OLED Molecular Doping Technology

OLED Molecular Doping Technology

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Description: OLED Lighting: The Challenges - Outline of the talk: Substrate Integration, High Power Efficiency, Brightness Levels, Light Outcoupling, Large area & Uniformity, Heat dissipation, Standardization & Designs.

 
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Contents:
Organic Light-Emitting Diodes for Lighting Applications
based on Molecular Doping Technology
Michael Hofmann, Senior Scientist
Business Line Technology & Product, Novaled AG
Organic Electronics Day @ MateriaNova, Mons/Belgium, 20th Oct 2011
Organic Electronics Day in Mons, Novaled AG, page 1

OLED: Addressing Two Markets

Display

Lighting

Organic Electronics Day in Mons, Novaled AG, page 2

Display: A Simpler Equation
A few OLED display makers to expect: the LCD makers
Products easy to identify: portable notebook, TV
Clear product expectations (green, contrast, speed, colors, design)
Limited number of customers (market consolidation)

A simple value chain with defined applications

Organic Electronics Day in Mons, Novaled AG, page 3

The Last Hundred Meters
Technical bricks available for a real display mass production
Some hurdles to overcome (TFT, tool efficiency)
Further improvements necessary to sustain business take-off (tool
generation, further energy saving)

OLED display is close to success:
a real teamwork between display tool and material/
technology makers to provide the last impulse

Organic Electronics Day in Mons, Novaled AG, page 4

OLED Lighting: A Very Appealing Business

Nedo/Panasonic
@ Light&Building 2010

Flying Future
Ingo Maurer with
Novaled
Tom Dixon collection
with Philips
Lumiblades

Room divider with Orbeos Samples
Osram booth at L&B 2010

Flos By Philipp Starck
With Blackbody OLEDs

Organic Electronics Day in Mons, Novaled AG, page 5

OLED Lighting: A Business Revolution
Towards a merge of light source with (product) design
From replacement business to integrated design

OLED will modify the lighting value chain
Cards reshuffled
New players
New business opportunities
Organic Electronics Day in Mons, Novaled AG, page 6

A New Business Model
OLED industry and lighting industry: 2 different worlds

A generational conflict
Transform OLED industry and lighting industry into
OLED lighting industry
Organic Electronics Day in Mons, Novaled AG, page 7

OLED Lighting: The Challenges
Outline of the talk:
Substrate Integration
High Power Efficiency
Brightness Levels
Light Outcoupling
Large area & Uniformity
Heat dissipation
Standardization & Designs

Low cost solutions needed

Organic Electronics Day in Mons, Novaled AG, page 8

Novaled OLED Technology
Novaled develops an
innovative highly efficient
OLED structure based
on proprietary doping
materials

World Leader in
Power Efficiency
Basic OLED scheme bottom emission

OLED Benefits
Ultra Thin ( 50nm)

Emissive Layer
Blocking Layer (optional)

ITO treatment required to
tune energy levels

Undoped Hole
Transport Layer

Rs

Rinj
Anode

Performance depends on
electrode material

Organic Electronics Day in Mons, Novaled AG, page 11

Novaled PIN OLED® Technology
Cathode
Rs


3V
+

Rinj
Novaled n-type
.
Undoped Electron
ETL
Transport Layer

Blocking Layer (optional)
Emissive Layer
Blocking Layer (optional)
Undoped Hole
Novaled p-type
Transport Layer
HTL
Rs
Rinj

Anode

No injection layer between
ETL or HTL and electrodes
required!
No ITO treatment necessary
due to doping technology
Results in maximum power
efficiency, longest lifetime
and freedom in OLED
design

Organic Electronics Day in Mons, Novaled AG, page 12

Substrate Options for OLEDs
Light
Emission

SUBSTRATE
Transport Layer
Emitting Layer
Transport Layer

Glass substrate

+
Metallic substrate

Thin film

Organic Electronics Day in Mons, Novaled AG, page 13

OLED Architectures

3 different architectures:
Bottom emission
Cathode
n-ETL
EML
p-HTL
Anode
Substrate

best established, cheap and lightweight
substrate

Transparent
Unique designs

Top emission (on metal)
Excellent heat dissipation, potentially
flexible & cheap roll-to-roll processing

Novaled PIN® technology as
enabler for all 3 approaches

Organic Electronics Day in Mons, Novaled AG, page 14

Power Efficiency
Today lighting technologies must be energy efficient

3 key issues for OLED

Voltage minimization:
PIN approach with charge carrier doping gives voltages close to the thermo-dynamical limits
only small further improvements expected

Most efficient emitters:
Fluorescent emitters only harvest up to 25% of the energy, phosphorescent emitters can use up to
100%
However: still no fully satisfactory phosphorescent blue widely available
large improvement potential in white

Light Extraction:
Most of the generated light is still trapped inside the OLED and further efforts are needed to change
that
large improvement potential (flat and low cost solution desired)
Organic Electronics Day in Mons, Novaled AG, page 15

