ENEA Portici Research CentreLaboratory for Nanomaterials and Devices (SSPT-PROMAS-NANO)Head of lab.: Carla Minarini

OLEDs for lightingState of the art and ENEA competence

Department for Sustainability of the productive and territorial systems (SSPT)

Division for Technologies and processes of the materials for the sustainability (SSPT-PROMAS)

Laboratory for Nanomaterials and Devices (SSPT-PROMAS-NANO)

Maria Grazia Maglione

LIMS 2015ENEA – FRASCATI

mariagrazia.maglione@enea.it

2

What is an OLED?OLED is the acronym for Organic Light Emitting Diode

An OLED is a solid-state device composed of thin films of organic molecules that create light with the application of electricity

• Doesn’t require any backlight• Self emitting• Light weight and thin (100 to 500

nanometers thick)• Flexible• Low power consumption• High contrast, brighter and wide

viewing angle (170)

3

Cathode

ETL

HTL

Anode

Substrate

-

+

LIGHT

Voltage

Electron Transport Layer /Electroluminescent Layer

Hole Transport Layer

Electrons injection

Holes injection

Recombination

Light emission

OLED Basic SchemeMultilayer device

4

Diagram of OLED emission process

Φel = γη1η2η3

h e

h – e pair

Singlet exciton Triplet exciton

Emission

ExternalEmission

InternalEmission

ThermalDeactivation

RadiationlessDeactivation

γ

η1

η2

η3

Φel = [χsΦfl ηs + χtΦph ηt]ηrηe

Exciton: excited bound pair state

Injection from cathodeInjection from anode

Maximum internal quantum efficiency for fluorescence emission = 25%Phosphorescent materials (heavy metal complexes, like Ir(ppy)3, PtEOP, etc)

can convert triplet states to singlet emitting ones,so internal quantum efficiency can reaches almost 100%

1 3

In the emitting region, the interaction between holes and electrons doesn’t lead directly to the carriers recombination

5

Efficiency of OLED Balance of electron and hole currents from injection: ≈ 1 can be reached

Injection and transport of charges must be efficient for good power efficiency

75% Triplet, 25% Singlet excitons: 25% for fluorescent materialsUsing phosphorescent materials (Forrest/Thompson) and optimizing recombination zone, almost 100% efficiency can be reached

Because of flat structure of the device and mismatching of refractive indexes of layers, up to 80% of generated light can be lost to wave guide modes

Light must be efficiently extracted from the device

30

6

Light outcouplingOLEDs are devices made of flat layers with different refractive indexes

Generated light presents total internal reflection at the interfaces

External radiation can be up to 20 - 30% only

of generated light!

Light extraction strategies

EQE

OLED encapsulationOrganic materials and low work-function metals react very quickly with water and

oxygen of atmosphere, degrading devices’ performances

Very good protection needed withsealing, encapsulation and getters

to achieve useful lifetime (> 10.000 h) of OLEDs for applications

RigidFor glass based displays

Utilizes a glass sealed by epoxy resin and a getter to absorb residual humidity

FlexibleFor FOLED displays

Utilizes thin film of flexible and impermeable material to insulate the device

8

OLEDs technology: several approaches

Two main materials:

Small Molecule OLED (SMOLED) Polymer LED (PLED)

Small Molecule materials• Use of small molecules

• High purity of materials

• Smooth surfaces

Light Emitting Polymers (LEP)• Use of light-emitting polymers

• Hosts with different dopants, dyes and nanoparticles in order to obtain several colors

Transparent Substrate

VReflecting Electrode

Light Emitting Material

Transparent Electrode

Light

Bottom emitting

Top emitting

VTransparent Electrode

Light Emitting Material

Reflecting Electrode

Light

Substrate

Two main architecture: Bottom Emitting OLEDs Top Emitting OLEDs

9

Fabrication Technologies

Small molecules Polymers

OLED basic

10

OLED: addressing two markets

Source: Novaled 2011

OLEDs… DISPLAYS!

Sony XEL-1, 11" TV set (2007)

From early samples… … to marketed products…

Epson 40" TV set, ink-jet printed, polymer-based (2004)

Kodak LS633 photocamera, 2.2" AMOLED display (2003)

PANASONIC TX-65CZ950, 65" curved 4K TV set (2015) (LG panel)

LG 55EC9300, 55" curved Full HD TV set, US$ 1999 (2014)

… OLEDs are an important success

of the Organic Electronics LG 77EG9900, 77" flexible

4K TV set, US$ 50,000 (!?) (2015) Images: www.oled-info.com; www.samsung.com; www.lg.com

LG G Flex LS995, 6.0" (2013)

Samsung S6 Edge, 5.1" (2015)

OLEDs for lightingOLEDs

It is a Solid State Lighting technology, with LEDs and EL sourcesIt is an answer for

• high efficiency• very small or zero

environmental impact

It is THE answer for• natural, large area,

glare-free light• tuneable colour• flexible, thin and

lightweight sources• transparent sources• dimmable sources

OLEDs for lightingOLED lighting development is moving fast too!

