl3): δ 8.66
(s, 1H), 8.29 (s, 1H), 7.73 (s, 1H), 2.59-2.56 (m, 4H), 1.77-1.75
(m, 2H), 1.31-1.23 (m, 64H), 0.88-0.85 (m, 12H). 13C NMR (150
MHz, CDCl3): δ 154.57, 147.72, 145.45, 143.46, 142.52, 140.79,
140.13, 135.70, 133.17, 129.11, 119.84, 117.07, 112.55, 38.55,
38.52, 34.41, 34.25, 33.40, 33.38, 31.94, 30.05, 30.04, 29.73,
29.69, 29.66, 29.38, 26.57, 22.71, 14.14.
Synthesis of PDTPT-2TF and PDTPT-2T. Compound
4 (0.2
photovoltaic
polymers.
More
in-depth
work
on
mmol), 2TF-Sn or 2T-Sn (0.2 mmol), tris(dibenzylideneacetone)
dipalladium(0) (Pd2(dba)3) (3.6 mg, 0.004 mmol), and tri(o-
tolyl)phosphine (P(o-tol)3) (7.2 mg, 0.0236 mmol) were added
to a 25 mL round-bottom flask. The mixture was flushed with
argon for 30 min. Then anhydrous toluene (5 mL) was added
and the solution was flushed with argon for another 30 min.
The solution was heated to 110 C under argon atmosphere.
The reaction mixture was cooled to room temperature when
the solution became gel. In both cases, the total reaction time
stereoregularity of fluorinated PT-containing polymer is
undergoing and further enhancement of photovoltaic
performance could be expected.
Experimental
o
Materials
4,7-Dibromo-[1,2,5]thiadiazolo[3,4-c]pyridine and monomer
2TF-Sn were purchased from SunaTech Inc. Other chemicals
and solvents were obtained from J&K Scientific or Energy
Chemical. Tetrahydrofuran (THF) and toluene were dried over
sodium/benzophenone. Compound 25,62 and monomer 2T-Sn63
were prepared according to published procedures. Compound
was
~2 h. The product was precipitated in methanol and
collected by filtration. Crude polymer was extracted by Soxhlet
extraction with methanol and chloroform successively. Then
the residue was stirred in 100 mL of DCB at 100 oC for 1 h. The
solution was filtered through a short path of silica (80−100
mesh). The polymer was obtained by precipitation from
methanol and dried under vacuum for 24 h at room
temperature.
5
3
was synthesized using the same procedure as for compound
.
o
Synthetic procedures
Synthesis of
[1,2,5]thiadiazolo[3,4-c]pyridine (3). Anhydrous toluene (40
mL) was added to a mixture of compound (5.88 g, 9 mmol),
PDTPT-2T. Yield: 68.72%. Mn: 47 kDa, PDI: 1.67. Td: 425 C.
Anal. Calcd for C61H89N3S5: C, 71.50; H, 8.75; N, 4.10. Found:
C, 71.27; H, 8.68; N, 3.85.
4,7-bis(4-(2-octyldodecyl)thiophen-2-yl)-
o
PDTPT-2TF. Yield: 75.28%. Mn: 77 kDa, PDI: 2.01. Td: 427 C.
2
Anal. Calcd for C61H87F2N3S5: C, 69.07; H, 8.27; N, 3.96.
Found: C, 68.76; H, 8.51; N, 3.62.
4,7-Dibromo-[1,2,5]thiadiazolo[3,4-c]pyridine (0.88 g, 3 mmol),
and tetrakis(triphenylphosphine)palladium (0.17 g, 0.15 mmol)
under an argon atmosphere. The solution was heated to 110
oC and stirred for 48 h. After cooling to room temperature,
toluene was removed by rotary evaporation. The crude
product was purified by silica gel column chromatography
using petroleum ether (PE) and dichloromethane (DCM) as the
Instruments and measurements
The optical absorption spectra of the polymers in solution and
as solid films were recorded on a Hitachi U-4100 UV-vis
spectrophotometer. Polymer molecular weights were
o
determined by GPC under 40 C. THF and polystyrene were
eluent to afford compound
3 as a red solid (1.82 g, 70% yield).
