Semitransparent Solar Cells over 12% Efficiency based on a New

Low Bandgap Fluorinated Small Molecule Acceptor Mei Luo+1, Chunyan Zhao2+, Jun Yuan1, Jiefeng Hai3, Fangfang Cai1, Yunbin Hu1,

Hongjian Peng1, Yiming Bai2,4, Zhan'ao Tan*2,4,Yingping Zou1*

1. College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China. Email: yingpingzou@csu.edu.cn(Y.Zou) 2. Beijing Key Laboratory of Energy Safety and Clean Utilization, North China Electric Power University, Beijing 102206, China. Email: 3. Guangxi Key Laboratory of Electrochemical and Magneto-chemical Functional Materials, College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541004, China 4. Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China. Email: tanzhanao@mail.buct.edu.cn (Z.Tan) + The authors contributed equally.

EXPERIMENTAL SECTION

1. Materials

PCE10, PBDB-T, PBPB-T-2F were purchased from Solarmer Materials

Inc. 1-Chloronaphthalene (CN) was obtained from Sigma-Aldrich Inc. All

Chemicals and solvents were commercially available products and used

without further purification. The synthetic of compound 1and compound

3 are according to the reported literature.[1]Starting from compound 1, the

abstraction of one α-proton with n-butyllithium afforded the mono

anion intermediate, which was quenched with tributyltin chloride to

furnish compound 2. Stille cross-coupling of two equivalents of

compound 2 with dibromides compound 3 using Pd(PPh3)4 as the catalyst

precursor afforded compound 4. Compound 5 was obtained via triethyl

Electronic Supplementary Material (ESI) for Materials Chemistry Frontiers.This journal is © the Partner Organisations 2019

phosphate mediated Cadogan reductive cyclization and the N-alkylation

with an excess amount of 2-ethylhexyl bromide in the presence of

potassium hydroxide. The treatment of compound 5 with n-butyllithium

produced the dianion intermediates, which were converted to dialdehydes

compound 6, by quenching with dimethylformamide (DMF). Subsequent

Knoevenagel condensation of compound 6 with 2-(fluoro-3-oxo

-2,3dihydro-1H-inden-1-ylidene)malononitrile (FIC) afforded the target

acceptor molecule Y14.

2. Device fabrication

Indium tin oxide (ITO) coated glass ITO (glass) substrates were cleaned

in an ultrasonic bath by standard chemical means. The substrates were

dried by the nitrogen gas. Then, they experienced a plasma oxidation in

an enclosed chamber for1 min. SnO2 layers were spin-coated onto the

ITO(glass) substrates. After this, they were immediately transferred into a

pure nitrogen-filled glove-box. PBDB-T and Y14 with certain percentage

were dissolved in the organic solvent CHCl3. The mixtures were

spin-coated onto ITO(glass)/SnO2 substrates with a spin-speed of 2500

rpm for 30 s. The thickness of polymer donor:Y14 based film was

measured to be approximately 100 nm. Finally, all samples were

transferred into an integrated thermal evaporation system; 10 nm

thickMoO3 films and 100 nm thick Al electrodes were thermally

evaporated onto ITO(glass)/SnO2/PBDB-T:Y14. With the same

fabrication method, other inverted polymer solar cells were fabricated by

changing the organic blends to (i) PM6:Y14, (ii) PCE10:Y14 and

changing electron transport layer (TIPD).

3. Instruments and general methods

1H NMR and 13C NMR spectra were recorded using a Bruker

AV-400 spectrometer in deuterated chloroform solution at 298 K, unless

specified otherwise. Chemical shifts were reported as δ values (ppm) with

tetramethylsilane (TMS) as the internal reference. Mass spectra were

measured using by using an Autoflex III matrix-assisted.UV-Vis

absorption spectra were recorded on the SHIMADZU UV-2600

spectrophotometer. The electrochemical cyclic voltammetry (CV) was

conducted on an electrochemical workstation (CHI660E) with Pt plate as

working electrode, Pt slice as counter electrode, and Ag/AgCl electrodes

reference electrode in tetrabutylammonium hexafluorophosphate

(Bu4NPF6, 0.1 M) acetonitrile solutions.

S

S

C11H23

S

S

C11H23

NN

N

Br Br

O2N NO2

THF, Pd(PPh3)4

NN

NS

C2H5

C4H9

S

C11H23S

S

C11H23

O2N NO2

NN

N

NN

S

S

S

S

C2H5

C4H9

C11H23C11H23

DMF, POCl3

1 2

3

4 5

81.2% 10%

45%

NN

N

NN

S

C4H9

C2H5

S

S

S

C11H23C11H23

CHOOHC

ONC

NC

NN

N

NN

S

C4H9

C2H5

S

S

S

C11 H

23

CHCl3, pyridine

6

50%

Y14

C4H9

C2H5

ONC

CNF

2. EHBr, DMF,KOH,KISn(C4H9)3Cl89%

C 11H 23

OCN

NC

(C4H9)3Sn

C4H9

C2H5

C2H5

C4H9 C4H9

C2H5

C4H9

C2H5

C4H9

C2H5

C4H9

C2H5

n-BuLi, THF

F F

1. P(OEt)3, o-DCB

Figure S1 Synthetic route of Y14.

