A medium-bandgap small molecule donor compatible with both fullerene and unfused-ring nonfullerene acceptors for efficient organic solar cells

Article abstract of DOI:10.1039/c9tc04680a

Here we designed and synthesized a new small molecule donor DRC4TB with an alkylthiothienyl-substituted benzodithiophene as the core and 3-butyl rhodanine as the terminal group, which showed an optical bandgap of 1.87 eV. DRC4TB was compatible with both a

Full text of DOI:10.1039/c9tc04680a

Journal of
Materials Chemistry C
View Article Online
View Journal | View Issue
COMMUNICATION
A medium-bandgap small molecule donor
compatible with both fullerene and unfused-ring
nonfullerene acceptors for efficient organic solar
cells†
Cite this: J. Mater. Chem. C, 2019,
, 13396
7
Received 24th August 2019,
Accepted 13th October 2019
ac
c
c
b
b
Xianjie Chen, Xueyan Ding, Qian Zhang, * Di Wang, Lingling Zhan,
DOI: 10.1039/c9tc04680a
e
a
d
cd
a
Xinhui Lu, Feifei Wu, Zheng Xu, Huayu Qiu,
Chang-Zhi Li
*
Wanzhi Chen * and
b
rsc.li/materials-c
*
13
14
15–24
Here we designed and synthesized a new small molecule donor as ITIC, Y6, etc.,
which possess strong and broad absorp-
DRC4TB with an alkylthiothienyl-substituted benzodithiophene as tion in the visible-near infrared wavelength range and high charge
the core and 3-butyl rhodanine as the terminal group, which mobilities. Besides, simple unfused-ring electron acceptors have
showed an optical bandgap of 1.87 eV. DRC4TB was compatible also been developed rapidly due to their merits of easier synthesis
25–32
with both a fullerene acceptor (PC71BM) and an unfused-ring non- compared to fused-ring acceptor (NFAs).
The PCEs of non-
fullerene acceptor (HF-PCIC). The optimized DRC4TB:PC71BM and fullerene organic solar cells with polymer donors have surpassed
1
4,16,33–38
DRC4TB:HF-PCIC solar cells delivered comparable power conversion 14%.
efficiencies (PCEs) of 8.53% and 8.68%, respectively. based on small molecule donors is still lagging behind.
Compared to conjugated polymers, small molecules possess
Solution-processed bulk heterojunction (BHJ) organic solar cells some unique advantages, such as easy purification, well-defined
OSCs), containing a photoactive blend film of a p-type donor and molecular structure, easier energy level control, and high
However, the development of nonfullerene OSCs
39–48
(
49
an n-type acceptor, have attracted considerable attention due to reproducibility. PCEs over 10% were achieved for fullerene-
their noteworthy advantages, including light weight, low cost, based small molecule organic solar cells (FSM-OSCs)
flexibility and potential to realize large-scale fabrication. Full- nonfullerene all-small-molecule solar cells (NFASM-OSCs).
7
,9,50,51
and
1–6
39–48
erene derivatives have been the most dominant acceptors in However, up to now, only a few small molecule donors have
OSCs for a long time due to their excellent electron mobility, been reported which could work well with both fullerene
4
6,52–54
high electron affinity, and easy formation of appropriate phase acceptors and nonfullerene small-molecule acceptors.
7
–12
separation with donor materials.
efforts have been devoted to the development of nonfullerene donor–acceptor (A–D–A)-type small molecule named DRCN5T,
acceptors, especially small molecule acceptors (SMAs), due to for which high PCEs of 10.08% and 9.89% were obtained for the
Meanwhile, tremendous For example, Chen and coworkers reported an acceptor–
51
46
their merits such as strong light-harvesting capability and easily PC71BM- and the nonfullerene F-2Cl-based devices, respectively.
tuned energy levels compared with fullerene derivatives, and Zhang and coworkers reported an A–p–D–p–A-type small molecule
great progress has been made. For example, many excellent DRBDT-TVT, and PCEs of 6.87% and 6.63% were obtained for
fused-ring electron acceptors (FREAs) have been reported, such DRBDT-TVT:PC BM- and DRBDT-TVT:IDIC-based devices,
7
1
respectively. Such A–D–A- or A–p–D–p–A-type small molecule
donors with wide- or medium-bandgaps could be an effective
way to construct more versatile small molecule donors.
a
b
Department of Chemistry, Zhejiang University, Hangzhou 310028, P. R. China.
E-mail: chenwzz@zju.edu.cn
MOE Key Laboratory of Macromolecular Synthesis and Functionalization,
State Key Laboratory of Silicon Materials, Department of Polymer Science and
Engineering, Zhejiang University, Hangzhou 310027, P. R. China.
