OLEDs for lighting State of the art and ENEA competence Maria Grazia Maglione

LIMS 2015 ENEA FRASCATI 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) OLEDs for lighting State of the art and ENEA competence Maria Grazia Maglione ENEA Portici Research Centre Laboratory for Nanomaterials and Devices (SSPT-PROMAS-NANO) Head of lab.: Carla Minarini mariagrazia.maglione@enea.it

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 ) 2

OLED Basic Scheme Multilayer device Voltage - + Cathode ETL Electron Transport Layer /Electroluminescent Layer HTL Hole Transport Layer Anode Substrate LIGHT Electrons injection Holes injection Recombination Light emission 3

Diagram of OLED emission process In the emitting region, the interaction between holes and electrons doesn t lead directly to the carriers recombination Injection from anode h γ e Injection from cathode η 1 h e pair 1 Singlet exciton 3 Exciton: excited bound pair state Triplet exciton η 3 η 2 Emission Thermal Deactivation Radiationless Deactivation External Emission Φ el = γη 1 η 2 η 3 Internal Emission Φ el = [χ s Φ fl η s + χ t Φ ph η t ]η r η e 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, 4 so internal quantum efficiency can reaches almost 100%

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 materials Using 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 5

Light outcoupling OLEDs 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! EQE Light extraction strategies 6

OLED encapsulation Organic materials and low work-function metals react very quickly with water and oxygen of atmosphere, degrading devices performances Very good protection needed with sealing, encapsulation and getters to achieve useful lifetime (> 10.000 h) of OLEDs for applications Rigid For glass based displays Flexible For FOLED displays Utilizes a glass sealed by epoxy resin and a getter to absorb residual humidity Utilizes thin film of flexible and impermeable material to insulate the device

OLEDs technology: several approaches Two main materials: Small Molecule OLED (SMOLED) Polymer LED (PLED) Two main architecture: Bottom Emitting OLEDs Top Emitting OLEDs Small Molecule materials Use of small molecules High purity of materials Smooth surfaces Bottom emitting Light V Reflecting Electrode Light Emitting Material Transparent Electrode Transparent Substrate Light Light Emitting Polymers (LEP) Use of light-emitting polymers Hosts with different dopants, dyes and nanoparticles in order to obtain several colors V Transparent Electrode Light Emitting Material Reflecting Electrode Substrate Top emitting 8

Fabrication Technologies Small molecules Polymers OLED basic 9

OLED: addressing two markets Source: Novaled 2011 10

OLEDs DISPLAYS! From early samples to marketed products Kodak LS633 photocamera, 2.2" AMOLED display (2003) Samsung S6 Edge, 5.1" (2015) Sony XEL-1, 11" TV set (2007) LG 55EC9300, 55" curved Full HD TV set, US$ 1999 (2014) LG G Flex LS995, 6.0" (2013) Epson 40" TV set, ink-jet printed, polymer-based (2004) OLEDs are an important success of the Organic Electronics LG 77EG9900, 77" flexible 4K TV set, US$ 50,000 (!?) (2015) PANASONIC TX-65CZ950, 65" curved 4K TV set (2015) (LG panel) Images: www.oled-info.com; www.samsung.com; www.lg.com

OLEDs for lighting OLEDs It is a Solid State Lighting technology, with LEDs and EL sources It 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 lighting OLED lighting development is moving fast too! Several prototypes LG Chem (2009) General Electric chandelier World s first OLED lamp by OSRAM and Ingo Maurer design (2008) (price: 25 000) Novaled transparent OLEDs (2010) Novaled Philips

OLEDs for lighting OLED 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/m 2 life = 10.000 hours price (at launch) = 72 @ 44 x 47 mm 2

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

OSRAM efficacy = 40 lm/w luminance = 2000 cd/m^2 CRI = 80 lifetime L70 = 10 000 h working voltage = 6 V active area = up to > 11 cm^2 cost = N.A. OLEDs for lighting Characteristics of some OLED lighting products Announced best performances of OLED devices NEC Lighting & Yamagata Univ. efficacy = 156 lm/w luminance = 1000 cd/m^2 active area = 4 mm^2 LG Chem efficacy = 50+ lm/w luminance = 3000+ cd/m^2 CRI = 90+ lifetime L70 = 30 000+ h working voltage = 6 or 8.5 V active area = up to 1000 cm^2 cost = $566/klm (680 US$/panel) OLED lighting average cost 200 US$/klm 20X LEDs IDTechEx (2014): market < $200 million @ 2019 $1.9 billion @ 2025 Konica Minolta efficacy = 64 lm/w luminance = 1000 cd/m^2 lifetime L50 = 10 000 h active area = 68 cm^2 cost = N.A. Konica Minolta efficacy = 139 lm/w luminance = 1000 cd/m^2 CRI = 81 lifetime L50 = 55 000 h active area = 15 cm^2 source: www.oled-info.com Cintelliq (2014): OLEDs become a strong competitor to LEDs by 2016 By 2020: OLED panels priced at 200/m^2 @ 5 000 cd/m^2, and less than 14/klm By 2023: OLED panel production > 500 million of 100mm x 100mm panel equivalents

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

Lab. ENEA NANO competence OLEDs OPV OTFTs Innovative process technologies Raw materials recovery from waste Laboratory NANO is organized as a lab-scale full processing line for 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 MATERIALS Images: 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 competence OLEDs on glass

Lab. ENEA NANO competence OLEDs on plastic

Lab. ENEA NANO competence ENEA NANO - OLEDs activity Objectives Improvement of 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 them Life 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 devices to develop and transfer useful knowledge to the companies and the public

