Efficient Organic Photovoltaics Utilizing Nanoscale Heterojunctions in Sequentially

SupplementaryInformation

Efficient Organic Photovoltaics Utilizing Nanoscale Heterojunctions in Sequentially DepositedPolymer/fullerene Bilayer

Jeesoo Seok1, Tae Joo Shin2, Sungmin Park3, Changsoon Cho4, Jung-Yong Lee4, Du Yeol Ryu3, Myung Hwa Kim1, Kyungkon Kim1*

(E-mail: )

1Department of Chemistry and Nano Science, Global Top 5 Research Program, Ewha Womans University, Seoul 120-750, Republic of Korea

2Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784, Republic of Korea

3Department of Chemical and Biomolecular Engineering, Yonsei University, Seoul 120-749, Republic of Korea

4Graduate School of Energy, Environment, Water, and Sustainability (EEWS), Graphene Research Center, KAIST, Daejeon 305-701, Republic of Korea

Figure S1|UV-visible absorption spectrafor thereference 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-preparedfilm and red line: film after removal of PC70BM from the PCDTBT/PC70BM SD-bilayer). cPL spectra of PCDTBT film and PCDTBT:PC70BM films with various blending ratios, and drelative PL intensity as a function of PC70BM content.

Figure S3|AFM images of athe as-prepared PCDTBT(OA) film, bthe PCDTBT(OA) film soaked in DIM for 60s and cthe 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).

FigureS4|Cross-section TEM images of aPCDTBT(N), bPCDTBT(N-T) and cPCDTBT(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) top-layer 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 Figure6

Figure S5|PL spectra of PCDTBT(N), PCDTBT(N-T) and PCDTBT(OA) films, and PCDTBT(N)/PC70BM(HA), PCDTBT(N-T)/PC70BM(HA) and PCDTBT(OA)/PC70BM(HA) SD-bilayer films

FigureS6|UV-visible absorption spectra of the PCDTBT(OA)/PC70BM(HA)SD-bilayer 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 tothat in the BHJ film.

Figure S7|UV-visible absorption spectrum of the PCDTBT(OA)/PC70BM(HA) SD-bilayer film measured in reflection mode.

FigureS8|Current density (J) vs. voltage (V) curves of PCDTBT/PC70BMSD-bilayer OPVs fabricated with different OA. The HA was fixed to DIM.

TableS1|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 / VOC
(V) / JSC
(mA/cm2) / FF / PCE
(%)
None / DIM / 0.87 / 3.30 / 0.47 / 1.36
DIM / 0.88 / 3.00 / 0.53 / 1.38
MT / 0.86 / 3.92 / 0.54 / 1.82
HT / 0.88 / 3.38 / 0.57 / 1.69
DIO / 0.90 / 12.02 / 0.66 / 7.12
CN / 0.91 / 10.29 / 0.64 / 6.02
ODT / 0.87 / 9.58 / 0.62 / 5.16

BesidesDIO and DIM, we have tested 1-chloronaphthanele (CN), 3-methylthiophene (MT), 3-hexylthiophene (HT) and 1,8-octanedithiol (OD) for use as theOA 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 tosolar cells made without OAs (Figure S2 and TableS1 of Supplementary Information). This implies DIO, CN and ODT can be used as anOA for the PCDTBT/PC70BM SD-bilayer OPV.

FigureS9|J vs. V curves of PCDTBT/PC70BM SD-bilayer OPVs fabricated with different HAs. The OA was fixed to DIM.

TableS2|Solar cell parameters of PCDTBT/PC70BMSD-bilayer OPVs fabricated with different HAs. The OA was fixed to DIO.

Type of OA / Type of HA / VOC
(V) / JSC
(mA/cm2) / FF / PCE
(%)
DIO / None / 0.92 / 3.30 / 0.38 / 1.16
DIM / 0.90 / 12.02 / 0.66 / 7.12
MT / 0.87 / 11.22 / 0.55 / 5.38
HT / 0.85 / 4.26 / 0.30 / 1.10
DIO / 0.84 / 10.17 / 0.59 / 5.06
CN / 0.85 / 10.14 / 0.47 / 4.05
ODT / 0.92 / 6.24 / 0.44 / 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 efficienciestosolar cells made without HAs (Supplementary FigureS8 and TableS2). This implies DIM, DIO, CN and MT can be used as the OA for the PCDTBT/PC70BM SD-bilayer OPV.