Multichromophore Donor Materials Derived from Diketopyrrolopyrrole and Phenoxazine: Design, Synthesis, and Photovoltaic Performance

Article abstract of DOI:10.1002/ejoc.201700845

Herein two conjugated donor molecules, TDPP-POCN and FDPP-POCN, with planar diketopyrrolopyrrole (DPP) as the core building-block acceptor unit and phenoxazine-capped acrylonitriles as arms are designed and synthesized. Solution-processed bulk-heterojunction organic solar cells based on blends of the small-molecule donors and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) exhibit promising photovoltaic device performance with a maximum power conversion efficiency up to 4.8 % for TDPP-POCN and 3.4 % for FDPP-POCN under the illumination of AM1.5G, 100 mW cm^–2. To the best of our knowledge, this is the highest efficiency reported so far in DPP–phenoxazine-based systems and among acrylonitrile-bridged donor-π-acceptor-π-donor-structured small-molecule donors for solution-processed small-molecule-based organic solar cells.

Full text of DOI:10.1002/ejoc.201700845

A Journal of
Accepted Article
Title: Multichromophore Donor Materials Derived from
Diketopyrrolopyrrole and Phenoxazine: Design, Synthesis and
Photovoltaic Performance
Authors: Narayanaswamy K, Yadagiri B, Anirban Bagui, Vinay Gupta,
and Surya Prakash Singh
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201700845
Link to VoR: http://dx.doi.org/10.1002/ejoc.201700845
Supported by

10.1002/ejoc.201700845
European Journal of Organic Chemistry
DOI: 10.1002/ ((please add manuscript number))
Article type: Full Paper
Multichromophore Donor Materials Derived from Diketopyrrolopyrrole
and Phenoxazine: Design, Synthesis and Photovoltaic Performance
K. Narayanaswamy,[a, b] B. Yadagiri,[a, b] Anirban Bagui,[a] Vinay Gupta,[c] Surya Prakash
Singh[a, b]
*
[a] K. Narayanaswamy, B. Yadagiri, Dr. Anirban Bagui, Dr. Surya Prakash Singh
Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology
(IICT), Uppal road, Tarnaka, Hyderabad, 500007, India
[b] K. Narayanaswamy, B. Yadagiri, Dr. Surya Prakash Singh
Academy of Scientific and Innovative Research (AcSIR), New Delhi, 110 025, India
[c] Dr. Vinay Gupta
CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi, 110012, India
E-mail: spsingh@iict.res.in
Abstract: Herein two conjugated donor molecules TDPP-POCN and FDPP-POCN
employing planar diketopyrrolopyrrole (DPP) as the core building block acceptor unit and
phenoxazine capped acrylonitrile as arms are designed and synthesized. Solution processed
bulk-heterojunction organic solar cells based on blends of the small molecule donors and
[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) exhibit promising photovoltaic device
performance with a maximum power conversion efficiency up to 4.8 % for TDPP-POCN
and 3.4 % for FDPP-POCN under the illumination of AM 1.5G, 100 mW∙cm-2. To the best
of our knowledge this is the highest efficiency reported so far in the DPP-Phenoxazine based
systems and among acrylonitrile bridged D-π-A-π-D structured small molecule donors for
solution processed small molecule based OSCs.
Introduction
The organic photovoltaic (OPV) technology has gained immense attention over past two
decades because of their assured advantages of low manufacturing cost utilizing simple
printing techniques, solution processable materials, light weight solar modules, and flexible
large-area applications.[1-3] Bulk heterojunction (BHJ) OPVs using p-type semiconducting
polymers or, small molecules as electron donor and fullerene derivatives as electron acceptor
1
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
have achieved a power conversion efficiency (PCE) over 10%.[4-14] In recent years,
photosensitive conjugated small molecules have attracted profound interest of scientific
community working in the field of organic solar cells (OSCs) due to their various advantages
over polymeric counterparts including well-defined molecular structure, definite molecular
weight and high purity without batch-to-batch variation.[15-17] The soluble small molecular
donors have the potential to produce low-cost and large-scale OSCs.[3, 18] Therefore, it is
believed that small molecule based BHJ solar cells are promising to realize their commercial
application in the future.
Among those outstanding materials, diketopyrrolopyrrole (DPP) based molecules
have emerged as promising candidates for fabrication of high performance OSCs. DPP
moiety is being utilized as an useful building motifs for designing p-type, n-type and
ambipolar organic semiconductors through the energy level engineering.[19] Moreover, DPP-
based small molecular derivatives also have served as an electron acceptors instead of
conventional fullerene derivatives in BHJ OSCs and moderate PCEs have been achieved
from those cells.[20] The DPP-based conjugated polymers often exhibit broad optical
absorption covering a wavelength range from 300 to 1000 nm.[21-24] The OSCs constructed
from DPP-based polymer donors demonstrated high short-circuit current density (Jsc) and fill
factors (FF) due to good film-forming characteristics as well as smooth film morphology. In
addition, DPP-based small molecules have greater tendency to self-assemble into ordered
domains, which leads to high charge-carrier mobility and overall conductivity. At present,
PCEs of the DPP-containing small molecule donors have reached up to 8%.[25] The
phenoxazine (POZ), which possesses unique electronic and optical properties, is a well
conjugated nonplanar fused heterocyclic ring system in a butterfly conformation with
dihedral angles of ~169° and it is widely used as central as well as terminal electron donating
building block in the construction of dye sensitized solar cells, perovskite solar cells and
BHJ-OSCs.[26, 27]
The molecules with D-π-A-π-D type design template, which is a combination of
donor (D) and acceptor (A) moieties through the vinylic π –bridge, exhibit high mobility and
wide absorption with high value of molar extinction coefficient (ε) owing to the efficient
conjugation in the molecular backbone and intramolecular charge transfer (ICT) between
terminal donor units and central acceptor building block.[28] Moreover, using acrylonitrile as
the π- linkage group results in low-lying highest occupied molecular orbital (HOMO) level,
which in turn increases the open circuit voltage (Voc) of the OSCs. In 2012, Y. Wang et al.
