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SUPPLEMENTARY INFORMATION ARTICLE NUMBER: 16089 | DOI: 10.1038/NENERGY.2016.89 NATURE ENERGY | www.nature.com/natureenergy 1 Fast charge separation in a non-fullerene organic solar cell with a small driving force Jing Liu 1 , Shangshang Chen 1 , Deping Qian 2 , Bhoj Gautam 3 , Guofang Yang 1,4 , Jingbo Zhao 1 , Jonas Bergqvist 2 , Fengling Zhang 2 , Wei Ma 4 , Harald Ade 3 , Olle Inganäs 2 , Kenan Gundogdu 3 *, Feng Gao 2 * & He Yan 1,5 * 1 Department of Chemistry and Energy Institute, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong. 2 Department of Physics Chemistry and Biology (IFM), Linköping University, Linköping SE-581 83, Sweden. 3 Department of Physics and Organic and Carbon Electronics Laboratory North Carolina State University, Raleigh, NC 27695, USA. 4 State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong University Xi’an 710049, China. 5 The Hong Kong University of Science and Technology-Shenzhen Research Institute No. 9 Yuexing 1st RD, Hi-tech Park, Nanshan Shenzhen 518057, China. *email: [email protected]; [email protected]; [email protected].

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Page 1: Fast charge separation in a non-fullerene organic solar cell with a … · 2016-06-27 · Fast charge separation in a non-fullerene organic solar cell with a small driving force Jing

SUPPLEMENTARY INFORMATIONARTICLE NUMBER: 16089 | DOI: 10.1038/NENERGY.2016.89

NATURE ENERGY | www.nature.com/natureenergy 1

Supplementary Information

Fast charge separation in a non-fullerene organic solar cell with a

small driving force

Jing Liu1†, Shangshang Chen1†, Deping Qian2, Bhoj Gautam3, Guofang Yang1,4, Jingbo Zhao1,

Jonas Bergqvist2, Fengling Zhang2, Wei Ma4, Harald Ade3, Olle Inganäs2, Kenan Gundogdu3*,

Feng Gao2* & He Yan1,5*

1 Department of Chemistry and Energy Institute, The Hong Kong University of Science and

Technology, Clear Water Bay, Hong Kong.

2 Department of Physics Chemistry and Biology (IFM), Linköping University, Linköping SE-581

83, Sweden.

3 Department of Physics and Organic and Carbon Electronics Laboratory North Carolina State

University, Raleigh, NC 27695, USA.

4 State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong University Xi’an

710049, China.

5 The Hong Kong University of Science and Technology-Shenzhen Research Institute No. 9

Yuexing 1st RD, Hi-tech Park, Nanshan Shenzhen 518057, China.

*email: [email protected]; [email protected]; [email protected].

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2 NATURE ENERGY | www.nature.com/natureenergy

SUPPLEMENTARY INFORMATION DOI: 10.1038/NENERGY.2016.89

Supplementary Note 1

In order to understand why we can achieve low energy loss, we need to understand where the

losses are from. The 𝑉𝑉𝑂𝑂𝑂𝑂 of any type of solar cells is determined by the ratio between short circuit

current (𝐽𝐽𝑆𝑆𝑂𝑂) and and dark saturation current (𝐽𝐽0), following this expression1:

𝑉𝑉𝑂𝑂𝑂𝑂 = 𝑘𝑘𝑘𝑘𝑞𝑞 𝑙𝑙𝑙𝑙 (𝐽𝐽𝑆𝑆𝑂𝑂𝐽𝐽0

+ 1) (1)

where k is the boltzmann constant, T is the temperature, and q is the elementary charge. The

expression for 𝐽𝐽𝑆𝑆𝑂𝑂 and 𝐽𝐽0 are given by:

𝐽𝐽𝑆𝑆𝑂𝑂 = 𝑞𝑞 ∙ ∫ 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑃𝑃(𝐸𝐸)∞

0∙ ∅𝐴𝐴𝐴𝐴1.5(𝐸𝐸)𝑑𝑑𝐸𝐸 (2)

𝐽𝐽0 = 𝑞𝑞𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸

∙ ∫ 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑃𝑃(𝐸𝐸)∞

0∙ ∅𝐵𝐵𝐵𝐵(𝐸𝐸)𝑑𝑑𝐸𝐸 (3)

The expression for 𝐽𝐽0 is the Rau’s reciprocity relation2, where 𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸 is radiative quantum

efficiency of the solar cell when charge carriers are injected into the device in dark, and ∅𝐵𝐵𝐵𝐵 is

the black body spectrum.