E-mail: czli@zju.edu.cn
0
The benzo[1,2-b:4,5-b ]dithiophene (BDT) moiety has been
widely used in the construction of both conjugated polymer
and small molecule donors due to its symmetric and planar
55
c
structure and moderate electron-donating property. Furthermore,
the p-electrons could be delocalized onto side chains for two-
dimensional dithiophene-substituted BDT (BDTT), which is
conductive to the enhancement of p–p stacking and charge
transfer as well as better absorption. For instance, Hou and
coworkers reported the polymer donor PBDB-T with BDTT as
College of Material, Chemistry and Chemical Engineering, Hangzhou Normal
University, Hangzhou, 311121, P. R. China. E-mail: qzhang@hznu.edu.cn,
hyqiu@hznu.edu.cn
d
e
Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of
Education, Hangzhou Normal University, Hangzhou, 311121, P. R. China
Department of Physics, Chinese University of Hong Kong, New Territories,
Hong Kong 999077, P. R. China
†
Electronic supplementary information (ESI) available. See DOI: 10.1039/c9tc04680a the electron-donating units and PBDB-T-based nonfullerene
13396 | J. Mater. Chem. C, 2019, 7, 13396--13401
This journal is ©The Royal Society of Chemistry 2019

View Article Online
Communication
Journal of Materials Chemistry C
14,16,33,35
OSCs show excellent photovoltaic performance (414%).
cross coupling reaction and Knoevenagel condensation within
In the case of small molecule donors, Sun and coworkers reported a few steps. The chemical structures of the intermediates and
56
1
13
a BDTT-based small molecule donor named BTR. Then Zhu and target molecules were characterized by H NMR, C NMR
coworkers fabricated ternary devices by using a combination of and mass spectroscopy (Fig. S1–S9, ESI†). DRC4TB shows good
BTR with PC BM and nonfullerene acceptor NITI and a high PCE solubility in common solvents, such as dichloromethane,
7
1
57
of 13.63% was achieved.
chloroform, and chlorobenzene. The thermal properties of
Noncovalent intramolecular interactions, such as Sꢀ ꢀ ꢀX DRC4TB were investigated by thermogravimetric analysis (TGA)
(
X = N, O, halide) interactions, can be used to restrict the and differential scanning calorimetry (DSC) measurements, and
rotation of the neighbouring single bonds and enhance the the plots are shown in Fig. S10 (ESI†). DRC4TB possesses good
coplanarity of the un-fused conjugated backbone, which could thermal stability with a decomposition temperature (T , 5%
d
further promote the exciton diffusion and charge transport of weight loss) of 368 1C under a nitrogen atmosphere (Fig. S10a,
devices. On the other hand, the un-fused structure can be easily ESI†). A clear melting peak at 257 1C upon heating and a
synthesized and the corresponding small molecules also show recrystallization peak at 229 1C upon cooling for DRC4TB could
good co-planarity, strong crystallinity and high charge carrier be observed in the DSC curves, indicating that DRC4TB has
5
8–61
mobility.
TBT) moiety based small molecules show good photovoltaic
performance due to their high absorption efficiency, proper solution and thin film are illustrated in Fig. 1b, together with
Furthermore, thiophene-(p-alkoxybenzene)-thiophene strong crystallinity (Fig. S10b, ESI†).
(
The UV-vis absorption spectra of DRC4TB in chloroform
2
5,40
energy levels, and good morphology.
We here design and the absorption spectra of the acceptors HF-PCIC and PC71BM
synthesize a new small molecule donor DRC4TB, with 4,8-bis(5- for comparison. In solution, DRC4TB exhibits strong absorp-
0
(
(
(2-ethylhexyl)thio)thiophen-2-yl)benzo[1,2-b:4,5-b ]dithiophene tion in the region 300–600 nm with a maximum absorption
0
SBDTT) as the central unit, 2,2 -(2,5-bis((2-ethylhexyl)oxy)-1,4- peak at 518 nm and the maximum extinction efficient is 1.40 ꢁ
5
ꢂ1
ꢂ1
phenylene)dithiophene (TBT) as the p-spacer, and 3-butyl- 10 M cm . From solution to the solid state, the absorption
rhodanine as the end-capping electron-withdrawing group, spectrum is significantly broadened and red-shifted with a
and its chemical structure is shown in Fig. 1a. DRC4TB exhibits maximum at 604 nm, and a shoulder peak at 560 nm appears,
a medium optical bandgap of 1.87 eV. DRC4TB could work well indicative of effective intermolecular p–p stacking. The optical
with both PC71BM and the unfused-ring electron acceptor bandgap for DRC4TB was calculated to be 1.87 eV from the
2
7
HF-PCIC, and best PCEs of 8.53% for FSM-OSCs and 8.68% absorption edge. As shown in Fig. 1b, the absorption of the
for NFASM-OSCs were obtained, respectively. The NFASM-OSCs DRC4TB film and HF-PCIC film are complementary in the
showed higher short-circuit current density ( J ) than the FSM- region 400–800 nm, which would be beneficial to obtain high
sc
OSCs, which was attributed to the complementary absorption
Jsc. In contrast, PC71BM exhibits poor absorption in the visible
between DRC4TB and HF-PCIC in the range 400–800 nm. region.