2
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
reported two novel D-π-A-π-D structured small molecular donors comprising
benzothiadiazole and triphenylamine for solution-processed OSCs based on acrylonitrile
linkage, resulting an impressive Voc up to 1.04 V with a maximum PCE of 3.85%.[29] In 2014,
Y. Li et al. reported a series of DPP and triphenylamine based D-π-A-π-D type donor
materials by incorporating acrylonitrile group as one of the π-linkages. The molecules
exhibited deeply lying HOMO energy level and gave rise to a highest PCE of 2.92%.[30]
Introduction of alkyl chains on π-conjugated backbone affects solubility of the molecule and
controls crystallization, molecular self-organization and morphology of blend film.[31-34]
Figure 1. Chemical structure of the TDPP-POCN and FDPP-POCN
In this communication, we report synthesis, characterization and photovoltaic
performance of two novel D-π-A-π-D structured conjugated small molecular donors, namely
TDPP-POCN and FDPP-POCN, employing TDPP and FDPP as the core building block
units and phenoxazine capped acrylonitrile as arms (Figure 1). The DPP, which has been
already established as one of the most efficient electron accepting moiety used in low band
gap materials, is chosen here as central core.[35] The aim of introducing long alkyl chains is to
improve the solubility of the targeted molecules in the organic solvents. We have focused our
studies on molecular engineering targeting highly efficient OPV devices. The strategies that
have been followed include designing of conjugated backbone and replacement of furan by
thiophene to control the energy levels and optical properties of resultant molecules.
3
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
Scheme 1. Synthetic routes to prepare TDPP-POCN and FDPP-POCN.
Results and discussion
Synthesis
The synthetic routes of the targeted molecules, viz. TDPP-POCN and FDPP-POCN, are
shown in Scheme 1. The important intermediates 3 and 4 were obtained by Knoevenagel
condensation and Suzuki Miyaura borylation reactions. The DPP-based intermediate
4
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
moieties, compound 7a and 7b, were synthesized by modifying the reported procedure[36] in
three steps starting from commercially available 2-thiophene carbonitrile and 2-furonitrile.
The targeted molecules were then synthesized by the Pd(PPh3)4-assisted Suzuki cross
coupling reaction in high yields. Purification was done by conventional silica gel column
chromatography and finally washed with methanol and acetonitrile, which offered the final
products with high purity. Compound TDPP-POCN and FDPP-POCN showed good
solubility in chloroform as 19 mg/mL and 16 mg/mL respectively. The detailed synthesis and
characterization data are provided in the experimental section and electronic supporting
information (ESI).
Absorption spectra
The normalized optical absorption spectra of TDPP-POCN and FDPP-POCN in solution
and thin-film form are presented in Figure 2. The important optical parameters are tabulated
in Table 1. In diluted chloroform solution, both molecules exhibit a broad absorption
covering entire UV and visible region ranging from 300 to 700 nm of wavelengths owing to
ICT transition. TDPP-POCN shows stronger absorption in solution than FDPP-POCN
almost throughout the wavelength range of interest (Figure S1). However, FDPP-POCN has
a highest ε value of 75485 M-1∙cm-1 at 632 nm; whereas TDPP-POCN shows highest ε of
66127 M-1∙cm-1 at 593 and 625 nm with comparatively broader absorption band. In
comparison with their absorption spectra in solution, the absorption spectra for both TDPP-
POCN and FDPP-POCN in thin films were obvious red-shifted due to a strong π-π
intermolecular stacking in the solid state. The thin film absorption spectra have respective
absorption onsets at 741 and 736 nm, which correspond to the optical band gap (Egopt) of 1.67
and 1.68 eV, respectively. Moreover, broader light harvesting capacity of TDPP-POCN in
solution as well as on thin film compared to that of FDPP-POCN is expected to improve
exciton generation efficiency, which in turn will lead to higher Jsc, and better photovoltaic
performance in BHJ OSC devices made with the former candidate.
5
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
1.0
0.8
0.6
0.4
0.2
0.0
Solution
Film
TDPP-POCN
Solution
Film
FDPP-POCN
1.0
0.8
0.6
0.4
0.2
0.0
400
500
600
700
800
900
Wavelength (nm)
Figure 2. Normalised UV-vis absorption spectra of TDPP-POCN and FDPP-POCN in
solution and on film.
Redox Properties
The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were
used to investigate the redox properties of TDPP-POCN and FDPP-POCN. The cyclic-
voltammograms of these compounds are demonstrated in Figure 3. The molecules exhibited
a reversible oxidation wave. The HOMO levels of these compounds are estimated from the
onset oxidation potentials, assuming 4.8 eV below the vacuum level is the energy level of
Fc/Fc+. The LUMO energy levels of these small molecules are calculated from the equation,
ELUMO = EHOMO-Eo-o, where E0-0 is derived from absorption onset and the corresponding data
are compiled in Table 1. The estimated HOMO and LUMO energy levels are −5.06 and
−3.23 eV for TDPP-POCN and −5.05 and −3.19 eV for FDPP-POCN, respectively. These
values are in well synchronization with the frontier molecular orbital energy levels of
promising fullerene acceptor PC71BM (HOMO = −6.1 eV, LUMO = −3.9 eV) to construct
BHJ OSCs. Also, the energy difference between the LUMO levels of our newly invented
donor materials and PC71BM are large enough for exciton dissociation and charge separation
at the donor - acceptor interface.15, 17
6
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
CV
DPV
2.50µ
0.00
-2.50µ
TDPP-POCN
-5.00µ
10.0µ
CV
DPV
0.0
-10.0µ
-20.0µ
FDPP-POCN
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
Potential (V) vs. Fc/Fc+
Figure 3. Cyclic voltammogram of TDPP-POCN and FDPP-POCN in 0.1 M
NBu4ClO4/CH2Cl2 solution under N2 at a scan rate of 100 mV∙s-1.
a
b
Table 1. Optoelectronic properties in thin film and solution, Redox properties of TDPP-
POCN and FDPP-POCN.
SMDs
aUv-vis solution
aUv-vis thin film
bRedox properties
λmax
(nm)
ε
λonset Egap
(nm) (eV)
λmax
(nm)
λonset Egap
(nm) (eV) (V)
Eox
E0-0
(eV) (eV)
HOMO
LUMO
(eV)
(M-1cm-1)
625
632
66127
75485
675
664
1.83
1.86
685
670
741
736
1.67 0.26 1.83 -5.06
1.68 0.25 1.86 -5.05
-3.23
-3.19
TDPP-POCN
FDPP-POCN
a Calculated from the formula, Egopt = 1240/λonset
Photoluminescence
The photoluminescence (PL) quenching experiments were carried out in o-
dichlorobenzene with increasing concentration of PC71BM to examine the charge separation
process and photoinduced electron transfer between small molecule donors and PC71BM
acceptor. The PL spectra of pristine TDPP-POCN and FDPP-POCN showed strong
emission bands with emission maxima at 671 and 663 nm, respectively (Figure 4a and b).
