Highly efficient near-infrared and semitransparent polymer solar cells based on an ultra-narrow bandgap nonfullerene acceptor

Article abstract of DOI:10.1039/c8ta11484f

In this work, we design and synthesize an acceptor-donor-acceptor structured non-fullerene acceptor (ACS8) with an ultra-narrow bandgap (1.3 eV). It possesses a well-ordered molecular orientation and π-π stacking, and hence exhibits a high electron mobility of 2.65 × 10^-4 cm² V^-1 s^-1. Polymer solar cells (PSCs) based on PTB7-Th:ACS8 (1:2, w/w) processed using toluene and 0.5% PN (1-phenylnaphthalene) treatment exhibited an optimal power conversion efficiency (PCE) of 13.2% with an open circuit voltage (V_oc) of 0.75 V, a short-circuit current density (J_sc) of 25.3 mA cm^-2 and a fill factor (FF) of 69.3% under the illumination of AM 1.5G, 100 mW cm^-2. This PCE is among the highest values reported in the literature to date for PSCs based on ultra-narrow bandgap acceptors (Eoptg ≤ 1.3 eV). Furthermore, semitransparent devices based on PTB7-Th:ACS8 exhibit an outstanding PCE up to 11.1% with an average visible transmittance of 28.6%.

Full text of DOI:10.1039/c8ta11484f

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Zhu, X. Guo, Q. Fan, W. Ma and M. Zhang, J. Mater. Chem. A, 2019, DOI: 10.1039/C8TA11484F.
Volume
4
Number
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January 2016 Pages 1–330
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ISSN 2050-7488
PAPER
Kun Chang, Zhaorong Chang et al.
Bubble-template-assisted synthesis of hollow fullerene-like
MoS nanocages as a lithium ion battery anode material
2
rsc.li/materials-a

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DOI: 10.1039/C8TA11484F
High Efficient Near-infrared and Semitransparent Polymer Solar Cells Based on an
Ultra-Narrow Bandgap Nonfullerene Acceptor
‡a
‡a
b
a
a
b
Juan Chen, Guangda Li, Qinglian Zhu, Xia Guo,* Qunping Fan, Wei Ma, and Maojie
Zhang*a
a
State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials,
Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical
Engineering and Materials Science, Soochow University, Suzhou 215123, China
*
E-mail: mjzhang@suda.edu.cn; guoxia@suda.edu.cn
b
State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University,
Xi’an 710049, China
‡
These authors contributed equally to this work.
Abstract: In this work, we design and synthesize an acceptor-donor-acceptor structured
non-fullerene acceptor (ACS8) with an ultra-narrow bandgap (1.3 eV). It possesses well-
ordered molecular orientation and π-π stacking, and hence exhibits a high electron mobility of
-4
2
−1 −1
2
.65×10 cm V s . The polymer solar cells (PSCs) based on PTB7-Th:ACS8 (1:2, w/w)
processed by toluene with 0.5% PN (1-phenylnaphthalene) treatment exhibited an optimal
power conversion efficiency (PCE) of 13.2% with an open circuit voltage (Voc) of 0.75 V, a
-2
short-circuit current density (Jsc) of 25.3 mA cm and a fill factor (FF) of 69.3% under the
-2
illumination of AM 1.5G, 100 mW cm . This PCE is among the highest values reported in the
literatures to date for the PSCs based on ultra-narrow bandgap acceptors (E opt
g
≤ 1.3 eV).
Furthermore, semitransparent devices based on PTB7-Th:ACS8 exhibit an outstanding PCE
up to 11.1% with the average visible transmittance of 28.6%.
Keywords: non-fullerene acceptor; polymer solar cells; alkylthio substituents; PN additive.
1

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DOI: 10.1039/C8TA11484F
1
. Introduction
Polymer solar cells (PSCs) as a promising renewable energy technology have attracted
great attention due to their unique advantages, such as light weight, low cost, easy fabrication
and capability to be fabricated into large area and flexible devices through roll-to-roll
processing.1-5 In typical bulk heterojunction (BHJ) PSCs, the active layer is generally
comprised of a p-type conjugated polymer as the donor and a n-type organic semiconductor
(n-OS) as the acceptor. In comparison with the fullerenes, non-fullerene (NF) n-OS acceptors
have exhibited great potential for high efficient PSCs due to their distinguished advantages of
easily tunable optical absorption and electronic energy levels, low production cost and good
morphology stability.6-15 Therefore, the NF-PSCs have drawn considerable attention and
made great progress in recent years with the power conversion efficiencies (PCEs) up to 11-
1
4% for single-junction devices16-25 and 14-17% for tandem devices26-30
Among the NF n-OS acceptors, the fused-ring electron acceptors (FREAs) with an
acceptor-donor-acceptor (A-D-A) structure based on fused aromatic cores with strong
.
electron withdrawing groups31-40, such as ITIC, IDIC, IT-4F, ATT-1, NFBDT, have
31
32
33
38
40
become dominant in highly efficient PSCs. These acceptors exhibits a strong absorption in
the wavelength of 500-800 nm with the optical bandgap (E opt
) over 1.5 eV. When blended
g
with wide bandgap polymer donors with complementary absorption and matched energy
levels, the devices can sufficiently utilized the visible light and the best PCE over 14% have
been achieved.41-43 Considering the trade-off between the open circuit voltage (Voc) and the
bandgap, it is a great challenge to further improve the performance of single-junction devices
limited by the absorption in the near-infrared (NIR) region and unavoidable energy loss
(E
loss=E
g
opt-eVoc). However, the exploitation of ultra-narrow bandgap non-fullerene acceptor
opt
(
NFA, E
g
≤ 1.3 eV) with high Voc and external quantum efficiency (EQE) in NIR is rather
rare and has impeded the progress of the tandem devices.27,29 For example, although the
2