When all the recombination is radiative (i.e. 𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸 = 1), 𝐽𝐽0 is minimized, and 𝑉𝑉𝑂𝑂𝑂𝑂 is

maximized:

𝐽𝐽0𝑟𝑟𝑟𝑟𝑟𝑟 = 𝑞𝑞 ∙ ∫ 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑃𝑃(𝐸𝐸)∞

0∙ ∅𝐵𝐵𝐵𝐵(𝐸𝐸)𝑑𝑑𝐸𝐸 (4)

𝑉𝑉𝑂𝑂𝑂𝑂𝑟𝑟𝑟𝑟𝑟𝑟 = 𝑘𝑘𝑘𝑘𝑞𝑞 ln( 𝐽𝐽𝑆𝑆𝑂𝑂𝐽𝐽0𝑟𝑟𝑟𝑟𝑟𝑟

+ 1) = 𝑘𝑘𝑘𝑘𝑞𝑞 𝑙𝑙𝑙𝑙 (

𝑞𝑞 ∙ ∫ 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑃𝑃(𝐸𝐸) ∙ ∅𝐴𝐴𝐴𝐴1.5(𝐸𝐸)𝑑𝑑𝐸𝐸∞0

𝑞𝑞 ∙ ∫ 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑃𝑃∞0 (𝐸𝐸) ∙ ∅𝐵𝐵𝐵𝐵(𝐸𝐸)𝑑𝑑𝐸𝐸

+ 1) (5)

In the Shockley-Queisser theory3, the general quantum efficiency 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑃𝑃𝑆𝑆𝑆𝑆(𝐸𝐸) can be defined

as follow:

𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑃𝑃𝑆𝑆𝑆𝑆(𝐸𝐸) = 1, 𝐸𝐸 ≥ 𝐸𝐸𝑔𝑔𝑟𝑟𝑔𝑔 ; 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑃𝑃

𝑆𝑆𝑆𝑆(𝐸𝐸) = 0, 𝐸𝐸 < 𝐸𝐸𝑔𝑔𝑟𝑟𝑔𝑔 . (6)

Substituting general quantum efficiency 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑃𝑃𝑆𝑆𝑆𝑆(𝐸𝐸) (equation 6) in equation 4, then we can

get the saturation current in the SQ limit, 𝐽𝐽0𝑆𝑆𝑆𝑆.

𝐽𝐽0𝑆𝑆𝑆𝑆 = 𝑞𝑞 ∙ ∫ 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑃𝑃

𝑆𝑆𝑆𝑆(𝐸𝐸)∞

𝐸𝐸𝑔𝑔𝑔𝑔𝑔𝑔 ∅𝐵𝐵𝐵𝐵(𝐸𝐸)𝑑𝑑𝐸𝐸 = 𝑞𝑞 ∙ ∫ ∅𝐵𝐵𝐵𝐵(𝐸𝐸)𝑑𝑑𝐸𝐸

𝐸𝐸𝑔𝑔𝑔𝑔𝑔𝑔 (7)

In the same way, we can calculate the value of the SQ open-circuit voltage limit, 𝑉𝑉𝑂𝑂𝑂𝑂𝑆𝑆𝑆𝑆,

according to equation 5,

𝑉𝑉𝑂𝑂𝑂𝑂𝑆𝑆𝑆𝑆 = 𝑘𝑘𝑘𝑘

𝑞𝑞 ln(𝐽𝐽𝑆𝑆𝑂𝑂𝐽𝐽0𝑆𝑆𝑆𝑆 + 1) = 𝑘𝑘𝑘𝑘

𝑞𝑞 𝑙𝑙𝑙𝑙(𝑞𝑞 ∙ ∫ 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑃𝑃(𝐸𝐸) ∙ ∅𝐴𝐴𝐴𝐴1.5(𝐸𝐸)𝑑𝑑𝐸𝐸∞

0𝑞𝑞 ∙ ∫ ∅𝐵𝐵𝐵𝐵(𝐸𝐸)𝑑𝑑𝐸𝐸∞

𝐸𝐸𝑔𝑔𝑔𝑔𝑔𝑔

+ 1) (8)

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NATURE ENERGY | www.nature.com/natureenergy 3

SUPPLEMENTARY INFORMATIONDOI: 10.1038/NENERGY.2016.89

The difference between 𝑉𝑉𝑂𝑂𝑂𝑂,𝑆𝑆𝑆𝑆 and 𝑉𝑉𝑂𝑂𝑂𝑂𝑟𝑟𝑟𝑟𝑟𝑟 is due to that in the SQ theory, the band edge of

the absorber is totally abrupt when calculating 𝑉𝑉𝑂𝑂𝑂𝑂𝑟𝑟𝑟𝑟𝑟𝑟, the band gap will be smeared out for the

existence of charge transfer state absorption.

Therefore, we can deduce the voltage loss of radiative recombination below the gap,

∆𝑉𝑉𝑂𝑂𝑂𝑂𝑟𝑟𝑟𝑟𝑟𝑟,𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏 𝑔𝑔𝑟𝑟𝑔𝑔.

