Thieno[3,4-c]pyrrole-4,6-dione-3,4-difluorothiophene Polymer Acceptors for Efficient All-Polymer Bulk Heterojunction Solar Cells

Article abstract of DOI:10.1002/anie.201604307

Branched-alkyl-substituted poly(thieno[3,4-c]pyrrole-4,6-dione-alt-3,4-difluorothiophene) (PTPD[2F]T) can be used as a polymer acceptor in bulk heterojunction (BHJ) solar cells with a low-band-gap polymer donor (PCE10) commonly used with fullerenes. The “all-polymer” BHJ devices made with PTPD[2F]T achieve efficiencies of up to 4.4 %. While, to date, most efficient polymer acceptors are based on perylenediimide or naphthalenediimide motifs, our study of PTPD[2F]T polymers shows that linear, all-thiophene systems with adequately substituted main chains can also be conducive to efficient BHJ solar cells with polymer donors.

Full text of DOI:10.1002/anie.201604307

Angewandte
Communications
Chemie
International Edition: DOI: 10.1002/anie.201604307
German Edition: DOI: 10.1002/ange.201604307
Solar Cells
Thieno[3,4-c]pyrrole-4,6-dione-3,4-Difluorothiophene Polymer
Acceptors for Efficient All-Polymer Bulk Heterojunction Solar Cells
+
+
Shengjian Liu , Zhipeng Kan , Simil Thomas, Federico Cruciani, Jean-Luc Brꢀdas, and
Pierre M. Beaujuge*
Abstract: Branched-alkyl-substituted poly(thieno[3,4-c]pyr-
role-4,6-dione-alt-3,4-difluorothiophene) (PTPD[2F]T) can
be used as a polymer acceptor in bulk heterojunction (BHJ)
solar cells with a low-band-gap polymer donor (PCE10)
commonly used with fullerenes. The “all-polymer” BHJ
devices made with PTPD[2F]T achieve efficiencies of up to
gradually improving device performance beyond currently
reported PCEs.
Nonfullerene acceptors, including polymers, have impor-
tant practical implications which span synthetic accessibility
and potentially low synthetic costs compared to those
incurred by the synthesis and extensive purifications of
[
2,12]
4
.4%. While, to date, most efficient polymer acceptors are
fullerene analogues.
In this contribution, we report on
based on perylenediimide or naphthalenediimide motifs, our
study of PTPD[2F]T polymers shows that linear, all-thiophene
systems with adequately substituted main chains can also be
conducive to efficient BHJ solar cells with polymer donors.
a set of branched-alkyl-substituted polymer acceptors com-
[13]
posed of thieno[3,4-c]pyrrole-4,6-dione (TPD)
and 3,4-
motifs, and show that the
appropriately functionalized all-thiophene analogue poly-
thieno[3,4-c]pyrrole-4,6-dione-alt-3,4-difluorothiophene),
[14]
difluorothiophene ([2F]T)
(
“
A
ll-polymer” bulk heterojunction (BHJ) solar cells, con-
namely PTPD[2F]T (Figure 1a), can achieve PCEs of up to
4.4% in BHJ solar cells with PCE10 (poly[4,8-bis(5-(2-
ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b’]dithiophene-2,6-
diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-
carboxylate-2–6-diyl)], also commonly referred to as PTB7-
Th) as the polymer donor (model system; Figure 1b). The
sisting of a p-conjugated polymer donor intimately mixed
with a polymer acceptor, which is used as an alternative to
fullerenes (e.g. PC BM, or its C analogue), have initially
6
1
71
[1]
met with limited power conversion efficiencies (PCEs). In
these systems, concurrently achieving the appropriate phase-
separated pattern and adequate charge transfer between
donor and acceptor components can be challenging and, to
date, only a few polymer acceptors have been shown to yield
BHJ device PCEs greater than 3%. In comparison, BHJ
solar cells composed of polymer donors and fullerenes can
achieve PCEs of greater than 11%, although the lack of
morphological stability and mechanical conformability of
fullerene-based BHJ solar cells remains a matter of exami-
donor (Eopt ꢀ 1.6 eV) and acceptor (E ꢀ 1.9 eV) counter-
opt
parts possess complementary absorption across the UV-vis
spectrum (l = 300–800 nm), and yield high short-circuit
[2]
ꢁ2
current densities (J ) of about 8.4 mAcm and some of
SC
the best open-circuit voltage (VOC) figures (ca. 1.1 V)
reported to date for BHJ solar cells. Considering the high
synthetic modularity of thiophene, adequately substituted all-
thiophene polymer acceptors pave the way to a broader class
of systems with tunable electronic and optical spectra for
efficient all-polymer BHJ solar cells.
