1

A New [5] Helicene Derivative as Novel Emissive Material for Organic Light-Emitting Diode

Siriporn Kamtonwong , Somboon Sahasithiwat , Waraporn Panchan, Laongdao Menbangpung, and Thanasat Sooksimuang

National Metal and Materials Technology Center (MTEC) , Thailand

Pure and Applied Chemistry International Conference 2013

The Tide Resort, January 25, 2013

2

Outline

Introduction

Experimental

Results and discussion

Conclusion

Light

+

3

Basic for light generation via OLED

OLED Device Operation Principle

Introduction

LightCathode

Anode

ETL

HTLHole +

++

--

-

EML

Excitation

-+

OLED Structure

Cathode

EML/ETL

HTL

Anode

Substrate

-

4

Helicenes

[5] Helicene [6] Helicene [7] Helicene

Under UVDDH in CHCl3

S. Sahasithiwat, T. Mophuang, L. Menbangpung, S. Kamtonwong and T. Sooksimuang.Synthetic Metals 160(2010)1148-1152.

DDH in CHCl3: Φf = 0.27

Φf = 0.02-0.04

3,12-Dimethoxy-7,8-dicyano-[5]helicene (DDH)

MeO

MeO

CN

CN

2

9

3

4 56

8

1011

12

141 7

13

Electrondonating

Electronwithdrawing

5

3,12-Dimethoxy-[i]furan-1,3-diono-[5]helicene (DFH)

MeO

MeO

O

O

O

as novel Emissive Material for Organic light-Emitting Diode

6

Experimental

7

Preparation of DFH

DDQ, xylene

reflux

MeO

MeO MeO

MeO

O

O

O

O

O

O

MeO

MeO

O

O

OMeO

MeO

O

O

O

+

NBS

DFH

1 2

3

70-80%

75%

70%

8

OLED fabrication

Configuration:

Glass

ITO

PEDOT:PSS

DFH

Ca/Al

J-V-L CharacteristicsMeasured

ITO/PEDOT:PSS(35nm)/DFH/Ca(10nm)/Al(100nm)

9

Results and discussions

250 300 350 400 450 500 550 600 650 700 7500.0

0.2

0.4

0.6

0.8

1.0

Wavelength (nm)

Norm

aliz

ed A

bso

rban

ce

0.0

0.2

0.4

0.6

0.8

1.0

451437

340

535

Flu

ore

scen

ce In

tensi

ty

10

UV in CHCl3, λmax : 340, 437, 451 nm

PL, λmax : 535 nm

Φf = 0.13

Normalized UV/Vis absorption and fluorescence spectra of DFH in dilute (3x10-6 M) CHCl3 solution.

FWHM : 78 nm

The optical properties of DFH

Under UV

MeO

MeO

O

O

O

DFH in dilute CHCl3 solution.

11

Thermal properties of DFH

DSC: Tm 315 oC

TGA: Td,5 360 oC

MeO

MeO

O

O

O

50 100 150 200 250 300 350

Endoth

erm

al

Temperature (oC)

DSC thermogram of DFH TGA thermogram of DFH

100 200 300 400 500 600 700 800 900 10000

10

20

30

40

50

60

70

80

90

100

Wei

ght (%

)

Temperature (oC)

12

Energy levels of DFH

Cyclic voltammetric technique

Cyclic voltammogram of DFH in 0.1 M Bu4NBF4 in acetonitrile solution performed in a three-electrode cell (a glassy carbon working, a platinum counter and a Ag/Ag+,0.1 M AgNO3, non-aqueous reference electrode) at a scan rate of 50 mV/s.

HOMO: Ip = -(E'ox + 4.4) eV (1)

LUMO: Ea= -(E‘red + 4.4) eV (2)

MeO

MeO

O

O

O

13

Structure of the OLED

HIL

EML

Anode

Cathode

h+

e-

ITO

PEDOT:PSS

DFH

Ca(10 nm)/Al (100 nm)

Glass

Light

Structure and energy level diagram of the OLED

Energy level diagram

ITO/PEDOT:PSS(35nm)/DFH/Ca(10nm)/Al(100nm)

Vacuum Level

ITO PEDOT:PSS DFH Ca

-4.9 eV-5.2 eV

-5.9 eV

-3.6 eV

-2.8 eV

LUMO

HOMO

14

Plots of current density-voltage-brightness characteristicof ITO/PEDOT:PSS/DFH(80 nm)/Ca/Al device

Current density-voltage-brightness characteristics of the OLED

ITO/PEDOT:PSS(35nm)/DFH/Ca(10nm)/Al(100nm)

ILV Characteristic of OLED with DFH

(0.41,0.55)-(0.46,0.52)

CIE Coordinate15

DFH

thickness

(nm)

Turn on voltage

(V)

Current Eff.