∆𝑉𝑉𝑂𝑂𝑂𝑂𝑟𝑟𝑟𝑟𝑟𝑟,𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏 𝑔𝑔𝑟𝑟𝑔𝑔 = 𝑉𝑉𝑂𝑂𝑂𝑂

𝑆𝑆𝑆𝑆 − 𝑉𝑉𝑂𝑂𝑂𝑂𝑟𝑟𝑟𝑟𝑟𝑟 (9)

The voltage loss due to non-radiative recombination, ∆𝑉𝑉𝑂𝑂𝑂𝑂𝑛𝑛𝑏𝑏𝑛𝑛−𝑟𝑟𝑟𝑟𝑟𝑟, can be rewritten as

∆𝑉𝑉𝑂𝑂𝑂𝑂𝑛𝑛𝑏𝑏𝑛𝑛−𝑟𝑟𝑟𝑟𝑟𝑟 = 𝑉𝑉𝑂𝑂𝑂𝑂𝑟𝑟𝑟𝑟𝑟𝑟 − 𝑉𝑉𝑂𝑂𝑂𝑂 = −𝑘𝑘𝑘𝑘𝑞𝑞 𝑙𝑙𝑙𝑙(𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸) (10)

Based on the previous discussions, we are now able to summarize the energy loss from the

𝐸𝐸𝑔𝑔𝑟𝑟𝑔𝑔 to the q𝑉𝑉𝑂𝑂𝑂𝑂 for any type of solar cells.

𝑞𝑞∆𝑉𝑉 = ∆𝐸𝐸1 + ∆𝐸𝐸2 + ∆𝐸𝐸3

= (𝐸𝐸𝑔𝑔𝑟𝑟𝑔𝑔 − 𝑞𝑞𝑉𝑉𝑂𝑂𝑂𝑂𝑆𝑆𝑆𝑆) + 𝑞𝑞∆𝑉𝑉𝑂𝑂𝑂𝑂

𝑟𝑟𝑟𝑟𝑟𝑟,𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏 𝑔𝑔𝑟𝑟𝑔𝑔 + 𝑞𝑞∆𝑉𝑉𝑂𝑂𝑂𝑂𝑛𝑛𝑏𝑏𝑛𝑛−𝑟𝑟𝑟𝑟𝑟𝑟 (11)

Therefore, we can get these three terms of energy losses based on related experiments and

calculations.

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4 NATURE ENERGY | www.nature.com/natureenergy

SUPPLEMENTARY INFORMATION DOI: 10.1038/NENERGY.2016.89

Supplementary Figures

Supplementary Figure 1: Measurement of bandgap and charge transfer state. The bandgap

(1.72 eV) of a, P3TEA and the bandgap (1.70 eV) of b, PffBT4T-2DT were determined from the

crossing point between the emission and absorption spectra. ECT of c, the P3TEA:SF-PDI2 (blend

A) (1.68 eV, but uncertainty still exists due to curve fitting); d, the PffBT4T-2DT:SF-PDI2 (blend

B) (1.54 eV); e, the P3TEA:diPDI (blend C) (1.52 eV); f, the PffBT4T-2DT:diPDI (blend D) (1.33

eV) blend films by fitting the FTPS-EQE spectra.

1.0 1.5 2.0 2.5

0.0

0.5

1.0

Norm

aliz

ed a

bsor

ptio

n

Norm

aliz

ed e

mis

sion

Energy (eV)

PffBT4T-2DT

1.5 2.0 2.5 3.0 3.5

10-4

10-3

10-2

10-1

100

Norm

aliz

ed F

TPS-

EQE

Energy (eV)

Blend A

1 2 3 4

10-4

10-3

10-2

10-1

100

Norm

aliz

ed F

TPS-

EQE

Energy (eV)

Blend B

1 2 3 4

10-4

10-3

10-2

10-1

100

Norm

aliz

ed F

TPS-

EQE

Energy (eV)

Blend C

1 2 3 4

10-4

10-3

10-2

10-1

100

Norm

aliz

ed F

TPS-

EQE

Energy (eV)

Blend D

a

c

b

fe

d

1.0 1.5 2.0 2.5

0.0

0.5

1.0

Nor

mal

ized

abs

orpt

ion

Nor

mal

ized

em

issi

on

Energy (eV)

P3TEA

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NATURE ENERGY | www.nature.com/natureenergy 5

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Supplementary Figure 2: IQE data of blend A. IQE as a function of wavelength λ was

calculated based on the optical transfer matrix modeling4. The absorption coefficients and

refractive indexes used in the optical model were determined by variable angle spectroscopic

ellipsometry. The IQE of the blend A is nearly 90%.

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6 NATURE ENERGY | www.nature.com/natureenergy

SUPPLEMENTARY INFORMATION DOI: 10.1038/NENERGY.2016.89

Supplementary Figure 3: Energy diagrams of inorganic and organic solar cells. Energy

diagram showing the relationship of optical bandgap (Egap), lowest singlet state (S1), charge-

transfer (CT) state, Voc and the three terms of energy losses for a, inorganic solar cell and b,

organic solar cell. The value of ∆𝐸𝐸2 is negligible for inorganic solar cells.

a Inorganic solar cells b Organic solar cells

Δ E2Δ E1

Δ E1Δ E3

Δ E3

CT

Conduction Band S1

Eg Eg

Voc

Voc

Valence band S0

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NATURE ENERGY | www.nature.com/natureenergy 7

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Supplementary Figure 4 : Transient Absorption data. a, Time evolution of singlet exciton

absorption for P3TEA and PffBT4T-2DT. b, Intensity dependent time evolution of polaron

absorption for blend A.