[
3]
[
4]
nation. At this time, most efficient polymer acceptors are
based on perylenediimide (PDI) or naphthalenediimide
[
5]
[
4,6]
(
NDI) motifs,
and a few recent studies have shown that
The PTPD[2F]T polymers with various branched-alkyl
side chains shown in Figure 1a [2-decyltetradecyl (2DT), 2-
octyldodecyl (2OD), 2-hexyldecyl (2HD)] were synthesized
by microwave-assisted Stille cross-coupling polymerization
(see synthetic methods in the Supporting Information) to
control polymer growth and molecular weight (MW), while
minimizing reaction times. Side-chain effects have been
shown to correlate with material performance in BHJ solar
PDI/NDI-based analogues can achieve PCEs greater than
[4–6]
5
% with selected polymer donors.
A number of promising
alternative acceptor motifs have been proposed, such as
diketopyrrolopyrrole, benzothiadiazole, isoindigo,
bridged thienylthiazole,
motifs,
the manifold of polymer acceptors which are rivaling
fullerenes in BHJ solar cells remains modest, and broadening
the class of polymer acceptors for further examination of the
all-polymer BHJ concept is a critically important step in
[
7]
[8]
[9]
!
N
B
[
10]
and various nitrile-derived
with reported PCEs in range of 1–5%. However,
[1,11]
[
13c]
cells with several polymer donors,
be accounted for in polymer acceptor designs.
PTPD[2F]T analogues were purified by established proto-
and those effects should
[
6b,15]
The
[
13c]
cols:
using the strongly complexing ligand N,N-diethyl-2-
phenyldiazenecarbothioamide to remove palladium residues,
and subjecting the polymers to Soxhlet extractions (methanol,
dichloromethane) to remove short-chain oligomers, thus
affording batches of comparable number-average MW
[
+]
[+]
[
*] Dr. S. Liu, Dr. Z. Kan, Dr. S. Thomas, F. Cruciani, Prof. J.-L. Brꢀdas,
Prof. P. M. Beaujuge
Physical Science and Engineering Division, Solar & Photovoltaics
Engineering Research Center (SPERC), King Abdullah University of
Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia)
(16.2–18.6 kDa) and polydispersity indexes (PDI = 1.8–2.0;
E-mail: pierre.beaujuge@kaust.edu.sa
see Table S1 in the Supporting Information). MWeffects have
been shown to impact charge transport and polymer effi-
ciency in BHJ solar cells. Here, we note that a total of six
batches of the PTPD[2F]T(2HD) were prepared to demon-
+
[
] These authors contributed equally to this work.
[
16]
Supporting information for this article can be found under:
http://dx.doi.org/10.1002/anie.201604307.
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1
These are not the final page numbers!

Angewandte
Communications
Chemie
ure S4, the potential-energy-surface (PES) plots obtained by
incremental rotation of the [2F]T unit relative to the TPD
motif shows two minima, corresponding to the 408 and fully
planar anti/1808 conformations, respectively (for details see
the Supporting Information). In PTPD[2F]T, anti conforma-
tions are predicted to be significantly more stable (by
ꢁ1
ꢁ1
2
.0 kcalmol ), and energetic barriers of about 3.8 kcalmol
are expected to impede interconversion between syn and anti
conformers at room temperature (thermal energy at 300 K =
ꢁ1
0
.6 kcalmol ). Figure 1c depicts the time-dependent (TD)
DFT tuned-wB97XD natural transition orbitals with the
largest contribution to the S –S transition for a TPD[2F]T
0
1
nonamer, and p-electron delocalization occurs over approx-
imately four repeat units (see the Supporting Information).
