Dietmar Keiper

Highly efficient yellow organic light emitting diode based on a layer-cross faded emission layer allowing easy color tuning

An easy way to adjust the color of yellow organic light emitting diodes (OLED) is realized by basing the emission layer on a cross-fading zone of two unipolar-conducting host materials doping parts of it either with a red or green phosphorescent emitter at varying thickness ratios. At color coordinates of 0.47/0.50, a current efficacy of 42.2 cd/A (16.2% external quantum efficiency) and a power efficacy of 32.9 lm/W (1000 cd/m2) are measured without light extraction enhancement. Mixed-host emission layer OLED without cross-fading are processed for comparison. Exciton distributions are studied. The concept is suggested to be useful for white OLED.

Employing exciton transfer molecules to increase the lifetime of phosphorescent red organic light emitting diodes

The lifetime of phosphorescent red organic light emitting diodes (OLEDs) is investigated employing either N,N′-diphenyl-N,N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine (NPB), TMM117, or 4,4′,4″-tris(N-carbazolyl)-triphenylamine (TCTA) as hole-conducting host material (mixed with an electron conductor). All OLED (organic vapor phase deposition-processed) show similar efficiencies around 30 lm/W but strongly different lifetimes. Quickly degrading OLED based on TCTA can be stabilized by doping exciton transfer molecules [tris-(phenyl-pyridyl)-Ir (Ir(ppy)3)] to the emission layer. At a current density of 50 mA/cm2 (12 800 cd/m2), a lifetime of 387 h can be achieved. Employing exciton transfer molecules is suggested to prevent the degradation of the red emission layer in phosphorescent white OLED.

Layer Cross-Fading at Organic/Organic Interfaces in OVPD-Processed Red Phosphorescent Organic Light Emitting Diodes as a New Concept to Increase Current and Luminous Efficacy

The current and luminous efficacy of a red phosphorescent organic light emitting diode (OLED) with sharp interfaces between each of the organic layers can be increased from 18.8 cd/A and 14.1 lm/W (at 1,000 cd/m 2 ) to 36.5 cd/A (+94%, 18% EQE) and 33.7 lm/W (+139%) by the introduction of a layer cross-fading zone at the hole transport layer (HTL) to emission layer (EL) interface. Layer cross-fading describes a procedure of linearly decreasing the fraction in growth rate of an organic layer during deposition over a certain thickness while simultaneously increasing the fraction in growth rate of the following layer. For OLED processing and layer cross-fading organic vapor phase deposition (OVPD) is used. The typical observation of a roll-off in current efficacy of phosphorescent OLED to higher luminance can be reduced significantly. An interpenetrating network of a prevailing hole and a prevailing electron conducting material is created in the cross-fading zone. This broadens the recombination zone and furthermore lowers the driving voltage. The concept of layer cross-fading to increase the efficacies is suggested to be useful in multi-colored OLED stacks as well.

Hybrid white organic light-emitting diode with a mixed-host interlayer processed by organic vapor phase deposition

Abstract. Organic light-emitting diodes (OLEDs) are a key technology in solid state lighting.Withoutalong-livedphosphorescentblueemitter,ahybridconceptbasedonphosphorescentredandgreenemittersandafluorescentblueemitterinawhiteOLEDstackisapromisingapproachfor pure-white emission. Several challenges such as exciton recombination on all emitters andtripletdiffusion,aswellasquenching,havetobeovercome.Toaddresstheseissues,amixed-hostphosphorescent emission layer is employed. The mixture ratio is locally varied in the emissionlayer. An interlayer separates the phosphorescent and fluorescent emission layer. Strategies totune the color coordinates are presented. The lifetime and color stability versus luminance areinvestigated. At Commission Internationale de I’Eclairage color coordinates of 0.44/0.44, acurrent efficacy of 28.0 cd/A (at 1000 cd/m 2 ), and a luminous efficacy of 20.6 lm/W can bemeasured. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE) . [DOI: 10.1117/1.3545966]

Carrier-gas enhanced vapor phase deposition for organic thin films: addressing mass manufacturing requirements for OLED devices, and overcoming existing challenges with OVPD

For OLEDs to become a mainstream technology, all major display companies are ramping up their efforts to enable cost efficient manufacturing on larger substrate sizes and higher throughput. This puts additional pressure on the suppliers of respective manufacturing equipment to address perceived challenges for scaling and throughput. This paper discusses perceived challenges in today’s manufacturing and how Organic Vapor Phase Deposition (OVPD®) can address these.

38.1: Invited Paper: Enabling High Throughput OLED Manufacturing by Carrier Gas Enhanced Organic Vapor Deposition (OVPD)

This paper describes a new Organic Vapor Phase Deposition source characterized by substantially reduced vaporization temperatures and extremely short thermal exposure time of the organic material. A vapor flux of 3 mg/s is practical while maintaining thickness non-uniformity under 2% and deposition efficiency of 70% at the Gen 4 scale.

Introduction to Organic Vapor Phase Deposition (OVPDⓇ) Technology for Organic (Opto-)electronics

In this chapter, the organic vapor phase deposition (OVPDⓇ) technology combined with the Close Coupled Showerhead (CCS) technology for the fabrication of sophisticated opto-electronic organic devices based on open literature will be shortly reviewed. Typically, organic (opto-)electronic devices are fabricated by vacuum thermal evaporation (VTE), which is in contrast with the OVPDⓇ technology. The deposition of single organic films, the morphology control by OVPD and the proposed benefits of mixing organic materials, and applying non-sharp interfaces for the overall organic light emitting diode (OLED) performance will be discussed.

Novel solutions for thin film layer deposition for organic materials

Innovative systems for carrier-gas enhanced vapor phase deposition of organic layers offer advanced methods for the precise deposition of complex thin-film layer stacks. The approach inherently avoids potential short-comings from solvent-based polymer deposition and offers new opportunities. The process operates at low pressure (thus avoiding complex vacuum setups), and, by employing AIXTRONs extensive experience in freely scalable solutions, can be adapted to virtually any production process and allows for R&D and production systems alike. Deposition of organic layers and stacks recommends the approach for a wide range of organic small molecule and polymer materials (including layers with gradual change of the composition), for conductive layers, for dielectric layers, for barrier systems, for OLED materials, and surface treatments such as oleophobic / hydrophobic coatings. With the combination of other vapor phase deposition solutions, hybrid systems combining organic and inorganic materials and other advanced stacks can be realized.