Synthesis of Compound 4

compound 2 (9.26, 17.83 mmol) and compound 3 (2.7 g, 5.64 mmol)

Pd(PPh3)2Cl2(0.17 g, 0.5 mmol) were dissolved in 30 mL of dry THF(40

ml) and stirred at 70℃ overnight ,under argon. The mixture was refluxed

for 24 h and then allowed to cool to room temperature. Water (100 mL)

was added and the mixture was extracted with CHCl3 (3×100 mL). The

organic phase was dried over anhydrous MgSO4. After removing the

solvent, the residue was purified using column chromatography on silica

gel employing petroleum ether/CH2Cl2 (1:1, v/v) as an eluent, yielding a

yellow solid (4.06 g, 81.2%).

1HNMR (400 MHz, CDCl3) δ 7.22 (d, J = 8.1 Hz, 2H), 6.94 (s, 2H), 2.71

(dd, J = 16.5, 8.7 Hz, 6H), 1.39-1.22 (m, 44H), 0.95-0.89 (m, 12H).

Synthesis of Compound 5

Compound 4 (8.577 g, 9.46 mmol) and triethyl phosphate (7.8 g, 47.3

mmol)were dissolved in the o-dichlorobenzene (o-DCB, 50 mL) under

nitrogen. After being heated at 180°C for 12 h, the aqueous phase was

extracted with ethylacetate and the organic layer was dried over Na2SO4.

The solvent was removed under vacuum. Crude product was obtained as

a dark green liquid without further purification.

Crude product, 1-bromo-2-ethylhexane (16.6 g, 86.25 mmol), potassium

iodide (0.6 g, 3.8 mmol) and potassium carbonate (5.26 g, 94.6 mmol)

were dissolved in the N,N-dimethylmethanamide (DMF, 30 mL). After

being heated at 90°C overnight, the solution was removed under vacuum

and extracted with ethylacetate and H2O. The organic layers were

combined and dried over MgSO4, filtered and purified with column

chromatography on silica gel using dichloromethane/petroleum ether (1/5,

v/v) as the eluent to give a light-yellow solid (1.5 g, 15% yield).

1HNMR (400 MHz, CDCl3) δ 6.98 (s, 2H), 4.71 (s, 2H), 4.57 (s, 3H),

2.83 (s, 4H), 1.87 (s, 4H), 1.69-1.10 (m, 48H), 0.90 (t, J = 38.7 Hz, 36H).

Synthesis of Compound 6

To a solution of compound 5 (1.5 g, 1.47 mmol) in DMF (50 mL) at 0°C

was added phosphorus oxychloride (2.1 ml, 22.05 mmol) dropwise

slowly under nitrogen. The mixture was stirred at 0°C for 2 h, and then

the solution was heated to 90°C and stirred overnight. The reaction

mixture was poured to ice water (100 mL), neutralized with saturated

sodium hydroxide solution, and then extracted with dichloromethane

twice. The combined organic layer was washed with water and brine,

dried over MgSO4, and evaporated under reduced pressure. The crude

product was purified by column chromatography (petroleum/

dichloromethane) to obtain compound 6 (540 mg, 45%) as a yellow solid.

1HNMR (400 MHz, CDCl3) δ 10.12 (s, 2H), 4.74-4.59 (m, 6H), 3.19 (t,

J=7.7 Hz,3H), 1.95-1.90 (m, 4H), 1.46-1.24 (m, 44H), 0.91 (dddd, J =

22.2, 17.4, 12.8, 4.9 Hz, 28H), 0.59 (ddd, J=37.5, 15.8, 7.2 Hz, 12H).

Synthesis of compound Y14

Compound 6 (0.138g, 0.12 mmol) and FIC (0.234 g, 1.21 mmol),

pyridine (1 mL) and chloroform (30 mL) were dissolved in a

roundbottom flask under nitrogen. Then the mixture was stirred and

refluxed overnight. After removing the solvent, the crude product was

purified on a silica-gel column chromatography to afford 80 mg of

compound Y14 in 50% yield as a dark blue solid.1H NMR (400 MHz,

CDCl3) δ 8.73 (d, J = 12.9 Hz, 1H), 8.40 (d, J = 9.0 Hz, 1H), 7.94 (dd, J

= 8.1, 5.2 Hz, 1H), 7.58 (d, J = 6.7 Hz, 1H), 7.42 (d, J = 6.6 Hz, 1H), 4.72

(d, J = 6.2 Hz, 3H), 3.21 (s, 2H), 1.89 (s, 2H), 1.56-1.30 (m, 14H), 1.16-

0.55 (m, 28H).13C NMR (101 MHz, CDCl3) δ 186.16, 158.81, 154.17,

145.18, 139.33, 138.88, 138.04, 136.92, 136.02, 135.68, 133.58, 130.06,

126.81, 124.89, 119.45, 115.21, 114.73, 112.16, 68.20, 59.75, 55.54,

40.40, 31.90, 31.27, 30.51, 30.09, 29.1, 28.42, 27.65, 24.03, 23.40, 22.92,

22.69, 14.03, 13.64, 10.53, 10.27, 1.00.

