Dialkoxymethano[60]fullerenes as electron acceptors in thin-film organic solar cells

Article abstract of DOI:10.1016/j.tet.2019.130514

This study presents the synthesis, characterization, and electrochemical properties of four new dialkoxymethanofullerenes, as well as their performance in organic solar cells (OSCs) devices. Dialkoxymethanofullerenes were synthesized in 27%–32% yield by thermolysis of dialkoxyoxadiazolines and reaction with C₆₀ under reflux in toluene. The prepared compounds were then characterized and used for the first time as electron-acceptor materials in thin-film bulk heterojunction OSCs with PBTZT-stat-BDTT-8 as the electron donor material. The devices made with ethoxy-hexyloxymethanofullerene and methoxy-hexyloxymethanofullerene exhibited optimal power conversion efficiencies (PCEs) of 3.79% and 4.65%, with open-circuit voltage of 0.832 and 0.831 V, respectively. In contrast, the devices made with ethoxy-ethoxymethanofullerene and methoxy-ethoxymethanofullerene exhibited very low PCEs of <0.01% for both, indicating a large impact of the substituents on device performance.

Full text of DOI:10.1016/j.tet.2019.130514

Tetrahedron xxx (xxxx) xxx
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Dialkoxymethano[60]fullerenes as electron acceptors in thin-film
organic solar cells
a
b
c
a
Mohammed Y. Suleiman , Yue Ma , Takafumi Nakagawa , Hiroshi Ueno ,
Yutaka Matsuo
a
a, b, c, *
School of Chemistry, Northeast Normal University, 5268 Renmin Street, Changchun, Jilin 130024, China
Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026,
b
China
c
Department of Mechanical Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 21 June 2019
Received in revised form
This study presents the synthesis, characterization, and electrochemical properties of four new dia-
lkoxymethanofullerenes, as well as their performance in organic solar cells (OSCs) devices. Dialkox-
ymethanofullerenes were synthesized in 27%e32% yield by thermolysis of dialkoxyoxadiazolines and
reaction with C60 under reflux in toluene. The prepared compounds were then characterized and used for
the first time as electron-acceptor materials in thin-film bulk heterojunction OSCs with PBTZT-stat-BDTT-
28 July 2019
Accepted 7 August 2019
Available online xxx
8
as the electron donor material. The devices made with ethoxy-hexyloxymethanofullerene and
methoxy-hexyloxymethanofullerene exhibited optimal power conversion efficiencies (PCEs) of 3.79%
and 4.65%, with open-circuit voltage of 0.832 and 0.831 V, respectively. In contrast, the devices made
with ethoxy-ethoxymethanofullerene and methoxy-ethoxymethanofullerene exhibited very low PCEs of
<0.01% for both, indicating a large impact of the substituents on device performance.
© 2019 Elsevier Ltd. All rights reserved.
Keywords:
Dialkoxymethanofullerenes
Dialkoxyoxadiazolines
Methanofullerene
Organic solar cells
Organic photovoltaics
1. Introduction
harvesting the energy invested during their life cycle [10,11].
However, the operational stability and PCEs of OSCs require further
Renewed attention has been given to research on organic solar
cell (OSC) devices, particularly after recent advances in power
conversion efficiency (PCE) over the past couple of years from 11%
to in excess of 17% as a result of novel materials and better device
engineering [1e4]. For many years, OSCs have attracted great in-
terest [5,6] and have been regarded as a promising technologies for
low-cost, sustainable, and renewable photovoltaic devices, thanks
to their promising properties [7] and their ability to form light-
weight, mechanically flexible, transparent photovoltaic panels by
high-speed, low-cost, continuous roll-to-roll manufacturing pro-
cesses [8,9]. Among all the various photovoltaic technologies, OSCs
in particular have the advantage of high-speed manufacturing with
a lower thermal budget because no high-temperature processes are
needed [4]. OSCs have the smallest environmental impact and the
shortest energy payback period, with the shortest time required for
improvement [12].
