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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
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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
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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
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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
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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
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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.
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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
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