0.1 1 10 100 1000-0.2

0.0

0.2

0.4

0.6

0.8

1.0 P3TEA PffBT4T-2DT

Nor

mal

ized

T/

T

Time (ps)

0.1 1 10 100 1000-0.2

0.0

0.2

0.4

0.6

0.8

1.0

7.3 J/cm2

4.8 J/cm2

3 J/cm2

1.5 J/cm2

1.1 J/cm2

T/

T

Time (ps)

a b

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8 NATURE ENERGY | www.nature.com/natureenergy

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Supplementary Figure 5: Transient Absorption data. At 0.1 ps, polaron (charge) absorption

signal ~1.4 eV is 30% of exciton signal in blend A whereas it is ~ 8% in the neat sample. This

means ~23% population charge separate within 0.1 ps in the blend A.

0.8 1.0 1.2 1.4 1.6-0.2

0.0

0.2

0.4

0.6

0.8

1.0

P

P3TEA Blend A

T/

T

Energy (eV)

0.1 ps

Ex

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NATURE ENERGY | www.nature.com/natureenergy 9

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Supplementary Figure 6: PL quenching spectra. Photoluminescence quenching spectra of pure

P3TEA and blend A films. Excitation of the films was at 633 nm. Each spectrum was corrected for

the absorption of the film at the excitation wavelength. The PL quenching efficiency of the blend

A is estimated to be about 87.4%.

650 700 750 800 850 9000.0

0.2

0.4

0.6

0.8

1.0

1.2

Nor

mal

ized

inte

nsity

(a.u

.)

Wavelength (nm)

P3TEA Blend A

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10 NATURE ENERGY | www.nature.com/natureenergy

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Supplementary Figure 7: AFM and TEM images of the blend A-based film. AFM image

(1μm × 1μm, left) of a, blend A film. TEM image (right) of b, blend A film.

15 nm

0 nm

20°

a b

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Supplementary Figure 8: Two-dimensional (2D) GIWAXS patterns. a, blend A film; b, blend

B film; c, blend C film and d, blend D film.

a b

c d

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12 NATURE ENERGY | www.nature.com/natureenergy

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Supplementary Figure 9: R-SoXS curves. R-SoXS profiles of the PffBT4T-2DT:SF-PDI2

(blend B), the P3TEA:SF-PDI2 (blend A), the PffBT4T-2DT:diPDI (blend D) and the

P3TEA:diPDI (blend C).

0.11E-9

1E-8

Inte

nsity

q2

(nm

-2)

q(nm-1)

Blend B Blend A Blend D Blend C

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Supplementary Figure 10: Chemical structures and energy levels. a, Chemical structures of

PffBT4T-2DT and diPDI. b, Energy levels (eV) of P3TEA, PffBT4T-2DT, SF-PDI2 and diPDI

were determined by CV measurements on film samples (Supplementary Figure 11). The bandgap

here determined by LUMO and HOMO values is the electrical bandgap.

b

Pff

BT4

T-2D

T

-3.49

-5.18

-3.73

-6.21

diP

DI

a

P3T

EA

-3.57

-5.37

-3.62

-5.99

SF-P

DI 2

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14 NATURE ENERGY | www.nature.com/natureenergy

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Supplementary Figure 11: CV measurement. Cyclic voltammetry curves of a, PffBT4T-2DT.

b, P3TEA. c, SF-PDI2. d, diPDI.

a

dc

b

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Supplementary Figure 12: CT EL spectra. a, EL spectra of pure P3TEA and P3TEA blended

with diPDI, which has a lower LUMO level than SF-PDI2. b, Gaussian fitting of the blend C. c,

EL spectra of blend C at different injection currents. d, EL spectra of the pure P3TEA at different

injections currents.

a b

c d

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Supplementary Figure 13: Jsc vs Voc for published efficient polymer solar cells and our work.

The ellipse is guide to our eyes (See Supplementary Table 2 for details).

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Supplementary Figure 14: UV absorption spectra. Ultraviolet–visible(UV-Vis) absorption

spectra of pure P3TEA, pure SF-PDI2 and blend A films. The onset absorption of P3TEA polymer

film is ~745 nm.

300 400 500 600 700 800

0.0

0.2

0.4

0.6

0.8

1.0

Nor

mal

ized

Abs

orpt

ion

Wavelength (nm)

P3TEA SF-PDI2 Blend A

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-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2-15

-10

-5

0

5

Cur

rent

Den

sity

(mA

/cm

2 )

Voltage (V)

forward scan reverse scan

Supplementary Figure 15: Current-voltage plots. J-V plots in both forward and backward direction of the cell based on blend A.