PCEs of organic photovoltaic devices are determined by three
parameters; open-circuit voltage (VOC), short-circuit current den-
sity (JSC), and fill factor (FF). To achieve high PCE, all three of these
parameters should be increased [13]. It is possible to increase VOC
by either raising the lowest unoccupied molecular orbital (LUMO)
level of the accepter or lowering the highest occupied molecular
orbital (HOMO) level of the donor. As for the fullerene acceptor, the
LUMO levels can be raised by installing organic addends across the
double bonds of C60. The increase in VOC is the result of shrinking
the 60
p-electron conjugated system of fullerene to a 58p-, 56p-, or
54 -electron system. JSC can be increased by introducing novel
p
low-bandgap materials that are well matched to the solar spectrum
[14]. The FF parameter indicates how “difficult” or “easy” it is for
photogenerated carriers to be extracted from a photovoltaic device
[15]. To obtain high FF, OSCs with the bulk heterojunction (BHJ)
structure are perhaps the best candidate [16]. In such OSCs, the
photoactive layer consists of a BHJ blend film of conjugated poly-
mers (electron donors) and organic semiconductors (electron ac-
ceptors). The BHJ structure is considered the most promising
*
Corresponding author. Department of Mechanical Engineering, School of En-
gineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656,
Japan.
E-mail address: matsuo@photon.t.u-tokyo.ac.jp (Y. Matsuo).
https://doi.org/10.1016/j.tet.2019.130514
0
040-4020/© 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: M.Y. Suleiman et al., Dialkoxymethano[60]fullerenes as electron acceptors in thin-film organic solar cells, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.130514

2
M.Y. Suleiman et al. / Tetrahedron xxx (xxxx) xxx
strategy because the interpenetrating morphology of the donor and
acceptor allows for better exciton generation and dissociation as
well as better charge carrier transport in the active layer [16,17]. To
improve the performance of OSCs, various strategies have been
used, such as controlling and enhancing the morphology of the
photoactive layer [18,19]; designing, engineering, and implement-
ing new device architectures [20,21]; employing interfacial layers
[
1,21]; and synthesizing new derivatives and/or novel donor and
acceptor fragments in the photoactive blend [1].
Fig. 1. Two possible isomers of methanofullerenes.
Among the above-mentioned strategies, the synthesis of new
organic photovoltaic materials remains the most important
because the synthesis of highly tunable optoelectronic properties of
organic materials enables precise optimization of the molecular
orbital energy levels, absorption spectra, and charge carrier mo-
bilities of these materials [22]. The main aim of synthesizing new
materials (particularly new fullerene derivatives) is to develop
materials with suitable properties to implement the aforemen-
tioned strategies. Fullerene derivative materials have been widely
used as semiconductor electron acceptor [23] thanks to their
outstanding electron affinity and reversible redox behavior, as well
as their excellent electron-transporting properties due to their
small reorganization energy for electron transfer [13]. Further
improving OSC efficiency through the synthesis of new organic
photovoltaic materials is a topic of great significance. Consequently,
many fullerenes derivatives have been developed such as PCBM
open isomer (p-homoaromatic), with different configurations of
the transannular bond (Fig. 1). However, the reaction of C60 with
dialkoxyoxadiazolines leads to only the 6-6 open isomer, because
the 6-6 ring junction bonds are shorter than the 6-5 ring junction
bonds. As a result, the 6-6 closed isomer with a s-homoaromatic
structure is energetically more favorable, and the bridgehead car-
bon is thus positioned at a smaller distance [30,31]. After consid-
erable experimentation, we found that the presence of excess
dialkoxyoxadiazolines reduced the yield of the desired compounds
and gave a mixture of mono-, di-, and triadducts, with no trace of
the desired products obtained in case of the presence of very large
excess dialkoxyoxadiazolines.
1
2
A unique property of dialkoxymethanofullerene C60(CO
2
R R ) is
the extensive structural variation that is possible. Variation of the
1
2
(
phenyl
C
61-butyric acid methyl ester) [24], SIMEFs (bis(si-
R and R substituents was utilized to form symmetric and non-
lylmethyl)[60]fullerenes) [25], and ICBA (indene-C60 bisadduct).