To the best of our knowledge, DRC4TB is among the very few
Cyclic voltammetry measurements were performed to study
small molecule donors that can produce a PCE of over 8.50% in the electrochemical properties of DRC4TB by using a saturated
4
6
+
both fullerene and nonfullerene solar cells. Notably, the PCE calomel electrode as the reference and Fc/Fc (4.8 eV below the
is the highest value for the NFASM-OSCs with unfused-ring core vacuum level) as the internal standard (Fig. S11, ESI†). The
nonfullerene acceptors.
highest occupied molecular orbital (HOMO) energy level and
The synthetic route of DRC4TB and detailed procedures are the lowest unoccupied molecular orbital (LUMO) energy level
presented in the ESI.† DRC4TB could be obtained via a Stille calculated from the onset oxidation and reduction potentials
were ꢂ5.25 and ꢂ3.21 eV, respectively. The electrochemical
bandgap of DRC4TB was 2.04 eV. From Fig. 1c, the energy levels
between DRC4TB and the two acceptors were suitable to con-
struct OSCs and the driving force was large enough for charge
separation. Theoretical calculations using density functional
theory (DFT) at the B3LYP/6-31G(d) level were also performed to
evaluate the electron density distribution of the frontier molecular
orbitals and the molecular geometries of DRC4TB (Fig. S12, ESI†).
The electron density of the HOMO level is mainly delocalized on
the central unit and p-spacers, while the electron density of the
LUMO level mainly populates the end-capping groups and
p-spacers. DRC4TB shows small dihedral angles (o101) between
all adjacent units, which indicates the relatively high planarity of
the molecules.
Normal devices with the structure of ITO/PEDOT:PSS/
DRC4TB:acceptor/PFN-Br/Ag utilizing HF-PCIC or PC71BM as
Fig. 1 (a) Chemical structures, (b) absorption spectra in chloroform
the acceptors were fabricated to evaluate the photovoltaic
performance of DRC4TB, where PFN-Br is an effective electron
solution and in the thin film state, and (c) energy level diagram of DRC4TB,
HF-PCIC and PC71BM.
This journal is ©The Royal Society of Chemistry 2019
J. Mater. Chem. C, 2019, 7, 13396--13401 | 13397

View Article Online
Journal of Materials Chemistry C
Communication
than the fullerene-based devices, which was ascribed to the
complementary absorption between DRC4TB and HF-PCIC in
the range 400–800 nm. The fullerene- and nonfullerene-based
devices presented comparable PCEs, which demonstrated that
the small molecule donor DRC4TB was compatible with both
the fullerene and the nonfullerene acceptors.
The external quantum efficiency (EQE) spectra of the devices
under different conditions are illustrated in Fig. 2b. The
nonfullerene-based devices show a broader EQE response in
the long wavelength range compared with their fullerene-based
counterparts due to the absorption of HF-PCIC, which led to
the higher J . For the nonfullerene devices, the as-cast device
sc
shows a very low photo response. After TA treatment, the EQE
values are significantly enhanced in the whole wavelength
range of absorption. For the fullerene-based devices, the EQE
values are slightly improved after SVA treatment. The calculated
Fig. 2 (a) J–V curves and (b) EQE spectra of the nonfullerene- and
fullerene-based devices under different conditions. (c) Variation of Jph
ꢂ2
J
calc from the EQE curves was 12.92 and 15.17 mA cm for the
with Veff and (d) dependence of Voc on the light intensity (Plight) of the optimal fullerene- and nonfullerene-based devices, respectively,
optimal nonfullerene- and fullerene-based devices.
which were consistent with the measured values from the J–V
curves within acceptable errors of 5%.
To further study the charge generation, collection and
transporting layer developed by Huang and its structure is recombination behaviours for both optimal devices, the photo-
6
2
shown in Fig. S13 (ESI†). The typical current density–voltage current density ( Jph) as a function of effective voltage (Veff) is
(
J–V) curves of the OSCs are displayed in Fig. 2a and the plotted in double logarithmic coordinates as shown in Fig. 2c.
