Post-annealing effect on the interface morphology and current efficiency of organic light-emitting diodes

Yoon, Youngwoon; Lee, Hanju; Kim, Tae‐Dong; Kim, Kyoungchul; Choi, Sula; Yoo, Hyung Keun; Friedman, Barry

doi:10.1016/j.sse.2012.07.016

Cited by 13 publications

(3 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For instance, the device's efficiency was significantly reduced and operating voltages increased by heating at 70 °C in high vacuum for 3 h, as shown in table 4. Such thermal degradations were completely avoided with the 60 °C ALD process: as also shown in table 4, upon the application of a 35 nm AZO film deposited with the 60 °C/H 2 O 2 process, the OLED device did not show any degradation on its OLED spectrum (shown in figure S7), but instead had moderate improvements in its efficiencies, which were likely attributable to improved interface quality by the annealing effects of the 60 °C thermal treatment, as reported previously [33,34]. The encapsulation effectiveness of the AZO film in terms of the lifetime of the encapsulated devices, however, could not be accurately evaluated, because the OLED devices did not have adequate intrinsic stability to allow for long-term lifetime tests.…”

Section: Encapsulation Of Oled Devicessupporting

confidence: 73%

Low-temperature gas-barrier films by atomic layer deposition for encapsulating organic light-emitting diodes

Tseng¹,

Yu²,

Chou³

et al. 2016

Nanotechnology

View full text Add to dashboard Cite

Dependences of gas-barrier performance on the deposition temperature of atomic-layer-deposited (ALD) AlO, HfO, and ZnO films were studied to establish low-temperature ALD processes for encapsulating organic light-emitting diodes (OLEDs). By identifying and controlling the key factors, i.e. using HO as an oxidant, laminating AlO with HfO or ZnO layers into AHO or AZO nanolaminates, and extending purge steps, OLED-acceptable gas-barrier performance (water vapor transmission rates ∼ 10 g m d) was achieved for the first time at a low deposition temperature of 50 °C in a thermal ALD mode. The compatibility of the low-temperature ALD process with OLEDs was confirmed by applying the process to encapsulate different types of OLED devices, which were degradation-free upon encapsulation and showed adequate lifetime during accelerated aging tests (pixel shrinkage <5% after 240 h at 60 °C/90% RH).

show abstract

Section: Encapsulation Of Oled Devicessupporting

confidence: 73%

Low-temperature gas-barrier films by atomic layer deposition for encapsulating organic light-emitting diodes

Tseng¹,

Yu²,

Chou³

et al. 2016

Nanotechnology

View full text Add to dashboard Cite

show abstract

“…As such, the accelerated testing process could lead to the OLEDs appearing to have shorter lifetimes than they might actually possess during normal operation. It is logical to consider that degradation of OLED performance under thermal stress could be related to the glass-transition temperatures ( T g ’s) of the materials in the active layers, , and consequently, there have been substantial efforts to develop high- T g compounds. − There are now a number of reports using different techniques that indicate that the drop in device performance is morphologically driven; that is, that the layered structure is altered during heating. − Changes in the layered structure of the device can lead to an imbalance in the injection and transport of charges, resulting in less exciton formation and radiative decay.…”

Section: Introductionmentioning

confidence: 99%

Dependence of Organic Interlayer Diffusion on Glass-Transition Temperature in OLEDs

McEwan

Clulow

Nelson³

et al. 2017

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

Organic light-emitting diodes (OLEDs) are subject to thermal stress from Joule heating and the external environment. In this work, neutron reflectometry (NR) was used to probe the effect of heat on the morphology of thin three-layer organic films comprising materials typically found in OLEDs. It was found that layers within the films began to mix when heated to approximately 20 °C above the glass-transition temperature (T) of the material with the lowest T. Diffusion occurred when the material with the lowest T formed a supercooled liquid, with the rates of interdiffusion of the materials depending on the relative T's. If the supercooled liquid formed at a temperature significantly lower than the T of the higher-T material in the adjacent layer, then pseudo-Fickian diffusion occurred. If the two T's were similar, then the two materials can interdiffuse at similar rates. The type and extent of diffusion observed can provide insight into and a partial explanation for the "burn in" often observed for OLEDs. Photoluminescence measurements performed simultaneously with the NR measurements showed that interdiffusion of the materials from the different layers had a strong effect on the emission of the film, with quenching generally observed. These results emphasize the importance of using thermally stable materials in OLED devices to avoid film morphology changes.

show abstract

“…The electroluminescent (EL) efficiency of such devices depends on many factors, including the active layer quantum yield, the recombination and transport properties as well as the device architecture and engineering of electrodes and interfaces [ 4 , 5 ]. High quality interfaces are very important in OLED applications to achieve efficient charge injection and avoid low dielectric breakdown voltage and dark spot formation [ 6 , 7 ]. The injection efficiency of holes from the most widely used indium tin oxide (ITO)/Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hole injection electrode (HIE) [ 8 ], strongly depends on the energy level alignment between the PEDOT:PSS/organic active layer [ 9 , 10 , 11 , 12 , 13 , 14 ] and the interfacial morphology between the various layers (e.g., ITO, PEDOT:PSS, organic active layer) [ 15 , 16 ].…”

Section: Introductionmentioning

confidence: 99%

Bottom Contact Metal Oxide Interface Modification Improving the Efficiency of Organic Light Emitting Diodes

et al. 2020

View full text Add to dashboard Cite

The performance of solution-processed organic light emitting diodes (OLEDs) is often limited by non-uniform contacts. In this work, we introduce Ni-containing solution-processed metal oxide (MO) interfacial layers inserted between indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) to improve the bottom electrode contact for OLEDs using the poly(p-phenylene vinylene) (PPV) derivative Super-Yellow (SY) as an emission layer. For ITO/Ni-containing MO/PEDOT:PSS bottom electrode structures we show enhanced wetting properties that result in an improved OLED device efficiency. Best performance is achieved using a Cu-Li co-doped spinel nickel cobaltite [(Cu-Li):NiCo2O4], for which the current efficiency and luminous efficacy of SY OLEDs increased, respectively, by 12% and 11% from the values obtained for standard devices without a Ni-containing MO interface modification between ITO and PEDOT:PSS. The enhanced performance was attributed to the improved morphology of PEDOT:PSS, which consequently increased the hole injection capability of the optimized ITO/(Cu-Li):NiCo2O4/PEDOT:PSS electrode.

show abstract

Post-annealing effect on the interface morphology and current efficiency of organic light-emitting diodes

Cited by 13 publications

References 19 publications

Low-temperature gas-barrier films by atomic layer deposition for encapsulating organic light-emitting diodes

Low-temperature gas-barrier films by atomic layer deposition for encapsulating organic light-emitting diodes

Dependence of Organic Interlayer Diffusion on Glass-Transition Temperature in OLEDs

Bottom Contact Metal Oxide Interface Modification Improving the Efficiency of Organic Light Emitting Diodes

Contact Info

Product

Resources

About