The emission bands of both the small molecules quench gradually upon systematic addition
of PC71BM. Figure 4c and d show the Stern-Volmer plots of TDPP-POCN and FDPP-
POCN, respectively. The values of Stern-Volmer coefficient (Ksv) are estimated from the
7
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
slope of linear fits of ηo/η vs. quencher concentration plots following the equation ηo/η = 1 +
Ksvc, where ηo and η are the PL intensities without and with quencher, i.e. PC71BM in our
case and c is the quencher concentration. The Ksv values are found to be 3.13×105 and
2.17×105 M-1 for TDPP-POCN and FDPP-POCN, respectively. The high value of Ksv
indicates an efficient photoinduced charge transfer mechanism from the donor to acceptor,
which is an essential requirement for potential OPV devices.
(a)
(b)
1:0
1:0.5
1:1
1:2
1:3
TDPP-POCN
FDPP-POCN
1:0
1:0.5
1:1
1:2
1:3
2.0
1.5
1.0
0.5
0.0
2.0
1.5
1.0
0.5
0.0
1:4
1:4
550
600
650
700
750
800
850
550
600
650
700
750
800
850
Wavelength (nm)
Wavelength (nm)
(d)
(c)
Stern-Volmer plot for TDPP-POCN
Stern-Volmer plot for FDPP-POCN
4
3
2
1
3
2
1





Ksv = 3.13 x 105 M-1
Ksv = 2.17 x 105 M-1
0
2
4
6
8
10
0
2
4
6
8
10
Quencher concentration (x10-6 M)
Quencher concentration (x10-6 M)
Figure 4. The PL quenching spectra of (a) TDPP-POCN and (b) FDPP-POCN in o-DCB
solution with increasing concentration of PC71BM; the corresponding Stern-Volmer plots for
(c) TDPP-POCN and (d) FDPP-POCN.
Thermal properties
The thermal properties of the two small molecules were explored by the thermogravimetric
analysis (TGA) under nitrogen atmosphere and the plots are shown in Figure 5. Both the
o
compounds exhibit very high thermal stability up to 395 C. High thermal stability of
photoactive molecules is crucial to build durable solar cells for outdoor applications.
8
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
TDPP-POCN
FDPP-POCN
100
80
60
40
Thermo-Gravimetric Analysis
20
0
200
400
600
800
Temperature (oC)
Figure 5. The TGA analysis confirms the thermal stability of newly synthesized small
molecular donors.
Photovoltaic performance
The solution-processed BHJ OPV devices were fabricated using TDPP-POCN and FDPP-
POCN as donor materials adopting
a
conventional device structure of
ITO/MoOx/donors:PC71BM/Al. The detailed device fabrication process is described in the
experimental section. The characteristic current density-voltage (J-V) curves for the best
performing devices are shown in Figure 6 and all device parameters, viz. Voc, Jsc, FF and
PCE are summarized in Table 2. The active layers were spin-coated from chlorobenzene +
diiodooctane (3 vol%) co-solvent with varying donor-to-acceptor (D/A) weight ratio from 1:1
to 1:4. After a series of experiments, the optimal D/A weight ratio was found to be 1:3 for
both TDPP-POCN/FDPP-POCN:PC71BM. The device with 1:3 weight ratio of FDPP-
POCN to PC71BM provided a Voc of 0.79 V, Jsc of 6.89 mA∙cm-2 and FF of 0.51, resulting in
an estimated PCE of 3.4%. In contrast, the device based on TDPP-POCN and PC71BM with
the same weight ratio delivered a superior performance with a Voc of 0.79 V, higher Jsc of
10.25 mA∙cm-2 and FF of 0.59, yielding a PCE of 4.8%. With the increment of acceptor
content in the blend active layer from 1:1 to 1:3, the Jsc and FF values also increase, while
Voc remains nearly unchanged due to approximately same HOMO values of both TDPP-
POCN and FDPP-POCN. The higher PCE of TDPP-POCN as compared with FDPP-
POCN is due to higher Jsc and FF owing to broad light absorption coverage within the solar
spectrum and good charge transport properties.
9
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
(b)
(a)
0
0
TDPP-POCN:PC71BM
FDPP-POCN:PC71BM
1:1
1:2
1:3
1:4
1:1
1:2
1:3
1:4
-5
-5
-10
-10
0.0
0.2
0.4
Applied voltage (V)
0.6
0.8
0.0
0.2
0.4
0.6
0.8
Applied voltage (V)
Figure 6. The characteristic J-V curves of the BHJ solar cells made from (a) TDPP-
POCN:PC71BM and (b) FDPP-POCN:PC71BM blends with different D/A weight ratios.
Measurements were done under an irradiance of 100 mW∙cm-2 (AM 1.5G).
Table 2. Photovoltaic parameters of the organic solar cells fabricated with
SM donor
D:A
1:1
1:2
1:3
1:4
1:1
1:2
1:3
1:4
Voc (V) Jsc (mA∙cm-2)
FF
PCE (%) (Av.)
3.1 (2.8)b
3.9 (3.6)b
4.8 (4.6)a
4.3 (4.1)a
2.5 (2.1)b
2.9 (2.6)b
3.4 (3.2)a
3.0 (2.8)b
0.802
0.797
0.796
0.791
0.799
0.796
0.796
0.791
8.22
9.10
10.25
9.80
6.89
7.67
8.37
8.20
0.48
0.54
0.59
0.55
0.45
0.47
0.51
0.46
TDPP-POCN
FDPP-POCN
a = 50 devices, b = 20 devices
External quantum efficiency
The external quantum efficiency (EQE) spectra of the best performing devices fabricated
from the blend films of TDPP-POCN/FDPP-POCN and PC71BM in 1:3 ratio are shown in
Figure 7. The EQE curve of TDPP-POCN: PC71BM exhibits efficient conversion efficiency
in the range of 300-800 nm, with the highest EQE value reaching 45.4% at 702 nm. The
highest obtained EQE value of the FDPP-POCN based device is comparatively low (36% at
672 nm), which possibly resulted in a lower Jsc value for the FDPP-POCN:PC71BM based
devices. These results are in agreement with their UV absorption and prove that the
incorporation of the thiophene unit as π-conjugation instead of furan could indeed improve
10
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
the PCEs considerably and broaden the spectral response range. The values of Jsc calculated
by integrating the EQE spectra of TDPP-POCN and FDPP-POCN based devices are in
good agreement (~2-3% error) with the Jsc values recorded during light J-V measurements.