The normalized thin-film UV-vis absorption spectra of the
PTPD[2F]T polymers and that of the polymer donor PCE10
(model system later used in the BHJ solar cell device study)
are superimposed in Figure 1d, and temperature-dependent
solution UV-vis spectra are provided in Figures S7 and S8.
Figure 1d indicates that the PTPD[2F]T polymers with
various branched side chains have near-identical absorption
spectra across the range l = 350–650 nm (peaking at ca. l =
5
50 nm) and equivalent optical band gaps (Eopt ꢀ 1.9 eV). The
DFT-simulated optical spectrum for the TPD[2F]T nonamer
peaks at l = 554 nm. In comparison, the thin-film absorption
spectrum of PCE10 extends into the range l = 425–800 nm,
thus showing significant spectral complementarity between
l = 620 and 800 nm (a critically important aspect in the
optimization of BHJ solar cell efficiency). The ionization
potentials (IPs) of the PTPD[2F]T polymers were determined
to be greater than 5.8 eV by photoelectron spectroscopy in air
(
PESA; vs. ꢀ 5.0 eV for PCE10; see Figure S9 and Table S3).
Expectedly, the large IP values are comparable to those
commonly inferred for fullerene acceptors ( ꢀ 5.9 eV for
PC BM by PESA). Figure S10 shows the oxidation and
7
1
reduction scans from which the electrochemically-estimated
IPs and electron affinities (EAs) were inferred: about 6.3 eV
(
vs. ꢀ 5.7 eV for PCE10) and 3.8 eV (vs. ꢀ 3.5 eV for PCE10),
respectively (see Table S4). EA values are 0.2–0.3 eV lower
than those of common fullerene acceptors such as PC BM
6
1
Figure 1. Chemical structures of a) PTPD[2F]T with various branched
substituents (2DT, 2OD, 2HD) and b) PCE10 (model system). c) Rep-
resentations of the TD-DFT tuned-wB97X-D natural transition orbitals
with the largest contribution to the S –S transition for a TPD[2F]T
nonamer (bottom: hole wavefunction; top: electron wavefunction).
d) Superimposed thin-film UV-vis optical absorption spectra of PTPD-
and PC BM (4.1–4.3 eV), and also lower than those of PDI/
71
[4–6]
NDI-based polymer acceptors.
From these estimates, we
note that the lower EAvalues should be amenable to high VOC
in BHJ solar cells.
0
1
Thin-film BHJ solar cells with the inverted device
architecture
ITO/ZnO/PCE10:PTPD[2F]T/MoO /Ag
[2F]T and the polymer donor PCE10 (normalized). The dotted curve
3
2
depicts the tuned-wB97XD simulated (Gaussian-broadened) optical
spectrum of a TPD[2F]T nonamer.
(device area: 0.1 cm ) were fabricated and tested under
ꢁ
2
AM1.5G solar illumination (100 mWcm ). The cells with
optimized PCE10:PTPD[2F]T blend ratios (1:2, wt/wt) were
cast from hot 1,2-dichlorobenzene (DCB; ca. 1158C) on
substrates preheated to about 1258C (see the Supporting
Information; film thicknesses in the range 80–90 nm). As
shown in Figure 2a and Table 1, optimized BHJ devices made
with PCE10 and the PTPD[2F]T polymers with various
appended substituents (2DT, 2OD and 2HD) achieved very
distinct efficiency patterns. The device statistics, including
standard deviations, are provided in Figure S11 and Table S5.
While optimized BHJ devices made with the most soluble
derivative PTPD[2F]T(2DT) reach only modest JSC and fill-
strate batch-to-batch repeatability (see Table S1) and consis-
tency across our device analyses.
Considerations for backbone conformation, p-electron
delocalization, and spectral absorption are of particular
importance in the design of efficient polymers for BHJ solar
[
2a]
cells. Density functional theory (DFT) modeling is a useful
tool in probing those effects and anticipating possible steric
hindrance as substituted thiophene motifs—here TPD and
[17]
[
2F]T—are combined within the same backbone. In Fig-
2
www.angewandte.org
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
These are not the final page numbers!