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representative ultra-narrow bandgap NFA, IEICO-4F, exhibited an ultra-narrow bandgap of
DOI: 10.1039/C8TA11484F
1
.24 eV, the device based on the blend of PTB7-Th and IEICO-4F only exhibited a medium
PCE of ~12%.44,45 In addition, as one of unique advantages of PSCs, semitransparent (ST)
devices have great potential for use in building integrated photovoltaics (BIPV) and power
generating windows.46-52 Recently, the ST-PSCs based on the NFAs have exhibited an
5
3
outstanding PCE of 10.2 % with an average visible transmittance (AVT) of 31%. However,
the lack of NIR acceptors also restrain to achieve high efficient and high transparent ST-PSCs.
Hence, to develop a new NIR NFA is an urgent issue for the PSCs application.
In this work, we designed and synthesized a small molecule acceptor ACS8 with
indacenodithiophene (IDT) as core, alkylthio-substituted thiophene as π-bridge and electron-
withdrawing 3-(1,1-dicyanomethylene)-5,6-difluoro-1-indanone (IC2F) as end groups (as
shown in Fig. 1a). ACS8 film shows a narrow-bandgap of 1.3 eV with strong absorption in
the region of 650-900 nm, and a redshift of 80 nm compared with that in solution. Moreover,
ACS8 film possesses well-ordered molecular orientation and π-π stacking, and hence
exhibited a high electron mobility of 2.65×10 cm V s−1. The PSCs based on PTB7-
-
4
2
−1
Th:ACS8 (1:2, w/w) with 0.5% PN (1-phenylnaphthalene) exhibited an optimal PCE of
-2
1
3.2% with a Voc of 0.75 V, a short-circuit current density (Jsc) of 25.3 mA cm and a fill
-
2
factor (FF) of 69.3% under the illumination of AM 1.5G, 100 mW cm . This PCE is the
highest value reported in the literatures to date for the PSCs based on NIR acceptors (E opt
g
≤
1
.3 eV). Furthermore, semitransparent devices based on PTB7-Th:ACS8 (1:2, w/w) exhibited
PCEs varying from 9.4% to 11.1% at different AVT (43.2-28.6%). These results indicate that
ACS8 is a very promising NIR acceptor material for semitransparent and tandem solar cells
applications.
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Fig. 1. (a) Molecular structures of ACS8, IEICO-4F and PTB7-Th, (b) UV-Vis absorption
spectra of ACS8 in CF solution and ACS8 and PTB7-Th in films, and (c) molecular energy
level diagrams of PTB7-Th and ACS8.
2
. Results and Discussion
The synthetic routes and molecular structure of ACS8 are shown in Scheme S1 and Fig.
a, respectively. The detailed synthesis and characterization data are provided in the
1
1
13
Supporting Information. ACS8 has been characterized by H NMR, C NMR and Matrix-
Assisted Laser Desorption/Ionization Time of Flight Spectrometry (MALDI-TOF MS). ACS8
shows good solubility in common organic solvents, such as chloroform (CF), chlorobenzene
(
CB) and toluene (TL) at room temperature. Moreover, ACS8 exhibits a decomposition
temperature (Td) of 334 °C at 5% weight loss as shown in the thermogravimetric analysis
TGA) plot in Fig. S1, which indicates that it has good thermal stability for application in
PSCs.
As shown in Fig. 1b, ACS8 in solution exhibits an absorption in the region of 600-850
(
4