50
40
30
20
TDPP-POCN:PC71BM
10
FDPP-POCN:PC71BM
0
300
400
500
600
700
800
Wavelength (nm)
Figure 7. The external quantum efficiency profile of champion solar cells from each category
of devices fabricated from blended films of TDPP-POCN/FDPP-POCN and PC71BM in
optimized 1:3 ratio.
Atomic force microscopy
In order to understand the effects of surface topology on photovoltaic performance of the
devices, we have conducted a morphology study of the photoactive layer using atomic force
microscopy (AFM). The topological images of both TDPP-POCN:PC71BM and FDPP-
POCN:PC71BM blend films captured on a scanning area of 10 µm × 10 µm are shown in
Figure 8. The TDPP-POCN:PC71BM blend film shows a very smooth surface (Figure 8 a,c)
with RMS roughness of only 2.4 ± 0.3 nm, whereas the FDPP-POCN:PC71BM based bulk
composite films show comparatively rough surface with RMS roughness value of 3.1 ± 0.4
nm. A smooth morphology is known to promote charge transport and collection in the
devices, which has been reflected in the photovoltaic performance of TDPP-POCN:PC71BM
based BHJ OSC devices.
11
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
Figure 8. The 3-dimentional view of surface topology for (a) TDPP-POCN:PC71BM and (b)
FDPP-POCN:PC71BM blend films as obtained from AFM measurements. The
corresponding 2-D representation of (c) TDPP-POCN:PC71BM and (d) FDPP-
POCN:PC71BM bulk-composite films.
Conclusion
In summary, we have designed and synthesized two D-π-A-π-D structured conjugated small
molecule donor materials, namely TDPP-POCN and FDPP-POCN, employing TDPP and
FDPP as the core building block units, respectively and phenoxazine capped acrylonitrile as
arm for solution processed BHJ-OSCs. Their unique characteristics, such as suitable energy
o
levels, strong optical absorption in the visible region and good thermal stability up to 395 C
prompted us to use them as electron donors blending with PC71BM in BHJ OSCs. A high
PCE of 4.8 % for TDPP-POCN and 3.4 % for FDPP-POCN was achieved from optimum
donor to acceptor weight ratio of 1:3. The high value of Stern-Volmer co-efficient indicates
efficient charge transfer from donor to acceptor. The blend films also showed very smooth
surface morphology. Therefore, these results clearly demonstrated that acrylonitrile bridged
phenoxazine in combination with DPP is a promising small molecule electron donor for
photovoltaic application. This work also reveals that the incorporation of the thiophene unit
as π-conjugation instead of furan on the DPP core and utilization of cyano group as a π bridge
in the D-π-A-π-D type small molecules can strongly improve the photovoltaic performance.
We predict that further optimization of morphology on an active layer and modification of an
electrode will greatly improve the performance of devices.
12
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
Experimental Section
Methods and Materials
All reagents from commercial sources were used without further purification, unless
otherwise noted. Tetrahydrofuran (THF) and 1, 4- dioxane were purchased from Alfa Aeser,
dried over sodium/benzophenone, distilled under vacuum and stored over 4 Å molecular
sieves. Chloroform and dichloroethane (DCE), were dried over calcium hydride, distilled
under nitrogen atmosphere and stored over molecular sieves (4 Å). N, N-dimethylformamide
(DMF) was dried and purified using standard techniques. Reactions were carried out under
nitrogen atmosphere; Glass TLC plate Silica gel 60G F254 from merck millipore was used to
monitor the reaction. Compounds were detected by UV irradiation, staining with I2 and/or
13
KMnO4.1H and C nuclear magnetic resonance (NMR) spectroscopy spectra were recorded
on a Bruker Avance-500 and 400 MHz spectrometer at 25 oC unless otherwise noted. 1H and
13C NMR spectra are referenced to SiMe4 using the residual solvent peak impurity of the
solvent CDCl3. UV-Vis absorption spectra was recorded on a Shimadzu UV-1800 PC dual
beam spectrometer at room temperature unless otherwise noted. All solution UV-vis
experiments were run in CHCl3. Films was prepared by spin coating CHCl3 solution onto
glass substrates. Cyclic voltammetry was performed on a CHI instrument with a three
electrode system consisting of Ag/AgCl reference electrode, a working electrode, and a
platinum wire counter-electrode. The redox potentials of the dyes were measured in
dichloromethane containing 0.1 M Bu4NClO4 at a scan rate of 100 mV s−1.
Fabrication of devices
Both the compounds were dissolved in chlorobenzene along with PC71BM to form the
blend with different donor-to-acceptor weight ratio. To improve the solubility of these
molecules, 1, 8-diiodooctane (DIO) was also added in 3 vol%. The ITO coated glass
substrates were first patterned by photolithography and then cleaned in water, acetone and
isopropyl alcohol in sequential order for 15 min each under ultrasonication. ITO glasses were
then exposed to UV-ozone irradiation for about 15 min. First a thin layer (about 10 nm) of
MoOx was thermally evaporated in a vacuum chamber at a base pressure of 10−7 torr. The
photoactive layers were then spin-coated from the as-prepared solutions at 1500 rpm in glove
box. Finally, 100 nm thick cathode layer of aluminum (Al) was thermally evaporated. The
fabricated solar cells were encapsulated using epoxy and cover glasses to protect from
13
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
degradation. The device structure and energy band diagram are shown in Figure 9a and b,
respectively.
(b)
-2.30
(a)
-3.23 -3.19
-3.90
-4.20
Al
-4.8
ITO
-5.06
-5.05
-5.30
-6.10
Figure 9. The cross-sectional view of the device and the related energy level diagram.
Characterization of devices
The light J-V characteristics of the solar cells were measured using a Keithley 236 source
meter unit. The solar simulator with an AM 1.5G filter was used as light source. The 1 sun
intensity (100 mW∙cm-2) of simulated irradiance was calibrated by an NREL certified silicon
based reference cell. During the electrical characterization, an aperture of 10 mm2 area was
used to accurately define photoactive area of the solar cells. The EQE was measured using a
PV measurement, Inc. system after monochromatic power calibration using reference Si-
diode.