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-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2-15

-10

-5

0

5

Cur

rent

Den

sity

(mA

/cm

2 )

Voltage (V)

pristine after 15 days in ambient conditions

Supplementary Figure 16: Current-voltage plots. J-V plots of pristine and aged device based on blend A after 15 days in ambient conditions.

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Supplementary Figure 17: PCE verification by Newport. Independent certification by Newport Corporation of blend A-based solar cell confirming a high Voc of 1.12 V and a high power conversion efficiency of 8.86 %.

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Supplementary Tables

Supplementary Table 1: Optical and Photovoltaic properties of four blends.

Materials Driving force

(meV) Voc (V)

Jsc (mA/cm2)

FF PCE (%)

Max. EQE (%)

Blend A negligible 1.11 13.27 0.643 9.5 66 Blend B 160 0.965 11.04 0.575 6.1 49 Blend C 200 0.954 12.46 0.591 7.0 62 Blend D 370 0.839 11.19 0.527 4.9 51

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Supplementary Table 2: Voc, Jsc and PCE for various published polymer solar cells.

Reference Polymer name Voc (V) Jsc (mA/cm2) PCE (%)

5 PTB7 0.75 17.46 9.21

6 TQ1 0.91 12.20 7.08

7 PCDTBT 0.90 14.40 7.94

8 PDPP3TaltTPT 0.75 15.90 8.0

9 PDTG-TPD 0.86 14.00 8.5

10 PThTPTI 0.87 13.69 7.8

11 PBDT-TS1 0.80 17.46 9.48

12 PiITVT 0.91 13.20 7.09

13 PPDT2FBT 0.86 11.40 7.26

14 PBDTTPD 0.97 12.60 8.5

15 PBDTTT-CT 0.78 17.20 8.4

16 P3HT 0.84 10.61 6.48

17 PBDTT-S-TT 0.84 15.32 8.42

18 PIDTT-DFBT-TT 0.96 11.90 7.2

19 PDTSTPD 0.90 10.95 6.2

20 PBDT-T8-TPD 1.00 9.790 6.17

21 PBTI3T 0.85 12.80 8.42

22 PIPCP 0.86 13.40 6.13

23 PDPP2Tz2T 0.92 8.80 5.1

24 PNOz4T 0.96 14.50 8.9

25 PCDTBT 0.88 10.60 6.1

26 PM6 0.98 12.70 9.2

27 PffBT4T-2OD 0.77 18.80 10.8

28 PTI-1 0.91 9.10 4.5

This work P3TEA 1.11 13.27 9.5

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Supplementary Table 3: Photovoltaic Performances of 30 blend A-based devices.

No. Voc (V) Jsc (mAcm-2) FF PCE (%) 1 1.11 12.03 0.697 9.30 2 1.11 13.13 0.616 8.98 3 1.11 13.25 0.621 9.13 4 1.11 13.37 0.632 9.36 5 1.11 12.63 0.648 9.08 6 1.11 13.20 0.642 9.41 7 1.10 12.59 0.627 8.72 8 1.11 12.97 0.642 9.26 9 1.11 13.51 0.621 9.28

10 1.11 13.61 0.605 9.16 11 1.11 13.58 0.613 9.26 12 1.11 13.32 0.622 9.21 13 1.11 13.47 0.613 9.18 14 1.11 13.53 0.627 9.42 15 1.10 12.12 0.630 8.42 16 1.11 12.36 0.672 9.24 17 1.11 13.41 0.636 9.44 18 1.11 13.30 0.626 9.25 19 1.10 13.83 0.583 8.87 20 1.11 13.21 0.640 9.40 21 1.11 13.27 0.643 9.47 22 1.09 13.26 0.605 8.78 23 1.11 12.56 0.632 8.85 24 1.10 13.10 0.624 9.02 25 1.10 13.22 0.601 8.75 26 1.10 13.14 0.622 9.01 27 1.11 13.07 0.640 9.28 28 1.10 13.47 0.609 9.03 29 1.10 13.40 0.617 9.11 30 1.11 13.74 0.603 9.23

average 1.11±0.01 13.15±0.44 0.627±0.022 9.13±0.24

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Supplementary Methods Characterizations of new compounds

1H and 13C NMR spectra were recorded on a Bruker AV-400 MHz NMR spectrometer.

Chemical shifts were reported in parts per million (ppm, δ). 1H NMR and 13C NMR spectra were

referenced to tetramethylsilane (0 ppm) for CDCl3, or solvent residual peak (5.98 ppm, 1H NMR

only) for C2D2Cl4 as internal standard. Mass spectra were collected on a MALDI Micro MX mass

spectrometer. Elemental analysis was performed by Midwest Microlab, LLC. Molecular weights

of the polymers were obtained on a PL GPC 220 (Polymer Laboratories) at 150 °C using a

calibration curve of polystyrene standards, with 1,2,4-trichlorobenezene as the eluent.

