Degradation of the materials in organic lightemitting devices oleds is the major impediment for the development of economically feasible, highly efficient and durable devices for commercial applications. Simplified organic lightemitting devices utilizing ultrathin electron transport layers and new insights on their roles. Abstract degradation of the materials in organic light. These mechanisms can be broadly grouped into three categories.
Degradation mechanisms of organic light emitting diodes based on thermally activated delayed fluorescence molecules. Understanding degradation of organic lightemitting diodes. A comprehensive model of the degradation of organic light. Pdf degradation of organic lightemitting diodes oleds operated continuously at a constant current density is. Apr 18, 20 chemical degradation in organic lightemitting devices. Highenergy excited state manager materials for longlived blue phosphorescent organic light emitting diodes, disclosed 101915,u. Abstract experimental and theoretical results are presented on the lifetime of organic light emitting diodes oleds for active matrix display applications. Studies on the longterm degradation of organic lightemitting devices oleds based on tris8hydroxyquinoline aluminum alq 3, the most widely used electroluminescent molecule, reveal that injection of holes in alq 3 is the main cause of device degradation. Investigation of electroluminescence degradation in anthracenebased organic lightemitting devices by qi wang a thesis. Degradation typically occurs when a current is forced through an insulating material. Published 1 september 2004 2004 iop publishing ltd journal of physics d.
The excitons are created by the recombination of electrons leaked from the emission layer. The main obstacle to the long lifetime of these devices was found to be the electrochemical reaction on interfaces of both electron and hole injecting. The effect of electrical stress on polymer degradation has been studied on the organic device structure itohtlppvcaag. Organic lightemitting diodes oleds have achieved tremendous progress in display and lighting applications. Here it is demonstrated that magnetic field effects can be used as a nondestructive. Direct evidence of molecular aggregation and degradation. Mechanism of darkspot degradation of organic lightemitting devices article pdf available in applied physics letters 864.
Mar 23, 2018 the short lifetime of bluephosphorescent organic light emitting devices owing to material degradation impedes their practical potential. To gain an insight into a chemical mechanism of operational degradation, we studied operationinduced changes in chemical compositions of fluorescent and phosphorescent. This trend reverses when the bias polarity is reversed, and the initial driving voltage can be recovered almost completely. A degradation mechanism of organic lightemitting devices. The operating lifetime of blue quantumdot lightemitting diodes qled is currently a short slab for this emerging display technology. To do so, the main limitation factor remains as the blue lightemitting material, for which the halflife has been progressively increased. Mechanisms and implications for the design of new materials susanna schmidbauer institut fur organische chemie, universitat regensburg, universitatsstra.
In addition, ideal material and device plans to reach the lifetimes required for commercialization in blue phosphorescent oleds are proposed. Photophysics of organic light emitting diodes device efficiency and degradation processes. Charge and exciton dynamics in organic optoelectronic devices. Organic lightemitting devices oleds have been attracted to both academia and industry, because of their wide applications and remarkable advances in display. The short lifetime of bluephosphorescent organic lightemitting devices owing to material degradation impedes their practical potential. In both cases, degradation is primarily due to the formation of nonemissive regions, or dark spot defects. The results and proposed mechanism provide a better understanding of magnetic field effects on organic lightemitting diodes and device degradation phenomena. Comparison of acetaminophen degradation in uvledbased. Water vapor and oxygen degradation mechanisms in organic light emitting diodes article in advanced functional materials 112. At this time, we know the degradation mechanisms of only few organic materials applied in organic light emitting devices oleds. Charge and exciton dynamics in organic optoelectronic devices by caleb coburn a dissertation submitted in partial ful llment of the requirements for the degree of doctor of philosophy physics in the university of michigan 2019 doctoral committee. Organic light emitting materials and devices xviii, edited by franky so, proc. Photophysics of organic light emitting diodes device.