Herein, we report the synthesis, characterization, and electro-
chemical properties of four new methanofullerene derivatives for
use in OSCs (Scheme 1). This is the first report of using dialkox-
symmetric derivatives, namely, ethoxy(hexyloxy)methanofuller-
ene)2a), hexyloxy(methoxy)methanofullerene (2b), di(ethoxy)
methanofullerene (2c), and ethoxy(methoxy)methanofullerene
(2d). These compounds are expected be useful in a wide variety of
studies owing to their diverse chemical and physical properties.
Altering the alkyl group substituents allow us to tune the physical
properties and the solubility of the molecules in common organic
solvents such as toluene. We found that the solubility of 2a and 2b,
which is an essential requirement for solution-based processes,
was relatively high. In contrast, the solubility of 2c and 2d was
relatively low, which was related to their high crystallinity. The
short ethyl chain in the dialkoxy part of 2c and 2d may increase
their propensity to form partly insoluble aggregates, which nega-
tively affects the thin-film morphology and OSC device perfor-
mance [32]. These results indicate to that a hexyl chain in the
dialkoxy part of the dialkoxymethanofullerenes is indispensable for
low crystallinity and good solubility.
2
ymethanofullerenes such as C60C(OR) in OSC devices, which gave
PCE values up to 4.6% in BHJ OSCs using a PBTZT-stat-BDTT-8
polymer donor system, which is considered one of the most sta-
ble OSCs reported to date [26e28].
2
. Results and discussion
1
2
2
Four new dialkoxymethanofullerenes C60(CO R R ) were syn-
thesized in 27%e32% yield by using the method reported by War-
kentin and coworkers for oxadiazolines as convenient sources of
dialkoxycarbenes [29]. The dialkoxymethanofullerenes were
exclusively prepared by thermolysis of dialkoxyoxadiazolines (1)
and reaction with C60 under reflux in toluene (Fig. 1). Starting
materials 1 were synthesized in up to 75% yield via oxidative
cyclization of alkoxycarbonyl hydrazone of acetone by treatment
with iodobenzene diacetate in alcohol ROH (Scheme S1, Supporting
Information).
The electrochemical properties of 2a, 2b, 2c, and 2d were
evaluated by cyclic voltammetry (CV; Fig. 2) and differential pulse
voltammetry (DPV; Fig. S9). The LUMO levels of the dialkox-
ymethanofullerenes, as determined via the electrochemical mea-
surements, are listed in Table 1. The LUMO levels of 2a and 2b were
The facile reaction of dialkoxyoxadiazolines with C60 was likely
due to the high electrophilicity of C60 and the nucleophilic nature of
the dialkoxyoxadiazolines. Methanofullerenes have two possible
isomers, namely, a 6-6 closed isomer (s-homoaromatic) and a 6-5
Fig. 2. Cyclic voltammograms of 2a (black), 2b (red), 2c (green), and 2d (blue) in
þ ꢀ
ꢁ
4 6
chlorobenzene containing n-Bu N PF (0.1 M) as a supporting electrolyte at 25 C.
Scheme 1. Synthesis of dialkoxymethanofullerenes.
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M.Y. Suleiman et al. / Tetrahedron xxx (xxxx) xxx
3
Table 1
LUMO levels, solubilities, and electron mobilities of dialkoxymethanofullerenes.
LUMO levels [eV]a
solubility in PhCl [g/mL] ([mol/L])
electron mobility [cm /Vs]
b
2
entry
fullerenes
2
ꢀ5
ꢀ5
1
2
3
4
2a
2b
2c
2d
3.73
3.73
3.58
3.53
3.8
79 (9.5 ꢂ 10ꢀ
)
)
)
2.5 ꢂ 10
ꢀ2
15 (1.7 ꢂ 10
3.3 ꢂ 10
ꢀ
3
7.0 (8.5 ꢂ 10
e
4.2 (5.3 ꢂ 10ꢀ3)
e
5
ref
PC61BM
3.4 ꢂ 10ꢀ
a
red1
LUMO levels ¼ e(4.8 þ E 1/2 ).
b
The electron-only device structure: ITO/ZnO/active layer (PBTZT-stat-BDTT-8:fullerene)/Al. A reference electron-only device with PC61BM showed 3.4 ꢂ 10ꢀ5 cm /V.