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry A
Page 8 of 10
ARTICLE
Journal Name
1
used as eluent and standard, respectively. All H NMR and 13C
NMR spectra were obtained by Bruker DRX-600 spectrometer.
Tetramethylsilane (TMS) was used as internal standard. TGA
was carried out using a SDT Q600 under a N2 atmosphere. The
4
T. L. Nguyen, H. Choi, S. J. Ko, M. A. Uddin, B. Walker, S. Yum,
J. E. Jeong, M. H. Yun, T. J. Shin, S. HwDaOngI:,1J0..1Y0.3VK9iei/mCw6ATartAnic0dle4O0Hn5.l9iYnDe.
Woo, Energy Environ. Sci., 2014,
Y. Liu, J. Zhao, Z. Li, C. Mu, W. Ma, H. Hu, K. Jiang, H. Lin, H.
Ade and H. Yan, Nat. Commun., 2014, , 5293.
J.-H. Kim, M. Lee, H. Yang and D.-H. Hwang, J. Mater. Chem.
A, 2014, , 6348-6352.
7, 3040-3051.
5
6
7
8
9
5
o
polymers were heated from 25 to 800 C at a scanning rate of
2
10 °C/min. Elemental analysis was performed by Vario EL cube.
XRD patterns of polymer films were collected on a Hitachi S-
4800. The annealed films were prepared by being heated on a
H. Yao, W. Zhao, Z. Zheng, Y. Cui, J. Zhang, Z. Wei and J. Hou,
J. Mater. Chem. A, 2016, DOI: 10.1039/c5ta08614k.
J. Wang, M. Xiao, W. Chen, M. Qiu, Z. Du, W. Zhu, S. Wen, N.
Wang and R. Yang, Macromolecules, 2014, 47, 7823-7830.
J. Zhao, Y. Li, A. Hunt, J. Zhang, H. Yao, Z. Li, J. Zhang, F.
Huang, H. Ade and H. Yan, Adv. Mater., 2015, DOI:
10.1002/adma.201504611.
o
hot plate at 100 C for 10 min. CV was performed by CHI660D
electrochemical workstation with a three-electrode system
consisting of Pt electrode (working electrode), Pt wire (counter
electrode), and SCE (reference electrode) at a scan rate of 100
10 M. Zhang, X. Guo, W. Ma, H. Ade and J. Hou, Adv. Mater.,
2015, 27, 4655-4660.
11 L. Han, T. Hu, X. Bao, M. Qiu, W. Shen, M. Sun, W. Chen and
mV/s.
The
electrolyte
was
tetrabutylammonium
hexafluorophosphate (Bu4NPF6, 0.1 M) acetonitrile solution.
AFM images were obtained by Agilent 5400 in tapping mode.
TEM images were obtained by JEOL JEM-1011 at an
accelerating voltage of 100 kV. EQE spectra were recorded on
a certified Newport incident photon conversion efficiency
(IPCE) measurement system.
R. Yang, J. Mater. Chem. A, 2015, 3, 23587-23596.
12 Z. Li, K. Feng, J. Liu, J. Mei, Y. Li and Q. Peng, J. Mater. Chem.
A, 2016, , 7372-7381.
13 C. Gu, Q. Zhu, X. Bao, S. Wen, M. Qiu, L. Han, W. Huang, D.
Zhu and R. Yang, Polym. Chem., 2015, , 6219-6226.
14 Y. Liu, W. Zhao, Y. Wu, J. Zhang, G. Li, W. Li, W. Ma, J. Hou
and Z. Bo, J. Mater. Chem. A, 2016, DOI: 10.1039/c6ta02622b.
15 C. E. Small, S. Chen, J. Subbiah, C. M. Amb, S.-W. Tsang, T.-H.
4
6
Fabrication of PSC devices and testing
Lai, J. R. Reynolds and F. So, Nat. Photonics, 2011, 6, 115-120.
