Novel wide band gap polymers based on dithienobenzoxadiazole for polymer solar cells with high open circuit voltages over 1 v

Article abstract of DOI:10.1039/c6ra07951b

A new monomer dithieno-[3′,2′:3,4;2′′,3′′:5,6]benzo[1,2-c]xadiazole (fDTBO) is first used as an electron-deficient acceptor to build D-A copolymers in a photovoltaic field. Two polymers PBDTT-fDTBO and PBDTO-fDTBO consist of fDTBO with thienyl-substituted-benzodithiophene (BDTT) or alkoxy-substituted benzodithiophene (BDTO). Both polymers show a deep HOMO around -5.5 eV with a wide band gap of over 1.9 eV. The polymer solar cells (PSCs) based on two polymers both show over 1 V high open circuit voltage (V_oc) independent of polymer/PCBM ratios and solvent additives content in the PSCs active layer. The power conversion efficiency (PCE) based on PBDTT-fDTBO devices is 4.5% for single junction PSCs, and these polymers can be applied in tandem PSCs due to their wide band gap (up to 1.99 eV). This work demonstrates that the fDTBO unit is a promising building block to design wide band gap photovoltaic polymers with high V_oc.

Full text of DOI:10.1039/c6ra07951b

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Novel Wide Band Gap Polymers Based on Dithienobenzoxadiazole for
Polymer Solar Cells with High Open Circuit Voltages over 1 V†
a,b
b,d
a
b
a
a
Dakang Ding, † Jiuxing Wang, † Weiye Chen, Meng Qiu, Junzhen Ren, Huilin Zheng, Deyu
Received 00th January 20xx,
Accepted 00th January 20xx
b
a,c
b
Liu, Mingliang Sun,* and Renqiang Yang*
DOI: 10.1039/x0xx00000x
A new monomer dithieno-*3’,2’:3,4;2”,3”:5,6+benzo*1,2-c]xadiazole (fDTBO) is first used as the electron-deficient acceptor
to build D-A copolymers in photovoltaic field. Two polymers PBDTT-fDTBO and PBDTO-fDTBO are consisted of fDTBO with
thienyl-substituted-benzodithiophene (BDTT) or alkoxy-substituted benzodithiophene (BDTO). Both polymers show deep
HOMO around -5.5eV with wide band gap of over 1.9 eV. The polymer solar cells (PSCs) based on two polymers both show
over 1V high open circuit voltage (Voc) independent on polymer/PCBM ratios and solvent additives content in PSCs active
layer. The power conversion efficiency (PCE) based on PBDTT-fDTBO devices is 4.5% for single junction PSCs, and these
polymer can be applied in tandem PSCs due to its wide band gap (up to 1.99 eV). This work demonstrates that fDTBO unit
is a promising building block to design high Voc wide band gap photovoltaic polymer.
www.rsc.org/
structure design strategies to obtain deep HOMO polymer.
One is introducing the electron-withdrawing atom (fluorine,
1
Introduction
25 26
sulfur or oxygen) to the conjugated polymer backbone . The
other is decreasing the effective conjugate degree by
incorporating large side groups or increasing the sinuosity of
The bulk heterojunction polymer solar cells based on blending
of polymer and PCBM have exhibited high PCE of over 10% for
single polymer solar cells (PSCs) in recent years . In order to
achieve higher PCE, the tandem solar cells based on wide band
gap (WBG) polymers were needed
promising route to reach PCE up to 15%. Thus , More and
more WBG polymers were synthesized
PSCs based on WBG polymers cannot provide very high power
conversion efficiency due to the limited light absorption
The PCE of PSCs is determined by short-circuit current density
1
-4
27, 28
conjugated backbone
. Dithienyl-2,1,3-benzothiadiazole
5
6 7
(DTBT) is a well-known electron-withdrawing acceptor, and it
and it may be the most
29
8
, 9
was first used for D-A copolymer by Andersson et al. in 2003 .
10-13
As shown in Chart 1, Wei You et al. synthesized a new
monomer 4,7-bis (5-bromothiophen-2-yl)-5,6-diuorobenzo-
[c][1,2,5]thiadiazole (DTffBT) by introducing F to DTBT for D-A
. Generally, the
14-18
.
13
co-polymer with a deeper HOMO. Li et al. used fusion
19-21
strategy to synthesis a new monomer dithieno-*3’,2’:3,4; 2”,
(
Jsc), fill factor (FF) and Voc
.