Synthesis
All reactants and reagents are commercially available and used as received, unless otherwise
noted. The intermediates 10-(2-ethylhexyl)-10H-phenoxazine (1), 10-(2-ethylhexyl)-10H-
phenoxazine-3-carbaldehyde (2), 3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-
dione (5a) and 3,6-di(furan-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (5b) were prepared
by methods similar to those reported in the literature.[37-39]
10-(2-ethylhexyl)-10H-phenoxazine-3-carbaldehyde (2): Dry phosphorus oxychloride
(1.89 mL, 20.28 mmol) was added dropwise very slowly to the dry N, N- dimethylformamide
o
(DMF) (1.2 mL, 15.23 mmol) at 0 C in a 100 mL two neck round bottom flask under
nitrogen atmosphere with stirring. After formation of white crystals, 10-(2-ethylhexyl)-10H-
phenoxazine (1.5 g, 5.07 mmol) in 30 mL of dry 1, 2-dichloroethane (DCE) was added drop
wise to the reaction mixture over 1 h. Then reaction mixture was heated to reflux for 24 h.
After cooling to room temperature, the reaction mixture was added drop wise into dilute
sodium hydroxide aqueous solution and extracted with ethylacetate (200 mL × 3). The
14
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
organic layer was dried with anhydrous Na2SO4 and then the solvent was removed in vacuo.
The residue was purified by silica gel column chromatography using and ethylacetate and
hexane as the eluent gave 2 as yellow liquid. Yield (1.4g, 87%).1H NMR (500.1 MHz,
CDCl3): δ 9.66 (s, 1 H), 7.29 (d, J = 6.5 Hz, 1 H), 7.08 (d, J = 1.6 Hz, 1 H), 6.80 (t, J = 7.3
Hz, 1 H), 6.73 (t, J = 7.4 Hz, 1H), 6.66 (m, 1 H), 6.58 (t, J = 6.7 Hz, 2 H), 3.48 (d, J = 7.5
Hz, 2H), 1.94 – 1.84 (m, 1 H), 1.44 – 1.28 (m, 8 H), 0.94 (t, J = 7.4 Hz, 3H), 0.88 (t, J = 7.0
13
Hz, 3H). C (75.4 MHz, CDCl3): δ 189.5, 145.1, 144.7, 140.1, 132.0, 129.7, 128.3, 123.6,
122.5, 115.8, 114.3, 112.7, 111.2, 47.7, 36.6, 30.6, 28.7, 24.0, 23.0, 13.9, 10.9.
(Z)-2-(4-bromophenyl)-3-(10-(2-ethylhexyl)-10H-phenoxazin-3-yl) acrylonitrile (3): To a
100 mL single neck round bottom flask capped with a rubber septum, compound 2 (1.15 g,
3.555 mmol), 4-bromophenyl acetonitrile (1.39 g, 7.112 mmol) were dissolved in 5:1 ratio of
THF and EtOH. Then aqueous solution of NaOH (7.112 mmol) was added dropwise into the
flask. The resulting mixture was stirred for 12 h at 70oC. After cool down to room
temparature the solvents were removed under reduced pressure extracted with ethylacetate,
washed with NH4Cl (aq) and finally purified by silica gel column chromatograph with n-
hexane/EtOAc to provide 3 as a red orange sticky solid. Yield (1.2 g, 78%). 1H NMR (400.1
MHz, CDCl3): δ 7.54 (d, J = 8.6 Hz, 2 H), 7.48 (d, J = 8.8 Hz, 2 H), 7.33 (d d, J = 2.0 Hz,
2.0, 1 H), 7.23 (s, 1H), 7.27 (s, 1H), 6.82 – 6.77 (m, 1H), 6.73 – 6.44 (m, 2H), 6.58 – 6.52 (m,
2H), 3.46 (d, J = 7.4 Hz, 2H), 1.92 – 1.84 (m, 1H),1.51 – 1.27 (m, 8H), 0.96 – 0.86 (m, 6H).
13C (125.7 MHz, CDCl3): δ 144.7, 141.1, 136.8, 133.9, 132.3, 132.0, 130.5, 127.0, 126.8,
126.0,123.5, 122.4, 122.0, 188.3, 115.7, 115.2, 112.4, 111.5, 105.7, 47.6, 36.6, 30.6, 28.7,
24.0, 23.0, 14.0, 10.9. HRMS (ESI) m/z [M+H+] calcd for C29H29BrN2O 501.1463, found
501.1529 and 503.1508 in 1:1 ratio.
(Z)-3-(10-(2-ethylhexyl)-10H-phenoxazin-3-yl)-2-(4-(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)phenyl)acrylonitrile (4): A dry flask (50 mL) was charged with
compound 3 (1.46 g, 2.911 mmol), bis(pinacolato) diboron (1.109 g, 4.367 mmol), potassium
acetate (0.852 g, 8.733 mmol) and 1,4-dioxane (40 mL) in inert nitrogen condition. Then the
reaction mixture was degassed for 15 minutes with nitrogen gas, followed by the addition 10
mol% of Pd (PPh3)4-catalyst and reflux it for 24 h at 100 oC. After completion of the reaction,
the organic solvents were removed under reduced pressure, workup by using
dichloromethane. The combined organic layer was washed with brine and dried over
anhydrous sodium sulphate. The residue was purified by column chromatography using
15
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
petroleum ether and dichloromethane (1:4) are elutes to afford product 4 orange sticky solid
1
yield 1.40 g (88%) H NMR (500.1 MHz, CDCl3): δ 7.84 (d, J = 7.8 Hz, 2H), 7.62 (d, J =
7.6 Hz, 2H), 7.35 (d, J = 6.5 Hz, 1H), 7.31 (s, 1H), 7.28 (d, J = 1.9 Hz, 1H), 6.81 – 6.77 (t,
1H), 6.72 – 6.64 (m, 2H), 6.58 – 6.52 (m, 2H), 3.46 (d, J = 7.4 Hz, 2H), 1.93 – 1.85 (m,1H),
3
1.41 – 1.30 (m, 20H), 0.94 (t, J = 7.4 Hz, 3H), 0.89 (t, J = 7.1 Hz, 3H). 1 C NMR (100.6
MHz, CDCl3): δ 144.7, 141.3, 137.4, 135.3, 128.1, 126.8, 124.7, 123.5, 121.9, 118.5, 115.7,
115.3, 112.4, 112.3 111.5, 111.3, 106.9, 84.0, 83.9, 47.6, 36.7, 30.6, 29.6, 28.7, 24.8, 24.1,
23.0, 14.0, 10.9. HRMS (ESI) m/z [M+H+] calcd for C35H41BN2O3 549.3210, found
549.3295.