Single junction BHJ-PSCs were fabricated with a conventional
~30 nm)/polymer:PC71BM/Ca
10 nm)/Al ( 100 nm). ITO-coated glasses were cleaned by
sequential ultrasonication in detergent, deionized water,
acetone, and isopropyl alcohol. Then they were treated with
oxygen plasma for 10 min. PEDOT:PSS (~30 nm) was spin-
16 S. Liu, K. Zhang, J. Lu, J. Zhang, H. L. Yip, F. Huang and Y. Cao,
J. Am. Chem. Soc., 2013, 135, 15326-15329.
17 T. Yang, M. Wang, C. Duan, X. Hu, L. Huang, J. Peng, F. Huang
structure of ITO/PEDOT:PSS (
(
~
~
and X. Gong, Energy Environ. Sci., 2012, 5, 8208-8214.
18 J. You, L. Dou, K. Yoshimura, T. Kato, K. Ohya, T. Moriarty, K.
Emery, C. C. Chen, J. Gao, G. Li and Y. Yang, Nat. Commun.,
2013, 4, 1446.
coated onto the ITO-coated substrates and then dried in an
oven at 160 °C for 20 min. The dried substrates were
transferred to a N2 glovebox. Active layer solutions (polymer
concentration: 6 mg/mL) were prepared in DCB. The solutions
were stirred on a hot plate at 100ꢀ°C for 2ꢀh before spin coated
onto the hot substrates which were preheated at 100 °C.
19 A. R. b. M. Yusoff, D. Kim, H. P. Kim, F. K. Shneider, W. J. da
Silva and J. Jang, Energy Environ. Sci., 2015, , 303-316.
20 H. Choi, S. J. Ko, T. Kim, P. O. Morin, B. Walker, B. H. Lee, M.
8
Leclerc, J. Y. Kim and A. J. Heeger, Adv. Mater., 2015, 27
,
3318-3324.
21 T. Ma, K. Jiang, S. Chen, H. Hu, H. Lin, Z. Li, J. Zhao, Y. Liu, Y.-
M. Chang, C.-C. Hsiao and H. Yan, Adv. Energy Mater., 2015,
DOI: 10.1002/aenm.201501282.
Under a pressure of 4.0 × 10−4 Pa, Ca (
~10 nm) and Al (~100
nm) layers were successively deposited onto the top of active
layer. The device active area was 10 mm2. The J-V
characteristics of PSCs were measured under AM 1.5G
illumination (100 mW/cm2) using a Keithley 2420 source
measurement from a Newport solar simulator. The light
intensity was calibrated using a standard silicon photodiode.
22 K. H. Hendriks, G. H. Heintges, V. S. Gevaerts, M. M. Wienk
and R. A. Janssen, Angew. Chem. Int. Ed., 2013, 52, 8341-
8344.
23 L. Dou, C.-C. Chen, K. Yoshimura, K. Ohya, W.-H. Chang, J.
Gao, Y. Liu, E. Richard and Y. Yang, Macromolecules, 2013, 46
3384-3390.
,
24 J. You, L. Dou, Z. Hong, G. Li and Y. Yang, Prog. Polym. Sci.,
2013, 38, 1909-1928.
25 L. Lu, W. Chen, T. Xu and L. Yu, Nat. Commun., 2015, 6, 7327.
26 T. Liu, L. Huo, X. Sun, B. Fan, Y. Cai, T. Kim, J. Y. Kim, H. Choi
and Y. Sun, Adv. Energy Mater., 2015, DOI:
10.1002/aenm.201502109.
Acknowledgements
This work was supported by the Ministry of Science and
Technology of China (2014CB643501, 2010DFA52310), and the
National Natural Science Foundation of China (21274161,
21402219, 51173199, 51573205 and 61107090).
27 W. Li, K. H. Hendriks, A. Furlan, W. S. Roelofs, M. M. Wienk
and R. A. Janssen, J. Am. Chem. Soc., 2013, 135, 18942-18948.