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nm with the maximum absorption peak (λmax) at 751 nm. In the thin film, the absorption peak
DOI: 10.1039/C8TA11484F
redshifts ca. 80 nm compared with that in solution, which should be attributed to the strong
aggregation of molecule chain in the solid state. The E opt
g
of ACS8 estimated from the
absorption edge (λedge= 950 nm) of the thin film is 1.30 eV with an increase of 0.06 eV in
4
4
comparison with that of IEICO-4F (1.24 eV) . Furthermore, the electron mobility of ACS8
was evaluated by the space-charge-limited current method (Fig. S8) and a higher value of
-4
2
−1 −1
-4
2
−1 −1
2
.65×10 cm V s was achieved than that of IEICO-4F (1.14×10 cm V s ).
The electrochemical property of ACS8 was investigated by cyclic voltammetry (CV). As
shown in Fig. 1c and Fig. S2, the highest occupied molecular orbital (HOMO) and the lowest
unoccupied molecular orbital (LUMO) energy levels of ACS8 estimated from the onset
oxidation potential (φox) and reduction potential (φred) are -5.54 eV and -4.05 eV, respectively.
Hence, ACS8 exhibits a lower HOMO and a similar LUMO relative to IEICO-4F (HOMO= -
5
.46 eV; LUMO= -4.08 eV). Moreover, theoretical calculations are performed by using the
density functional theory (DFT) to investigate the influence of alkoxyl and alkylthiol on the
properties of the small molecule acceptors as show in Fig. S3. There are no obvious
differences for ACS8 and IEICO-4F in their optimized molecular conformations and the
electron distributions of the frontier molecular orbitals. In comparison with IEICO-4F, ACS8
shows a similar LUMO and a downshifted HOMO, which is consistent with the CV
measurement results.
To investigate the photovoltaic properties of ACS8, the PSCs with an inverted structure
of
ITO/ZnO/poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-
/Al were fabricated using TL as the host
dioctylfluorene)] (PFN)/PTB7-Th:ACS8/MoO
3
processing solvent. Firstly, the influence of D/A weight ratio of the blend active layer was
investigated. As shown in Fig. S4 and Table S1, the optimal D/A weight ratio was 1:2 (w/w),
-2
and a PCE of 9.8% was obtained with a Voc of 0.75 V, a Jsc of 22.1 mA cm and an FF of
5

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5
8.8%. In order to further improve the photovoltaic performance, PN was utilized as solvent
DOI: 10.1039/C8TA11484F
additive to optimize the morphology of the active layers as shown in Fig. S5 and Table S2.
Fig. 2a-b shows the current density-voltage (J-V) characteristics and EQE curves of the solar
cells based on the PTB7-Th:ACS8 without and with 0.5% PN. It was found that using PN as
solvent additive can remarkably improve the PCEs of the devices due to the significantly
enhanced Jsc and FF. Furthermore, when 0.5% PN was added, the devices exhibited the best
-2
PCE of 13.2% with a Voc of 0.75 V, a Jsc of 25.3 mA cm and an FF of 69.3% . Moreover,
under the same device processing conditions, the devices based on IEICO-4F just exhibited a
moderate PCE of 9.4% (Fig. S6). To our knowledge, the PCE of 13.2 % is the highest value
reported in the literatures to date for the PSCs based on NIR acceptors (E opt ≤ 1.3 eV).41,45 As
g
shown in Fig. 2b, when adding 0.5% PN as solvent additive, the EQE curves was signicifantly
enhanced and redshifted in the long wavelength region of 600-900nm. Moreover, a maximum
EQE value of 82.6% at 650 nm was recorded for the optimal device. The integrated Jsc from
-2
the EQE curves were 21.3 and 24.2 mA cm for the PSCs based on the blend film without
and with 0.5% PN treatment, respectively, which agrees well with the J-V measurements. The
variations of EQE and Jsc should be related to the absorption and carrier mobilities of the
blend films. As shown in Fig. S7, the absorption spectrum of the blend film with PN treatment
exhibited an obvious redshift and an enhanced absorption peak in the long wavelength, which
is in agreement with the EQE curves. As shown in Fig. S8 and Table S3, the hole/electron
-4
-4
2
-1 -1
mobilities (μ
h
/μ ) were estimated to be 1.47/1.30 × 10 and 2.25/2.01 × 10 cm V s for the
e
blend film without and with 0.5% PN treatment, respectively. The higher and more balanced
carrier mobilities for the blend film are beneficial to suppress space charge accumulation and
promote the charge transport and extraction.
6