2,5-bis(2-ethylhexyl)-3,6-di(thien-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (6a): In a
250 mL of round bottom flask was charged with 5a (10 g, 15.0 mmol), potassium carbonate
(14.6 g, 45.0 mmol), 18-crown-6 (0.264 g, 1.0 mmol) and dry DMF (300 mL). The reaction
contents were stirred at 120 °C for 3 h before 2-ethylhexyl bromide (7.24 g, 37.5 mmol) was
added to the mixture. After the reaction mixture was heated at 130 °C for 20 h, it was filtered
through celite into a 500 mL round-bottom flask to remove salt by products and washed with
chloroform. The solvent was removed from the crude product under reduced pressure. The
crude material was purified by silica gel column chromatography with CHCl3 and hexane to
1
yield 1.24 g of 6a as a dark red-purple tacky solid (16 % yield). H NMR (500.1 MHz,
CDCl3): δ 8.89 (d d, J = 3.8 Hz, 2H), 7.63 (d, J = 4.8 Hz 2H), 7.27 (t, J = 3.9 Hz, 2H), 4.07 –
3.98 (m, 4H), 1.90-1.82 (m, 2H), 1.41-1.20 (m, 16H), 0.90 - 0.83 (m, 12H). 13C NMR (125.7
MHz, CDCl3): δ 161.5, 140.2, 135.1, 130.4, 129.7, 128.2, 107.7, 45.7, 38.9, 30.1, 28.2, 23.4,
22.9, 13.9, 10.3.
2,5-bis(2-ethylhexyl)-3,6-di(furan-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (6b): In a
250 mL of round bottom flask was charged with 5b (5 g, 18.6 mmol), potassium carbonate
(7.7 g, 55.9 mmol) 18-crown-6 (0.132 g, 0.5 mmol) and dry DMF (150 mL). The reaction
contents were stirred at 120 °C for 3 h before 2-ethylhexyl bromide (10.7 g, 55.9 mmol) was
added to the mixture. After the reaction mixture was heated at 130 °C for 20 h, it was filtered
through celite into a 500 mL round-bottom flask to remove salt by products and washed with
chloroform. The solvent was removed from the crude product under reduced pressure. The
crude material was purified by silica gel column chromatography with CHCl3 and hexane to
1
yield 2.12 g of 6b as a dark red-purple tacky solid (25.8% yield). H NMR (500.1 MHz,
CDCl3): δ 8.33 (d d, J = 4.1 Hz, 2 H), 7.61 (d, J = 1.0 Hz, 2 H), 6.69 (d d, J = 1.7 Hz, 1.9 Hz,
16
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
2 H), 4.04 - 4.01 (m, 4 H), 1.78 – 1.71 (m, 2 H), 1.39 – 1.25 (m, 16 H), 0.93 – 0.85 (m, 12 H).
13C (100.6 MHz, CDCl3): δ 161.2, 144.8, 144.6, 133.8, 120.1, 113.4, 106.4, 46.1, 39.9, 30.5,
28.6, 23.8, 23.0, 14.0, 10.7.
3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-
dione (7a):In a 100 mL two neck round bottom flask covered with aluminium foil,
compound 6a (1.5 g 2.8 mmol) was dissolved in dry 50 mL of CHCl3, the flask was cooled to
0oC under nitrogen atmosphere. Then, N-bromo succinimide (NBS) (1.1 g 6.2 mmol) was
added portion - wise and the reaction was monitored using TLC. After complete consumption
of starting material, the reaction was quenched with H2O and the organic phases were
extracted with CHCl3, dried over Na2SO4 and concentrated under reduced pressure. The
crude product was precipitated in methanol then sonicated for 15 minutes and filtered,
washed with methanol to remove the impurities dried under vacuum yields the product 7a as
a purple solid (1.3g, 66.6 %).1H NMR (500.1 MHz, CDCl3): δ 8.64 (d, J = 4.2 Hz, 2 H),
7.22 (d, J = 4.1 Hz, 2 H), 3.98 - 3.88 (m, 4 H), 1.88 – 1.78 (m, 2 H), 1.40 – 1.19 (m, 16 H),
0.91 – 0.85 (m, 12 H). 13C (100.6 MHz, CDCl3): δ 161.3, 139.3, 135.3, 131.4, 131.1, 118.9,
107.9, 45.9, 39.0, 30.1, 28.2, 23.5, 23.0, 13.9, 10.4.
3,6-bis(5-bromofuran-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione
(7b): In a 100 mL two neck round bottom flask covered with aluminium foil, compound 6b
o
(1.0 g 2.02 mmol) was dissolved in dry 50 mL of CHCl3, the flask was cooled to 0 C under
nitrogen atmosphere. Then, N-bromo succinimide (NBS) (0.78 g 4.4mmol) was added
portion-wise, the reaction was monitored using TLC. After complete consumption of starting
material, the reaction was quenched with H2O and the organic phases were extracted with
CHCl3, dried over Na2SO4 and concentrated under reduced pressure. The purification was
carried out by flash column chromatography on silica gel as the stationary phase with a
mixture of petroleum ether/CHCl3 as a mobile phase afforded the product 7b as a red solid
(1.1g, 83.3 %). 1H NMR (300.1 MHz, CDCl3): δ 8.31 (d, J = 3.7 Hz, 2 H), 6.33 (d, J = 3.7
Hz, 2 H), 3.99, (d, J = 7.5 Hz, 4 H), 1.81 – 1.67 (m, 2 H), 1.43 – 1.23 (m, 16 H), 0.97 – 0.84
(m, 12 H). 13C (100.6 MHz, CDCl3): δ 160.8, 146.1, 132.7, 126.2, 122.2, 115.4, 106.2, 46.2,
40.0, 30.4, 28.7, 23.7, 23.1, 14.0, 10.6.