corresponding photovoltaic parameters are summarized in The Jph/Jsat ratio can be employed to evaluate the overall exciton
Table 1. The detailed optimization processes are shown in the separation and charge collection efficiency and Jsat is estimated
ESI.† For the nonfullerene-based devices, the best performance when Veff B 2.0 V for both devices. Under short-circuit condi-
was achieved with a donor/acceptor (D/A) weight ratio of 1.5 : 1 tions, the Jph/Jsat ratios are 92% for the nonfullerene devices
together with thermal annealing (TA) treatment. The as-cast and 93% for the fullerene-based devices, respectively, which
devices gave a poor PCE of 0.62% with a moderate open-circuit suggest that the exciton dissociation process is highly efficient
ꢂ2
voltage (Voc) of 0.94 V and a very low Jsc of 2.41 mA cm and a in both devices. At maximal power output conditions, the
fill factor (FF) of 0.27. After TA treatment, the PCE was sharply
Jph/Jsat ratios are 69% for the nonfullerene devices and 67%
enhanced to 8.68% accompanied by a significantly improved for the fullerene-based devices, respectively, which indicate
ꢂ1
J
sc of 15.51 mA cm and FF of 0.62. The improvement of the slightly higher charge collection efficiency for the nonfullerene
Jsc and FF was closely associated with the better developed devices. Furthermore, light intensity (Plight)-dependent mea-
morphology and matched charge mobility between the donor surements of Jsc and Voc were conducted. Jsc as a function of
and acceptor as discussed below. In the case of the fullerene- light intensity is shown in Fig. S14 (ESI†), and the fitted linear
a
based devices, conditions of a D/A weight ratio of 1 : 0.8 and lines can be described as Jsc p Plight, in which the a value
6
3
solvent vapor annealing (SVA) treatment delivered the optimal represents the degree of charge recombination. The closer to
performance. For the as-cast devices, a PCE of 4.73% was 1 the value of a is, the less charge recombination there is. It was
ꢂ2
obtained with a high Voc of 1.00 V, a Jsc of 10.85 mA cm
found that the a values of the two optimal devices are over 0.99,
and an FF of 0.51. After SVA treatment, the PCE was improved indicating that there is little charge recombination for both
ꢂ2
to 8.53% with a Jsc of 13.16 mA cm and an FF of 0.69. The devices. The dependence of Voc on the light intensity (Plight) is
higher Voc of the fullerene-based devices was derived from the shown in Fig. 2d. The slope of Voc versus the natural logarithm of
higher LUMO energy level of PC71BM than that of HF-PCIC. the light intensity gives 2kT/q (where q is the elementary charge,
However, the nonfullerene-based devices showed higher Jsc k is the Boltzmann constant, and T is the Kelvin temperature)
Table 1 Photovoltaic parameters of the OSCs
ꢂ2
a
d
ꢂ2
Blend
Treatment
As-cast
V
oc (V)
J
sc (mA cm
)
FF
PCE (%)
J
calc (mA cm
)
DRC4TB:HF-PCIC
0.94
0.90
1.00
0.94
2.41
0.27
0.62
0.51
0.69
0.62 (0.57)
8.68 (8.43)
5.57 (5.30)
8.53 (8.34)
2.34
b
TA
15.51
10.85
13.16
15.17
10.62
12.92
DRC4TB:PC71BM
As-cast
c
SVA
a
b
c
Average data in parentheses were obtained from over 20 devices. Thermal annealing at 120 1C for 10 min. Solvent vapor annealing with
d
chloroform for 60 s.
Jcalc was obtained by integrating the EQE curves.
13398 | J. Mater. Chem. C, 2019, 7, 13396--13401
This journal is ©The Royal Society of Chemistry 2019

View Article Online
Communication
Journal of Materials Chemistry C
implying that trap-assisted recombination dominates the
64,65
recombination mechanisms.
The slope values of the fullerene-
and nonfullerene-based devices are 1.14kT/q and 1.45kT/q,
respectively, which suggest more trap-assisted recombination in
the nonfullerene-based devices and thus relatively lower charge
carrier mobility and lower FF.
The thermal stability of the OSCs was tested and the results
are shown in Fig. S15 (ESI†). After heating at 80 1C for 32 h in
a glove box, the nonfullerene-based devices kept about 80%
of their initial PCEs. However, the PCEs of the fullerene-based
devices reduced to B70% of their initial values. The result
demonstrated that the nonfullerene-based devices exhibited
better thermal stability than their fullerene counterparts.
Atomic force microscopy (AFM) and transmission electron Fig. 4 GIWAX patterns of DRC4TB:HF-PCIC blend films (a) as-cast and
(
b) with TA treatment; GIWAX patterns of DRC4TB:PC71BM blend films
microscopy (TEM) were used to investigate the morphology of
the active layers (Fig. 3). The AFM images revealed that all
the blend films showed a smooth surface without severe
aggregation. The as-cast and TA-treated DRC4TB:HF-PCIC
(
c) as-cast and (d) with SVA treatment. (e) Out-of-plane and (f) in-plane
line-cut profiles.
blend films showed surface root-mean-square (RMS) roughness PC BM showed no obvious lamellar peak in both directions
7
1
values of 0.39 and 1.17 nm, respectively (Fig. 3a and b). The (Fig S16, ESI†). As depicted in Fig. 4, the as-cast DRC4TB:
as-cast and SVA-treated DRC4TB:PC BM blend films showed HF-PCIC blends showed weaker scattering intensity compared
7
1
RMS roughness values of 0.44 and 0.52 nm, respectively to the neat DRC4TB films, indicating that the acceptor
(
Fig. 3c and d). The increased RMS roughness indicated that decreased its crystallinity. After TA treatment, the DRC4TB:
ꢂ1
the crystallinity and phase separation were enhanced after HF-PCIC blends showed enhanced peaks at 0.40 Å (d = 15.7 Å)
optimization. From the TEM images, the as-cast DRC4TB: in the OOP direction and at 0.36 Å (d = 17.4 Å) in the in-plane
ꢂ1
HF-PCIC blends showed no obvious phase separation. After (IP) direction. In the case of the fullerene-based blends,
ꢂ1
TA treatment, clear phase separation and an interpenetrating enhanced peaks at 0.40 Å (d = 15.7 Å) in the OOP direction
ꢂ1
network with well-defined nanofibrils could be observed and at 0.37 Å (d = 17.0 Å) in the IP direction were observed
(
Fig. 3e and f). Similarly, for the DRC4TB:PC BM blends, obvious after SVA treatment, which illustrated the higher crystallinity of
71
phase separation formed after SVA treatment (Fig. 3g and h). The the films. Furthermore, both the fullerene- and nonfullerene-
good interpenetrating network of the donor/acceptor in the blend based blends showed enhanced crystallinity, which would be
films was helpful for exciton dissociation and charge transport, beneficial for charge transport and thus enhanced Jsc and FF.