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DOI: 10.1039/C8TA11484F
Fig. 2. (a) J-V characteristics, (b) EQE curves, (c) Jph versus Veff characteristics, and (d)
dependence of Jph on light intensity for the PSCs based on PTB7-Th:ACS8 (1:2, w/w)
without or with 0.5% PN.
Table 1. Photovoltaic parameters of PSCs based on PTB7-Th:ACS8 (1:2, w/w) without PN or
-2
with 0.5% PN under the illumination of AM 1.5G, 100 mW cm .
a
PCEb
(%)
V
oc
J
sc
FF
Thickness
(nm)
Conditions
As-cast
-2
(V)
(mA cm )
22.5(21.3)
(%)
0.75
0.75
58.8
69.3
9.9 (9.7±0.2)
115
115
0
.5% PN
25.3(24.2)
13.2 (13.1±0.1)
a
b
Values calculated from EQE in brackets. Average PCEs in brackets for over 30 devices.
As shown in Fig. 2c, the dependence of the photocurrent (Jph) on the effective voltage
Veff) was measured to investigate the impact of adding solvent additive on the exciton
(
dissociation and charge collection process for PSCs. Here, Jph is defined as J
L
-J
D
, where J
L
and J are the current densities under illumination and in the dark, respectively. Veff is
D
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DOI: 10.1039/C8TA11484F
defined as V
0
-V, where V is the voltage at which the photocurrent is zero and V is the
0
5
4
applied voltage. The Jph reaches the saturation current density (Jsat) at high Veff (≥ 2 V in
this case). Thus, the exciton dissociation probability (P(E, T)) is determined from the ratio of
Jph/Jsat. Under maximal power output and short-circuit conditions, the values of P(E, T) are
6
7.3/89.8% for the as-cast device, and 75.0/92.6% for the device with 0.5% PN treatment,
respectively. The higher P(E, T) indicates that solvent additive treatment leads to more
efficient exciton dissociation and charge extraction efficencies, which is consistent with the
better performance of the corresponding devices. Furtheremore, in oder to investigate the
charge recombination process in the devices, the dependence of Jph under different light
intensities (P) was measured as shown in Fig. 2d. The relationship between Jph and P is
S
defined as Jph ∝P . Weak bimolecular recombination in the device would result in a linear
55
dependence of Jph on P with S value close to 1. The S values of the PSCs based on the
blend without and with 0.5% PN are 0.92 and 0.93, respectively, implying the additive
treatment has negligible effect on the biomolecualr recombination process in this blend.
Grazing incidence wide-angle X-ray scattering (GIWAXS) was performed to probe the
effect of PN additive treatment on the molecular orientation and packing of the blend films.56
Fig. 3a-b shows the 2D GIWAXS patterns and the corresponding scattering profiles in the in-
plane (IP) and out-of-plane (OOP) direction. For the pure ACS8 film, the IP direction shows
−
1
obvious (100) diffraction peak at 0.30 Å with a d-spacing of 20.73 Å, whereas the OOP
−
1
shows a sharper and stronger peak at 1.79 Å , corresponding to the (010) π-π staking with a
d-spacing of 3.51 Å, indicating that the pure ACS8 film exhibits a dominated face-on
molecular orientation relative to the substrate. The lamellar (100) diffraction peak of PTB7-
Th film is located at 0.26 Å−1 with a d-spacing of 24.02 Å in the IP direction. In as-cast
PTB7-Th:ACS8 film, there is no apparent change at the lamellar (010) diffraction peak
−
1
−1
compared with the pure films, which is located at 1.79 Å for ACS8 and 1.57 Å for PTB7-
8

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Th in the OOP direction, respectively. When adding PN additive, the blend film shows a
DOI: 10.1039/C8TA11484F
stronger and tighter (100) diffraction peak and (010) diffraction peak at 0.31 and 1.80 Å−1
respectively, corresponding to smaller lamellar distance of 20.00 and 3.50 Å respectively. The
improved π-π staking ordering and enhanced face-on π-π stacking can be clearly observed
after PN additive treatment, which is favorable for charge transport and thus obtaining high Jsc
and FF. At the same time, we calculated the coherence length (CL) of π-π staking, which was
calculated from the full width at half maximum (FWHM) of OOP using Scherrer equation.57
Moreover, in the OOP direction, PTB7-Th: ACS8 film blend with PN additive treatment
shows a larger CL of 10.11 nm compared to as-cast film blend with a CL of 3.97 nm, which
means the overall crystallinity of the ACS8 was enhanced with PN additive treatment.
Obviously, appropriate PN additive treatment promotes high crystalline behavior of the blend
film and strong face-on orientation, which are desirable to vertical charge transport, thereby
higher Jsc and FF.
The resonant soft X-ray scattering (R-SoXS) was used to probe the phase separation and
58
average domain purity in PTB7-Th:ACS8 blend films. The resonant photon energy of 284.8
5
9
eV was selected, where the material contrast dominates the scattering. The PTB7-Th:ACS8
−
1
blend film without PN shows scattering peaks at q∼0.096 nm , corresponding to the domain
size of ≈32 nm. The scattering peak of PTB7-Th:ACS8 blend film with 0.5% PN locates at
−
1
q~0.083 nm , corresponding to the domain size of ≈38 nm, which is slightly larger than the
as-cast blend films. Moreover, as shown in Fig. 3c, the relative domain purity of the blends
without and with PN additive treatment are 74% and 100%, respectively. The purer domains
can reduce bimolecular recombination and thus lead to high performance. In a word, the
appropriate domain sizes and the purer domains are beneficial to exciton dissociation and
6
0
charge transport. As a result, the devices based on PTB7-Th:ACS8 with 0.5% PN show
higher Jsc, FF, and PCE.
9