400 600 800 1000 12000.0

0.2

0.4

0.6

0.8

1.0

Norm

alize

d Ab

sorp

tion

(a.u

.)

Wavelength (nm)

Y9 Film Y9 Solution

(a)

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Potential (V vs. Ag/AgCl)

Curre

nt

LUMO HOMO

(b)

Figure S2 the absorption spectra of Y9(a) and Ered anEox of the Y14(b).

-0.2 0.0 0.2 0.4 0.6 0.8-30

-25

-20

-15

-10

-5

0

5

10

Cur

rent

den

sity

(mA

/cm

2 )

Voltage (V)

110°C 120°C 130°C 140°C 150°C

(a)

300 400 500 600 700 800 900 1000

0

20

40

60

80

110°C 120°C 130°C 140°C 150°C

EQ

E (%

)

Wavelength (nm)

(b)

FigureS3 (a) the J-V curves;(b) EQE of the PBDB-T:Y14-based devices at different temperatures. TableS1 Photovoltaic parameters of the PBDB-T:Y14-based devices at different temperatures.

Condition Voc(V) Jsc(mA/cm2) PCE(%) FF(%) Integrated Jsc(mA/cm2)

110℃ 0.818 26.09 13.81 64.73 23.986

120℃ 0.815 26.27 14.05 65.58 24.664

130℃ 0.809 26.24 14.43 67.90 24.856

140℃ 0.801 26.25 14.49 68.93 24.847

150℃ 0.790 26.34 14.72 70.76 25.268

Table S2 Summary of photovoltaic properties of the semitransparent OSCs Active layer Voc

[V] Jsc

[mAcm-2] FF PCE

[%] AVT [%]

Ref.

PSBTBT:PC71BM 0.608 10.7 0.42 2.8 _ [2] PBDTTT-C-T:PC71BM 0.76 13.01 0.63 6.22 25 [3] PIDT-PhanQ:PC71BM 0.84 9.99 0.61 5.10 24.35 [4]

P3HT:PCBM 0.61 8.4 0.54 2.7 11 [5] PCDTBT:PC71BM 0.90 6.6 0.51 3.0 16 [5] PBDTTT-CT:PC71BM 0.82 13.8 0.46 5.2 14 [5] PBDTTT-EFT:PC71BM 0.84 11.0 0.61 5.6 10 [5] PBT7-Th:ATT-2 0.712 18.53 0.59 7.74 37 [6] PffBT4T-2OD:PC71BM 0.764 13.7 0.56 5.8 6 [7] PDTP-DFBT:PC71BM 0.67 12.4 0.45 3.7 54 [8] PM6:Y6 PTB7-Th:IEICO-4F PBDB-T:IEICO-4F J71:IT-M J71:IEICO-4F J51:IEICO-4Cl PBDB-T:IEICO-4Cl PTB7-Th:IEICO-4Cl

0.825 0.713 0.711 0.930 0.769 0.673 0.724 0.725

21.56 19.52 17.85 12.75 11.12 17.2 15.4 19.6

72.41 62.76 52.30 60.98 52.01 0.551 0.560 0.590

12.88 8.74 6.64 7.23 4.45 6.37 6.24 8.38

25.6 25.08 26.50 25.05 27.26 35.1 35.7 25.6

[9] [9] [9] [9] [9] [10] [10] [10]

Figure S4 1HNMR spectrum of 4 in CDCl3.

Figure S5 1HNMR spectrum of 5 in CDCl3.

NN

NS

C2H5

C4H9

S

C11H23S

S

C11H23

O2N NO2

NN

N

NN

S

S

S

S

C11H23C11H23

C4H9

C2H5

C2H5

C4H9 C4H9

C2H5

Figure S6 1HNMR spectrum of 6 in CDCl3.

NN

N

NN

S

C4H9

C2H5

S

S

S

C11H23C11H23

CHOOHC

C4H9

C2H5

C4H9

C2H5

Figure S71HNMR spectrum ofY14 in CDCl3.

Figure S8 13C NMR spectrum of Y14 in CDCl3.

NN

N

NN

S

C2H5

C4H9

S

S

S

C 11H 23

C11 H

23

O O

CN

NCCN

CNC4H9

C2H5

C4H9

C2H5

F F

NN

N

NN

S

C2H5

C4H9

S

S

S

C 11H 23

C11 H

23

O O

CN

NCCN

CNC4H9

C2H5

C4H9

C2H5

F F

Figure S9 Mass spectrum of Y14.

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