Microstructure of Thin Films of Ruthenium Bipyridine Derivatives in Organic Light Emitting Devices - PowerPoint PPT Presentation

Loading...

PPT – Microstructure of Thin Films of Ruthenium Bipyridine Derivatives in Organic Light Emitting Devices PowerPoint presentation | free to download - id: 10ae01-ZDc1Z



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Microstructure of Thin Films of Ruthenium Bipyridine Derivatives in Organic Light Emitting Devices

Description:

Microstructure of Thin Films of Ruthenium Bipyridine Derivatives in Organic Light Emitting Devices – PowerPoint PPT presentation

Number of Views:90
Avg rating:3.0/5.0
Slides: 34
Provided by: danielr46
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Microstructure of Thin Films of Ruthenium Bipyridine Derivatives in Organic Light Emitting Devices


1
Microstructure of Thin Films of Ruthenium
Bipyridine Derivatives in Organic Light Emitting
Devices
Daniel R. Blasini Abruña Group February 2nd,
2005 G-Line Science Symposium Department of
Chemistry and Chemical Biology, Cornell University
2
Motivation
Why OLEDs?
  • Active emitters
  • Higher contrast, greater viewing angles
  • Energy-efficient

Flat
3
Approach
Transition Metals Complexes Ruthenium Derivatives
Electrochemical cell
  • Used of air stable electrodes
  • Low operating voltages

Material
-Electrochemically active -Stable in multiple
oxidation states -High quantum efficiency -Electro
n and hole transporter
  • Efficiency
  • Turn-on time
  • Color emission