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DOI: 10.1039/C8TA11484F
Fig. 3. (a) 2D GIWAXS patterns, (b) scattering profiles for pure films of ACS8, PTB7-Th and
blend films of PTB7-Th: ACS8 (1:2, w/w) without PN or 0.5% PN and (c) R-SoXS profiles
for PTB7-Th: ACS8 (1:2, w/w) blend films without PN or with 0.5% PN.
The surface and bulk morphologies of BHJ-films were probed using atomic force
microscopy (AFM) and transmission electron microscopy (TEM). As shown in Fig. S9, the
blend film with 0.5% PN treatment exhibits a relatively smooth surface with a root-mean-
square (RMS) roughness of 1.03 nm in comparison with the as-cast blend film with RMS
value of 1.26 nm. Moreover, as shown in Fig. S9f, when using the 0.5% PN as solvent
additive, the phase separation and domain sizes of the blend film have been effectively
optimized and the clear needle crystals of the ASC8 can be observed, which are beneficial for
the exciton separation and charge transport.
Considering the blend of PTB7-Th:ASC8 shows a weak absorption in the region of 400-
6
00 nm, the ST-PSCs with the structure of ITO/ZnO/PFN/PTB7-Th:ACS8/MoO
3
/Au/Ag were
fabricated. The ultrathin Au (1 nm) was used to reduce percolation of Ag film and enhance the
6
1
Ag film uniformity, leading to optimal transmittance and low electrical resistance. The J-V
characteristics, EQE curves and transmission spectra are shown in Fig. 4a-c, and the
corresponding photovoltaic parameters of the optimized devices summarized in Table 2. The
photovoltaic performances of the devices with different Ag thickness (10 nm, 15 nm and 20
1
0

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nm) were investigated. An obvious trade-off between the AVT and the PCE could be observed
DOI: 10.1039/C8TA11484F
when changing the Ag thickness. When 10 nm Ag was used, the device showed good AVT of
-
2
4
2
3.2 % with a PCE of 9.4% and Jsc of 19.9 mA cm . When the Ag thickness was increased to
-1
0 nm, the AVT decreased to 28.6 % with a PCE of 11.1% and Jsc of 22.5 mA cm , which are
among the highest values for the ST-PSCs reported in the literatures.20,47,52,62 The Comission
Internationale de I’Eclairage (CIE) 1931 color coordinate of the transmitted light under CIE
standard illuminant D65 (Fig. 4d), correlated color temperature (CCT) and coloring rendering
index (CRI) of the ST devices are summarized in Table 2. The champion ST-PSCs with a 20
nm Ag show a CIE of (0.2621,0.2976) close to the white color point (1/3,1/3), demonstrating
their good neutral color feature and possess a CCT of 11528K and a CRI of 84.
Fig. 4. (a)The J-V characteristics, (b) the corresponding EQE curves of the ST-PSCs based on
PTB7-Th:ACS8 (1:2, w/w) with different Ag thickness, (c) transmittance spectra of the ST-
OSC with different Ag thicknesses (the inset graph is a photo of the semitrasparent device
with a 10 nm thick Ag) and (d) the representation of color coordinates of the semitransparent
1
1

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devices with different Ag thickness (10 nm, red dot; 15 nm, blue dot and 20 nm, green dot) on
DOI: 10.1039/C8TA11484F
CIE.
Table 2. Photovoltaic parameters of the ST-PSCs based on PTB7-Th:ACS8 (1:2, w/w) with
different Ag thickness under the illumination of AM 1.5G, 100 mw/cm2.
a
PCEb
(%)
Ag
AVT
(%)
CIE
CCT CRI
(k)
V
oc
J
sc
FF
-2
thickness
coordinate
(V)
0.74
0.74
0.74
(mA cm )
(%)
(
nm)
1
1
2
0
5
0
43.2
36.1
28.6
(0.2958,
7547
8665
91
86
19.9
(18.9)
21.3
63.8
65.7
66.5
9.4
0
.3239)
(0.2808,
.3201)
(0.2621, 11528 84
.2976)
(9.3±0.1)
10.4
0
(20.2)
22.5
(10.2±0.2)
11.1
0
(21.3)
(11.0±0.1)
a
b
Values calculated from EQE in brackets. Average PCEs in brackets for over 30 devices.
3
. Conclusions
In summary, a new small molecule acceptor (ACS8) based on IDT as core, alkylthio-
substituted thiophene as π-bridge and electron-withdrawing IC2F as end groups has been
designed and synthesized for PSCs applications. ACS8 shows a narrow-bandgap of 1.30 eV
with strong absorption in the region of 650-900 nm and a relatively low LUMO energy level
of -4.05 eV. Furthermore, ACS8 film possesses well-ordered molecular orientation and tightly
-
4
2
−1 −1
face-on packing, and hence exhibits a high electron mobility of 2.65×10 cm V s . The
PSCs based on PTB7-Th:ACS8 (1:2, w/w) with 0.5% PN exhibited an optimal PCE of 13.2%
-2
with a Voc of 0.75 V, a Jsc of 25.3 mA cm and an FF of 69.3% under the illumination of AM
-2
1
.5G, 100 mW cm . Furthermore, semitransparent devices based on PTB7-Th: ACS8 (1:2,
1
2