28 H. Zhou, L. Yang, S. Stoneking and W. You, ACS Appl. Mater.
Interfaces, 2010, 2, 1377-1383.
29 Y. J. Cheng, S. H. Yang and C. S. Hsu, Chem. Rev., 2009, 109
,
5868-5923.
References
30 W. Ying, X. Zhang, X. Li, W. Wu, F. Guo, J. Li, H. Ågren and J.
Hua, Tetrahedron, 2014, 70, 3901-3908.
31 J. Mao, J. Yang, J. Teuscher, T. Moehl, C. Yi, R. Humphry-
Baker, P. Comte, C. Grätzel, J. Hua, S. M. Zakeeruddin, H.
Tian and M. Grätzel, J. Phys. Chem. C, 2014, 118, 17090-
17099.
1
2
3
C. Liu, K. Wang, X. Gong and A. J. Heeger, Chem. Soc. Rev.,
2015, DOI: 10.1039/c5cs00650c.
J. Y. Kim, K. Lee, N. E. Coates, D. Moses, T. Q. Nguyen, M.
Dante and A. J. Heeger, Science, 2007, 317, 222-225.
X. Guo, A. Facchetti and T. J. Marks, Chem. Rev., 2014, 114
8943-9021.
,
32 H. Zhou, L. Yang, S. C. Price, K. J. Knight and W. You, Angew.
Chem. Int. Ed., 2010, 49, 7992-7995.
8 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 9 of 10
Journal of Materials Chemistry A
Please do not adjust margins
Journal Name
ARTICLE
33 Y. Hua, J. He, C. Zhang, C. Qin, L. Han, J. Zhao, T. Chen, W.-Y. 61 S. Guo, J. Ning, V. Körstgens, Y. Yao, E. M. Herzig, S. V. Roth
View Article Online
Wong, W.-K. Wong and X. Zhu, J. Mater. Chem. A, 2015,
3
,
and P. Müller-Buschbaum, Adv. EnerDgOyI:M10a.1t0e3r.9,/C260T1A50,40D5O9DI:
3103-3112.
10.1002/aenm.201401315.
34 T. Jiang, Y. Qu, B. Li, Y. Gao and J. Hua, RSC Adv., 2015,
5
,
62 K.-H. Ong, S.-L. Lim, J. Li, H.-K. Wong, H.-S. Tan, T.-T. Lin, L. C.
1500-1506.
H. Moh, J. C. de Mello and Z.-K. Chen, Polym. Chem., 2013, 4,
35 Y. Hua, H. Wang, X. Zhu, A. Islam, L. Han, C. Qin, W.-Y. Wong
and W.-K. Wong, Dyes Pigments, 2014, 102, 196-203.
36 C. P. Yau, Z. Fei, R. S. Ashraf, M. Shahid, S. E. Watkins, P.
Pattanasattayavong, T. D. Anthopoulos, V. G. Gregoriou, C. L.
Chochos and M. Heeney, Adv. Funct. Mater., 2014, 24, 678-
687.
1863-1873.
63 K. Kawabata and H. Goto, J. Mater. Chem., 2012, 22, 23514-
23524.
37 H. Kang, B. Zhao, Z. Cao, J. Zhong, H. Li, Y. Pei, P. Shen and S.
Tan, Eur. Polym. J., 2013, 49, 2738-2747.
38 Y. Sun, S.-C. Chien, H.-L. Yip, Y. Zhang, K.-S. Chen, D. F. Zeigler,
F.-C. Chen, B. Lin and A. K. Y. Jen, J. Mater. Chem., 2011, 21
,
13247-13255.
39 N. Blouin, A. Michaud, D. Gendron, S. Wakim, E. Blair, R.
Neagu-Plesu, M. Belletête, G. Durocher, Y. Tao and M.
Leclerc, J. Am. Chem. Soc., 2008, 130, 732-742.