Light Extraction
Practical
Limit
Extraction
fade
Loss

Improved
OLED
Standard
OLED
0

20

40

60

80

100

» ca. 20% extraction efficiency for standard OLED

» > 40% extraction efficiency demonstrated by Novaled
» > 60% extraction efficiency may be possible
Organic Electronics Day in Mons, Novaled AG, page 16

Outcoupling problem in OLEDs
metal cathode

Light absorbed by cathode
Surface-plasmon mode

organic layers, n~1.8

Light trapped in organic/ITO layers
organic mode

ITO, n~1.9
total internal
reflection

glass substrate, n=1.5

air, n=1

Light trapped in substrate
substrate mode
Light coupled out
air mode

Light is trapped in organic/ITO layers and
glass substrate because of total internal
reflection at ITO/glass and glass/air
interface
Only 20-30% of the generated light is
coupled out (air mode)

Organic Electronics Day in Mons, Novaled AG, page 17

Combination of Internal and External Outcoupling
External outcoupling is limited to the substrate modes
Only internal outcoupling allows the extraction of the organic modes
Combination of both gives the best results
Novaled materials NLE-17 and NET-61 for optical outcoupling in top and
bottom emission offer simple and cost efficient solutions

OLED

OLED

OLED

No outcoupling

External outcoupling foil

Internal scattering and
outcoupling foil
Organic Electronics Day in Mons, Novaled AG, page 18

Production Requirements for Internal Outcoupling
Different outcoupling methods with very good enhancements were
demonstrated in the past
Scattering particles between ITO and glass substrates (Tyan et al.)
Glass substrates with high-index scattering layers (Nakamura et al.)
Use of high index glass (Werner et al., Reinecke et al.)
However these methods are mostly quite complex, cost intensive and
adaptation for mass manufacturing has yet to be demonstrated

Internal outcoupling has to come at a low price!
Novaled has two materials for light management
NET 61 – scattering material inside the ETL
NLE 17 – scattering material for top emission OLEDs
Both materials are vacuum processable and single evaporation step is
needed

Organic Electronics Day in Mons, Novaled AG, page 19

Cathode morphology with NET-61

Ag cathode

organic layers
Organic layers

ITO anode

The interface between
cathode and last
organic layer is wavelike due to NET-61 in
the stack
The wavy cathode
causes scattering of
organic modes and
suppression of surfaceplasmon modes

glass substrate

Organic Electronics Day in Mons, Novaled AG, page 20

Novaled Current Status:
Novaled NET-61 Internal Outcoupling for Bottom Emission

Silver Cathode

n-NET18
NET61

2nd unit

Phos. R/G-EML
p-NHT18
n-NET18

1st unit

Fluor. B-EML
p-NHT18
ITO

Substrate

A thin layer of Novaled NET-61 induces
scattering inside the OLED - internal
outcoupling
Simple evaporation process, fully compatible
with existing manufacturing lines
Power efficiency of plain OLED is increased from
26.9 lm/W to 38.5 lm/W
IV characteristics are unchanged
With an external MLA film the power efficiency
goes up to 50.1 lm/W @1000 cd/m²
(+ 80% quantum efficiency compared to plain
OLED)
Approach requires a highly reflective cathode
(silver)
Organic Electronics Day in Mons, Novaled AG, page 21

Novaled Current Status:
Novaled NLE-17 Internal Outcoupling - Top Emission on Steel
NLE-17

Hybrid tandem architecture on steel substrates

Thin metal cathode
n-ETL
Fl. G-EML

2nd unit

Fl. B-EML

Additional G-EML in blue unit increases green
contribution in the emission spectrum

p-HTL
n-ETL

1st unit

Ph. G+O-EML
Ph. G-EML

Detrimental microcavity effects depressed by
Novaled NLE-17 scattering cap layer

p-HTL
Anode

Substrate

PEff of 35 lm/W can be achieved with a CRI
of 70
Organic Electronics Day in Mons, Novaled AG, page 22

Brightness Levels
OLED is a surface emitter, light output can be increased through
size
brightness
stacking
OLED size is cost dependent
Brightness is limited by technology (lifetime reduces super-linearly with
enhanced brightness) and by human perception (glare!)
Reasonable brightness for applications between 1,000 to 6,000 cd/m²
OLED must keep the advantage to other technologies as inherently
moderate brightness light source
Organic Electronics Day in Mons, Novaled AG, page 23

Large Area Issues for OLED
Homogeneity:
Transparent electrode materials are limited in conductivity
(3 - 50 Ω/square) but large currents need to be distributed
With increasing size of an OLED the voltage stays constant but the
current goes up
Power Supply:
Larger size OLEDs require larger currents, which is not only a
homogeneity issue but could also bring the drivers and connectors to
their limit
Yield:
Small defects in production or during operation can lead to device
failure, with larger size the defect density has to be reduced dramatically

Organic Electronics Day in Mons, Novaled AG, page 24

Current Consumption of Large Area OLEDs

Besides the current distribution on
the substrate the current supply
in the periphery (drivers etc.)
becomes increasingly difficult