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w/w) exhibited PCEs varying from 9.4% to 11.1% at different AVT (43.2-28.6%). These
DOI: 10.1039/C8TA11484F
results indicate that ACS8 is a very promising NIR acceptor material for semitransparent and
tandem solar cells applications.
Acknowledgements
J. Chen and G.D. Li contributed equally to this work.This work was supported by
National Natural Science Foundation of China (NSFC) (No. 51573120, 51503135, 51773142,
2
2
1704082, 21875182 and 91633301), Ministry of science and technology (No.
016YFA0200700), China Postdoctoral Science Foundation (2017M623162). The X-ray data
was acquired at beamlines 7.3.3 and 11.0.1.2 at the Advanced Light Source, which is
supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S.
Department of Energy under Contract No. DE-AC02-05CH11231. The authors thank Chenhui
Zhu at beamline 7.3.3, and Cheng Wang at beamline 11.0.1.2 for assistance with data
acquisition.
References
1
2
3
4
. Y. F. Li, Acc. Chem. Res. 2011, 45, 723.
. J. W. Chen, Y. Cao, Acc. Chem. Res. 2009, 42, 1709.
. G. Li, R. Zhu, Y. Yang, Nat. Photonics. 2012, 6, 153.
. S. M. Ryno, M. K. Ravva, X. K. Chen, H. Y. Li, J. L. Brédas, Adv. Energy Mater. 2016,
6
, 1601370.
5
6
7
8
9
1
. C. J. Brabec, M. Heeney, I. McCulloch, J. Nelson, Chem. Soc. Rev. 2011, 40, 1185.
. J. Hou, O. Inganas, R. H. Friend, F. Gao, Nat. Mater. 2018, 17, 119.
. W. Li, H. Yao, H. Zhang, S. Li, J. Hou, Chem-Asian. J. 2017, 12, 2160.
. R. Yu, H. Yao, J. Hou, Adv. Energy Mater. 2018, 8, 1702814.
. P. Cheng, G. Li, X. Zhan, Y. Yang, Nat. Photonics. 2018, 12, 131.
0. B. Fan, L. Ying, Z. Wang, B. He, X. F. Jiang, F. Huang, Y. Cao, Energy Environ. Sci.
1
3

Journal of Materials Chemistry A
Page 14 of 18
View Article Online
DOI: 10.1039/C8TA11484F
2
017, 10, 1243.
1
1
1
1
1. Y. Lin, X. Zhan, Acc. Chem. Res. 2016, 49, 175.
2. Y. Lin, Y. Li, X. Zhan, Chem. Soc. Rev. 2012, 41, 4245.
3. Y. Lin, X. Zhan, Mater. Horiz. 2014, 1, 470.
4. X. Zhan, A. Facchetti, S. Barlow, T. J. Marks, M. A. Ratner, M. R. Wasielewski, S. R.
Marder, Adv. Mater. 2011, 23, 268.
1
1
5. V. A. Trukhanov, D. Y. Paraschuk, Polym. Sci. Ser. C. 2014, 56, 72.
6. H. Yao, L. Ye, J. Hou, B. Jang, G. Han, Y. Cui, G. M. Su, C. Wang, B. Gao, R. Yu, H.
Zhang, Y. Yi, H. Y. Woo, H. Ade, J. Hou, Adv. Mater. 2017, 29, 1700254.
7. Z. Xiao, X. Jia, D. Li, S. Wang, X. Geng, F. Liu, J. Chen, S. Yang, T. P. Russell, L. Ding,
Sci. Bull. 2017, 62, 1494.
1
1
8. J. Wang, W. Wang, X. Wang, Y. Wu, Q. Zhang, C. Yan, W. Ma, W. You, X. Zhan, Adv.
Mater. 2017, 29, 1702125.
1
2
9. S. Li, L. Ye, W. Zhao, X. Liu, J. Zhu, H. Ade, J. Hou, Adv. Mater. 2017, 29, 1704051.
0. J. Wang, J. Zhang, Y. Xiao, T. Xiao, R. Zhu, C. Yan, Y. Fu, G. Lu, X. Lu, S. R. Marder,
X. Zhan, J. Am. Chem. Soc. 2018, 140, 9140.
2
2
2
2
2
1. J. Sun, X. Ma, Z. Zhang, J. Yu, J. Zhou, X. Yin, L. Yang, R. Geng, R. Zhu, F. Zhang, W.
Tang, Adv. Mater. 2018, 30, 1707150.
2. W. Gao, M. Zhang, T. Liu, R. Ming, Q. An, K. Wu, D. Xie, Z. Luo, C. Zhong, F. Liu, F.
Zhang, H. Yan, C. Yang, Adv. Mater. 2018, 30, 1800052.
3. S. J. Xu, Z. Zhou, W. Liu, Z. Zhang, F. Liu, H. Yan, X. Zhu, Adv. Mater. 2017, 29,
1
704510.
4. J. Zhu, Z. Ke, Q. Zhang, J. Wang, S. Dai, Y. Wu, Y. Xu, Y. Lin, W. Ma, W. You, X.
Zhan, Adv. Mater. 2017, 30, 1704713.
5. (a) Y. Yang, Z. G. Zhang, H. Bin, S. Chen, L. Gao, L. Xue, C. Yang, Y. Li, J. Am. Chem.
1
4