and therefore Jsc, the FF and the PCEs were significantly
h e
The hole mobility (m ) and electron mobility (m ) of the blend
improved.
films were tested by the space-charge-limited-current (SCLC)
Grazing-incidence wide-angle X-ray scattering (GIWAXS) was method (Fig. S17 and Table S7, ESI†). Without any treatment,
further employed to investigate the morphology of the blend mh and me for the DRC4TB:HF-PCIC and DRC4TB:PC BM
71
6
6,67
ꢂ4
ꢂ4
2
2
ꢂ1 ꢂ1
films along with the neat materials.
showed a strong (100) lamellar peak at 0.38 Å (d = 16.5 Å) in 0.04) and 0.67 ꢁ 10 /1.15 ꢁ 10 cm V
the out-of-plane (OOP) direction whereas the neat HF-PCIC and respectively. After optimization, m and m
The neat DRC4TB film devices were 0.06 ꢁ 10 /0.47 ꢁ 10 cm
V
s
(m
h e
/m =
(m /m = 0.58),
for the DRC4TB:
ꢂ1
ꢂ4
ꢂ4
ꢂ1 ꢂ1
s
h e
h
e
ꢂ4
ꢂ4
HF-PCIC and DRC4TB:PC71BM devices were 0.13 ꢁ 10
/
/
ꢂ4
2
ꢂ1 ꢂ1
0
3
.12 ꢁ 10
cm
V
s
(m
h
/m
e
= 1.08) and 2.39 ꢁ 10
ꢂ4
2
ꢂ1 ꢂ1
.27 ꢁ 10 cm V
s
h
(m /m
e
= 0.73), respectively. Overall,
both devices showed enhanced and more balanced hole/
electron mobilities, which contributed to their improved FFs
after optimization. Besides, the charge mobilities of the DRC4TB:
HF-PCIC devices without/with treatment were lower than those of
the DRC4TB:PC71BM devices, which was partially responsible for
their lower FF.
In conclusion, a medium-bandgap small molecule DRC4TB
was designed and synthesized, which presented strong absorp-
tion in the region 300–650 nm. The photovoltaic performance
of FSM-OSCs and NFASM-OSCs using DRC4TB as the donor
was systematically investigated. The optimal FSM-OSCs and
NFASM-OSCs showed PCEs of 8.53% and 8.68%, respectively.
The fullerene-based devices exhibited relatively higher Voc and
FF due to the high-lying LUMO energy level of PC71BM and
Fig. 3 AFM height images of DRC4TB:HF-PCIC blend films (a) as-cast and
(
(
b) with TA treatment; AFM height images of DRC4TB:PC71BM blend films
c) as-cast and (d) with SVA treatment. TEM images of DRC4TB:HF-PCIC
blend films (e) as-cast and (f) with TA treatment; TEM images of
DRC4TB:PC71BM blend films (g) as-cast and (h) with SVA treatment.
(The scale bar is 50 nm.)
This journal is ©The Royal Society of Chemistry 2019
J. Mater. Chem. C, 2019, 7, 13396--13401 | 13399

View Article Online
Journal of Materials Chemistry C
Communication
higher charge carrier mobilities. The nonfullerene-based devices 12 Z. Zhuang, X. Guo, B. Liu, F. Hu, Y. Li, T. Tao, J. Dai, T. Zhi,
showed higher Jsc, which was because the absorption of DRC4TB
Z. Xie, P. Chen, D. Chen, H. Ge, X. Wang, M. Xiao, Y. Shi,
was complementary to that of HF-PCIC. Besides, suitable phase
Y. Zheng and R. Zhang, Adv. Funct. Mater., 2016, 26, 36–43.
separation, better donor/acceptor interpenetrating networks and 13 Y. Lin, J. Wang, Z. G. Zhang, H. Bai, Y. Li, D. Zhu and
enhanced crystallinity were formed for both the DRC4TB:HF-PCIC
X. Zhan, Adv. Mater., 2015, 27, 1170–1174.
and DRC4TB:PC71BM blend films after optimization. Our 14 J. Yuan, Y. Zhang, L. Zhou, G. Zhang, H.-L. Yip, T.-K. Lau,
research demonstrated that medium-bandgap small-molecule
donors can work well with different types of acceptors in high-
X. Lu, C. Zhu, H. Peng, P. A. Johnson, M. Leclerc and Y. Cao,
Joule, 2019, 3, 1140–1151.
performance small-molecule organic solar cells. In addition, 15 S. Holliday, R. S. Ashraf, A. Wadsworth, D. Baran, S. A.
the easy synthesis of both the donor and acceptor may become
a new choice for constructing NFASM-OSCs with unfused-ring
core acceptors instead of their fused-ring counterparts.