General information

All reagents and solvents were purchased from commercial sources (Aldrich, Acros, and

J&K) and used without further purification unless stated otherwise. Solvents were purified by

distillation when necessary. 4,7-dibromo-5,6-difluorobenzo[c][1,2,5]thiadiazole (3), tributyl(4-(2-

hexylnonyl)thiophen-2-yl)stannane (4), 5,5'-bis(trimethylstannyl)-2,2'-bithiophene (5) and 5,6-

difluoro-4,7-bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole(6) were synthesized

using literature reported procedures. SF-PDI2 and was synthesized according to literature

procedure and then further purified by recrystallization of CHCl3/MeOH. PffBT4T-2DT was

synthesized according to modified literature procedure29,30.

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Synthetic procedures and characterization

Supplementary Figure 18: Synthesis route of DibromoffBT-E.

2-octyldodecyl thiophene-3-carboxylate (S1). A solution of thiophene-3-carboxylic acid (1,

5.126 g, 40 mmol) in 150 mL DCM was stirred at room temperature under N2. Then 4-

Dimethylaminopyridine (1.466 g, 12 mmol), a DCM solution of N,N'-dicyclohexylcarbodiimide

( 9904 mg , 48 mmol ) and 2-octyldodecan-1-ol (2, 23.88 g, 80 mmol ) were added to the system.

The reaction mixture was stirred for another 12 hours. 50 mL distilled water was added and the

reaction mixture was filtered, diluted with hexane and washed with water and brine. The organic

layer was dried over Na2SO4, filtered and concentrated. Then the residue was purified with silica

gel chromatography to provide pure product as transparent liquid (17.25 g, 92% yield).

1H NMR (400 MHz, CDCl3) δ 8.08 (d, J = 1.7 Hz, 1H), 7.54 – 7.51 (m, 1H), 7.31 – 7.28 (m,

1H), 4.18 (d, J = 5.6 Hz, 2H), 1.74 (d, J = 4.4 Hz, 1H), 1.41 – 1.22 (m, 32H), 0.88 (t, J = 6.3 Hz,

6H).

13C NMR (101 MHz, CDCl3) δ 163.13, 134.27, 132.57, 128.09, 126.07, 67.68, 37.63, 32.12,

32.11, 31.64, 30.15, 29.85, 29.80, 29.76, 29.55, 29.51, 26.96, 22.89, 22.88, 14.31.

HRMS (MALDI+) Calcd for C25H44O2S (M +): 408.3062, Found: 408.3080.

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2-octyldodecyl 2-(trimethylsilyl)thiophene-3-carboxylate (S2). A solution of 3-(2-

octyldodecyl)thiophene (S1, 2.468 g, 7 mmol) in 40 mL THF was cooled to -78 °C under N2. A

solution of lithium diisopropylamide (2 M, 4.2 mL, 8.4 mmol) was added dropwise and the

mixture was stirred at -78 °C for 1h. Then liquid Chlorotrimethylsilane (1.1 mL, 8.4 mmol) was

added dropwise and the reaction mixture was return to room temperature and stirred overnight. 30

mL distilled water was added and the reaction mixture was filtered, diluted with hexane and

washed with water and brine. The organic layer was dried over Na2SO4, filtered and concentrated.

Then the residue was purified with silica gel chromatography to provide pure product as

transparent liquid ( 1.28 g, 43% yield)

1H NMR (400 MHz, CDCl3) δ 7.63 (d, J = 4.8 Hz, 1H), 7.47 (d, J = 4.8 Hz, 1H), 4.19 (d, J =

5.8 Hz, 2H), 1.77 (d, J = 5.3 Hz, 1H), 1.43 – 1.23 (m, 32H), 0.89 (t, J = 6.6 Hz, 6H), 0.41 (s, 9H).

13C NMR (101 MHz, CDCl3) δ 164.05, 150.07, 139.27, 130.85, 129.65, 67.61, 37.68, 32.15,

32.13, 31.61, 30.20, 29.88, 29.82, 29.78, 29.58, 29.54, 26.94, 22.92, 22.90, 14.33, -0.23.

HRMS (MALDI+) Calcd for C28H52O2SSi (M +): 480.3457, Found: 480.3477.