Page 15 of 18
Journal of Materials Chemistry A
View Article Online
Soc. 2016, 138, 15011; (b) C. Li, T. Xia, J. Song, H. Fu, H. Ryu, K. Weng, L. Ye H. Y.
DOI: 10.1039/C8TA11484F
Woo, Y. Sun, J. Mater. Chem. A. 2018, DOI:10.1039/C8TA11197A.
6. Y. Zhang, B. Kan, Y. Sun, Y. Wang, R. Xia, X. Ke, Y. Q. Yi, C. Li, H. L. Yip, X. Wan,
Y. Cao, Y. Chen, Adv. Mater. 2018, 30, 1707508.
2
2
2
7. L. X. Meng, Y. M. Zhang, X. J. Wan, C. X. Li, X. Zhang, Y. B. Wang, X. Ke, Z. Xiao, L.
M. Ding, R. X. Xia, H. L. Yip, Y. Cao, Y. S. Chen, Science. 2018. 361, 1094.
8. Y. Cui, H. Yao, B. Gao, Y. Qin, S. Zhang, B. Yang, C. He, B. Xu, J. Hou, J. Am. Chem.
Soc. 2017, 139, 7302.
2
3
3
9. Y. Cui, H. F. Yao, C. Y. Yang, S. Q. Zhang, J. H. Hou, Acta Polym. Sin. 2018, 2, 223.
0. X. Che, Y. Li, Y. Qu, S. R. Forrest, Nat. Energy. 2018, 3, 422.
1. Y. Lin, J. Wang, Z. G. Zhang, H. Bai, Y. Li, D. Zhu, X. Zhan, Adv. Mater. 2015, 27,
1
170.
3
3
3
3
3
2. Y. Lin, Q. He, F. Zhao, L. Huo, J. Mai, X. Lu, C. J. Su, T. Li, J. Wang, J. Zhu, Y. Sun, C.
Wang, X. Zhan, J. Am. Chem. Soc. 2016, 138, 2973.
3. W. Zhao, S. Li, H. Yao, S. Zhang, Y. Zhang, B. Yang, J. Hou, J. Am. Chem. Soc. 2017,
1
39, 7148.
4. Y. Lin, F. Zhao, Q. He, L. Huo, Y. Wu, T. C. Parker, W. Ma, Y. Sun, C. Wang, D. Zhu,
A. J. Heeger, S. R. Marder, X. Zhan, J. Am. Chem. Soc. 2016, 138, 4955.
5. Y. Lin, Z.-G. Zhang, H. Bai, J. Wang, Y. Yao, Y. Li, D. Zhu, X. Zhan, Energy Environ.
Sci. 2015, 8, 610.
6. (a) Z. Zhang, L. Feng, S. Xu, J. Yuan, Z. G. Zhang, H. Peng, Y. Li, Y. Zou, J. Mater.
Chem. A. 2017, 5, 11286; (b) G. Zhang, G. Yang, H. Yan, J. H. Kim, H. Ade, W. Wu, X.
Xu, Y. Duan, Q. Peng, Adv. Mater. 2017, 29, 1606054.
3
7. (a) Y. Li, D. Qian, L. Zhong, J.-D. Lin, Z. Q. Jiang, Z. G. Zhang, Z. Zhang, Y. Li, L. S.
Liao, F. Zhang, Nat. Energy. 2016, 27, 430; (b) B. Xiao, A. L. Tang, J. Q. Zhang, A.
1
5