World’s first OLED lamp by OSRAM and Ingo Maurer

design (2008)(price: € 25 000)

General Electric chandelier

Philips

Novaled

LG Chem (2009)

Novaled transparent OLEDs (2010)

Several prototypes…

OLEDs for lightingOLED lighting development is moving fast too!… first commercial devices in 2009… OSRAM Orbeos diameter = 80 mm efficacy = 25 lm/W CRI (Colour Rendering Index) = 80 price (at launch) = 375 US$

PHILIPS Lumiblade various dimensions and forms efficacy = 20 lm/W (white & RGB) luminance = 1.000 cd/m2

life = 10.000 hours price (at launch) = 72 € @ 44 x 47 mm2

OLEDs for lightingOLED lighting development is moving fast too!… to present (and coming) products OSRAM Novaled Blackbody (FIAMM) LG Chem Konica Minolta Fraunhofer COMEDD AUDI etc.

Novaled

Blackbody (FIAMM) LG Chem

OSRAM

AUDI

Konica Minolta

Fraunhofer COMEDD

OLEDs for lightingCharacteristics of some OLED lighting products

OSRAMefficacy = 40 lm/Wluminance = 2000 cd/m^2CRI = 80lifetime L70 = 10 000 hworking voltage = 6 Vactive area = up to > 11 cm^2cost = N.A.

Konica Minoltaefficacy = 64 lm/Wluminance = 1000 cd/m^2lifetime L50 = 10 000 hactive area = 68 cm^2cost = N.A.

Announced best performances of OLED devices NEC Lighting & Yamagata Univ.

efficacy = 156 lm/Wluminance = 1000 cd/m^2active area = 4 mm^2

Konica Minoltaefficacy = 139 lm/Wluminance = 1000 cd/m^2CRI = 81lifetime L50 = 55 000 hactive area = 15 cm^2

LG Chemefficacy = 50+ lm/Wluminance = 3000+ cd/m^2CRI = 90+lifetime L70 = 30 000+ hworking voltage = 6 or 8.5 Vactive area = up to ≈ 1000 cm^2cost = $566/klm (680 US$/panel)

OLED lighting average cost ≈ 200 US$/klm ≈ 20X LEDs

source: www.oled-info.com

IDTechEx (2014): market < $200 million @ 2019 $1.9 billion @ 2025

Cintelliq (2014): OLEDs become a strong competitor to LEDs by 2016By 2020: OLED panels priced at €200/m^2 @ 5 000 cd/m^2, and less than €14/klmBy 2023: OLED panel production > 500 million of 100mm x 100mm panel equivalents

Anyway, there are still "red brick walls" to face Lifetime Encapsulation New Barriers

• for large area and flexible devices• integrated in-line production

Devices Efficiency Light Outcoupling/Extraction• intelligent glass substrates and lenses (micro lenses, pyramid array, prism foil)• index-matched materials and adhesives• encapsulation, for matched index plastic substrates

Standardization Manufacturing Costs Improved Processes

Lower Prices and High Production Volumes • high throughput and material utilization efficiency for vacuum deposition• solution processing and printing tooling promises must turn into reality

for lower cost manufacturing, but must deliver high performance devices• this red brick wall is becoming the most dominant one

Investments, to move from R&D and pilot lines to real production

OLEDs for lighting

source: OE-A - White Paper - Roadmap for Organic and Printed Electronics, 6th Ed. (June 2015)

• OLEDs• OPV• OTFTs• Innovative process technologies• Raw materials recovery from waste

Lab. ENEA NANO competence

Laboratory NANO is organized as a lab-scale full processing linefor simulation, design, fabrication and test of materials, devices and systems

of ORGANIC and PRINTED ELECTRONICS,its applications in horticulture,

and study the recovery and recycling of raw materials from waste

Activities address the EIT priorities for RAW MATERIALSImages: ENEA SSPT-PROMAS-NANO; COATEMA

• thin film deposition of organic and inorganic materials through high vacuum

techniques and from solution (thermal evaporation, sputtering, CVD, ALD,

spin-coating, inkjet printing, roll to roll printing))

• development of : innovative phosphorescent materials Innovative hybrid conductive transparent materials barrier layer by ALD