Yousaf, C. B. Nielsen, C. H. Tan, S. D. Dimitrov, Z. Shang,
N. Gasparini, M. Alamoudi, F. Laquai, C. J. Brabec, A. Salleo,
J. R. Durrant and I. McCulloch, Nat. Commun., 2016, 7,
11585–11595.
1
1
1
6 Y. Cui, H. Yao, J. Zhang, T. Zhang, Y. Wang, L. Hong,
K. Xian, B. Xu, S. Zhang, J. Peng, Z. Wei, F. Gao and
J. Hou, Nat. Commun., 2019, 10, 2515–2522.
7 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 and X. Zhan, J. Am. Chem.
Soc., 2016, 138, 2973–2976.
8 Z. Yao, X. Liao, K. Gao, F. Lin, X. Xu, X. Shi, L. Zuo, F. Liu,
Y. Chen and A. K. Jen, J. Am. Chem. Soc., 2018, 140,
2054–2057.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (No. 51703046, 21572203 and 21722404), 19 Y. Li, J. D. Lin, X. Che, Y. Qu, F. Liu, L. S. Liao and S. R.
and the National Key Research and Development Program
Forrest, J. Am. Chem. Soc., 2017, 139, 17114–17119.
2017YFB0307700). C.-Z. Li is thankful for the support from 20 W. Wang, C. Yan, T. K. Lau, J. Wang, K. Liu, Y. Fan, X. Lu
(
the Zhejiang Natural Science Fund for Distinguished Young
Scholars (LR17E030001).
and X. Zhan, Adv. Mater., 2017, 29, 1701303.
21 H. Yao, Y. Chen, Y. Qin, R. Yu, Y. Cui, B. Yang, S. Li,
K. Zhang and J. Hou, Adv. Mater., 2016, 28, 8283–8287.
2
2 B. Guo, W. Li, X. Guo, X. Meng, W. Ma, M. Zhang and Y. Li,
Adv. Mater., 2017, 29, 1702291.
References
1
2
R. F. Service, Science, 2011, 332, 293.
J. Zhang, H. S. Tan, X. Guo, A. Facchetti and H. Yan, Nat.
Energy, 2018, 3, 720–731.
23 Q. Fan, Y. Wang, M. Zhang, B. Wu, X. Guo, Y. Jiang, W. Li,
B. Guo, C. Ye, W. Su, J. Fang, X. Ou, F. Liu, Z. Wei, T. C. Sum,
T. P. Russell and Y. Li, Adv. Mater., 2018, 30, 1704546.
3
4
5
L. Lu, T. Zheng, Q. Wu, A. M. Schneider, D. Zhao and L. Yu, 24 Q. Fan, W. Su, Y. Wang, B. Guo, Y. Jiang, X. Guo, F. Liu,
Chem. Rev., 2015, 115, 12666–12731.
J. Hou, O. Inganas, R. H. Friend and F. Gao, Nat. Mater.,
T. P. Russell, M. Zhang and Y. Li, Sci. China: Chem., 2018,
61, 531–537.
2
018, 17, 119–128.
25 Z. P. Yu, Z. X. Liu, F. X. Chen, R. Qin, T. K. Lau, J. L. Yin,
X. Kong, X. Lu, M. Shi, C.-Z. Li and H. Chen, Nat. Commun.,
2019, 10, 2152–2160.
D. Qian, Z. Zheng, H. Yao, W. Tress, T. R. Hopper, S. Chen,
S. Li, J. Liu, S. Chen, J. Zhang, X.-K. Liu, B. Gao, L. Ouyang,
Y. Jin, G. Pozina, I. A. Buyanova, W. M. Chen, O. Ingan ¨a s, 26 R. Qin, W. Yang, S. Li, T.-K. Lau, Z. Yu, Z. Liu, M. Shi, X. Lu,
V. Coropceanu, J.-L. Bredas, H. Yan, J. Hou, F. Zhang,
A. A. Bakulin and F. Gao, Nat. Mater., 2018, 17, 703–709.
S. Li, W. Liu, C.-Z. Li, M. Shi and H. Chen, Small, 2017,
C.-Z. Li and H. Chen, Mater. Chem. Front., 2019, 3, 513–519.
27 S. Li, L. Zhan, W. Zhao, S. Zhang, B. Ali, Z. Fu, T.-K. Lau,
X. Lu, M. Shi, C.-Z. Li, J. Hou and H. Chen, J. Mater. Chem. A,
2018, 6, 12132–12141.
6
7
8
13, 1701120.
J. Wan, X. Xu, G. Zhang, Y. Li, K. Feng and Q. Peng, Energy 28 Y.-Q.-Q. Yi, H. Feng, N. Zheng, X. Ke, B. Kan, M. Chang,
Environ. Sci., 2017, 10, 1739–1745.
