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Ultrafast Energy Transfer in Oligofluorene-Aluminum Bis(8-hydroxyquinoline)acetylacetone Coordination Polymers. Victor A. Montes, Grigory V. Zyryanov, Evgeny Danilov, Neeraj Agarwal, Manuel A. Palacios, and Pavel Anzenbacher Jr.*. J. Am. Chem. Soc. , 2009 , 131 (5), 1787-1795. Outline.

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Victor A. Montes, Grigory V. Zyryanov, Evgeny Danilov, Neeraj

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Victor a montes grigory v zyryanov evgeny danilov neeraj
Ultrafast Energy Transfer in Oligofluorene-AluminumBis(8-hydroxyquinoline)acetylacetone Coordination Polymers

Victor A. Montes, Grigory V. Zyryanov, Evgeny Danilov, Neeraj

Agarwal, Manuel A. Palacios, and Pavel Anzenbacher Jr.*

J. Am. Chem. Soc., 2009, 131 (5), 1787-1795


Outline
Outline

  • Introduction

    Resonance energy transfer

    Organic light-emitting diode

  • Experiment

    Synthesis

    Optical properties

    Ultrafast energy migration

    Solid-state electroluminescence

  • Conclusions


Resonance energy transfer ret
Resonance Energy Transfer (RET)

T. Förster in 1959 proposed the Förster theory of resonance energy transfer

S*+Q → S+Q*

http://micro.magnet.fsu.edu/primer/techniques/fluorescence/fret/fretintro.html


Resonance energy transfer ret1

Emission spectra of Donor

Absorption spectra

of acceptor

Overlaps

Resonance Energy Transfer (RET)

  • Energy transfer is efficient when:

    1.The energy donor and acceptor are separated by a

    short distance.(30~100 Å)

    2.Photons emitted by the excited state of the donor can

    be absorbed directly by the acceptor.

Et: efficiency of energy transfer

R0: Förster distance

r : distance between donor and acceptor



Oled v s lcd
OLED v.s LCD

萬能科技大學光電系張興華OLED投影片


Device structures

Electroluminescence Layer

Device structures

Cathode : CsF:Al

ElectroluminescenceLayer

Hole Injection Layer :PEDOT:PSS

Anode :Indium-tin-oxide

萬能科技大學光電系張興華OLED投影片


Oled v s pled
OLED v.s PLED

萬能科技大學光電系張興華OLED投影片


Structure of alq 3 type complexes
Structure of Alq3-type complexes

Complex 2

Red-shift

Montes, V. A; Pohl, R.; Shinar, J.; Anzenbacher, P., Jr. Chem.-Eur. J. 2006, 12, 4523.


Electroluminescence spectra of alq 3 type complexes
Electroluminescence Spectra of Alq3-type Complexes

Montes, V. A; Pohl, R.; Shinar, J.; Anzenbacher, P., Jr. Chem.-Eur. J. 2006, 12, 4523.


Victor a montes grigory v zyryanov evgeny danilov neeraj

Oligofluorene :OF

Alq2acac

X.; Wang, Y.Appl. Phys. Lett. 2008, 92, 103305.

Anzenbacher, P., Jr. Chem. Commun. 2007, 3708.


Synthesis of oligofluorene
Synthesis of Oligofluorene

  • Pd(PPh3)4, Et4N+OH- in MeOH, toluene, 60°C

  • 1,4-cyclohexadiene, Pd-C (10%), isopropanol, reflux.

Anzenbacher, P., Jr. Chem. Commun. 2007, 3708.


1 h nmr spectra of oligofluorene
1H NMR spectra of Oligofluorene

Figure 1. 1H NMR spectra of the ditopic ligands. Residual CHCl3 signals are marked with an asterisk.


Synthesis of alq 2 acac and 1a e

n

Synthesis of Alq2(acac) and 1a-e

5 days

Yield=76% ~ 98%

Scheme 1. Synthesis of Alq2(acac) and Coordination Polymers 1a-e Using Tris(acetylacetonate)aluminum(III), and X-ray Structure of Alq2(acac)


Uv vis absorption spectra of 1a e

475 nm

340 nm

UV-vis absorption spectra of 1a-e

Table 1. Summarized Absorption Data for Bichromophoric Systems 1a-e

Figure 2. UV-vis absorption spectra of 1a-e in a CH2Cl2 solution showing contribution of both oligofluorene (OF) and AlIII quinolinolate chromophores.