2
0
.15e0.2 eV lower than those of 2c and 2d, meaning that 2a and 2b
Table 2
Photovoltaic performance of the devices using fullerene derivatives.
were electrochemically superior to 2c and 2d as electron acceptors.
Given the promising fundamental properties of the dialkox-
ymethanofullerenes, we next assessed their OSC performance in
standard BHJ devices using a PBTZT-stat-BDTT-8 polymer donor
system. The OSC conformation was indium tin oxide (ITO)/poly(3,4-
entry
fullerenes
JSC [mA/cm2]
VOC [V]
FF [ꢀ]
PCE [%]
1
2
3
4
2a
2b
2c
2d
10.183
9.621
0.002
0.003
11.536
0.832
0.831
0.140
0.440
0.845
0.447
0.581
0.476
0.345
0.673
3.79
4.65
<0.01
<0.01
6.56
ethylenedioxythiophene):poly(styrenesulfonate)
(PEDOT:PSS)/
ref
PC61BM
PBTZT-stat-BDTT-8 polymer (Fig. S15):dialkoxymethanofullerene/
LiF/Al, and the results are shown in Fig. 3 and Table 2.
The OSC devices using 2a and 2b had much higher JSC values of
0.183 and 9.621 mA/cm with PCEs of 4.65% and 3.79%, respec-
2
with these compounds as acceptors. In addition, the good
morphology of the thin films facilitated charge generation at the
donoreacceptor interface. By contrast, the PCE values of essentially
zero for devices using 2c and 2d were due to their relatively low
solubility, which led to fabrication of thin films with poor
morphology. Furthermore, the low solubility of 2c and 2d was
found to be unsuitable for spin coating. The thin films of 2a and 2b
had substantially higher film quality in comparison with 2c and 2d.
This difference can be attributed to the very low crystallinity of 2a
and 2b due to the presence of the hexyloxy chain and their asym-
metric structures. VOC for 2a and 2b was substantially and signifi-
cantly higher than that for 2c and 2d, by 0.69e0.39 V. Considering
the high VOC (0.83 V) obtained for the devices of 2a and 2b, we
surmise that the LUMOeLUMO gap between the donor (PBTZT-
stat-BDTT-8) and the acceptor is close to the theoretical limit (ca.
1
tively, compared with the devices using 2c and 2d, which showed
negligible JSC of 0.002 and 0.003, respectively, with PCEs of <0.01%
for both (Table 2). The relatively high PCEs of the 2a- and 2b-based
devices were associated with the compounds' relatively high sol-
ubility (Table 1), which led to fabrication of thin films with good
morphology and then to higher performance for the OSC devices
0.3 eV) for charge separation [33,34] due to the low-lying LUMO
level of PBTZT-stat-BDTT-8. Compounds 2c and 2d have shallower
LUMO levels than 2a and 2b, which may prevent electron transfer
from the donor to the acceptor. Electron mobility of electron-only
devices with the structure of ITO/ZnO/active layer (PBTZT-stat-
BDTT-8:fullerene)/LiF/Al using 2a and 2b showed similar electron
mobilities as the reference device using PC61BM (Table 1). Overall,
all those factors together achieved high PCEs in 2a- and 2b-based
devices. Although performance of the devices using dialkox-
ymethano[60]fullerenes were lower than the PCBM device, the
authors think the dialkoxymethano[60]fullerenes are tunable and
promising materials.
3. Conclusion
In summary, we have designed, synthesized, and characterized
new dialkoxymethanofullerenes. These compounds were then
utilized as electron acceptors in thin-film OSCs for the first time.