Journal of Materials Chemistry A
Page 16 of 18
View Article Online
DOI: 10.1039/C8TA11484F
Mahmood, Z. X. Wei, E. J. Zhou, Adv. Energy Mater. 2017, 7, 1602269.
3
3
8. F. Liu, Z. Zhou, C. Zhang, T. Vergote, H. Fan, F. Liu, X. Zhu, J. Am. Chem. Soc. 2016,
38, 15523.
1
9. (a) Y. Liu, Z. Zhang, S. Feng, M. Li, L. Wu, R. Hou, X. Xu, X. Chen, Z. Bo, J. Am.
Chem. Soc. 2017, 139, 3356; (b) Y. Chen, T. Liu, H. Hu, T. Ma, J. Y. L. Lai, J. Zhang, H.
Ade and H. Yan, Adv. Energy Mater. 2018, 8, 1801203.
4
4
4
0. B. Kan, H. Feng, X. Wan, F. Liu, X. Ke, Y. Wang, Y. Wang, H. Zhang, C. Li, J. Hou and
Y. Chen, J Am Chem Soc. 2017, 139, 4929.
1. B. Kan, H. Feng, H. Yao, M. Chang, X. Wan, C. Li, J. Hou, Y. Chen, Sci. China Chem.
2
018, 61, 1307.
2. Z. Zheng, Q. Hu, S. Zhang, D. Zhang, J. Wang, S. Xie, R. Wang, Y. Qin, W. Li, L. Hong,
N. Liang, F. Liu, Y. Zhang, Z. Wei, Z. Tang, T. P. Russell, J. Hou, H. Zhou, Adv. Mater.
2
018, 30, 1801801.
4
4
3. S. Zhang, Y. Qin, J. Zhu, J. Hou, Adv. Mater. 2018, 30, 1800868.
4. H. F. Yao, Y. C. R. N. Yu, B. W. Gao, H. Zhang, J. H. Hou, Angew. Chem. Int. Ed. 2017,
5
6, 3045.
5. X. Song, N. Gasparini, L. Ye, H. F. Yao, J. H. Hou, H. Ade, D. Baran, ACS Energy Lett.
018. 3, 669.
4
2
4
4
6. C. J. Traverse, R. Pandey, M. C. Barr, R. R. Lunt, Nat. Energy. 2017, 2, 849.
7. Y. Xie, L. Huo, B. Fan, H. Fu, Y. Cai, L. Zhang, Z. Li, Y. Wang, W. Ma, Y. Chen, Y.
Sun, Adv. Funct.Mater. 2018, 1800627.
4
4
5
8. M. Zhang, X. Guo, W. Ma, H. Ade, J. Hou, Adv. Mater. 2015, 27, 4655.
9. Y. Li, G. Xu, C. Cui, Y. Li, Adv. Energy Mater. 2018, 8, 1701791.
0. Y. Li, J. D. Lin, X. Che, Y. Qu, F. Liu, L. S. Liao, S. R. Forrest, J. Am. Chem. Soc. 2017,
1
39, 17114.
1
6

Page 17 of 18
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C8TA11484F
5
5
1. S. Dai, X. Zhan, Adv. Energy Mater. 2018, 8, 1800002.
2. F. Liu, Z. Zhou, C. Zhang, J. Zhang, Q. Hu, T. Vergote, F. Liu, T. P. Russell, X. Zhu,
Adv. Mater. 2017, 29,1606574.
5
5
3. B. Jia, S. Dai, Z. Ke, C. Yan, W. Ma, X. Zhan, Chem. Mater. 2017, 30, 239.
4. J. L. Wu, F. C. Chen, Y. S. Hsiao, F. C. Chien, P. Chen, C. H. Kuo, M. H. Huang, C. S.
Hsu, ACS. Nano. 2011, 5, 959.
5
5
5
5. P. W. M. Blom, V. D. Mihailetchi, L. J. A. Koster, D. E. Markov, Adv. Mater. 2007, 19,
1
551.
6. A. Hexemer, W. Bras, J. Glossinger, E. Schaible, E. Gann, R. Kirian, A. MacDowell, M.
Church, B. Rude, H. Padmore, J. Phys. Conf. Ser. 2010, 247, 012007.
7. S. J. Ko, W. Lee, H. Choi, B. Walker, S. Yum, S. Kim, T. J. Shin, H. Y. Woo, J. Y. Kim,
Adv. Energy Mater. 2015, 5, 1401687.
5
5
8. Y. Wu, Z. Y. Wang, X. Y. Meng, W, Prog. Chem. 2017, 29, 93.
9. E. Gann, A. T. Young, B. A. Collins, H. Yan, J. Nasiatka, H. A. Padmore, H. Ade, A.
Hexemer, C. Wang, Rev. Sci. Instrum. 2012, 83, 045110.
6
6
6
0. H. B. Naveed, W. Ma, Joule. 2018, 2, 621.
1. S. Schubert, J. Meiss, L. Müller-Meskamp, K. Leo, Adv. Energy Mater. 2013, 3, 438.
2. W. Wang, C. Yan, T. K. Lau, J. Wang, K. Liu, Y. Fan, X. Lu, X. Zhan, Adv. Mater. 2017,
2
9, 1701308.
1
7

Journal of Materials Chemistry A
Page 18 of 18
View Article Online
DOI: 10.1039/C8TA11484F
The table of contents entry
The non-fullerene polymer solar cells based on a low bandgap polymer PTB7-Th and a
ultra-narrow bandgap acceptor ACS8 exhibited optimal PCE of 13.2%, indicating that the
blend of PTB7-Th/ACS8 is potential for the practical applcation of PSCs.
Keywords: non-fullerene acceptor; polymer solar cells; alkylthio substituents; PN additive.
High Efficient Near-infrared and Semitransparent Polymer Solar Cells Based on an
Ultra-Narrow Bandgap Nonfullerene Acceptor
Juan Chen, Guangda Li, Qinglian Zhu, Xia Guo, Qunping Fan, Wei Ma, and Maojie Zhang*
1