• structural, morphological, optical and electrical material characterizations

• evaluation of energy levels of materials

• design of device architectures, circuit and system layouts

• simulation of materials and devices

• OLEDs fabrication, encapsulation and electro-optical characterizations

• OLEDs lifetime optimization

ENEA OLED expertise

Lab. ENEA NANO competenceOLEDs on glass

Lab. ENEA NANO competenceOLEDs on plastic

Performances of the devices, through materials devices’ architecture fabrication technologies (high through-put methods, printing techniques, etc.) simulations (physical and electrical)

Stability and lifetime, and methods to improve themLife cycle of devices and systems

to study low eco-impact materials and processes, to reduce the waste and improve the recovery of valuable materials

Usefulness of the devicesto develop and transfer useful knowledge to the companies and the public

Lab. ENEA NANO competenceENEA NANO - OLEDs activity Objectives

Improvement of …

Lab. ENEA NANO competence• Substrate

Glass; PET; PEN; etc.• Anode

ITO; doped PEDOT:PSS; ZnO; AZO; etc.• HIL - Hole Injection Layer

PEDOT:PSS, Metal Oxides (MoO3), CuPc• HTL - Hole Transport Layer

α-NPD, TPD• EML - Emitting Layer

Small Molecules, Polymers, Blends and Nanocompositesdeposited by evaporation in vacuum and from solutionhost materials: CBP, SimCPguest materials: Ir(Fppy)3, Ir(ppy)3, etc.

• HBL - Hole Blocking LayerBCP

• ETL - Electron Transport LayerAlq3

• CathodeLiF + Al; Ca + Al; Li + Al; etc.

• Encapsulationrigid: glass lid + epoxy resin sealant + getter flexible: thin film encapsulation:

inorganic barriers, organic-inorganic multilayer

ENEA NANO OLEDsMaterials and architecture

Substrate

HILHTL

Anode

HBLETL

EML

EIL

Cathode

Encapsulation

• Anode surface treatments• Charge injection layers (HIL, EIL)

• PEDOT:PSS, CuPc, LiF, etc.

• Low work-function cathodes• Phosphorescent emitting materials• Light outcoupling

Lab. ENEA NANO competenceImprovement of the devices’ performances

• Materials: CBP + Ir(ppy)3; LiF/Al• Turn-on voltage ≈ 2.0 V• Luminance ≈ 40 000 cd/m^2 @ 9 V• Current efficiency ≈ 20 cd/A• Efficacy ≈ 15 lm/W

No light outcoupling

DEV A

Lab. ENEA NANO competenceWhite OLEDs

300 400 500 600 700 800-0,050,000,050,100,150,200,250,300,350,400,450,500,550,600,650,70

EL S

pect

rum

(a.u

.)

W avelength (nm)

1mA 2,5mA 5mA 10mA 15mA

no interlayer - red 3% 10nm - green 6% 10nm

437 nm 672 nmVery wide spectrum

Confidential - Unpublished results

Blue OLEDs Violet OLEDs

Dimensions: few mm2 up to some square cmThreshold voltage: 3.0 V Luminance: up to several thousands of cd/m2

ENEA OLEDs

warm natural white cold white

White OLED for Lighting applicationsLuminance: 40000 cd/m2 @ 9 V

“Encapsulated Organic Electronic Device With Improved Resistance To Degradation”, P. Tassini, M. G. Maglione, E. Romanelli, P. Vacca, C.Minarini, United States Patent Application 20090066244 (2009)

ENEA OLEDs in white goods

27

OLED prototypes to light the

interior of refrigerator.

Developed for Electrolux in

the frame of the ALADIN

Project, in collaboration with

CRP, SAES, FERRANIA, CRF,

CNR .

Some wavelengths of light are able

to maintain the freshness and

nutritional properties of

vegetables.

Innovation: OLED light in horticultureto enhance the growth of some vegetables

An efficient lamp for plant growth must convert as much electrical energy as possible into Photosynthetically Active Radiation region energy (PAR 400-700nm)

300 400 500 600 700 800-0,05

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0,40

0,45

0,50

Wavelength (nm)

EL S

pect

rum

(a.u

.)