3
”:5,6+benzo[1,2-c] [1,2,5] thiadiazole (fDTBT) by fusing two
Increasing Voc of PSCs is usually as a simple and feasible
thienyl units on the benzothiadiazole (BT), and they got a high
method to increase the PCE. The Voc is proportional to energy
difference between the lowest unoccupied molecular orbital
Voc of 0.84 based on polymer with fDTBT and benzodith
30
iophene (BDT) derivative
.
(
LUMO) of the fullerene derivatives and the highest occupied
9
molecular orbital (HOMO) of polymers. Higher Voc may be
achieved by deeper HOMO of polymer as the fullerene
derivatives remains the same . Deep HOMO of polymer also
may improve the oxidative stability and decrease energy loss
of PSCs devices
The band gap is an important parameter for PSCs and it is
tuned by electron-rich donor and electron-deficient acceptor
22
31
unit . BDT is a good donor unit for high photovoltaic
performance, and some WBG polymers based on BDT unit
2
3, 24
. Typically, there are two molecular
3
2-34
were synthesized and showed high PCEs
. N-alkylthieno
33, 35-37
[
[
3,4-c]pyrrole-4,6-dione(TPD)
derivatives, 2-alkyl-benzo[d]
1,2,3]triazole(TAZ) derivatives, thiazolo[5,4d]thiazole(TTz)
derivatives and 1,3-bis (thiophen-2-yl)-5,7–bis(2-ethyl-hexyl)
benzo-[1,2-c:4,5-c]dithiophene-4,8-dione (BDD)
a
38
39,
Institute of Material Science and Engineering, Ocean University of China, Qingdao
66100, People’s Republic of China.; E-mail: mlsun@ouc.edu.cn
CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and
2
4
0
b
41
Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, People’s
et al were
Republic of China. E-mail: yangrq@qibebt.ac.cn
c
main acceptor donors for BDT-based WBG polymers. To the
best of our knowledge, the PSCs of wide band gap polymers
based on BDT unit rarely show the Voc over 1V with high PCE.
State Key Laboratory of Luminescent Materials and Devices ，South China
University of Technology, Guangzhou 510640, China
d
University of Chinese Academy of Sciences, Beijing 100049, China
†
Dakang Ding and Jiuxing Wang contributed equally to this work
‡ElectronicSupplementary Information (ESI) available: See DOI : 10.1039 /x0 xx 00
This journal is © The Royal Society of Chemistry 20xx
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Chart 1 Polymers based on BDT and different acceptors
Hou and coworkers synthesized a new polymer with BDT-F and
BDD, and the Voc based on the new polymer was 1.02 V which
was reduced to 0.96 V after adding the solvent additives.
The fDTBT was a new promising electron-accepting moiety
with good π-electron delocalization and planarity, and we can
further get dithieno-[3’,2’:3,4; 2”,3”:5,6+benzo[1,2c]zoxadiaz
ole (fDTBO) with stronger intermolecular interactions and
electron-withdrawing ability by replacing sulfur with oxygen
Fig.1 TGA curves of PBDTT-fDTBO and PBDTO-fDTBO
(
Chart 1) .The fDTBO unit is first used in photovoltaic field in
this work. Compared with sulfur atom, the oxygen had higher
electronegativity and electron withdrawing ability, so higher
2
Results and discussion
Voc exceeding 1 V can be achieved. In this work, we use fDTBO 2.1 Synthesis and Characterization
to build two D-A copolymers: PBDTT-fDTBO and PBDTO-fDTBO.
The synthetic routes of fDTBO, PBDTT-fDTBO and PBDTO-
As shown in Scheme 1, two polymers were synthesized by
stille coupling with fDTBO and BDTT or BDTO. As a result,
PBDTT-fDTBO and PBDTO-fDTBO show high Voc with 1.04V and
fDTBO are shown in Scheme 1. The detailed synthetic routes
were described in experimental section and the monomer
42
fDTBO was synthesized according to reported method
.
1
.02V, with wide band gap of 1.99 eV and 1.91 eV, respectively.
Polymer PBDTT-fDTBO and PBDTO-fDTBO were synthesized by
Stille coupling reaction using Pd (dba) /P(o-tol) as catalysts
What’s more, the Voc of PSCs devices can maintain above 1V
during different polymers/PCBM ratios and solvent additives
contents optimization. BHJ PSCs based on PBDTT-fDTBO
obtained Voc of 1.04V with decent PCE around 4.52%. We
believe the fDTBO unit will be a promising building block to
achieve high photovoltaic performances due to its good
2
3
3
and 5 ml toluene as the solvent. The color of two polymers
was both deep red. Both of polymers could only be slowly
dissolved in DCB at 90
℃ because of their poor solubility. The
number-average molecular weights of PBDTT-fDTBO and
PBDTO-fDTBO were 88.4kDa and 89.3kDa, with
polydispersity index of 1.40 and 1.93, respectively.
a
planarity and strong electron withdrawing
.