Angewandte
Communications
Chemie
The large differences in JSC values achieved in BHJ solar
cells with the various branched-alkyl-substituted PTPD[2F]T
polymer acceptors (Table 1) are reflected in the J-V curves
provided in Figure 2a, and consistent with the external
quantum efficiency (EQE) spectra shown in Figure 2b (ꢂ
ꢁ
2
0
.5 mAcm ; ꢂ 5%). PTPD[2F]T(2HD)-based BHJ devices
have the most prominent spectral response in the l = 350–
50 nm range, thus showing EQE values reaching about 50%
7
at l = 550 nm (abs. max. of PTPD[2F]T; EQE > 40% in the
range l = 475–625 nm). In comparison, PTPD[2F]T(2DT)-
based devices afford less than 15% EQE across the visible
spectrum, thus confirming the critical effect of the side-chain
pattern on material and BHJ solar cell performance.
To examine the potential contributions of morphological
effects to the distinct EQE and device efficiency character-
istics obtained for the various branched-alkyl-substituted
PTPD[2F]T polymer acceptors, we turned to an examination
of the aggregation patterns of the polymers by atomic-force
microscopy (AFM; see details and notes on TEM analyses in
the Supporting Information). The AFM topography and
phase images provided in Figure 3 shows various extents of
Figure 2. a) Characteristic J-V curves and b) EQE spectra of optimized
BHJ solar cells fabricated with the polymer donor PCE10 (model
system) and the PTPD[2F]T polymer acceptors. AM1.5G solar illumina-
ꢁ
2
tion (100 mWcm ).
Table 1: PV Performance of the PTPD[2F]T derivatives in inverted BHJ
[
a,b]
devices with PCE10.
Polymer
acceptor
Jsc
VOC
[V]
FF
[%]
Avg. PCE
[%]
Max. PCE
[%]
ꢁ2
[mAcm
]
2
2
2
DT
OD
HD
2.1
6.5
8.4
0.8
1.0
1.1
29.9 0.5
36.9 2.4
44.4 4.1
0.7
2.9
4.4
[a] Average values across more than 10 devices. [b] Device statistics in
Figure S11.
ꢁ2
factor (FF) values of about 2.1 mAcm and 29.9%, respec-
tively, the less bulky branched analogue PTPD[2F]T(2OD)
ꢁ2
yields a substantially higher JSC value of about 6.5 mAcm ,
and concurrently improved FF (36.9%) and VOC (ca. 1.0 V).
Overall, PTPD[2F]T(2OD)-based devices achieve about
a fivefold PCE improvement, reaching up to 2.9% (avg.
2
.4%) following the same film-casting conditions. It is
Figure 3. AFM topography (a–c) and phase (d–f) images (tapping
mode) for optimized BHJ active layers composed of PCE10 and the
PTPD[2F]T polymer acceptors (a,d: 2HD, b,e: 2OD, and c,f: 2DT).
Root mean square (RMS) roughness: 2HD, 8.2 nm; 2OD, 2.5 nm;
interesting to note that, in spite of their rigid-planar backbone
conformations (discussed in earlier sections, and depicted in
Figure 1c), PTPD[2F]T polymers show adequate solubility in
2DT, 0.6 nm.
common organic solvents [CHCl , chlorobenzene (CB), 1,2-
3
dichlorobenzene (DCB)]. Turning to the shorter-chain deriv-
ative PTPD[2F]T(2HD), optimized BHJ devices show further
improved figures of merit, combining a high J value of
aggregation and indicate that the PTPD[2F]T polymers with
distinct substituents do not form identical active-layer mor-
phologies with PCE10. In particular, the coarser aggregation
pattern observed for PTPD[2F]T(2HD) (RMS roughness:
8.2 nm) contrasts with that for PTPD[2F]T(2DT) (RMS
roughness: 0.6 nm), and may correlate with a more pro-
nounced, favorable degree of phase separation between
polymer donor and acceptor (a detailed morphology study
is beyond the scope of this concise report). Preliminary X-ray
analyses suggest that aggregates formed in the BHJ thin films
are disordered (see Figure S14).