Emission spectra of 1a e
Emission spectraof 1a-e

410 nm

550 nm

Figure 3.Corrected emission spectra of the coordination polymers 1a-e in CH2Cl2 upon excitation at 340 nm


Excitation spectra of 1a e
Excitation spectra of 1a-e

UV-vis absorption spectra of 1a-e

Figure 4. Excitation spectra of the polymers when monitored at 550 nm.


Transient absorption spectra
Transient Absorption Spectra

清華大學化學研究所 2005 陳學穎碩士論文


Victor a montes grigory v zyryanov evgeny danilov neeraj

Model 3

Model 2


Model compound 2
Model compound 2

excitation at 475 nm

( -  * of Alq3)

τ=9200 ps

Figure 5. (A) Absorption and emission spectra of model compound 2. (C) Transient absorption spectra of 2 0.2 ps after pump pulse at 475 nm and its decay monitored at 750 nm (inset).


Model compound 3
Model compound 3

excitation at 340 nm

(  -  * of oligofluorene )

τ=642 ps

Figure 5.(B) Absorption and emission spectra of model compound 3. (D) Transient absorption spectra of 3 0.2 ps after pump pulse at 340 nm and its decay monitored at 750 nm(inset).


Transient absorption spectra of 1a e
Transient absorption spectra of 1a-e

520 nm

640 nm

0.2 ps after excitation at475 nm

( -  * of Alq3)


Transient absorption spectra of 1a e1
Transient absorption spectra of 1a-e

475 nm

0.2 ps after excitation at340 nm

(  -  * of oligofluorene )


Transient absorption spectra for 1d
Transient absorption spectra for 1d

τ=1.4 ps

Figure 6. Left : Transient absorption spectra for 1d after excitation at 340 nm (0.5mW) at various times . Right : Exponential fit of the kinetic profile at 750 nm.


Rate constants for energy transfer

Table 2. Calculated Rate Constants for Energy Transfer in the Coordination Polymers 1c-e Monitored by Decay at 750 nm

Rate Constants for Energy Transfer

kET = Obs-1 - Fl-1

kET is the overall rate of energy transfer

Obs is the lifetime observed for the spectral change in the transient experiment

Fl represents the fluorescence lifetime


Mechanism for intramolecular energy transfer

1e

Mechanism for Intramolecular Energy Transfer

kET = keh+kfq

keh = exciton hopping between the fluorene moieties

kfq = strongly exothermic transfer from fluorene to AlIII quinolinolate


Mechanism for intramolecular energy transfer1

1c

1d

1e

Mechanism for Intramolecular Energy Transfer

kET=keh+kfq

kET=6.9x1011 (s-1)

kET=7.1x1011 (s-1)

kET=3.3x1011 (s-1)

Figure 7. Schematic representation of the mechanism for intramolecular energy transfer as proposed for the behavior of the bichromophoric systems 1c-e.Only one pathway of energy migration is shown for simplicity purposes.


Simplified oled architectures
Simplified OLED architectures

Cathode : CsF (10 Å) : Al (1200 Å)

Electroluminescence Layer : 1a-c (600 Å)

Hole Injection Layer : PEDOT:PSS (500 Å)

Anode : Indium-tin-oxide


1a oled
1a-OLED

external quantum efficiency of 1.2%.

maximum luminance was 6000 cd/m2

turn-on voltage of ∼6 V

Figure 8. Left: Electroluminescence spectra of 1a-OLED at a voltage of 9 V. The inset shows a photograph of the operating device. Right: I-V and luminance curves of the ITO/PEDOT:PSS/1a /CsF:Al OLED.


Conclusions
Conclusions

  • Novel coordination polymers comprising oligofluorene moieties of a varying size (n = 1-9) connected via aluminum(III) bis(8-quinolinolate)acetylacetone (Alq2(acac)) complexes were synthesized and their photophysical properties were studied.

  • The energy migration from oligofluorene to the quinolinolate moieties was observed proceeding at a rate order of 1011 s-1.

  • In the solid state, complete energy transfer from oligofluorene fragments to the quinolinolate centers was observed due to intermolecular energy transfer.


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