2
.2 Thermal analysis
The thermal properties of PBDTT-fDTBO and PBDTO-fDTBO
were analyzed by thermogravimetric analysis (TGA). As is
shown in Fig. 1, the decomposition temperatures (5% weight
loss) of PBDTT-fDTBO and PBDTO-fDTBO are 394
10 , respectively. This result indicts that both polymers
show high thermal stability for PSCs applications.
℃ and
3
℃
2
.3 Optical properties
The ultraviolet-visible absorption spectra (UV-vis) of these two
polymers in thin films and dilute DCB solution is shown in Fig.2.
The corresponding optical data is listed in Table 1. In DCB
solution, the absorption peak wavelength of PBDTT-fDTBO and
PBDTO-fDTBO is at 536 and 530 nm, respectively, which is
43
attributed to intramolecular charge transfer (ICT) between
BDT unit and fDTBO unit. The sharp shoulder peak of PBDTT-
fDTBO and PBDTO-fDTBO at 580 nm and 568 nm is due to the
aggregations of the polymer chains. Compared with the
absorption spetra in DCB solution, two polymers in thin film
Scheme 1. Synthetic routes of fDTBO and two polymers
2
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Table 1.Optical absorption properties and molecular levels of two polymers
opt
cv
cv
DFT
DFT
DFT
polymers
λ
max film
λ
max solution
(nm)
λ
onset film
(eV)
E
g
E
(V)
ox
HOMO
(eV)
LUMO
(eV)
E
g
HOMO
(eV)
LUMO
(eV)
(nm)
(eV)
1.91
1.99
(eV)
2.63
2.74
PBDTT-fDTBO
PBDTO-fDTBO
369, 546 ,596
392, 532, 571
361, 534, 580
403, 530, 564
648
623
1.23
1.15
-5.64
-5.56
-3.73
-3.57
-5.48
-5.39
-2.85
-2.65
Fig.2 UV-vis absorption spectra of PBDTT-fDTBO and PBDTO-fDTBO in dilute Fig.3 Cyclic voltammograms of PBDTT-fDTBO and PBDTO-fDTBO
DCB solution and in thin films
and PBDTO-fDTBO were calculated by EHOMO = -e(E +4.8-
ox
have stronger intermolecular force, and show about 13 nm
red-shifted. In addition, the localized π−πꢀ transitions can
(Fc/Fc )
+
E1/2
) and the corresponding LUMO were calculated by
opt 44
bring about absorption peak in short-wavelength area. The HOMO and Eg
absorption spectra of PBDTT-fDTBO showed red-shifted
. These two polymers both had deep HOMO
energy levels regardless of the donor unit, which were mainly
attributed to the strong electron-withdrawing group fDTBO
compared with the spectra of PBDTO-fDTBO which may be
ascribed to the 2D conjugated structures of the polymer
opt
PBDTT-fDTBO. The optical band gap (Eg ) of PBDTT-fDTBO unit. Thus high Voc of PSCs could be expected when polymers
and PBDTO-fDTBO are 1.91 eV and 1.99 eV respectively, which
based on fDTBO unit blended with PCBM
.5 Theoretical Calculations
.
were calculated from their absorption onset of thin film.
.4 Electrochemical properties
2
In order to understand the optoelectronic properties of two
polymers, density functional theory (DFT) calculations were
carried out using Gaussian 09 program. The optimized
molecular geometries were recognized as the minimum energy
conformations when calculating vibrational frequencies at the
same level. Some methods were implemented to simplify the
calculations, such as choosing one repeating unit and replacing
alky side chains by methyl groups. The optimized molecular
geometry and frontier molecular orbitals are shown in Fig. 4
and detailed energy levels are depicted in Table 1. The
simulated data from the DFT calculations coincided well with
2
The electrochemical properties of two polymers were
measured by cyclic voltammetry (CV) .The CV curves are
shown in Fig.3 and detailed onset oxidation potentials (E ) and
ox
HOMO , LUMO energy levels are shown in Table 1. The Eox of
PBDTT-fDTBO and PBDTO-fDTBO were 1.23V and 1.15V vs
saturated calomel electrode (SCE), respectively. Half-wave
+
potential of theferrocene/ferrocenium (Fc/Fc ) redox couple
was as the internal standard, and the potential (E1/2(Fc/Fc )) vs
+
SCE was measured to be 0.39 V. The HOMO of PBDTT-fDTBO
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experimental results estimated from the cyclic voltam- Table
Journal Name
2
Photovoltaic properties of two polymers VwieiwthArtidclieffOenrelinnet
polymer/PC71BM ratios without Chloronaphthalene (CN)
mograms. Two polymers showed similar distributions of
electron density .The LUMO was mainly delocalized in the
fDTBO unit, while the HOMO was located both in donor unit
and acceptor unit.