SC
ꢁ
2
about 8.4 mAcm , a slightly larger V value (ca. 1.1 V), and
OC
a significantly increased FF nearing 44.4%. As a result,
PTPD[2F]T(2HD)-based devices outperform their counter-
parts made with PTPD[2F]T(2OD) and PTPD[2F]T(2DT),
thus achieving up to 4.4% (avg. 4.1%) in a stark sevenfold
PCE improvement over devices made with the longer-chain
analogue PTPD[2F]T(2DT). The VOC of 1.1 V, consistent with
the reduced EAs estimated for PTPD[2F]T, compared to
PCBM (see Table S4), represents one of the highest reported
[
18]
to date for BHJ solar cells with fullerene and nonfullerene
[
4–6]
[19]
acceptors.
.5 eV (with Eloss = Eopt ꢁeVOC, and Eopt the smallest band
gap of either donor and acceptor) is one of the lowest
In parallel, the photon energy loss (Eloss) of
Figure 4 and Table 2 summarize the results of our carrier
mobility examinations in optimized BHJ thin films (see
Figure S15), and indicate that hole (m ) and electron (m )
min
min
0
h
e
[
4–6]
reported values for all-polymer BHJ solar cells,
noting that
mobilities are the most balanced in PTPD[2F]T(2HD)-based
ꢁ
5
2
ꢁ1 ꢁ1
Eloss values of less than or equal to 0.5 eV are especially
BHJ devices, where m reaches 2.35 ꢀ 10 cm V
s
[vs.
e
[
19]
ꢁ8
2
ꢁ1 ꢁ1
difficult to achieve in fullerene-based BHJ devices.
3.16 ꢀ 10 cm V
s
for PTPD[2F]T(2DT)].
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
3
These are not the final page numbers!

Angewandte
Communications
Chemie
Keywords: density-functional calculations ·
electron microscopy · materials science · polymers · solar cells
[
1] J. J. M. Halls, C. A. Walsh, N. C. Greenham, E. A. Marseglia,
R. H. Friend, S. C. Moratti, A. B. Holmes, Nature 1995, 376,
4
98 – 500.
2] a) P. M. Beaujuge, J. M. J. Frꢁchet, J. Am. Chem. Soc. 2011, 133,
0009 – 20029; b) A. Facchetti, Mater. Today 2013, 16, 123 – 132;
c) H. Benten, D. Mori, H. Ohkita, S. Ito, J. Mater. Chem. A 2016,
, 5340 – 5365.
[
Figure 4. Dark current density-voltage characteristics for a) hole-only
ITO/MoO /PCE10:PTPD[2F]T/MoO /Ag) and b) electron-only (ITO/
Al/PCE10:PTPD[2F]T/Al) diodes made with optimized BHJ active
layers composed of PCE10 and the PTPD[2F]T polymer acceptors (2DT,
2
(
3
3
4
[
3] a) J. Zhao, Y. Li, G. Yang, K. Jiang, H. Lin, H. Ade, W. Ma, H.
Yan, Nat. Energy 2016, 1, 15027; b) Z. Wu, C. Sun, S. Dong, X.
Jiang, S. Wu, H. Wu, H. Yip, F. Huang, Y. Cao, J. Am. Chem. Soc.
2
OD, and 2HD).
2
016, 138, 2004 – 2013.
Table 2: Carrier mobility estimates obtained by space charge-limited
current (SCLC) analyses for optimized BHJ thin films with PTPD[2F]Tand
PCE10.
[
4] T. Kim, J.-H. Kim, T. E. Kang, C. Lee, H. Kang, M. Shin, C.
Wang, B. Ma, U. Jeong, T.-S. Kim, B. J. Kim, Nat. Commun. 2015,
6, 8547.
2
ꢁ1 ꢁ1
2
ꢁ1 ꢁ1
[5] a) E. Zhou, J. Cong, Q. Wei, K. Tajima, C. Yang, K. Hashimoto,
Polymer acceptor
m [cm V
h
s
]
m [cm V
s
]
mh/me
e
Angew. Chem. Int. Ed. 2011, 50, 2799 – 2803; Angew. Chem.