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2-octyldodecyl 5-(tributylstannyl)-2- (trimethylsilyl)thiophene-3- carboxylate (S3). A

solution of 2-octyldodecyl 2-(trimethylsilyl)thiophene-3-carboxylate 3-(2-octyldodecyl)thiophene

(S2, 2.124 g, 5 mmol) in 30 mL THF was cooled to -78 °C under N2. A solution of lithium

diisopropylamide (2 M, 2.8 mL, 5.5 mmol) was added dropwise and the mixture was stirred at -

78 °C for 1h. Then tributyltin chloride ( 1.6 mL, 6 mmol) was added dropwise and the reaction

mixture was return to room temperature and stirred overnight. A solution of KF in water was

added and the reaction mixture was filtered, diluted with hexane and washed with KF solution,

water and brine. The organic layer was dried over Na2SO4, filtered and the solvent was evaporated

to get the crude product as yellow oil, which is directly used without further purification.

bis(2-octyldodecyl)5,5'-(5,6-difluorobenzo[c][1,2,5]thiadiazole-4,7-diyl)bis(2-

bromothiophene-3-carboxylate) (DibromoffBT-E). A mixture of 2-octyldodecyl 5-

(tributylstannyl)-2-(trimethylsilyl)thiophene-3-carboxylate (S3, 3.388 g, ~4.4 mmol), 4, 7-

dibromo-5,6-difluoro-2,1,3-benzothiadiazole (3, 607 mg, 2 mmol), Pd2(dba)3(92 mg, 0.1 mmol)

and P(o-tol)3(122 mg, 0.4 mmol) in 20 mL Toluene was refluxed at 100 oC overnight under N2. A

solution of KF in water was added and the reaction mixture was filtered, diluted with hexane and

washed with KF solution, water and brine. The organic layer was dried over Na2SO4, filtered and

concentrated. Then the residue was simply purified with silica gel chromatography by a short

column to give crude product as yellow oil, which is directly used without further purification.

The crude product mixture was added to a mixture of N-Bromosuccinimide (784 mg, 4.4

mmol) and silica gel (10 mg) in 30 mL chloroform and 6 mL trifluoroacetic acid at 0 °C. The

reaction mixture was warmed to r.t. and stirred overnight. After washed with water, the organic

phase was dried with Na2SO4 and the solvent was evaporated. Then the residue was purified with

silica gel chromatography to provide pure product as orange solid (1.715 g, 75 % yield).

1H NMR (400 MHz, CDCl3) δ 8.44 (s, 2H), 4.26 (d, J = 5.6 Hz, 4H), 1.80 (dd, J = 11.1, 5.5

Hz, 2H), 1.52 – 1.21 (m, 64H), 0.90 – 0.83 (m, 12H).

13C NMR (101 MHz, CDCl3) δ 162.00, 151.51, 151.30, 148.90, 148.70, 148.27, 148.23,

148.20, 132.96, 132.90, 132.86, 132.03, 131.80, 123.74, 123.71, 111.07, 111.03, 110.98, 110.94,

68.31, 37.62, 32.14, 32.13, 31.67, 30.23, 29.90, 29.88, 29.85, 29.80, 29.58, 29.56, 27.01, 22.89,

14.31.

19F NMR (376 MHz, CDCl3) δ -126.87.

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HRMS (MALDI+) Calcd for C56H84Br2F2N2O4S3 (M +): 1142.3908, Found: 1142.4729.

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Supplementary Figure 19: Synthesis of S4.

bis(2-octyldodecyl)5,5''-(5,6-difluorobenzo[c][1,2,5]thiadiazole-4,7-diyl)bis(4'-(2-

hexylnonyl)-[2,2'-bithiophene]-3-carboxylate) (S4). A mixture of DibromoffBT-E (1.144 g, 1

mmol), tributyl(4-(2-hexylnonyl)thiophen-2-yl)stannane (4, 1.343 g, 2.3 mmol), Pd2(dba)3 (46 mg,

0.05 mmol) and P(o-tol)3 (61 mg, 0.2 mmol) in 20 mL THF was refluxed at 80 oC overnight under

N2. A solution of KF in water was added and the reaction mixture was filtered, diluted with

hexane and washed with KF solution, water and brine. The organic layer was dried over Na2SO4,

filtered and concentrated. Then the residue was purified with silica gel chromatography to give

product as red oil (1.429 g, 91% yield).

1H NMR (400 MHz, CDCl3) δ 8.64 (s, 2H), 7.42 (d, J = 1.1 Hz,2H), 7.03 (s, 2H), 4.22 (d, J =

5.8 Hz, 4H), 2.58 (d, J = 6.7 Hz, 4H), 1.76 (s, 2H), 1.66 (s, 2H), 1.28 (dd, J = 24.6, 14.4 Hz,

108H), 0.93 – 0.82 (m, 24H).

13C NMR (101 MHz, CDCl3) δ 163.41, 151.63, 151.43, 149.03, 148.80, 148.76, 148.72,

146.35, 142.59, 142.12, 134.38, 132.85, 131.86, 129.19, 129.01, 127.90, 124.96, 124.54, 120.83,

111.34, 111.25, 111.21, 68.07, 39.12, 37.61, 35.16, 33.55, 32.15, 31.65, 30.26, 30.24, 29.95,

29.93, 29.89, 29.87, 29.83, 29.60, 29.58, 27.01, 26.87, 26.83, 22.92, 22.90, 14.33, 14.31.

19F NMR (376 MHz, CDCl3) δ -127.21.