The dialkoxymethanofullerenes were prepared with various sub-
stitution patterns for the dialkoxy part of the dialkox-
ymethanofullerenes, namely, ethoxy-hexyloxy, methoxy-hexyloxy,
ethoxy-ethoxy, and methoxy-ethoxy substituents, to study the
impact of the substituents on thin-film morphology and OSC device
performance. The dialkoxymethanofullerenes were used in OSC
devices with a structure of ITO/PEDOT:PSS/PBTZT-stat-BDTT-8
polymer:dialkoxymethanofullerenes/LiF/Al. The devices fabricated
Fig. 3. Photovoltaic performance. (a) Current densityevoltage curves of OSC devices
based on PBTZT-stat-BDTT-8 polymer:2a (black), the polymer:2b (red), the polymer:2c
with
ethoxy-hexyloxymethanofullerene
and
methoxy-
(
green), and the polymer:2d (blue). (b) Photocurrent action spectra of OSC devices
based on 2a.
hexyloxymethanofullerene exhibited the highest JSC values of
Please cite this article as: M.Y. Suleiman et al., Dialkoxymethano[60]fullerenes as electron acceptors in thin-film organic solar cells, Tetrahedron,
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M.Y. Suleiman et al. / Tetrahedron xxx (xxxx) xxx
2
1
0.183 and 9.621 mA/cm , with VOC of 0.832 and 0.831 V as well as
0.278 mmol) and oxadiazolines (192 mg, 0.834 mmol) in toluene
(100 mL) was refluxed for 18 h under stirring. After removal of
solvent by rotary evaporation, the reaction mixture was diluted
FF of 0.447 and 0.581, giving PCEs of 3.79% and 4.65%, respectively,
as a result of good solubility, which enabled the fabrication of thin
films with good morphology. By contrast, the devices fabricated
with CS and subjected to silica gel column chromatography
2
(eluent, CS ) to remove remaining C60 and separates all of mono-,
2
with
ethoxy-ethoxymethanofullerene
and
methoxy-
ethoxymethanofullerene exhibited very low JSC of 0.002 and
di-, and triadducts from each other to obtain the crude product.
Purification by Buckyprep column separation (eluent: toluene/2-
propanol ¼ 7/3) was executed to obtain 2b which was washed
with MeOH, dissolved in toluene, reprecipitated with MeOH, and
2
0
.003 mA/cm , with VOC of 0.140 and 0.440 V as well as FF of 0.476
and 0.345, respectively, leading to the PCEs of <0.01% for both. For
these compounds, poor solubility related to high crystallinity led to
poor morphology of the thin films, and then to negligible JSC and
ultimately near-zero PCE. For the dialkoxymethanofullerenes
examined in this study, a hexyl chain in the dialkoxide part with an
asymmetric structure was indispensable for achieving good solu-
bility, leading to good film morphology and then satisfactory PCE.
dried to obtained the target dark red crystal (77 mg, 0.089 mmol,
1
32% isolated yield, analytically pure). H NMR (600 MHz, CDCl
3
):
), 1.38e1.43 (m, 4H,
), 1.52e1.59 (m, 2H, OCH CH CH CH
), 1.86e1.90 (m, 4H, OCH CH CH CH CH CH ), 3.97 (s, 3H,
), 4.25 (t, 2H, OCH CH CH CH CH CH CH
(150 MHz, CS -CDCl ): 145.35, 145.12, 145.01, 144.88, 144.85,
44.81, 144.48, 144.32, 144.26, 143.63, 143.41, 143.40, 143.16, 142.94,
d
0.94 (t, 3H, OCH
OCH CH CH CH CH CH
CH CH
OCH
2 2 2 2 2 3
CH CH CH CH CH
2
2
2
2
2
3
2
2
2
2
2
3
2
2
2
2
2
3
1
3
1
3
2
2
2
2
2
3
2
). C{ H} NMR
4
. Experimental
2
3
d
1
4
.1. General
142.52, 142.50, 142.36, 141.39, 141.38, 137.78, 137.70. The remaining
resonances at 84.65, 68.11, 54.81, 32.10, 30.16, 26.40, 23.27, and
14.58 belong to the fullerene-sp C-atoms and dialkoxy C-atoms.