ꢁ
4
4
4
ꢁ8
ꢁ6
ꢁ5
2
2
2
DT
OD
HD
2.13ꢁ10
1.81ꢁ10
1.96ꢁ10
3.16ꢁ10
4.30ꢁ10
2.35ꢁ10
6740
42
8
2011, 123, 2851 – 2855; b) Y. Zhou et al., Adv. Mater. 2014, 26,
ꢁ
3767 – 3722; c) S. Li, H. Zhang, W. Zhao, L. Ye, H. Yao, B. Yang,
ꢁ
S. Zhang, J. Hou, Adv. Energy Mater. 2016, 6, 1501991.
6] a) Y.-J. Hwang, B. A. E. Courtright, A. S. Ferreira, S. H. Tolbert,
S. A. Jenekhe, Adv. Mater. 2015, 27, 4578 – 4584; b) J. W. Jung,
J. W. Jo, C.-C. Chueh, F. Liu, W. H. Jo, T. P. Russell, A. K. Y. Jen,
Adv. Mater. 2015, 27, 3310 – 3317; c) X. Zhan, Z. Tan, B.
Domercq, Z. An, X. Zhang, S. Barlow, Y. Li, D. Zhu, B.
Kippelen, S. R. Marder, J. Am. Chem. Soc. 2007, 129, 7246 –
[
In summary, we show that branched-alkyl-substituted
PTPD[2F]T polymers can be used as fullerene alternatives in
BHJ solar cells, thus achieving some of the best VOC figures
ca. 1.1 V) reported to date for BHJ devices, and PCEs of up
to 4.4% with the polymer donor PCE10 (as model system).
Our DFT analyses indicate that PTPD[2F]T backbones are
expected to be rigid-planar, with main-chain conformations
dominantly anti and well delocalized frontier orbitals. In
PTPD[2F]T-based BHJ active layers, we find that side-chain-
induced morphological effects translate into distinct charge-
transport patterns, with the shorter-chain derivative PTPD-
7247; d) C. Mu et al., Adv. Mater. 2014, 26, 7224 – 7230; e) L.
(
Gao, Z.-G. Zhang, L. Xue, J. Min, J. Zhang, Z. Wei, Y. Li, Adv.
Mater. 2016, 28, 1884 – 1890; f) L. Gao, Z.-G. Zhang, L. Xue, J.
Min, J. Zhang, Z. Wei, Y. Li, Adv. Mater. 2016, 28, 1884 – 1890.
7] W. Li, W. S. C. Roelofs, M. Turbiez, M. M. Wienk, R. A. J.
Janssen, Adv. Mater. 2014, 26, 3304 – 3309.
8] C. R. McNeill, A. Abrusci, J. Zaumseil, R. Wilson, M. J.
McKiernan, J. H. Burroughes, J. J. M. Halls, N. C. Greenham,
R. H. Friend, Appl. Phys. Lett. 2007, 90, 193506.
[
[
[
9] R. Stalder, J. Mei, J. Subbiah, C. Grand, L. A. Estrada, F. So, J. R.
Reynolds, Macromolecules 2011, 44, 6303 – 6310.
[
2F]T(2HD) concurrently yielding the most balanced carrier
mobilities and the best EQE response across the UV-visible
spectrum. While, at this time, most efficient polymer accept-
ors are based on PDI/NDI motifs, adequately substituted all-
thiophene polymer acceptors pave the way to a broader class
of systems with tunable electronic and optical spectra for
further examinations of the all-polymer BHJ concept. The
examination of other polymer donors will be of importance in
future work with PTPD[2F]T polymers.
[10] R. Zhao, C. Dou, Z. Xie, J. Liu, L. Wang, Angew. Chem. Int. Ed.
016, 55, 5313 – 5317; Angew. Chem. 2016, 128, 5399 – 5403.
2
[
11] T. W. Holcombe, C. H. Woo, D. F. J. Kavulak, B. C. Thompson,
J. M. J. Frꢁchet, J. Am. Chem. Soc. 2009, 131, 14160 – 14161.
12] C. B. Nielsen, S. Holliday, H.-Y. Chen, S. J. Cryer, I. McCulloch,
Acc. Chem. Res. 2015, 48, 2803 – 2812.
[
[13] a) A. Pron, P. Berrouard, M. Leclerc, Macromol. Chem. Phys.