(2Z,2'Z)-2,2'-((5,5'-(2,5-bis(2-ethylhexyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-
c]pyrrole-1,4-diyl)bis(thiophene-5,2-diyl))bis(4,1-phenylene))bis(3-(10-(2-ethylhexyl)-
17
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
10H-phenoxazin-3-yl)acrylonitrile) (TDPP-POCN): A dry flask (50 mL) was charged with
compound 7a (300 mg, 0.461 mmol), compound 4 (771mg, 1.406 mmol), 2M sodium
carbonate and THF (30 mL) in inert nitrogen condition. Then the reaction mixture was
degassed for 15 minutes with nitrogen gas, followed by the addition 10 mol% of Pd (PPh3)4
o
as a catalyst and refluxed for 24 h at 70 C. After completion of the reaction, the solvents
were removed by rotary evaporation and then organic phase was extracted by using
dichloromethane. The combined organic layer was washed with brine and dried over
anhydrous sodium sulphate and then the organic solvents were completely removed by rotary
evaporation. The residue was purified by column chromatography using petroleum ether and
dichloromethane (1:4) are elutes, to afford the product as blue colour solid yield 400mg
(67%). 1H NMR (400.1 MHz, CDCl3): δ 9.00 (d, J = 4.1 Hz, 2H), 7.65 (d, J = 8.5 Hz, 4H),
7.61 (d, J = 8.5 Hz, 4H), 7.47 (d, J = 3.9 Hz, 2H), 7.31 (dd, J = 1.9 Hz, J = 1.9 Hz, 2H), 7.27
(s, 2H, merged in CDCl3), 7.23 (s, 2H), 6.78 (t, J = 7.4 Hz, 2H), 6.70 (t, J = 6.8 Hz, 4H), 6.67
– 6.63 (m, 2H), 6.52 (t, J = 8.8 Hz, 4H), 4.12 – 4.01 (m, 4H), 3.42 (d, J = 7.4 Hz, 4H), 1.99
– 1.91 (m, 2H), 1.89 – 1.83 (m, 2H), 1.46 – 1.27 (m, 32H), 0.94 (t, J = 7.3 Hz, 12H), 0.90 (t,
13
J = 5.3 Hz, 12H), . C (125.7 MHz, CDCl3): δ 161.5, 148.4, 144.7, 144.6, 140.6, 139.5,
136.9, 136.7, 135.1, 132.9, 132.3, 129.1, 127.1, 126.2, 126.1, 126.0, 124.7, 123.5, 122.0,
118.4, 115.7, 115.1, 112.4, 111.5, 108.3, 105.8, 47.6, 46.0, 39.3, 36.7, 30.7, 30.3, 29.6, 28.7,
28.5, 24.1, 23.6, 23.0, 14.1, 14.0, 10.9, 10.6. HRMS: calcd.for C88H96N6O4S2, [M+H]+ m/z
1365.70072; found: 1365.69420. FT-IR (KBr, cm-1): 2955, 2924, 2856, 2206, 1659, 1629,
1600, 1550, 1489, 1434, 1380, 1283, 1235, 1136, 899, 808, 734.
(2Z,2'Z)-2,2'-((5,5'-(2,5-bis(2-ethylhexyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-
c]pyrrole-1,4-diyl)bis(furan-5,2-diyl))bis(4,1-phenylene))bis(3-(10-(2-ethylhexyl)-10H-
phenoxazin-3-yl)acrylonitrile) (FDPP-POCN): A dry flask (50 mL) was charged with
compound 7b (300mg, 0.461 mmol), compound 4 (809.57mg, 1.475 mmol), 2M sodium
carbonate and THF (30 mL) in inert nitrogen condition. Then the reaction mixture was
degassed for 15 minutes with nitrogen gas, followed by the addition of 10 mol% Pd (PPh3)4
o
catalyst then reflux the reaction mixture for 24 h at 70 C. After completion of the reaction,
the solvents were removed by rotary evaporation and then organic phase was extracted by
using dichloromethane. The combined organic layer was washed with brine and dried over
anhydrous sodium sulphate and then the organic solvents were completely removed by rotary
evaporation. The residue was purified by column chromatography using petroleum ether and
dichloromethane (1:4) are elutes, to afford product as blue colour solid yield 400mg (65%).
18
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
1H NMR (500.1 MHz, CDCl3): δ 8.47 (d, J = 3.8 Hz, 2H), 7.69 (d, J = 8.5 Hz, 4H), 7.62 (d,
J = 8.6 Hz, 4H), 7.29 (d, J = 1.9 Hz, 2H) 7.27 (s, 2H, merged in CDCl3), 7.21 (s, 2H), 6.97
(d, J = 3.8 Hz, 2H), 6.77 (t, J = 6.4 Hz, 2H), 6.69 (t, J = 7.9 Hz, 2H), 6.64 (dd, 2H), 6.53-6.46
(m, 4H), 4.11 (d, J = 7.6 Hz, 4H), 3.40 (d, J = 7.3 Hz, 4H), 1.95 – 1.83 (m, 4H), 1.48 – 1.27
(m, 32H), 0.95 – 0.88 (m, 18H), 0.84 (t, J = 6.8 Hz, 6H). 13C (125.7 MHz, CDCl3): δ 160.9,
155.8, 144.6, 144.6, 144.3, 140.4, 136.7, 135.0, 132.6, 132.2, 128.8, 127.3, 126.0, 125.8,
124.7, 123.5, 122.8, 122.0, 118.3, 115.7, 115.0, 112.4, 111.5, 109.8, 107.1, 105.6, 47.6, 46.7,
39.3, 36.7, 30.7, 30.3, 29.6, 28.7, 28.5, 24.1, 23.6, 23.2, 23.0, 14.0, 10.9, 10.5. HRMS:
calcd.for C88H96N6O6, [M+H]+ m/z 1333.74641; found: 1333.74139. FT-IR (KBr, cm-1):
2956, 2919, 2850, 2207, 1656, 1563, 1490, 1382, 1282, 1029, 830, 736.
Acknowledgements
We gratefully acknowledge DST-UK (APEX-Phase-II) for financial support. KN and BY
would like to thank University Grants Commission (UGC), Government of India for
providing the junior and senior research fellowship. AB is thankful to Department of Science
& Technology, Government of India for his National Postdoctoral Fellowship with number
PDF/2016/001853.
Keywords – Small molecule donor, diketopyrrolopyrrole, phenoxazine end cap, solution
processed, organic photovoltaics
References
[1]
[2]
[3]
[4]
S. Günes, H. Neugebauer, N. S. Sariciftci, Chem. Rev. 2007, 107, 1324-1338.
R. F. Service, Science 2011, 332, 293-293.
B. Walker, C. Kim, T.-Q. Nguyen, Chem. Mater. 2011, 23, 470-482.
B. Kan, Q. Zhang, M. Li, X. Wan, W. Ni, G. Long, Y. Wang, X. Yang, H. Feng, Y.
Chen, J. Am. Chem. Soc. 2014, 136, 15529-15532.
[5] Y. Liu, J. Zhao, Z. Li, C. Mu, W. Ma, H. Hu, K. Jiang, H. Lin, H. Ade, H. Yan, Nat.
Commun. 2014, 5, 5293.
[6]
J.-D. Chen, C. Cui, Y.-Q. Li, L. Zhou, Q.-D. Ou, C. Li, Y. Li, J.-X. Tang, Adv. Mater.
2015, 27, 1035-1041.
[7]
C. Cui, X. Guo, J. Min, B. Guo, X. Cheng, M. Zhang, C. J. Brabec, Y. Li, Adv. Mater.
2015, 27, 7469-7475.