Lab. ENEA NANO competence ENEA NANO OLEDs Materials and architecture Encapsulation Cathode EIL ETL HBL EML HTL HIL Anode Substrate Substrate Glass; PET; PEN; etc. Anode ITO; doped PEDOT:PSS; ZnO; AZO; etc. HIL - Hole Injection Layer PEDOT:PSS, Metal Oxides (MoO 3 ), CuPc HTL - Hole Transport Layer α-npd, TPD EML - Emitting Layer Small Molecules, Polymers, Blends and Nanocomposites deposited by evaporation in vacuum and from solution host materials: CBP, SimCP guest materials: Ir(Fppy)3, Ir(ppy)3, etc. HBL - Hole Blocking Layer BCP ETL - Electron Transport Layer Alq3 Cathode LiF + Al; Ca + Al; Li + Al; etc. Encapsulation rigid: glass lid + epoxy resin sealant + getter flexible: thin film encapsulation: inorganic barriers, organic-inorganic multilayer

Lab. ENEA NANO competence Improvement of the devices performances Anode surface treatments Charge injection layers (HIL, EIL) PEDOT:PSS, CuPc, LiF, etc. Low work-function cathodes Phosphorescent emitting materials Light outcoupling 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

Lab. ENEA NANO competence White OLEDs Blue OLEDs Violet OLEDs Very wide spectrum 437 nm 672 nm DEV A EL Spectrum (a.u.) 0,70 0,65 0,60 0,55 0,50 0,45 0,40 0,35 0,30 0,25 0,20 0,15 0,10 0,05 0,00 no interlayer - red 3% 10nm - green 6% 10nm -0,05 300 400 500 600 700 800 W avelength (nm) 1mA 2,5mA 5mA 10mA 15mA Confidential - Unpublished results

ENEA OLEDs Dimensions: few mm 2 up to some square cm Threshold voltage: 3.0 V Luminance: up to several thousands of cd/m 2 Luminance: 40000 cd/m 2 @ 9 V White OLED for Lighting applications warm natural white cold white 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 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. 27

Innovation: OLED light in horticulture to 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) we use ENEA violet OLED obtained with a combination of blue and red wavelenghts Luminance (9V) 5000 Cd/cm 2 EL Spectrum (a.u.) 0,50 0,45 0,40 0,35 0,30 0,25 0,20 0,15 0,10 0,05 0,00 Glass/ITO/PEDOT:PSS/NDP/EML/BCP/Alq 3 /Ca(Al) -0,05 300 400 500 600 700 800 Wavelength (nm) Drogaggio EML 2% Drogaggio EML 4% Wavelength emission(nm) Peak 1 434 Peak 2 620 Peak 3 673

ENEA innovative materials for OLED in collaboration with Dept. of Chemistry, University of Naples 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 this reason growing attention is paid to the design and development of nature-inspired materials for organic 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 of new melanin-inspired photoluminescent materials for OLED applications; 2) the development of melanin-based material for ITO replacement. Melanin precursors HO HO HO N H NH 2 Chemical and physical properties Extremely low radiative quantum yield Photo- and electrical conductivity Broad band absorption in the entire UV-Vis spectrum Free radical and redox behavior HO Main goals of the melanin-inspired research line Design, synthesis and characterization of new melanin-inspired photoluminescent materials for OLED applications. Development of a melanin-based material for ITO replacement. Photovoltaic devices Melanins Photoactive and photoprotective materials Optoelectronic and energy storage devices Fields of application Sensors

OLED encapsulation results Not Encapsulated Devices Encapsulated Devices Not-Encapsulated Encapsulated SEM image optical image Visible Aging: A combination of Electrical and Time effect Very little effect on Encapsulated devices Encapsulation reduces electroluminescence decay and voltage shift Encapsulation problems Side penetration of oxygen and water-vapour through organic layers and metal-encapsulation interface O 2 Water vapour O 2 Water vapour Encapsulation Al Organic layers ITO Substrate Encapsulation Al Organic layers ITO Substrate 30

Lab. ENEA NANO competence getter Encapsulation and lifetime studies Rigid encapsulation getter Water vapour transmission rate (WVTR) of 10-5 g/m 2 /day at room temperature (T = 25 C, RH = 50%; measured by ENEA electrical Ca test) has been obtained. 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 In progress Study of the intrinsic degradation phenomena through shelf life experiments, performed at different storage conditions (by using a climate chamber). Flexible encapsulation Multilayer barrier of sputtered Al 2 O 3, on the device (Thin Film Encapsulation (TFE)). WVTR of 10-3 g/m 2 /day at room conditions (T = 25 C, RH = 50%; below the detection limit of our permeabilimeter (< 10-2 g/m 2 /day)) can be reached. Lamination of transparent barrier film (Foil Encapsulation (FE)). WVTR of 10-1 to 10-3 g/m 2 /day at room conditions (T = 25 C, RH = 50%; measured by permeabilimeter) has been achieved.

Lab. ENEA NANO competence OLEDs fabrication facilities 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 competence OLEDs fabrication facilities Clean room (class 100), for photolithography and chemical processes Excimer laser processing: Laser assisted deposition Crystallization PECVD cluster system Mask Aligner with Nano Imprint Lithography (NIL) (EVG620 NT) Direct Writing Laser system, for high resolution photolithography Ink-jet printing system Hot embossing system

Lab. ENEA NANO competence OLEDs fabrication facilities SEM Electro-optical bench Probe station Organic Material Analyzer Profilometer Spectrofluorometer Climatic chamber Contact angle

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 C. R. ENEA Portici P.le E. Fermi, 1 80055 Portici (NA), Italy mariagrazia.maglione@enea.it +39 081 7723 249 ENEA Portici Research Centre Laboratory for Nanomaterials and Devices (SSPT-PROMAS-NANO) Head of lab.: Carla Minarini carla.minarini@enea.it