DOI: 10.1039/C6RA07951B
2
polymer
D/A
V
oc(V)
J
sc(mA/cm ) FF(%) PCEmax/PCEave(%)
PBDTT-fDTBO
PBDTT-fDTBO
PBDTT-fDTBO
1:1
1:2
1:3
1.07
1.05
1.06
1.03
1.02
1.00
2.72
5.53
3.56
3.78
5.41
3.30
40.13
49.57
53.59
43.66
50.67
41.38
1.16/1.10
2.88/2.75
2.02/1.87
1.69/1.55
2.80/2.75
1.36/1.25
2.6 Hole mobility
PBDTO-fDTBO 1:1
Hole mobility is an another import parameter influencing the PBDTO-fDTBO 1:2
PBDTO-fDTBO 1:3
PSCs performances. It was measured by space-charge-limited-
current (SCLC) with polymer and PC BM blend film. As shown
71
in Fig. 5, the hole mobility of PBDTT-fDTBO and PBDTO-fDTBO
-4
-5
2 -1 -1
Table 3 Photovoltaic properties of two polymers/PC71BM (1:2) with different
CN amounts
is 3.11×10 and 2.90×10 cm V s , respectively. The polymer
PBDTT-fDTBO has higher hole mobility than PBDTO-fDTBO,
which may induce the PSCs device based on PBDTT-fDTBO
showing higher performances. The hole mobilities values of
two polymers make a great difference, which should be partly
attributed to the difference of their structures. Previous
2
polymer
CN
Voc(V)
J
sc(mA/cm ) FF(%) PCEmax/PCEave(%)
PBDTT-fDTBO
PBDTT-fDTBO
PBDTT-fDTBO
0
1
2
3
4
0
1
2
3
1.05
1.02
1.03
1.04
1.04
1.02
1.01
1.00
1.01
5.53
5.32
5.33
7.95
7.57
5.41
3.33
3.30
3.31
49.57
40.12
48.38
54.59
55.02
50.67
45.15
44.26
46.65
2.88/2.75
2.18/2.13
2.66/2.51
4.52/4.36
4.33/4.23
2.80/2.75
1.52/1.48
1.46/1.40
1.48/1.39
reports have revealed that 2D-structure can enhance the hole PBDTT-fDTBO
48,49
PBDTT-fDTBO
PBDTO-fDTBO
PBDTO-fDTBO
mobility effectively
. The polymer PBDTT-fDTBO is based
on alkylthienyl-substituted BDT (2D structure) and PBDTO-
fDTBO is based on alkoxyl-substituted BDT, thus PBDTT-fDTBO PBDTO-fDTBO
exhibits higher hole mobility.
PBDTO-fDTBO
2
.7 Photovoltaic properties
The bulk heterojunction(BHJ) polymer solar cells were
fabricated with the traditional structure of ITO/PEDOT (poly
(
3,4-ethylenedioxythiophene)):PSS(poly(styrenesulfonate))/
PBDTT-fDTBO(PBDTO-fDTBO):PC BM/Ca/Al to investigate the
71
photovoltaic properties of two polymers. These polymers
blended with PC BM were heated to 80 °C for 1 hour before
71
spin-coated as the active layer due to their poor solubility. As
shown in Table 2, and Fig.6, different ratios of
polymer/PC BM and different proportions of solvent additives
3
71
45
(
CN) had obvious influences on the photovoltaic properties
Fig.4 Optimized molecular geometries and frontier molecular orbitals from
DFT calculations on PBDTT-fDTBO and PBDTO-fDTBO
of PSCs devices. With different D/A ratios and the proportion
of CN devices performances were tested, and the optimal D/A
ratios of two polymers were both probed to be 1:2 and the
optimal proportion of CN of PBDTT-fDTBO and PBDTO-fDTBO
was 3% and 0% , respectively. In addition, the Voc of PSCs
based on two polymers both showed over 1V with different
polymer /PC BM ratios and CN proportions .