[8]
Z. He, B. Xiao, F. Liu, H. Wu, Y. Yang, S. Xiao, C. Wang, T. P. Russell, Y. Cao, Nat.
Photon. 2015, 9, 174-179.
[9]
B. Kan, M. Li, Q. Zhang, F. Liu, X. Wan, Y. Wang, W. Ni, G. Long, X. Yang, H.
Feng, Y. Zuo, M. Zhang, F. Huang, Y. Cao, T. P. Russell, Y. Chen, J. Am. Chem. Soc. 2015,
137, 3886-3893.
[10] L. Nian, W. Zhang, N. Zhu, L. Liu, Z. Xie, H. Wu, F. Würthner, Y. Ma, J. Am. Chem.
Soc. 2015, 137, 6995-6998.
19
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
[11] V. Vohra, K. Kawashima, T. Kakara, T. Koganezawa, I. Osaka, K. Takimiya, H.
Murata, Nat. Photon. 2015, 9, 403-408.
[12] J. Zhang, Y. Zhang, J. Fang, K. Lu, Z. Wang, W. Ma, Z. Wei, J. Am. Chem. Soc.
2015, 137, 8176-8183.
[13] T. Liu, L. Huo, X. Sun, B. Fan, Y. Cai, T. Kim, J. Y. Kim, H. Choi, Y. Sun, Adv.
Energy. Mater. 2016, 6, 1502109-n/a.
[14] H. Hu, K. Jiang, G. Yang, J. Liu, Z. Li, H. Lin, Y. Liu, J. Zhao, J. Zhang, F. Huang,
Y. Qu, W. Ma, H. Yan, J. Am. Chem. Soc. 2015, 137, 14149-14157.
[15] Y. Lin, Y. Li, X. Zhan, Chem. Soc. Rev. 2012, 41, 4245-4272.
[16] A. Mishra, P. Bäuerle, Angew. Chem., Int. Ed. 2012, 51, 2020-2067.
[17] Y. Li, R. G. Clevenger, L. Jin, K. V. Kilway, Z. Peng, J. Mater. Chem. C 2014, 2,
7180-7183.
[18] G. Long, X. Wan, P. Yun, J. Zhou, Y. Liu, M. Li, M. Zhang, Y. Chen, Chin. J. Chem.
2013, 31, 1391-1396.
[19] A. Tang, C. Zhan, J. Yao, E. Zhou, Adv. Mater. 2017, 29, 1600013-n/a.
[20] J. W. Jung, W. H. Jo, Chem. Mater. 2015, 27, 6038-6043.
[21] E. Zhou, S. Yamakawa, K. Tajima, C. Yang, K. Hashimoto, Chem. Mater. 2009, 21,
4055-4061.
[22] E. Zhou, Q. Wei, S. Yamakawa, Y. Zhang, K. Tajima, C. Yang, K. Hashimoto,
Macromolecules 2010, 43, 821-826.
[23] E. Zhou, J. Cong, K. Hashimoto, K. Tajima, Energy Environ. Sci. 2012, 5, 9756-9759.
[24] W. Li, K. H. Hendriks, M. M. Wienk, R. A. J. Janssen, Acc. Chem. Res. 2016, 49, 78-
85.
[25] K. Gao, L. Li, T. Lai, L. Xiao, Y. Huang, F. Huang, J. Peng, Y. Cao, F. Liu, T. P.
Russell, R. A. J. Janssen, X. Peng, J. Am. Chem. Soc. 2015, 137, 7282-7285.
[26] H. Tian, X. Yang, J. Cong, R. Chen, J. Liu, Y. Hao, A. Hagfeldt, L. Sun, Chem.
Commun. 2009, 6288-6290.
[27] M. Cheng, C. Chen, X. Yang, J. Huang, F. Zhang, B. Xu, L. Sun, Chem. Mater. 2015,
27, 1808-1814.
[28] K. Narayanaswamy, A. Venkateswararao, V. Gupta, S. Chand, S. P. Singh, Chem.
Commun. 2016, 52, 210-213.
[29] S. Zeng, L. Yin, C. Ji, X. Jiang, K. Li, Y. Li, Y. Wang, Chem. Commun. 2012, 48,
10627-10629.
[30] C. Ji, L. Yin, L. Wang, T. Jia, S. Meng, Y. Sun, Y. Li, J. Mater. Chem. C 2014, 2,
4019-4026.
[31] Y. Liu, X. Wan, F. Wang, J. Zhou, G. Long, J. Tian, J. You, Y. Yang, Y. Chen, Adv.
Energy. Mater. 2011, 1, 771-775.
[32] T.-Y. Chu, J. Lu, S. Beaupré, Y. Zhang, J.-R. Pouliot, J. Zhou, A. Najari, M. Leclerc,
Y. Tao, Adv. Funct. Mater. 2012, 22, 2345-2351.
[33] J. Woong Jung, J. Woong Jo, F. Liu, T. P. Russell, W. Ho Jo, Chem. Commun. 2012,
48, 6933-6935.
[34] I. Osaka, T. Kakara, N. Takemura, T. Koganezawa, K. Takimiya, J. Am. Chem. Soc.
2013, 135, 8834-8837.
[35] S. Qu, H. Tian, Chem. Commun. 2012, 48, 3039-3051.
[36] A. T. Yiu, P. M. Beaujuge, O. P. Lee, C. H. Woo, M. F. Toney, J. M. J. Fréchet, J.
Am. Chem. Soc. 2012, 134, 2180-2185.
[37] M. Cheng, B. Xu, C. Chen, X. Yang, F. Zhang, Q. Tan, Y. Hua, L. Kloo, L. Sun, Adv.
Energy Mater. 2015, 5, 1401720.
20
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
[38] Z. Liu, E. Shi, Y. Wan, N. Li, D. Chen, Q. Xu, H. Li, J. Lu, K. Zhang, L. Wang, J.
Mater. Chem. C, 2015, 3, 2033–2039.
[39] A. T. Yiu, P. M. Beaujuge, O. P. Lee, C. H. Woo, M. F. Toney, J. M. J. Frechet, J. Am.
Chem.Soc. 2012, 134, 2180−2185.
21
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700845
European Journal of Organic Chemistry
TOC
Donor
Spacer
Acceptor
Spacer
Donor
-2.30
-3.23 -3.19
-3.90
-6.10
-4.20
Al
-4.8
ITO
-5.06
-5.30
-5.05
22
This article is protected by copyright. All rights reserved.