3
C60 was purchased from Frontier Carbon Corporation. Other
reagents were used as received without further purification. All
solvents were purified using standard procedures. All reactions
dealing with air- or wetness-sensitive compounds were carried out
in a dry reaction container under nitrogen. Column chromatog-
We appointed the peak at 96.76 to the bridgehead C-atom. MALDI-
þ
TOF-HRMS (þ) (m/z): Calcd for C68
O
2
H16 (M þ H ): 865.1230, found
865.1225.
raphy was performed on a silica gel column using CS
2
or CH
2
Cl
2
as
2 3 2
4.4. Synthesis of C60C(OCH CH ) (2c)
eluent. HPLC analyses were performed on a Shimadzu LC-10A
system supplied with UV spectrophotometric detector and equip-
ped using a Buckyprep column (Nacalai Tesque Inc., 4.6 mm ID x
Under a nitrogen atmosphere, a solution of C60 (200 mg,
0.278 mmol) and oxadiazolines (157 mg, 0.834 mmol) in toluene
(100 mL) was refluxed for 18 h under stirring. After removal of
solvent by rotary evaporation, the reaction mixture was diluted
2
50 mm) with mobile phase of 7:3 v/v mixture of toluene and 2-
1
13
propanol (flow rate 1 mL/min). H NMR and C NMR were
measured at 600.38 MHz and 150.97 MHz respectively, on a Varian
Unity JEOL ECA-500 instrument at 296e299 K. Cyclic voltammetry
was performed using a Hokuto Denko HZ-5000 voltammetric
analyzer.
with CS
(eluent, CS
2
and subjected to silica gel column chromatography
) to remove remaining C60 and separates all of mono-,
2
di-, and triadducts from each other to obtain the crude product.
Purification by Buckyprep column separation (eluent: toluene/2-
propanol ¼ 7/3) was executed to obtain 2c which was washed
with MeOH, dissolved in toluene, reprecipitated with MeOH, and
2 3 2 5 3
4.2. Synthesis of C60C(OCH CH )(O(CH ) CH ) (2a)
dried to obtained the target dark red crystal (65 mg, 0.079 mmol,
1
Under a nitrogen atmosphere, a solution of C60 (200 mg,
.278 mmol) and oxadiazolines (204 mg, 0.834 mmol) in toluene
28% isolated yield, analytically pure). H NMR (600 MHz, CDCl
3
):
). C{ H} NMR
145.39, 145.14, 145.02, 144.87, 144.81,
13
1
0
(
d
1.54 (t, 6H, OCH
2
CH
):
3 2 3
), 4.37 (q, 4H, OCH CH
100 mL) was refluxed for 18 h under stirring. After removal of
solvent by rotary evaporation, the reaction mixture was diluted
with CS and subjected to silica gel column chromatography
eluent, CS ) to remove remaining C60 and separates all of mono-,
(150 MHz, CS -CDCl
2
3
d
144.64,144.29,144.28,143.66,143.38,143.15,142.95,152.55,142.35,
141.37, 137.70. The remaining resonances at 84.57, 64.02, and 15.64
belong to the fullerene-sp C-atoms and dialkoxy C-atoms. We
2
3
(
2
di-, and triadducts from each other to obtain the crude product.
Purification by Buckyprep column separation (eluent: toluene/2-
propanol ¼ 7/3) was executed to obtain 2a which was washed
with MeOH, dissolved in toluene, reprecipitated with MeOH, and
appointed the peak at 96.46 to the bridgehead C-atom. MALDI-TOF-
þ
HRMS (þ) (m/z): calcd for C65
O
2
H10 (M þ H ): 823.0761, found
823.0758.