Holeinduced degradation in the presence of excited states is found to be a major culprit for the fast degradation in solutionprocessed devices. In this work, we investigate the performance and operational stability of solutionprocessed organic lightemitting diodes oleds, which comprise polyethylenimine pei as an electron injection layer eil. Degradation in organic light emitting devices oleds is generally driven by reactions involving excitons and polarons. Degradation mechanisms in organic lead halide perovskite. Excitoninduced degradation of interfaces in organic light. Depth profiling of organic lightemitting diodes by tofsims coupled with waveletprincipal component analysis. During the past decades, the improvement on device lifetime and efficiency has made oled technology possible to be used in ubiquitous consumer gadgets such as smartphones.
Basic principles of organic light emitting diodes, device preparation, materials and stack design, experimental techniques, comprehensive efficiency analysis of oleds, degradation processes in oleds. Chemical degradation mechanisms of organic semiconductor. Photochemical reactions in organic semiconductor thin films org. Ultraviolet light emitting diode uvledbased advanced oxidation processes aops including uvledchloramine uvlednh 2 cl, uvledhydrogen peroxide uvledh 2 o 2 and uvledpersulfate uvledps, were adopted for acetaminophen aap removal. Nanoscale investigation of moistureinduced degradation. Chemical degradation mechanisms of organic semiconductor devices. A numerical device model and approach to degradation. The degradation mechanism of organic light emitting devices. Degradation mechanisms and reactions in organic lightemitting.
Professor stephen forrest, chair professor jay guo professor jennifer ogilvie associate professor. Simplified phosphorescent organic lightemitting devices pholeds have better efficiency performance but their lifetime is shorter compared to that of standard pholeds. Depending upon the materials and the device architectures used, the degradation mechanism can be very different. To resolve the issue of which of the indium migration model and the unstable alq3 cationic model plays a more important role in luminescence degradation of organic lightemitting devices, we investigated the effect of the device structures on device operational stability. The mechanism by which organic materials degrade involves radical species as byproducts and key reaction intermediates5,6,7,8,9,10. In this study, we evaluated the degradation mechanisms of. Liquid organic lightemitting diodes liquid oleds are unique devices consisting only of liquid organic semiconductors in the active layer, and the device performances have been investigated recen.
Degradation of bluephosphorescent organic light emitting devices involves excitoninduced generation of polaron pair within emitting layers. By studying the degradation of a population of oleds, we show that the lifetime of encapsulated devices is increased by more than two orders of magnitude over that of unencapsulated devices. Chemical degradation in organic light emitting devices. Jan 25, 2017 in this work, we investigate the performance and operational stability of solutionprocessed organic light emitting diodes oleds, which comprise polyethylenimine pei as an electron injection layer eil. The degradation mechanisms of solution processed small molecule phosphorescent oleds are investigated along with thermal evaporated devices. Excitoninduced degradation of interfaces in organic lightemitting devices by qi wang a thesis presented to the university of waterloo in fulfillment of the thesis requirement for the degree of doctor of philosophy in electrical and computer engeering waterloo, ontario, canada, 2015 qi wang 2015. Mechanisms and implications for the design of new materials. Degradation mechanism study and electron scattering device structure for long lifetime in blue phosphorescent organic lightemitting diodes. The underlying degradation mechanism is a topic of crucial importance. To detect specific reaction products, we introduced laser desorptionionization timeofflight mass spectrometry lditofms, a method which allows to distinguish between desired and undesired compounds in thin film. Degradation mechanisms in organic lightemitting diodes with.
Degradation mechanisms of silver nanowire electrodes under. Pdf degradation mechanisms of organic lightemitting diodes. Pdf mechanism of darkspot degradation of organic light. Degradation due to trapped charges at sharp organic and organic electrode interfaces.