(cd/A)

Power Eff.

(lm/W)

Max.

Brightness (cd/m2)

CIE

Coordinate

(x,y)

60 3.4 0.16 0.09 696 (0.44,0.58)-(0.46,0.54)

80 4.9 0.33 0.15 881 (0.41,0.55)-(0.46,0.52)

100 4.4 0.30 0.13 760 (0.44,0.53)-(0.47,0.52)

ITO/PEDOT:PSS(35nm)/DFH/Ca(10nm)/Al(100nm)

increasing applied voltage

OLED

Excimer formation

Green yellow

5.5 V 6.5 V 8.5 V

16

Conclusion

MeO

MeO

O

O

O

DFH

Easy to synthesized with good yield

Good thermal stability

Excellent optical properties

DFH was successfully utilized as a new emitter for OLED.

17

National Metal and Materials Technology Center (MTEC)

Acknowledgments

National Science and Technology Development Agency(NSTDA)

Ministry of Science and Technology (MOST), Thailand

under grant number MT-B-55-POL-07-523-I

18

Thank you for your kind attention

19

20

LUMO LUMO

HOMO HOMO

Donormolecule

Acceptormolecule

Excimeremission

Excitedmonomer

Excimer

Monomeremission

Excimeremission

Ground State

Energy

High

Low

The formation of excimer in organic molecule

Light emission from excimer is red shiftedfrom the excited monomer

Excimer: a single excited molecule can interact with an unexcited neighbor to produce the excited dimer, or excimer

21

+

Cathode

Anode

EILETL

EML

ExcitationHIL

HTL+

++

+

--

--

Hole

-

Light

Fig. Basis for light generation via OLED

Cathode

EIL

ETL

EML

HTL

HIL

Anode

Light

The multi-layered device

22

23

OLED fabrication

ITO/PEDOT:PSS/DFH/Ca/Al Configuration:

ITO coated-glass slide was cleaned.

PEDOT:PSS was spin-coated onto ITO substrate.

then it was baked at 140 oC for 10 min.

DFH was deposited by thermal evaporation

onto the PEDOT:PSS coated substrate.

Calcium was evaporated onto the organic layer.

Aluminum was coated onto calcium layer.

24

NMR

MeO

MeO

O

O

O

25

FT-IR spectrum

MeO

MeO

O

O

O

1827, 1762

26

Helical structure

Enantiomers

(M) [5] Helicene (P) [5] Helicene

Clockwise helix Anticlockwise helix

3,12-Dimethoxy-7,8-dicyano-[5]helicene (DDH)

UV 365 nm

DDH in CH2Cl2

under

MeO

MeO

CN

CN

S. Sahasithiwat, T. Sooksimuang, T. Mophuang, L. Menbangpung and S. Kamtonwong Synthetic Metals 160(2010)1148-1152

28

Fig. 3. OLED Research

29

H3CO OCH3

OO O

1

23

4

5

67 8

9

10

1112

1314H3CO OCH3

OO O

1

23

4

5

67 8

9

10

1112

1314

Vacuum Level

ITO PEDOT:PSS DFH Ca

-4.9 eV-5.2 eV

-5.9 eV

-3.6 eV

-2.8 eV

31

ศู�นย์�เทคโนโลย์�โลหะและวั�สดุ�แห�งชาติ�114 อุ�ทย์านวั�ทย์าศูาสติร์�ปร์ะเทศูไทย์ ถนนพหลโย์ธิ�น ติ!าบลคลอุงหน#$ง อุ!าเภอุคลอุงหลวัง จั�งหวั�ดุปท�มธิาน� 12120

โทร์. +(66)2564-6500

โทร์สาร์ +(66)2564-6501-5

 

National Metal and Materials Technology Center

114 Thailand Science Park Paholyothin Rd., Klong 1, Klong Luang, Pathumthani 12120 Thailand

Tel. +(66)2564-6500

FAX +(66)2564-6501-5

32