71
The best photovoltaic performance of PSCs device based on
polymer PBDTT-fDTBO was 4.52% with a V of 1.04 V, a Jsc of
oc
2
7
.95 mA/cm and FF of 54.59%, while the PCE of PBDTO-fDTBO
based PSCs device reached maximum value of 2.88%, with a
2
30
Voc of 1.05V, Jsc of 5.53mA/cm and FF of 49.57%. Wei-Shi Li
group synthesized several polymers based on BDT and DTBT
fDTBT) and the polymer PBDT -fDTBT achieved the best
(
16
photovoltaic performance. The PSCs based on PBDT -DTBT
20
showed maximum PCE of 3.98% with Voc of 0.76V, and the
Fig.5 Current density (J)-voltage (V) curves for PBDTT-fDTBO and PBDTO- PSCs based on PBDT -fDTBT showed maximum PCE of 4.50%
16
fDTBO based devices.
with Voc of 0.85V. Thus, the Voc of our polymer PBDTT-fDTBO
4
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Fig.7 EQE curves of the PSCs based on PBDTT-fDTBO:PC71BM (1:2) and
PBDTO-fDTBO:PC71BM (1:2).
As shown in Fig.8 (a, b, e, f), the surface of PBDTT-fDTBO
/
PC BM blended film without CN was smooth with the root-
71
mean-square (RMS) roughness value of 0.7 nm. While 3% CN
was added, the RMS value of the blended film was 1.35 nm
due to larger domains. Meanwhile, the surface of PBDTO-
fDTBO/PC71BM blended film without CN and with 3% CN
showed similar RMS value of 0.91 nm and 0.89 nm,
respectively. As shown in Fig.8 (c, d, g, h), the aggregations of
PC BM and PBDTO-fDTBO without CN was more evident than
71
Fig.6 J-V curves of PSCs based on PBDTT-fDTBO and PBDTO-fDTBO with those with CN, while the aggregations of polymer PBDTT-
different CN amounts.
fDTBO and PC BM became evident after adding 3% CN. (Fig.8
71
(
a, b, e, f)). What’s more, the better surface morphology and
phase separation of PBDTT-fDTBO was another reason for its
higher hole mobility.
or PBDTO-fDTBO based device was nearly 0.2 V higher than
Voc of PBDT -fDTBT, which agreed well with our expectation.
16
Furthermore, the higher Voc of PBDTT-fDTBO based PSCs
agreed well with CV curves.
3
Conclusion
The external quantum efficiency (EQE) spectra of the In summary, new monomer fDTBO is first used as acceptor to
optimized polymer solar cells based on PBDTT-fDTBO and build D-A copolymers in photovoltaic polymer field. The PSCs
PBDTO-fDTBO are shown in Fig.7. The EQE curves exhibited based on two polymers both showed high Voc of above 1 V,
absorption region from 300 to 640 nm. The maximum EQE of and the PSCs devices can remained 1 V high Voc during
PBDTT-fDTBO based PSCs devices was 58.63% at 480nm, while polymer/PCBM ratios and solvent additives content
the maximum EQE of PBDTO-fDTBO based PSCs devices was optimization. Compared with the polymer PBDT16-fDTBT, the
4
3.76% at 530 nm. The calculated current densities from the Voc of our polymer increased nearly 0.2 V. Therefore, this may
2
EQE curves were 8.02 and 5.40 mA/cm of PBDTT-fDTBO and provide us a new strategy by replacing the sulfur atom with
PBDTO-fDTBO respectively, which were consistent with the Jsc oxygen for achieving stable higher Voc photovoltaic devices.
obtained by J-V curves.
2.8 Morphology Characterization
4
Experimental section
The influences of CN on the morphology characterizations of
the blended films were investigated by atomic force
microscopy (AFM) and transmission electron microscopy (TEM).
4
.1 Materials
All solvents and chemicals were purchased by reagent
companies, and all of the solvents except toluene and tetrahy
drofuran (THF) were used directly. Toluene and THF were used
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Fig.8 AFM (a, b) topography and TEM (c, d) images of the PBDTT-fDTBO:PC71BM (1:2) without and with 3% CN
AFM (e, f) topography and TEM (g, h) images of the PBDTO-fDTBO:PC71BM (1:2) without and with 3% CN
for water sensitive reactions after dried by sodium under
argon atmosphere. Compound BDTT, BDTO, fDTBO were
synthesized according to reported methods.