Degradation mechanism in simplified phosphorescent organic. Material degradation of liquid organic semiconductors. A novel mechanism is revealed for the degradation and failure of the recently developed organic light emitting device oled made of ito polypphenylene vinylenealuminum or magnesium. In this progress report, using examples in both small molecule and polymer oleds, the different degradation mechanisms in two types of devices are examined. We present a simple encapsulation technique for organic light emitting devices oleds. Materials science and engineering the light extraction efficiency of common bottom emission oleds is limited to 2530%. Isolating degradation mechanisms in mixed emissive layer. Excitontriggered luminance degradation of organic light. Here, the effect of exciton density on device degradation is analyzed in a. We address mechanisms of bulk polymer degradation in these devices and show through in situ fourier transform infrared characterization of working lightemitting devices with active layers of poly. One of the commonly used approaches to exceed this limitation is to corrugate the interfaces. For display applications, which require a moderate brightness, there are a wide range of. Stable, high efficiency white phosphorescent organic light.
Mechanism of darkspot degradation of organic light. A novel mechanism is revealed for the degradation and failure of the recently developed organic lightemitting device oled made of indiumtin oxide itopolypphenylenevinylenealuminum or magnesium. In the case of al, the deterioration in oled performance. Organic light emitting diode having a mixed blocking layer, disclosed 9815, u. Direct evidence of molecular aggregation and degradation mechanism of organic lightemitting diodes under joule heating. Popovic,2 nanxing hu,2 ahmee hor,2 gu xu1 studies on the longterm degradation of organic lightemitting devices oleds based on tris8hydroxyquinoline aluminum alq 3, the most widely used.
Degradation mechanisms and reactions in organic lightemitting devices by sebastian scholz, denis kondakov, bjorn lussem and karl leo no static citation data no static citation data cite. Degradation mechanism of small moleculebased organic. Constantstress accelerated degradation life test of an. Degradation of bluephosphorescent organic lightemitting devices. Although many different degradation mechanisms have similar effects and appearances, they can be.
Organic light emitting devices oleds have been attracted to both academia and industry, because of their wide applications and remarkable advances in display. Water vapor and oxygen degradation mechanisms in organic. Degradation mechanisms in organic lightemitting devices. However, their structural degradation during environmental exposure e. Theoretical investigation of the degradation mechanisms in host and.
Apr 24, 2020 improving the lifetime of organic light emitting diodes requires that degradation processes are understood. The organic light emitting diode oled technology made reliable progress from its first viable prototypes in the late 1980s 1. Although the lifetime and reliability of organic light emitting diodes oleds have been improved greatly over the last decade, a complete understanding of the device degradation mechanisms remains elusive. In this thesis, excitoninduced degradation of interfaces in oleds, including organic electrode and organic organic interfaces, is studied. This leads to a conclusion that alq3 cations are unstable, and to our proposal that the same mechanism is responsible for degradation of organic lightemitting devices oleds based on alq3. Degradation in organic lightemitting devices oleds is generally driven by reactions involving excitons and polarons. Degradation mechanism and lifetime improvement strategy.
A main obstacle to obtaining a long lifetime for these devices is found to be the electrochemical reaction on interfaces of both electron and hole injecting electrodes. As a promising candidate for efficient, scalable, and inexpensive solar cells, hybrid organic inorganic halide perovskites have attracted tremendous research attention. Using chemically sensitive xray photoelectron microscopy, we investigate the mechanism of darkspot formation and degradation of organic lightemitting devices. Apr 16, 2008 at this time, we know the degradation mechanisms of only few organic materials applied in organic light emitting devices oleds. Nanoscale investigation of moistureinduced degradation mechanisms of tris8hydroxyquinoline aluminiumbased organic lightemitting diodes. One common observation regarding the oled reliability is the gradual increase of the diode driving voltage under forward bias. Analysis of intrinsic degradation mechanism in organic light. Despite the importance of the operational lifetime of organic lightemitting diodes oleds in practical applications, little is known about the nature of chemical reactions associated with efficiency losses during operation.
