Supplementary Information
Efficient Organic Photovoltaics Utilizing Nanoscale Heterojunctions
in Sequentially Deposited Polymer/fullerene Bilayer
Jeesoo Seok1, Tae Joo Shin2, Sungmin Park3, Changsoon Cho4, Jung-Yong Lee4, Du
Yeol Ryu3, Myung Hwa Kim1, Kyungkon Kim1*
(E-mail: kimkk@ewha.ac.kr)
1Department
of Chemistry and Nano Science, Global Top 5 Research Program, Ewha
Womans University, Seoul 120-750, Republic of Korea
2
Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784, Republic of Korea
3
Department of Chemical and Biomolecular Engineering, Yonsei University, Seoul
120-749, Republic of Korea
4
Graduate School of Energy, Environment, Water, and Sustainability (EEWS),
Graphene Research Center, KAIST, Daejeon 305-701, Republic of Korea
Figure S1| UV-visible absorption spectra for the reference PC70BM solution dissolved
in CB (black) and PC70BM in the DIM solution containing PC70BM removed from
PCDTBT/PC70BM SD-bilayer film. The PC70BM solution was further diluted with
CB to have the same absorbance with reference to the PC70BM solution.
Figure S2| PL spectra of a PCDTBT(N-T) films (blue line: as-prepared film and red
line: film after removal of PC70BM from the PCDTBT/PC70BM SD-bilayer) and b
PCDTBT(OA) films (blue line: as-prepared film and red line: film after removal of
PC70BM from the PCDTBT/PC70BM SD-bilayer). c PL spectra of PCDTBT film and
PCDTBT:PC70BM films with various blending ratios, and d relative PL intensity as a
function of PC70BM content.
Figure S3|AFM images of a the as-prepared PCDTBT(OA) film, b the
PCDTBT(OA) film soaked in DIM for 60s and c the PCDTBT(OA) film soaked twice
in DIM for 60s. All the images were obtained by AFM in tapping mode (2.5 μm×2.5
μm).
Figure S4|Cross-section TEM images of a PCDTBT(N), b PCDTBT(N-T) and c
PCDTBT(OA) films after removing the PC70BM(HA) top-layer from the
corresponding PCDTBT/PC70BM SD-bilayers.
Aluminum of 10 nm thickness was thermally evaporated on the PC70BM(HA) toplayer removed PCDTBT(N), PCDTBT(N-T) and PCDTBT(OA) bottom-layers to
discern PCDTBT from the background. Above TEM images were contracted to fit
with AFM height profiles and shown in Figure 6
Figure S5| PL spectra of PCDTBT(N), PCDTBT(N-T) and PCDTBT(OA) films, and
PCDTBT(N)/PC70BM(HA),
PCDTBT(N-T)/PC70BM(HA)
PCDTBT(OA)/PC70BM(HA) SD-bilayer films
and
Figure S6|UV-visible absorption spectra of the PCDTBT(OA)/PC70BM(HA) SDbilayer film (solid red line) and the PCDTBT:PC70BM BHJ film (solid blue line),
PC70BM removed PCDTBT(OA)/PC70BM(HA) SD-bilayer film (dashed red line) and
PC70BM removed PCDTBT:PC70BM BHJ film (dashed blue line). The blending ratio
for PCDTBT:PC70BM for the BHJ film was 1:4.
The absorption spectrum of the PCDTBT/PC70BM SD-bilayer film almost coincides
with that of the BHJ film (PCDTBT:PC70BM=1:4). (Figure S5 in Supplementary
Information). Furthermore, the absorption intensities of the PCDTBT films after
removing the PC70BM from the BHJ film and SD-bilayer film are similar. This
implies the amount of PCDTBT in the SD-bilayer film is similar to that in the BHJ
film.
Figure S7|UV-visible absorption spectrum of the PCDTBT(OA)/PC70BM(HA) SDbilayer film measured in reflection mode.
PCDTBT(N)/PC70BM(DIM)
PCDTBT(DIM)/PC70BM(DIM)
PCDTBT(MT)/PC70BM(DIM)
PCDTBT(HT)/PC70BM(DIM)
PCDTBT(DIO)/PC70BM(DIM)
PCDTBT(CN)/PC70BM(DIM)
PCDTBT(ODT)/PC70-BM(DIM)
2
J (mA/cm )
0
-5
-10
0.0
0.5
1.0
V (V)
Figure S8|Current density (J) vs. voltage (V) curves of PCDTBT/PC70BM SD-bilayer
OPVs fabricated with different OA. The HA was fixed to DIM.
Table S1|Solar cell parameters of PCDTBT(OA)/PC70BM(HA) SD-bilayer OPVs
fabricated with different OAs. The HA was fixed to DIM.
Type of OA Type of HA
None
DIM
MT
HT
DIO
CN
ODT
DIM
VOC
(V)
JSC
(mA/cm2)
FF
PCE
(%)
0.87
0.88
0.86
0.88
0.90
0.91
0.87
3.30
3.00
3.92
3.38
12.02
10.29
9.58
0.47
0.53
0.54
0.57
0.66
0.64
0.62
1.36
1.38
1.82
1.69
7.12
6.02
5.16
Besides DIO and DIM, we have tested 1-chloronaphthanele (CN), 3methylthiophene (MT), 3-hexylthiophene (HT) and 1,8-octanedithiol (OD) for use as
the OA or HA of PCDTBT/PC70BM SD-bilayer OPV. PCDTBT/PC70BM SD-bilayer
OPVs with different OAs were tested by fixing the HA to DIM. The OPVs utilizing
DIO, CN and ODT as the OA exhibited considerable enhancement in the efficiency,
whereas those utilizing DIM, MT and HT as the OA exhibited efficiencies similar to
solar cells made without OAs (Figure S2 and Table S1 of Supplementary
Information). This implies DIO, CN and ODT can be used as an OA for the
PCDTBT/PC70BM SD-bilayer OPV.
PCDTBT(DIO)/PC70BM(N)
PCDTBT(DIO)/PC70BM(DIM)
PCDTBT(DIO)/PC70BM(MT)
PCDTBT(DIO)/PC70BM(HT)
PCDTBT(DIO)/PC70BM(DIO)
PCDTBT(DIO)/PC70BM(CN)
PCDTBT(DIO)/PC70-BM(ODT)
2
J (mA/cm )
0
-5
-10
0.0
0.5
1.0
V (V)
Figure S9|J vs. V curves of PCDTBT/PC70BM SD-bilayer OPVs fabricated with
different HAs. The OA was fixed to DIM.
Table S2|Solar cell parameters of PCDTBT/PC70BM SD-bilayer OPVs fabricated
with different HAs. The OA was fixed to DIO.
Type of OA
Type of HA
DIO
None
DIM
MT
HT
DIO
CN
ODT
VOC
(V)
0.92
0.90
0.87
0.85
0.84
0.85
0.92
JSC
(mA/cm2)
3.30
12.02
11.22
4.26
10.17
10.14
6.24
FF
0.38
0.66
0.55
0.30
0.59
0.47
0.44
PCE
(%)
1.16
7.12
5.38
1.10
5.06
4.05
2.53
In the same manner, PCDTBT/PC70BM SD-bilayer OPVs with different HAs
were tested by fixing the OA to DIO. The devices utilizing DIM, DIO, CN and MT
as the HA exhibited significant enhancement in efficiency, whereas those utilizing
HT and ODT as the HA exhibited similar efficiencies to solar cells made without
HAs (Supplementary Figure S8 and Table S2). This implies DIM, DIO, CN and MT
can be used as the OA for the PCDTBT/PC70BM SD-bilayer OPV.