4
.2 Measures
1
13
42, 46, 47
H NMR (nuclear magnetic resonance) and C NMR spectra
were tested by the Bruker DRX with 600MHZ spectrometer
with tetramethylsilane (TMS) as zero for a standard. Elemental
analysis data was recorded on a Vario El Cube elementar
analyzer. Under a nitrogen atmosphere, TGA curves were
4
.1.1 Synthesis of PBDTT-fDTBO and PBDTO-fDTBO The
mixture of compound fDTBO (78.01mg,0.2mmol), BDTT
(
(
242.63mg,0.2mmol) or BDTO (221.79,0.2mmol), Pd dba
2 3
-1
recorded by a SDT Q600 with a heating rate of 10°C min . The
molecular weights (M ) of two polymers were performed by
2.67 mg), P(o-tol) (5.34 mg) and toluene (5ml) were added
3
n
into 25ml flask, and then it was cooled to -78℃ to remove the
GPC with polystyrene as the standard and THF as the solvent
at 35 °C. UV−vis absorption spectra were got with solvents and
thin films using the Hitachi U-4100 spectrophotometer. CV
curves were recorded by
workstation using the
electrochemical cell system with
Tetrabutylammonium phosphorus hexafluoride (0.1 M) in
acetonitrile (under an argon atmosphere) at a scan rate of 100
mV/s. In the three-electrode system, Pt electrode with the
polymer film was as the working electrode, SCE was as the
reference electrode and Pt wire was as the auxiliary electrode
at the ambient temperature. The DFT calculations were
measured by Gaussian 09 program at the B3LYP/6-31G(d,p)
oxygen dissolved in toluene. The reaction was stirred at 110
℃
for 24 or 15 hours and then was dropped into methanol after
cooling to the room temperature. The raw solid after filtration
was further conducted by Soxhlet extraction in turn using
acetone, hexane, dichloromethane and chloroform. Finally, the
dark red solid (158mg, 69% yield; or 142mg , 57% yield) was
got. These two polymers could not be recorded by nuclear
magnetic resonance due to their poor solubility. Elemental
analysis was conducted, and the results were as follows.
PBDTT-fDTBO, elemental analysis calcd (%) for C H N OS : C
a CHI 660D electrochemical
standard
three-electrode
solution of
a
68
92
2
6
7
1.28%, H 8.09%, found: C 71.12%, H 8.27%. PBDTO-fDTBO,
elemental analysis calcd (%) for C H N O S : C 71.10%, H
60 88 2 3 4
8
.75%, found: C 70.86%, H 9.02%.
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levels at gas phase. AFM pictures were exhibited by an Alilgent Park and M. H. Hyun, Polymer, 2015, 80, 95.
ARTICLE
View Article Online
1
2 W. Li, A. Furlan, W. S. Roelofs, K. H. HendrDikOsI,: 1G0..1W03. 9v/aCn6PRrAu0i7s9s5e1nB,
M. M. Wienk and R. A. Janssen, Chem. Commun., 2014, 50, 679.
3 S. C. Price, A. C. Stuart, L. Yang, H. Zhou and W. You, J Am. Chem.
Soc., 2011, 133, 4625.
4 J. Huang, X. Wang, C. Zhan, Y. Zhao, Y. Sun, Q. Pei, Y. Liu and J.
Yao, Polym. Chem, 2013, 4, 2174.
M. M. Wienk, J. M. Kroon, W. J. H. Verhees, J. Knol, J. C.
Hummelen, P. A. van Hal and R. A. J. Janssen, Angewandte Chemie,
5
(
400 at ambient conditions. Transmission electron microscopy
TEM) images were recorded by a JEOL JEM-1011 transmission
electron microscope at the high voltage of 100 kV.
1
1
4.3 Fabrication and characterization of PSCs
15
Conventional polymer solar cells devices were fabricated with
the structure of ITO/PEDOT:PSS/PBDTT-fDTBO(PBDTO-
fDTBO):PC BM/Ca/Al . The ITO-coated glasses were cleaned in
the ultrasonic bath with water, and washed with acetone,
toluene, methanol and isopropyl alcohol subsequently. After
2
1
003, 115, 3493-3497.
S. Subramaniyan, H. Xin, F. S. Kim, N. M. Murari, B. A. E.
71
6
Courtright and S. A. Jenekhe, Macromolecules, 2014, 47, 4199-4209.
7 J. Gilot, M. M. Wienk and R. A. Janssen, Adv Mater, 2010, 22,
1
about 20 min oxygen plasma treatment, the layer of E67-71.
1
8 V. Tamilavan, K. H. Roh, R. Agneeswari, D. Y. Lee, S. Cho, Y. Jin, S.
H. Park and M. H. Hyun, J POLYM SCI POL CHEM, 2014.
9 L. Dou, J. You, Z. Hong, Z. Xu, G. Li, R. A. Street and Y. Yang, Adv
Mater, 2013, 25, 6642.