Drogaggio EML 2% Drogaggio EML 4%

Glass/ITO/PEDOT:PSS/NDP/EML/BCP/Alq3/Ca(Al)

Wavelength emission(nm)

Peak 1 434

Peak 2 620

Peak 3 673

Luminance (9V)

5000 Cd/cm2

we use ENEA violet OLED obtained with a combination of blue and red wavelenghts

ENEA innovative materials for OLEDin collaboration with Dept. of Chemistry, University of Naples

NH

OH

OH

OH

OH

NH2

Melanin precursors

Melanins

Extremely low radiative quantum

yield

Broad band absorption in the entire UV-Vis

spectrum

Free radical and redox behavior

Photo- and electrical conductivity

Chemical and physical properties

Fields of application

Photovoltaic devices

Sensors

Optoelectronic and energy storage devices

Photoactive and photoprotective materials

Main goals of the melanin-inspired research line

• Design, synthesis and characterization of new melanin-inspiredphotoluminescent materials for OLED applications.

• Development of a melanin-based material for ITO replacement.

Natural Pigments Inspire the Design of Biocompatible Materials in Organic Electronics: Melanins

The use of such biodegradable materials can be an answer to the problem of electronic waste. For thisreason growing attention is paid to the design and development of nature-inspired materials fororganic electronics applications.Our idea is to use natural pigments (melanins) in OLED applications.Our main goals of the melanin-inspired research are: 1) the design, synthesis and characterization ofnew melanin-inspired photoluminescent materials for OLED applications; 2) the development ofmelanin-based material for ITO replacement.

30

OLED encapsulation resultsNot Encapsulated Devices Encapsulated Devices Encapsulated

optical image Not-Encapsulated

SEM image

Encapsulation reduceselectroluminescence decay and voltage shift

Visible Aging: A combination of Electrical and Time effect

Very little effect on Encapsulated devices

O2

Water vapourEncapsulation

AlOrganic layers

ITOSubstrate

Encapsulation

AlOrganic layers

ITOSubstrate

O2

Water vapour

Encapsulation problemsSide penetration of oxygen and water-vapour through organic layers and metal-encapsulation interface

Lab. ENEA NANO competenceEncapsulation and lifetime studies

Rigid encapsulation Flexible encapsulation

• US Patent 2009/0066244 A1: "Encapsulated organic electronic device with improved resistance to degradation", 12/03/2009

• Italian patent TO2007U000116: "Dispositivo elettronico organico incapsulato, con migliorata resistenza al degrado", 11/09/2007

getter getter

Lamination of transparent barrier film (Foil Encapsulation (FE)).WVTR of 10-1 to 10-3 g/m2/dayat room conditions (T = 25°C, RH = 50%; measured by permeabilimeter) has been achieved.

Multilayer barrier of sputtered Al2O3, on the device (Thin Film Encapsulation (TFE)).WVTR of 10-3 g/m2/dayat room conditions (T = 25°C, RH = 50%; below the detection limit of our permeabilimeter (< 10-2

g/m2/day)) can be reached.

In progressStudy of the intrinsic degradation phenomena through shelf life experiments, performed at different storage conditions (by using a climate chamber).

Water vapour transmission rate (WVTR) of 10-5 g/m2/dayat room temperature (T = 25°C, RH = 50%; measured by ENEA electrical Ca test) has been obtained.

KURT J. LESKER integrated process system: Evaporator, Sputter, Spin-coaters, integrated in a glove box with inert atmosphere

OXFORD OpAL Atomic Layer Deposition system (ALD), for barrier layers deposition: Al2O3, SiN, SiO2

Modular and upgradable COATEMA Smartcoater roll-to-roll printing system: gravure and screen-printing, slot-die coating, lamination, inert atmosphere

Lab. ENEA NANO competenceOLEDs fabrication facilities

Ink-jet printing system

Mask Aligner with Nano Imprint Lithography (NIL) (EVG620 NT)

Clean room (class 100), for photolithography and

chemical processes

Direct Writing Laser system,

for high resolution photolithography

PECVD cluster system

Excimer laser processing:

• Laser assisted deposition

• Crystallization

Hot embossing system

Lab. ENEA NANO competenceOLEDs fabrication facilities

Electro-optical benchSEM

Profilometer

Contact angle

Spectrofluorometer

Probe station

Climatic chamber

Organic Material Analyzer

Lab. ENEA NANO competenceOLEDs fabrication facilities

Maria Grazia MaglioneC. R. ENEA PorticiP.le E. Fermi, 180055 Portici (NA), Italymariagrazia.maglione@enea.it+39 081 7723 249

Department for Sustainability of the productive and territorial systems (SSPT)Division for Technologies and processes of the materials for the sustainability (SSPT-PROMAS)Laboratory for Nanomaterials and Devices (SSPT-PROMAS-NANO)

ENEA Portici Research CentreLaboratory for Nanomaterials and Devices (SSPT-PROMAS-NANO)Head of lab.: Carla Minarinicarla.minarini@enea.it