dried to obtained the target dark red crystal (76 mg, 0.086 mmol,
3 2 3
4.5. Synthesis of C60C(OCH )(OCH CH ) (2d)
1
3
d
1% isolated yield, analytically pure). H NMR (600 MHz, CDCl
3
):
),
), 1.55e1.57 (m, 2H,
1.86e1.88 (m, 2H, OCH CH CH CH
CH CH CH CH CH CH ), 4.32 (q, 2H,
). C{ H} NMR (150 MHz, CS -CDCl ): 145.40, 145.13,
0.94 (t, 3H, OCH
2
CH
2
CH
2
CH
CH
2
CH
CH
2
CH
CH
3
), 1.39 (t, 3H, OCH
CH
2
CH
3
Under a nitrogen atmosphere, a solution of C60 (200 mg,
0.278 mmol) and oxadiazolines (145 mg, 0.834 mmol) in toluene
(100 mL) was refluxed for 18 h under stirring. After removal of
solvent by rotary evaporation, the reaction mixture was diluted
1.51e1.54 (m, 4H, OCH
2
CH
2
2
2
2
3
OCH
CH
OCH
2
CH
2
CH
2
CH
2
CH
2
CH
3
)
2
2
2
2
2
CH
3
), 4.26 (t, 2H, OCH
2
2
2
2
2
3
2
13
1
2
CH
3
2
3
d
with CS and subjected to silica gel column chromatography
2
(eluent, CS ) to remove remaining C60 and separates all of mono-,
2
1
1
45.01, 144.87, 144.80, 144.68, 144.63, 144.29, 144.26, 143.66, 143.37,
43.14, 142.95, 142.55, 142.52, 142.34, 141.36, 137.68, 137.67. The
remaining resonances at 84.54, 68.09, 63.97, 32.07, 30.12, 26.36,
di-, and triadducts from each other to obtain the crude product.
Purification by Buckyprep column separation (eluent: toluene/2-
propanol ¼ 7/3) was executed to obtain 2d which was washed with
MeOH, dissolved in toluene, reprecipitated with MeOH, and dried
3
2
3.23, 15.61, and 14.53 belong to the fullerene-sp C-atoms, and
dialkoxy C-atoms. We appointed the peak at 96.33 to the bridge-
head C-atom. MALDI-TOF-HRMS (þ) (m/z): Calcd for C69
O
2
H
18
to obtained the target dark red crystal (60 mg, 0.074 mmol, 27%
þ
1
(
M þ H ): 879.1387, found 879.1382.
isolated yield, analytically pure). H NMR (600 MHz, CDCl
3
):
d
1.54
1
3
1
(
t, 3H, OCH
NMR (150 MHz, CS
44.85, 144.81, 144.48, 144.72, 143.63, 143.42, 143.40, 143.17, 142.95,
142.54, 142.52, 142.37, 141.40, 141.38, 137.80, 137.71. The remaining
2
CH
3
), 4.01 (s, 3H, CH
3 2 3
), 4.36 (q, 2H, OCH CH ). C{ H}
4.3. Synthesis of C60C(OCH
3
2
)(O(CH )
5
CH
3
) (2b)
2
-CDCl ): 145.34, 145.33, 145.13, 145.02, 144.88,
3
d
1
Under a nitrogen atmosphere, a solution of C60 (200 mg,
Please cite this article as: M.Y. Suleiman et al., Dialkoxymethano[60]fullerenes as electron acceptors in thin-film organic solar cells, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.130514

M.Y. Suleiman et al. / Tetrahedron xxx (xxxx) xxx
5
resonances at 84.67, 64.08, 54.83 and 15.64 belong to the fullerene-
sp C-atoms and dialkoxy C-atoms. We appointed the peak at 96.46
Grants-in-Aid for Scientific Research (JSPS KAKENHI Grant
Numbers JP15H05760, JP16H04187), MEXT, Japan.
3
to the bridgehead C-atom. MALDI-TOF-HRMS (þ) (m/z): calcd for
þ
C
64
O
2
H
8
(M ): 808.0524, found 808.0520.
Appendix A. Supplementary data
4
.6. Device fabrication and evaluation
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tet.2019.130514.
Fabrication and evaluation of BHJ OSCs: Regioregular Merck
polymer and PEDOT:PSS (H.C. Starck, Clevios PVP AI4083) were
purchased from Aldrich and H.C. Starck, respectively, and used as
received. Active-layer solutions were prepared by using Merck
polymer and dialkoxymethanofullerenes in a 1:1 wt ratio (con-
centration, 20 mg/mL in PhCl). These blended solutions were
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This work was supported by the thousand talent program in
Northeast Normal University. This work was also supported by the
Please cite this article as: M.Y. Suleiman et al., Dialkoxymethano[60]fullerenes as electron acceptors in thin-film organic solar cells, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.130514