PEDOT:PSS (30 nm) was spin-coated onto the ITO glasses and
then dried at 120 °C under argon atmosphere for 20 min. The
polymer blended with PC BM (1:1, 1:2 and 1:3) were
dissolved in CN/DCB (0%, 1%, 2% or 3%) solution. The solution
was maintained at 90 °C for 1 hour before being spin-coated as
1
71
2
2
0 L. Ye, S. Zhang, L. Huo, M. Zhang and J. Hou, Acc. Chem. Res.,
014, 47, 1595.
the active layer (90 nm) onto the ITO/PEDOT:PSS substrate. At 21 J. Ren, X. Bao, L. Han, J. Wang, M. Qiu, Q. Zhu, T. Hu, R. Sheng, M.
last Ca (10 nm) and Al (100 nm) layers were in sequence Sun and R. Yang, Polym. Chem., 2015, 6, 4415.
2
2 J. Wang, M. Xiao, W. Chen, M. Qiu, Z. Du, W. Zhu, S. Wen, N.
thermal evaporated onto the active layer with a pressure of
−
4
Wang and R. Yang, Macromolecules, 2014, 47, 7823.
23 D. Veldman, S. C. J. Meskers and R. A. J. Janssen, Adv Funct
Mater, 2009, 19, 1939.
3
*10 Pa. The active area of the PSCs device in this work was
2
about 0.1 cm . The current density−voltage characteristics
were measured by a Keithley 2420 source measurement under
2
4 K. Vandewal, Z. Ma, J. Bergqvist, Z. Tang, E. Wang, P. Henriksson,
2
illumination (AM 1.5 G, 100 mW/cm ) from a Newport solar
K. Tvingstedt, M. R. Andersson, F. Zhang and O. Inganäs, Adv Funct
simulator. A standard silicon solar cell was used to calibrate Mater, 2012, 22, 3480.
the light intensity. The external quantum efficiency (EQE) of 25 H.-Y. Chen, J. Hou, S. Zhang, Y. Liang, G. Yang, Y. Yang, L. Yu, Y. Wu
and G. Li, Nature Photonics, 2009, 3, 649-653.
the PSCs were recorded by a certified Newport incident
photon conversion efficiency (IPCE) measurement system.
2
6 Y. Huang, L. Huo, S. Zhang, X. Guo, C. C. Han, Y. Li and J. Hou,
Chem. Commun., 2011, 47, 8904.
7 D. Liu, C. Gu, M. Xiao, M. Qiu, M. Sun and R. Yang, Polym. Chem.,
2015, 6, 3398.
8 R. S. Kularatne, F. J. Taenzler, H. D. Magurudeniya, J. Du, J. W.
2
Acknowledgements
The authors gratefully acknowledge financial support from the
NSFC (21274134, 51573205), and State Key Laboratory of
Luminescent Materials and Devices (2016-skllmd-01).
2
Murphy, E. E. Sheina, B. E. Gnade, M. C. Biewer and M. C. Stefan, J
Mater Chem, 2013, 1, 15535.
29 M. Z. Svensson, F.; Veenstra, S. C.; Verhees, W. J. H.; and J. C. K.
Hummelen, J. M.; Inganas, O.; Andersson, M. R, Adv. Mater, 2003,
15, 988.
References
30 C.-Y. Mei, L. Liang, F.-G. Zhao, J.-T. Wang, L.-F. Yu, Y.-X. Li and W.-S.
1
L. Lu, T. Zheng, Q. Wu, A. M. Schneider, D. Zhao and L. Yu, Chem
Rev, 2015, 115, 12666.
Z. Wu, C. Sun, S. Dong, X. F. Jiang, S. Wu, H. Wu, H. L. Yip, F. Huang
and Y. Cao, J Am Chem Soc, 2016, 138, 2004.
Y. Liu, J. Zhao, Z. Li, C. Mu, W. Ma, H. Hu, K. Jiang, H. Lin, H. Ade
and H. Yan, Nat Commun, 2014, 5, 5293.
S. H. Liao, H. J. Jhuo, P. N. Yeh, Y. S. Cheng, Y. L. Li, Y. H. Lee, S.
Sharma and S. A. Chen, Sci Rep, 2014, 4, 6813.
A. R. b. M. Yusoff, D. Kim, H. P. Kim, F. K. Shneider, W. J. da Silva
and J. Jang, Energy Environ. Sci., 2015, 8, 303.
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.
V. Vohra, K. Kawashima, T. Kakara, T. Koganezawa, I. Osaka, K.
Takimiya and H. Murata, Nature Photonics, 2015, 9, 403.
M. Lenes, G.-J. A. H. Wetzelaer, F. B. Kooistra, S. C. Veenstra,
J. C. Hummelen and P. W. M. Blom, Adv Mater., 2008, 20,2116
M. C. Scharber, D. Mühlbacher, M. Koppe, P. Denk, C. Waldauf, A. J.
Heeger and C. J. Brabec, Adv Mater, 2006, 18, 789-794.