HRMS (MALDI+) Calcd for C94H150F2N2O4S5 (M +): 1570.0201, Found: 1570.0461.

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Supplementary Figure 20: Synthesis of DibromoffBT-E,A.

bis(2-octyldodecyl)5,5''-(5,6-difluorobenzo[c][1,2,5]thiadiazole-4,7-diyl)bis(5'-bromo-4'-

(2-hexylnonyl)-[2,2'-bithiophene]-3-carboxylate) (DibromoffBT-E,A). N-Bromosuccinimide

(320 mg, 1.8 mmol) was added to a mixture of S4 (1.414 g, 0.9 mmol) and silica gel (10 mg) in 10

mL chloroform at 0 °C. The reaction mixture was stirred for 15 minutes. After washed with water,

the organic phase was dried with Na2SO4 and the solvent was evaporated. The residue was

purified with flash column chromatography (eluent: n-hexane) to get the product as orange solid

(1.540 g, 99% yield).

1H NMR (400 MHz, CDCl3) δ 8.61 (s, 2H), 7.28 (s, 2H), 4.23 (d, J = 5.8 Hz, 4H), 2.53 (d, J

= 7.1 Hz, 4H), 1.78 (d, J = 4.4 Hz, 2H), 1.71 (s, 2H), 1.30 (t, J = 23.5 Hz, 108H), 0.92 – 0.81 (m,

24H).

13C NMR (101 MHz, CDCl3) δ 163.27, 151.66, 151.46, 149.06, 148.86, 148.71, 148.67,

145.45, 141.74, 134.35, 132.77, 131.18, 129.23, 127.85, 114.26, 111.27, 111.19, 111.15, 68.25,

38.79, 37.62, 34.38, 33.58, 32.15, 31.67, 30.28, 30.23, 29.93, 29.89, 29.88, 29.83, 29.59, 27.02,

26.78, 26.74, 22.92, 22.90, 14.34, 14.32.

19F NMR (376 MHz, CDCl3) δ -126.97.

HRMS (MALDI+) Calcd for C94H148Br2F2N2O4S5 (M +): 1726.8357, Found: 1726.8539.

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Synthesis of P3TEA.

Supplementary Figure 21: Synthesis of polymer P3TEA.

Microwave assisted polymerization. To a mixture of monomer DibromoffBT-E (25.9 mg,

0.015 mmol), 5,6-difluoro-4,7-bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole

(6, 10.0 mg, 0.015 mmol), Pd2(dba)3 (0.6 mg,0.0007 mmol) and P(o-tol)3 (1.2 mg, 0.004 mmol) in

a microwave vial equipped with a stirring bar, 0.20 mL of chlorobenzene was added in a glove

box protected with N2.The reaction mixture was then sealed and heated to 140 °C for 2 hours

using a microwave reactor. The mixture was cooled to r.t. and 10 mL of chlorobenzene was added

before precipitated with methanol. The solid was collected by filtration, subsequently subjected to

Soxhlet extraction with chloroform. This solution was then concentrated by evaporation,

precipitated into methanol. The solid was collected by filtration and dried in vacuum to get the

polymer as dark purple solid (13.4 mg, 37 %).

1H NMR (400 MHz, CDCl3) δ 8.71 (s, 1H), 8.37 (d, J = 3.6 Hz, 1H), 7.56 (s, 1H), 7.43 (d, J

= 3.8 Hz, 1H), 4.34 (d, J = 5.8 Hz, 2H), 2.93 (d, J = 6.2 Hz, 2H), 1.89 (s, 2H), 1.55 – 1.25 (m,

54H), 1.00 – 0.86 (m, 12H).

GPC: Mn: 48.4 kDa; Mw: 100.2 kDa; PDI=2.07.

Anal.Calcd for C108H152F4N4O4S8: C, 68.17; H, 8.05; N, 2.94. Found C, 68.20; H, 7.90; N,

2.84.

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Supplementary Figure 22: 1H NMR spectrum of S1.

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Supplementary Figure 23: 13C NMR spectrum of S1.

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Supplementary Figure 24: 1H NMR spectrum of S2.

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Supplementary Figure 25: 13C NMR spectrum of S2.

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Supplementary Figure 26: 1H NMR spectrum of DibromoffBT-E.

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Supplementary Figure 27: 13C NMR spectrum of DibromoffBT-E.

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Supplementary Figure 28: 19F NMR spectrum of DibromoffBT-E.

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Supplementary Figure 29: 1H NMR spectrum of S4.

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Supplementary Figure 30: 13C NMR spectrum of S4.

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Supplementary Figure 31: 19F NMR spectrum of S4.

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Supplementary Figure 32: 1H NMR spectrum of DibromoffBT-E,A.

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Supplementary Figure 33: 13C NMR spectrum of DibromoffBT-E,A.

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Supplementary Figure 34: 19F NMR spectrum of DibromoffBT-E,A.

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Supplementary Figure 35: High temperature 1H NMR spectrum of polymer P3TEA.

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