X. Liu, L. Nian, K. Gao, L. Zhang, L. Qing, Z. Wang, L. Ying,
Z. Xie, X. Wan, C. Li and Y. Chen, Chem. Mater., 2019, 31,
904–911.
Z. Xie, Y. Ma, Y. Cao, F. Liu and J. Chen, J. Mater. Chem. A, 29 T. Lee, Y. Eom, C. E. Song, I. H. Jung, D. Kim, S. K. Lee,
017, 5, 17619–17631.
W. S. Shin and E. Lim, Adv. Energy Mater., 2019, 9, 1804021.
D. Deng, Y. Zhang, J. Zhang, Z. Wang, L. Zhu, J. Fang, B. Xia, 30 S. Li, L. Zhan, F. Liu, J. Ren, M. Shi, C.-Z. Li, T. P. Russell
2
9
Z. Wang, K. Lu, W. Ma and Z. Wei, Nat. Commun., 2016, 7,
3740–13748.
0 J. B. Zhao, Y. K. Li, G. F. Yang, K. Jiang, H. R. Lin, H. Ade,
and H. Chen, Adv. Mater., 2018, 30, 1705208.
31 S. Li, L. Zhan, C. Sun, H. Zhu, G. Zhou, W. Yang, M. Shi,
C.-Z. Li, J. Hou, Y. Li and H. Chen, J. Am. Chem. Soc., 2019,
141, 3073–3082.
1
1
1
W. Ma and H. Yan, Nat. Energy, 2016, 1, 15027–15033.
1 M. Zhang, X. Guo, W. Ma, H. Ade and J. Hou, Adv. Mater., 32 Z. Zhang, S. Zhang, Z. Liu, Z. Zhang, Y. Li, C.-Z. Li and
2015, 27, 4655–4660.
H. Chen, Acta Phys.-Chim. Sin., 2019, 35, 394–400.
13400 | J. Mater. Chem. C, 2019, 7, 13396--13401
This journal is ©The Royal Society of Chemistry 2019

View Article Online
Communication
Journal of Materials Chemistry C
3
3
3
3
3
3
3
3 H. Zhang, H. Yao, J. Hou, J. Zhu, J. Zhang, W. Li, R. Yu, 51 B. Kan, M. Li, Q. Zhang, F. Liu, X. Wan, Y. Wang, W. Ni,
B. Gao, S. Zhang and J. Hou, Adv. Mater., 2018, 30, 1800613.
4 Y. Cui, H. Yao, L. Hong, T. Zhang, Y. Xu, K. Xian, B. Gao, J. Qin,
J. Zhang, Z. Wei and J. Hou, Adv. Mater., 2019, 31, 1808356.
G. Long, X. Yang, H. Feng, Y. Zuo, M. Zhang, F. Huang,
Y. Cao, T. P. Russell and Y. Chen, J. Am. Chem. Soc., 2015,
137, 3886–3893.
5 S. Zhang, Y. Qin, J. Zhu and J. Hou, Adv. Mater., 2018, 52 Y. Lin, J. Wang, T. Li, Y. Wu, C. Wang, L. Han, Y. Yao, W. Ma
0, 1800868. and X. Zhan, J. Mater. Chem. A, 2016, 4, 1486–1494.
6 B. Kan, H. Feng, H. Yao, M. Chang, X. Wan, C. Li, J. Hou and 53 N. Liang, D. Meng, Z. Ma, B. Kan, X. Meng, Z. Zheng,
3
Y. Chen, Sci. China: Chem., 2018, 61, 1307–1313.
7 X. Xu, K. Feng, Z. Bi, W. Ma, G. Zhang and Q. Peng, Adv.
Mater., 2019, 31, 1901872.
8 B. Fan, D. Zhang, M. Li, W. Zhong, Z. Zeng, L. Ying,
F. Huang and Y. Cao, Sci. China: Chem., 2019, 62, 746–752.
W. Jiang, Y. Li, X. Wan, J. Hou, W. Ma, Y. Chen and
Z. Wang, Adv. Energy Mater., 2017, 7, 1601664.
54 Y. Huo, C. Yan, B. Kan, X. F. Liu, L. C. Chen, C. X. Hu,
T. K. Lau, X. Lu, C. L. Sun, X. Shao, Y. Chen, X. Zhan and
H. L. Zhang, ACS Appl. Mater. Interfaces, 2018, 10, 9587–9594.
9 H. Wu, Q. Yue, Z. Zhou, S. Chen, D. Zhang, S. Xu, H. Zhou, 55 H. Yao, L. Ye, H. Zhang, S. Li, S. Zhang and J. Hou, Chem.
C. Yang, H. Fan and X. Zhu, J. Mater. Chem. A, 2019, 7,
5944–15950.
0 X. Li, Y. Wang, X. Guo, Q. Zhu, W. Ma, X. Ou, M. Zhang and
Y. Li, J. Mater. Chem. A, 2019, 7, 3682–3690.
Rev., 2016, 116, 7397–7457.