40 L. Yang, H. Zhou, S. C. Price and W. You, J. Am. Chem. Soc.,
2012, 134, 5432-5435.
41 M. Wang, H. Wang, T. Yokoyama, X. Liu, Y. Huang, Y. Zhang, T.
Q. Nguyen, S. Aramaki and G. C. Bazan, J. Am. Chem. Soc.,
2014, 136, 12576-12579.
42 J. Yuan, X. Huang, H. Dong, J. Lu, T. Yang, Y. Li, A. Gallagher
and W. Ma, Org. Electron., 2013, 14, 635-643.
43 W. Wen, L. Ying, B. B. Hsu, Y. Zhang, T. Q. Nguyen and G. C.
Bazan, Chem. Commun., 2013, 49, 7192-7194.
44 R. C. Coffin, J. Peet, J. Rogers and G. C. Bazan, Nat. Chem.,
2009, 1, 657-661.
45 H. Zhou, L. Yang and W. You, Macromolecules, 2012, 45, 607-
632.
46 H.-Y. Chen, J. Hou, S. Zhang, Y. Liang, G. Yang, Y. Yang, L. Yu,
Y. Wu and G. Li, Nat. Photonics, 2009, 3, 649-653.
47 M. C. Scharber, D. Mühlbacher, M. Koppe, P. Denk, C.
Waldauf, A. J. Heeger and C. J. Brabec, Adv. Mater., 2006, 18
,
789-794.
48 N. E. Jackson, B. M. Savoie, K. L. Kohlstedt, M. Olvera de la
Cruz, G. C. Schatz, L. X. Chen and M. A. Ratner, J. Am. Chem.
Soc., 2013, 135, 10475-10483.
49 J. Lee, S. B. Jo, M. Kim, H. G. Kim, J. Shin, H. Kim and K. Cho,
Adv. Mater., 2014, 26, 6706-6714.
50 H. Zhou, L. Yang, A. C. Stuart, S. C. Price, S. Liu and W. You,
Angew. Chem. Int. Ed., 2011, 50, 2995-2998.
51 K. Reichenbacher, H. I. Suss and J. Hulliger, Chem. Soc. Rev.,
2005, 34, 22-30.
52 A. Maurano, R. Hamilton, C. G. Shuttle, A. M. Ballantyne, J.
Nelson, B. O'Regan, W. Zhang, I. McCulloch, H. Azimi, M.
Morana, C. J. Brabec and J. R. Durrant, Adv. Mater., 2010, 22
,
4987-4992.
53 H. J. Snaith, N. C. Greenham and R. H. Friend, Adv. Mater.,
2004, 16, 1640-1645.
54 G. Garcia-Belmonte and J. Bisquert, Appl. Phys. Lett., 2010,
96, 113301.
55 J. Liu, Y. Shi and Y. Yang, Adv. Funct. Mater., 2001, 11, 420-
424.
56 R. Lampande, G. W. Kim, J. Boizot, Y. J. Kim, R. Pode and J. H.
Kwon, J. Mater. Chem. A, 2013, 1, 6895-6900.
57 S. Han, W. S. Shin, M. Seo, D. Gupta, S.-J. Moon and S. Yoo,
Org. Electron., 2009, 10, 791-797.
58 L. Dong, W. Li and W. S. Li, Nanoscale, 2011, 3, 3447-3461.
59 S. H. Park, A. Roy, S. Beaupré, S. Cho, N. Coates, J. S. Moon, D.
Moses, M. Leclerc, K. Lee and A. J. Heeger, Nat. Photonics,
2009, 3, 297-302.
60 J. S. Kim, Y. Lee, J. H. Lee, J. H. Park, J. K. Kim and K. Cho, Adv.
Mater., 2010, 22, 1355-1360.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
Please do not adjust margins

Journal of Materials Chemistry A
Page 10 of 10
View Article Online
DOI: 10.1039/C6TA04059D
Fluorine substitute was firstly introduced into PT-containing polymer, resulting in significantly
improved photovoltaic performance.