2013, 214, 7 – 16; b) X. Guo, A. Facchetti, T. J. Marks, Chem. Rev.
2014, 114, 8943 – 9021; c) C. Cabanetos, A. El Labban, J. A.
Bartelt, J. D. Douglas, W. R. Mateker, J. M. J. Frechet, M. D.
McGehee, P. M. Beaujuge, J. Am. Chem. Soc. 2013, 135, 4656 –
4
659.
Acknowledgements
[
[
14] a) J. Wolf, F. Cruciani, A. El Labban, P. M. Beaujuge, Chem.
Mater. 2015, 27, 4184 – 4187; b) C. J. Mueller, C. R. Singh, M.
Fried, S. Huettner, M. Thelakkat, Adv. Funct. Mater. 2015, 25,
2725 – 2736.
15] C. Lee, H. Kang, W. Lee, T. Kim, K.-H. Kim, H. Y. Woo, C.
Wang, B. J. Kim, Adv. Mater. 2015, 27, 2466 – 2471.
The authors acknowledge financial support under Baseline
Research Funding from King Abdullah University of Science
and Technology (KAUST) and from ONR-Global (Award
N62909-15-1-2003 to JLB). The authors thank M. Neophytou
for some contributions in the early project developments, R.-
Z. Liang for the morphology characterizations by TEM, and
P. Wucher for the melting point examinations by DSC.
[
[
16] N. Zhou et al., J. Am. Chem. Soc. 2016, 138, 1240 – 1251.
17] a) M. J. Frisch, et al., Gaussian, Inc.: Wallingford, CT, USA,
2009; b) T. Stein, L. Kronik, R. Baer, J. Am. Chem. Soc. 2009,
131, 2818 – 2820; c) T. Kçrzdçrfer, J.-L. Brꢁdas, Acc. Chem. Res.
2014, 47, 3284 – 3291.
4
www.angewandte.org
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
These are not the final page numbers!

Angewandte
Communications
Chemie
[
18] S.-H. Liao, H.-J. Jhuo, Y.-S. Cheng, S.-A. Chen, Adv. Mater. 2013,
12576 – 12579; c) K. Kawashima, Y. Tamai, H. Ohkita, I. Osaka,
25, 4766 – 4771; H.-J. Jhuo, Y.-S. Cheng, S.-A. Chen, Adv. Mater.
K. Takimiya, Nat. Commun. 2015, 6, 10085.
2013, 25, 4766 – 4771.
[
19] a) W. Li, K. H. Hendriks, A. Furlan, M. M. Wienk, R. A. J.
Janssen, J. Am. Chem. Soc. 2015, 137, 2231 – 2234; b) M. Wang,
H. Wang, T. Yokoyama, X. Liu, Y. Huang, Y. Zhang, T.-Q.
Nguyen, S. Aramaki, G. C. Bazan, J. Am. Chem. Soc. 2014, 136,
Received: May 3, 2016
Revised: July 22, 2016
Published online: && &&, &&&&
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
5
These are not the final page numbers!

Angewandte
Communications
Chemie
Communications
Solar Cells
S. Liu, Z. Kan, S. Thomas, F. Cruciani,
J.-L. Brꢁdas,
P. M. Beaujuge*
&&&& — &&&&
Thieno[3,4-c]pyrrole-4,6-dione-3,4-
Difluorothiophene Polymer Acceptors for
Efficient All-Polymer Bulk Heterojunction
Solar Cells
Better performance through polymers:
Branched-alkyl-substituted poly(thieno-
[3,4-c]pyrrole-4,6-dione-alt-3,4-difluoro-
thiophenes) (PTPD[2F]T) can be used as
polymer acceptors in bulk heterojunction
date for BHJ devices, and power conver-
sion efficiencies of up to 4.4%, with
a low-band-gap polymer donor (PCE10)
commonly used with fullerenes. 2DT=2-
decyltetradecyl, 2OD=2-octyldodecyl,
2HD=2-hexyldecyl.
(
BHJ) solar cells, achieving some of the
best VOC figures (ca. 1.1 V) reported to
6
www.angewandte.org
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
These are not the final page numbers!