4
Electrochemical Device Model
Au
ITO


5
Electrochemical Device Model
e-
h
e-
Au
ITO
e-
h
diffusion of counter ions
PF6-
Ru(bpy)3n
Hopping electron/holes
6
Energy Level Diagram
Octahedral
Color tuning
7
Ligand Effects on Efficiency
Ru(L)3(PF6)2 Based Devices
External Quantum Efficiency ()
Ligands-L
?PL(nm)
0.5
605
0.25
609
0.75
610
8
Ligand Effects on Efficiency
Ru(L)3(PF6)2 Based Devices
External Quantum Efficiency ()
Ligands-L
?PL(nm)
0.5
605
0.25
609
0.75
610
9
Ruthenium Complexes
10
Why grazing incidence?
Taking advantage of the total external reflection
phenomena in the X-ray regime we can control the
X-ray penetration depth and achieve a surface
sensitive analysis. ( qz (2?/?) (sin a sin b)
)
I0
I
Simulated penetration depth profile for different
values of ba /d
b
a
qz
D1000Å
ITO
Penetration Depth Å
a / ac
11
Experimental Set Up
Horizontal Diffractometer
g
Instrumental Resolution
? 2? 0.2 ? g 0.08
12
Experimental Set Up
Horizontal Diffractometer
g
Instrumental Resolution
? 2? 0.2 ? g 0.08
13
Diffraction Geometry
Surface normal
g
b
a
2q
a
z-axis geometry
Pseudo z-axis geometry
qxk cos(b)cos(y) - cos(a)
qxk cos(g)sin(2q)
qyk cos(b)sin(y)
qyk cos(g)cos(2q) - 1
qzk sin(a) sin(b)
qzk sin(g)
y 2q (for small a)
The angles coincide with the respective
diffractometer axes
For small a, g arbitrary 2q
b g - a cos(2q)
14
X-ray Reflectivity
Spill over
l1.34 Å
15
Reducing the Background
a0.18?
a0.13?
a0.27?
a0.4?
16
GIWAXS of OLED devices
(Grazing-Incidence Wide-Angle X-ray Scattering)
Ru(bpy)3 - a 0.13 deg
Integrated intensity, a.u.
1
2
3
2q, deg
17
Crystal Structure- Ru(bpy)3
b
L 41Å
8.29
0
a
18
GIWAXS of OLED devices
(Grazing-Incidence Wide-Angle X-ray Scattering)
1
Ru(bpy)32 ? 0.13
Ru(bpy)32 ? 0.13
Ru(bpy)3 - a 0.13 deg
Integrated intensity, a.u.
1
2
3
2q, deg
19
GIWAXS of OLED devices
(Grazing-Incidence Wide-Angle X-ray Scattering)
Ru(diethylphenylbpy)32 ? 0.15
Ru(diethylphenylbpy)32 ? 0.15
1
ITO
2
Ru(ethylphenylbpy)32 ? 0.15
Ru(ethylphenylbpy)32 ? 0.15
1
2
ITO
20
GIWAXS on OLED devices
(Grazing-Incidence Wide-Angle X-ray Scattering)
Ru(dtbubpy)32 ? 0.15
Ru(dtbubpy)32 ? 0.15
1
2
ITO
Ru(2,2'-bpy)2(4,4'-bpy)22 ? 0.15
Ru(dtbubpy)32 ? 0.15
Ru(2,2'-bpy)2(4,4'-bpy)22 ? 0.15
21
GIWAXS on OLED devices
(Grazing-Incidence Wide-Angle X-ray Scattering)
Ru(dmbpy)(bpy)22 ? 0.15
Ru(dmbpy)(bpy)22 ? 0.15
1
2
3
Ru(4,4pentylbpy)(bpy)22 ? 0.15
Ru(4,4pentylbpy)(bpy)22 ? 0.15
1
2
3
22
Summary of Results
Molecules L, ang d, ang
Ru(bpy)32 41.4 9.4
Ru(2,2'-bpy)2(4,4'-bpy)22 35.7 9.6
Ru(dmbpy)(bpy)22 36.4 9.6
Ru(ethylphenyl)32 27.9 10.1
Ru(4,4pentylbpy)(bpy)22 27.9 10.3
Ru(tbubpy)32 33.4 11.8
Ru(diethylphenyl)3 2 32.1 12.4
23
Correlation with Device Efficiency (?)
24
Summary
  • We have characterized device-grade thin films
    with reciprocal space mapping under grazing
    incidence, and could find various characteristic
    d-spacings.
  • The crystalline order turned out to be
    short-range, with similar crystallite sizes for
    all the molecules studied (20-40 ang).
  • We observe an increase in the device efficiency
    as a function of the average Ru-Ru distance
    (within the range studied), this might suggest
    that there could be an optimal distance between
    Ru chromophores that minimizes self-quenching.

25
Acknowledgements
26
Acknowledgements
  • Prof. Héctor D. Abruña
  • Prof. Joel D. Brock
  • Prof. George G. Malliaras
  • Samuel Flores (synthesis-Abruña Lab)
  • Alon Gorodetsky and Jason Slinker (Malliaras
    Lab)
  • G-line students, G-line staff, CHESS staff,
    Brian Clasby, Jerry Houghton
  • Funding
  • NSF
  • CHESS G Line
  • CCMR

27
Old Experimental Setup
28
G2 cave transfer pipe installed (Aug 03)
Jerry Brian
29
G2 mono installation (Summer 04)
Old Mono Setup
New Mono Setup
30
G2 Hutch Layout
Incident Beam 1012 photons/sec Transmitted
Beam 96 Reflected Beam 2.5 Be single
crystal 0.03mosaic DE/E 0.1
S1
S2
31
Ligand Effects on Turn-on Time
32
Available Energy for Emission
-- EL _ PL
- ?Hº Eºoxid. Eºred. - T?Sº
?E ? 2.57 eV ? 474 nm
Os(bpy)2(dppe)2
?
?
?E ? 2.57 eV
t2g
?
t2g
?
33
Efficiency vs. Film Thickness
Ru(bpy)3(PF6)2 Films
Au
Organic
ITO
About PowerShow.com