Request pdf degradation mechanisms and reactions in organic light emitting devices degradation mechanisms and reactions in organic light emitting. Degradation of organicorganic interfaces in organic light. A numerical device model and approach to degradation mechanisms in organic light emitting diodes oleds tadahiko hirai, karl weber, jenny oconnell, mark bown, kazunori ueno materials science and engineering, csiro bayview avenue, clayton, victoria 3168, australia phone. Reliability and degradation of organic light emitting devices. Pss on the rectification and degradation of organic photovoltaic cells calvyn t. A main obstacle to obtaining a long lifetime for these devices is found to be the electrochemical reaction on interfaces of both electron. Chemical degradation in organic lightemitting devices. Understanding the underlying degradation mechanism is therefore a prerequisite for the realization of devices with prolonged stability. Even though this chemical degradation is complex and the least understood of the different degradation modes in oleds, scientists were successful in providing insight into some of the. The transport of holes into alq 3 caused a decrease in its fluorescence quantum efficiency, thus showing that cationic alq 3. Operational stability enhancement in organic light. In this work, we find that their shorter lifetime is due to excitoninduced degradation of the indium tin oxide ito organic interface. Degradation mechanisms in electrically stressed organic. When properly stacked, these materials result in a device that can achieve the required high efficiency and long lifetime.
Since the insulator does not support conduction waves in its ground state, chemical restructuring must occur. The impact of organic light emitting diodes oleds in modern life is. Emitting diodes are known to be unstable under ambient conditions. We show that the primary degradation mechanism in these oleds depends on the cathode metal that is used in contact with the eil. This thesis is about the fundamental causes of degradation in tris8hydroxyquinoline aluminum alq3based organic light emitting diodes oleds. Results showed that aap could be effectively degraded by the hybrid processes compared to solely using with uv irradiation and oxidants. Investigation of electroluminescence degradation in anthracenebased organic lightemitting devices by qi wang a thesis presented to the university of waterloo in fulfillment of the thesis requirement for the degree of master of applied science in electrical and computer engineering waterloo, ontario, canada, 2010 qi wang 2010.
New approaches towards phosphorescent iridium complexes for. In this work, i study how chemical degradation is driven by the excited carrier in. Operational degradation of organic lightemitting diodes. We report the degradation mechanisms of the silver nanowire ag nw electrodes that play a significantly important role in the stability of wearable and flexible devices. Accordingly, a common design strategy to improve oled lifetime is to reduce the density of these species by engineering an emissive layer architecture to achieve a broad exciton recombination zone. Investigation of electroluminescence degradation in. Progress in understanding degradation mechanisms and. Loss in quantum yield versus loss in charge balance. Mechanisms and implications for the design of new materials 2 1. As a general trend, the drive voltage tends to increase and the electroluminescence efficiency tends to decrease with operating time. Unravelling degradation mechanisms and atomic structure of. Degradation mechanisms and reactions in organic light. Degradation mechanisms in blue phosphorescent organic lightemitting devices by excitonpolaron interactions.
View the article pdf and any associated supplements and figures for a period of 48 hours. Despite the conspicuous advances in oleds and even their successful implementation in commercial displays, device degradation issues still remain as one of the most important problems. In recent years, a major issue has been to increase their lifetime. Degradation mechanisms and reactions in organic lightemitting devices. Degradation of bluephosphorescent organic lightemitting. Recent citations a comparative study via photophysical and electrical characterizations on interfacial and bulk exciplexforming systems for efficient organic light emitting diodes nurul ridho al amin et al degradation mechanisms and reactions in organic light. Unravelling degradation mechanisms and atomic structure of organic inorganic halide perovskites by cryoem yanbin li,1,7 weijiang zhou,2,7 yuzhang li,1,7 wenxiao huang,1 zewen zhang,1 guangxu chen,1 hansen wang,1 gongher wu,3 nicholas rolston,4 rafael vila,1 wah chiu,2,3,5, and yi cui1,6,8, summary. Dc aging tests on the oleds show that the driving voltage increases under forward bias and then reverse its trend when the bias polarity is reversed, which reproduce our previous test under. Degradation mechanisms in organic lightemitting diodes. Degradation study of organic lightemitting diodes with.
1113 45 1 7 297 71 14 708 66 313 1069 1029 1046 680 988 1118 722 1020 808 1204 306 689 952 424 1115 1381 774 91 241