0 Q. Liu, X. Bao, Y. Yan, Z. Du, V. A. L. Roy, D. Zhu, M. Sun, C. S. Lee
and R. Yang, J Mater Sci, 2014, 50, 2263.
1 V. Tamilavan, J. Lee, R. Agneeswari, D. Y. Lee, S. Cho, Y. Jin, S. H.
Li, Macromolecules, 2013, 46, 7920.
31 L. Huo and J. Hou, Polym. Chem, 2011, 2, 2453.
2
3
2 J. Yuan, Y. Zou, R. Cui, Y.-H. Chao, Z. Wang, M. Ma, Y. He, Y. Li, A.
Rindgen, W. Ma, D. Xiao, Z. Bo, X. Xu, L. Li and C.-S. Hsu,
3
Macromolecules, 2015, 48, 4347.
33 J. Yuan, H. Dong, M. Li, X. Huang, J. Zhong, Y. Li and W. Ma, Adv
4
Mater, 2014, 26, 3624.
3
2
3
4 J. Wolf, F. Cruciani, A. El Labban and P. M. Beaujuge, Chem Mater,
015, 27, 4184.
5 Y. Zhang, S. K. Hau, H.-L. Yip, Y. Sun, O. Acton and A. K. Y. Jen,
5
6
Chem Mater, 2010, 22, 2696.
6 A. N. Y.Zou , P. Berrouard , and B. B. R. d. A. c. S. Beaupré, Y.
Tao , M. Leclerc , J. Am. Chem. Soc. , 2010, 132, 5330.
7 E. T. Hoke, K. Vandewal, J. A. Bartelt, W. R. Mateker, J. D. Douglas,
3
7
3
8
R. Noriega, K. R. Graham, J. M. J. Fréchet, A. Salleo and M. D.
McGehee, Adv. Energy Mater., 2013, 3, 220-230.
9
38 S. C. Price, A. C. Stuart, L. Yang, H. Zhou and W. You, J. Am. Chem.
Soc. 2011, 133, 8057.
1
39 L. Huo, X. Guo, S. Zhang, Y. Li and J. Hou, Macromolecules, 2011,
44, 4035.
1
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
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ARTICLE
Journal Name
40 Z. G. Zhang, J. Min, S. Zhang, J. Zhang, M. Zhang and Y. Li, Chem
View Article Online
Commun (Camb), 2011, 47, 9474.
DOI: 10.1039/C6RA07951B
4
2
4
1
4
1 M. Zhang, X. Guo, W. Ma, H. Ade and J. Hou, Adv Mater, 2015,
7, 4655.
2 C. A. R. Frank A. Arroyave, and John R. Reynolds, Ogr Lett, 2012,
4, 6138.
3 Y.-J. Cheng, J.-S. Wu, P.-I. Shih, C.-Y. Chang, P.-C. Jwo, W.-S. Kao
and C.-S. Hsu, Chem Mater, 2011, 23, 2361.
4 Q. Liu, X. Bao, S. Wen, Z. Du, L. Han, D. Zhu, Y. Chen, M. Sun and
R. Yang, Polym. Chem, 2014, 5, 2076.
5 W. Nie, C. M. Macneill, Y. Li, R. E. Noftle, D. L. Carroll and R. C.
Coffin, Macromol Rapid Commun, 2011, 32, 1163.
6 M.-H. P. Jianhui Hou, Shaoqing Zhang, Yan Yao, Li-Min Chen, Juo-
Hao Li, and and Y. Yang, Macromolecules, 2008, 41, 6012.
7. C. Duan, A. Furlan, J. J. van Franeker, R. E. Willems, M. M. Wienk
and R. A. Janssen, Adv Mater, 2015, 27,4461.
4
4
4
4
48. Y. F. Li, Y. P. Zou, Adv. Mater. 2008, 20, 2952
4
9. L. J. Huo, S. Q. Zhang, X. Guo, F. Xu, Y. F. Li, J. H. Hou,
Angew. Chem., Int. Ed. 2011, 50, 9697
8
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DOI: 10.1039/C6RA07951B
Novel Wide Band Gap Polymers Based on Dithienobenzoxadiazole for Polymer
Solar Cells with High Open Circuit Voltages over 1V
a,b
b
a
b
a
a
Dakang Ding, † Jiuxing Wang, † Weiye Chen, Meng Qiu, Junzhen Ren, Huilin Zheng,
b
a
b
Deyu Liu, Mingliang Sun,* and Renqiang Yang*
Just by replacing sulfur with oxygen atom, the Voc of PBDT-fDTBO based PSCs is 0.2 V higher
than PBDT-fDTBT based devices.