Simulation at
3,000 cd/m²

Single unit

150
Current [A]

Increasing diode size give rise to a
higher current demand at
constant voltage

75

Tandem
device

3,0

For certain sizes a serial
connection of OLEDs on the
substrate becomes mandatory

1,5
1,0

0,01
Area [m²]

Organic Electronics Day in Mons, Novaled AG, page 25

Stacked OLED Devices - Enhanced Homogeneity
1000
100
10

2

10000

1
0,1

1000

0,01
1E-3

100

Luminance / cd/m

Current Density / mA/cm

2

Cathode

pn junction

100000

1E-4
1E-5
6

pn junction

Anode (ITO)
Glass Substrate

8

10

10
12

Voltage / V

Novaled PIN® Technology is well suited for
stacked OLED architectures
Stacked OLEDs reduce the current and
increase the voltage
Luminance voltage curves get flatter
Both effects improve the homogeneity
Organic Electronics Day in Mons, Novaled AG, page 26

Improved Electrode Structures

Large Area Electrodes:
Metal grid can be used for
improved current
distribution on large areas
(lower sheet resistance of
the transparent electrode)
Serial connection on very
large area will be needed

Organic Electronics Day in Mons, Novaled AG, page 27

OLED100.eu Project - Structured OLED Demonstrator

Forerunner Olla project: Demo with smaller sub tiles

33 x 33 cm² demonstrator
featuring:
⇒ structured approach incl.
defect tolerant structures
⇒ 5 OLED segments in serial
connection
⇒ Tandem OLEDs based on
PIN® approach
250 mA current supply at 42 V
25 lm/W efficiency

OLED100.eu: 33×33cm2 OLED Demo/ FhG IPMS
×
Organic Electronics Day in Mons, Novaled AG, page 28

OLED Heat Management
OLEDs generate the light (and heat) already
on a large area, the heat sink (substrate) is
already integrated
In many cases heat generation of
OLEDs is not an issue
However glass is a poor heat conductor,
large area OLEDs can show an
inhomogeneous heat distribution
Inhomogeneous ageing can be the
consequence
At higher brightness more heat is generated
Heat dissipation can become an issue
for OLED in high brightness applications
Source: Merck

Organic Electronics Day in Mons, Novaled AG, page 29

OLEDs on Metal Substrate - Ideal Solution for Large Area Lighting?
Device A
Emission area: 100x100 mm2

Lmax/Lmin at 1000 cd/m²
Device A

1.21

Device B

Device B
Emission area: 4x 28x129 mm2

1.10

Metal substrates show a good luminance homogeneity because of high
conductive of metal electrodes (transparent metal contact ~3.5 W/square)
Metal substrates have superior heat conductivity to glass
better heat dissipation is possible
Metal can be conformable or flexible and it is more robust than glass
Cost efficient production: Indium free electrodes, roll-2-roll or roll-2-sheet
processing,…
Organic Electronics Day in Mons, Novaled AG, page 30

Costs
Several topics will be addressed to reduce costs in the future:
Current tools manufacture between Gen 2 and Gen 4,5 substrates, future
manufacturing lines will operate with larger size substrates
Material utilization will go up from currently 5 - 10% to 50 - 70%
Roll-2-roll and roll-2-sheet processing at high throughput will become
available

Tile costs of 100 €/m² achievable?

Organic Electronics Day in Mons, Novaled AG, page 31

Can We Standardize Designs?
Traditional Approach

or

Taking Advantage

Organic Electronics Day in Mons, Novaled AG, page 32

A new chapter: Novaleds branches out in Luxury Lighting

The world’s latest in avant garde lighting – unique luxury light-art masterpieces hand-crafted from innovative high-tech light
sources and high-edge materials. Liternity®, a trademark of German company Novaled AG. The limited-edition
Liternity luminaires combine advanced (Organic Light Emitting Diode) technologies just a few nanometers thick and exotic
high-end materials to enable completely new and imaginative ways of designing with light in ultra-flat form factors. The
first product of the Liternity series, a new desk lamp named Victory, also was introduced. It is the world’s first luminaire to
showcase OLED lighting in an ultra-thin, ultra-strong carbon-fabric base. www.liternity.com

Organic Electronics Day in Mons, Novaled AG, page 33

Acknowledgements
SFC for their blue emitters
Financial support from EU project OLED100.eu (224122), and Saxony
Project NKOE (FKZ12715) and PAFTO (FKZ14459).
Novaled OLED Team

Thank you for your attention!

Organic Electronics Day in Mons, Novaled AG, page 34

Thank you for your attention!
Organic Electronics Day in Mons, Novaled AG, page 35

..................................
..................................
Novaled AG
Tatzberg 49 · 01307 Dresden · Germany
Phone: +49 351 796580 · Fax: +49 351 7965829
www.novaled.com

Organic Electronics Day in Mons, Novaled AG, page 36