1
56 K. Sun, Z. Xiao, S. Lu, W. Zajaczkowski, W. Pisula,
E. Hanssen, J. M. White, R. M. Williamson, J. Subbiah,
J. Ouyang, A. B. Holmes, W. W. Wong and D. J. Jones, Nat.
Commun., 2015, 6, 6013–6021.
4
4
1 J. Guo, H. Bin, W. Wang, B. Chen, J. Guo, R. Sun, Z.-G.
Zhang, X. Jiao, Y. Li and J. Min, J. Mater. Chem. A, 2018, 6, 57 Z. Zhou, S. Xu, J. Song, Y. Jin, Q. Yue, Y. Qian, F. Liu,
5675–15683. F. Zhang and X. Zhu, Nat. Energy, 2018, 3, 952–959.
2 L. Yang, S. Zhang, C. He, J. Zhang, Y. Yang, J. Zhu, Y. Cui, 58 K. Wang, X. Guo, C. Ye, Y. Wang, Y. Meng, X. Li and
1
4
4
4
W. Zhao, H. Zhang, Y. Zhang, Z. Wei and J. Hou, Chem.
Mater., 2018, 30, 2129–2134.
3 B. Qiu, L. Xue, Y. Yang, H. Bin, Y. Zhang, C. Zhang, M. Xiao,
K. Park, W. Morrison, Z.-G. Zhang and Y. Li, Chem. Mater.,
M. Zhang, ChemPhysChem, 2019, 20, 2674–2682.
59 H. Huang, N. Zhou, R. P. Ortiz, Z. Chen, S. Loser, S. Zhang,
X. Guo, J. Casado, J. T. L. Navarrete, X. Yu, A. Facchetti and
T. J. Marks, Adv. Funct. Mater., 2014, 24, 2782–2793.
60 T. Dong, L. Lv, L. Feng, Y. Xia, W. Deng, P. Ye, B. Yang,
S. Ding, A. Facchetti, H. Dong and H. Huang, Adv. Mater.,
2017, 29, 1606025.
61 Q. Zhang, Y. Sun, X. Chen, Z. Lin, X. Ke, X. Wang, T. He,
S. Yin, Y. Chen and H. Qiu, J. Mater. Chem. C, 2019, 7,
5381–5384.
2017, 29, 7543–7553.
4 H. Bin, J. Yao, Y. Yang, I. Angunawela, C. Sun, L. Gao, L. Ye,
B. Qiu, L. Xue, C. Zhu, C. Yang, Z.-G. Zhang, H. Ade and
Y. Li, Adv. Mater., 2018, 30, 1706361.
5 Y. Wang, Y. Wang, B. Kan, X. Ke, X. Wan, C. Li and Y. Chen,
Adv. Energy Mater., 2018, 8, 1802021.
4
46 H. Li, Q. Wu, R. Zhou, Y. Shi, C. Yang, Y. Zhang, J. Zhang, 62 F. Huang, H. Wu, D. Wang, W. Yang and Y. Cao, Chem.
W. Zou, D. Deng, K. Lu and Z. Wei, Adv. Energy Mater., 2018,
, 1803175.
7 K. Gao, S. B. Jo, X. Shi, L. Nian, M. Zhang, Y. Kan, F. Lin,
Mater., 2004, 16, 708–716.
63 L. J. A. Koster, K. Martijn, M. M. Wienk, M. Klar ´a and
R. A. J. Janssen, Adv. Mater., 2011, 23, 1670–1674.
9
4
B. Kan, B. Xu, Q. Rong, L. Shui, F. Liu, X. Peng, G. Zhou, 64 S. R. Cowan, A. Roy and A. J. Heeger, Phys. Rev. B: Condens.
Y. Cao and A. K.-Y. Jen, Adv. Mater., 2019, 31, 1807842. Matter Mater. Phys., 2010, 82, 245207.
8 Y. Huo, H.-L. Zhang and X. Zhan, ACS Energy Lett., 2019, 4, 65 M. M. Mandoc, W. Veurman, L. J. A. Koster, B. de Boer and
241–1250. P. W. M. Blom, Adv. Funct. Mater., 2007, 17, 2167–2173.
9 Q. Zhang, Y. Sun, X. Chen, Z. Lin, X. Ke, X. Wang, T. He, 66 P. Bi, T. Xiao, X. Yang, M. Niu, Z. Wen, K. Zhang, W. Qin,
4
4
1
S. Yin, Y. Chen and H. Qiu, J. Mater. Chem. C, 2019, 7,
381–5384.
S. So, G. Lu, X. Hao and H. Liu, Nano Energy, 2018, 46,
81–90.
5
50 C. Cui, X. Guo, J. Min, B. Guo, X. Cheng, M. Zhang, 67 H. Fu, C. Li, P. Bi, X. Hao, F. Liu, Y. Li, Z. Wang and Y. Sun,
C. J. Brabec and Y. Li, Adv. Mater., 2015, 27, 7469–7475. Adv. Funct. Mater., 2019, 4, 1807006.
This journal is ©The Royal Society of Chemistry 2019
J. Mater. Chem. C, 2019, 7, 13396--13401 | 13401