Diffusion – the Hidden Menace in Organic Optoelectronic Devices

Smith, Arthur R. G.; Lee, Kwan H.; Nelson, Andrew; James, M. R.; Burn, Paul L.; Gentle, Ian R.

doi:10.1002/adma.201104029

Cited by 38 publications

(32 citation statements)

References 48 publications

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“…This explains the sustained growth of the pores, even after the removal of the bias. The above results are also consistent with the results from prior studies 10,13,14,18,21,23,49,50 on which bubble formation, black spots, and pinholes were attributed to the diffusion of entrapped gases and atomic species within the OLED layers. Furthermore, as the bubbles grow, they interact and coalesce, giving rise to the formation of larger bubbles as shown in Figures 11(a)-11(d).…”

Section: E Stress Distributions and Crack Driving Forcessupporting

confidence: 92%

“…Subsequent degradation processes include the oxidation and diffusion of gases through defects also reported in earlier studies. 10,14,18 Further studies are clearly needed to refine the design of HOILED structures in ways that can reduce the stress concentrations associated with incorporated TiO 2 -nanoparticle reinforcements. These might include efficient methods for orienting and dispersing nanoparticles in the active layer.…”

Section: G Implicationsmentioning

confidence: 99%

“…8 OLEDs also have low quantum efficiencies and undergo a range of degradation mechanisms during exposure to light and water vapor/oxygen in the environment. [9][10][11][12][13][14][15] The effects of environment have been partly solved by the development of encapsulation strategies. 16,17 However, encapsulation does not totally prevent degradation of OLEDs, although it has been shown to significantly improve device lifetimes.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Adhesion and degradation of organic and hybrid organic-inorganic light-emitting devices

Momodu

Tong

Kana

et al. 2014

Journal of Applied Physics

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This paper presents the results of a combined analytical, computational, and experimental study of adhesion and degradation of Organic Light Emitting Devices (OLEDs). The adhesion between layers that are relevant to OLEDs is studied using an atomic force microscopy technique. The interfacial failure mechanisms associated with blister formation in OLEDs and those due to the addition of TiO2 nanoparticles into the active regions are then elucidated using a combination of fracture mechanics, finite element modeling and experiments. The blisters observed in the models are shown to be consistent with the results from adhesion, interfacial fracture mechanics models, and prior reports of diffusion-assisted phenomena. The implications of the work are then discussed for the design of OLED structures with improved lifetimes and robustness.

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Section: E Stress Distributions and Crack Driving Forcessupporting

confidence: 92%

Section: G Implicationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Adhesion and degradation of organic and hybrid organic-inorganic light-emitting devices

Momodu

Tong

Kana

et al. 2014

Journal of Applied Physics

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“…In contrast, although there have been several reports on the interfacial analyses in OLEDs, in fact, the effects of the interfacial structures on the device characteristics have almost not been discussed. 5,17,18 Especially, to our best of knowledge, there have been no detailed reports of how solution-and thermal-annealed interfaces affect the OLED characteristics, despite of the intrinsic importance. The interfacial structures can largely affect the charge injection, charge transport, and charge and exciton confinements.…”

Section: Introductionmentioning

confidence: 99%

Molecular Interdiffusion between Stacked Layers by Solution and Thermal Annealing Processes in Organic Light Emitting Devices

Ohisa

Yamada

et al. 2015

ACS Appl. Mater. Interfaces

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In organic light emitting devices (OLEDs), interfacial structures between multilayers have large impacts on the characteristics of OLEDs. Herein, we succeeded in revealing the interdiffusion in solution processed and thermal annealed OLEDs by neutron reflectometry. We investigated interfaces between a polymer under layer and small molecules upper layer. The small molecules diffused into the swollen polymer layer during the interfacial formation by the solution process, but the polymer did not diffuse into the small molecules layer. At temperatures close to the glass transition temperatures of the materials, asymmetric molecular diffusion was observed. We elucidated the effects of the interdiffusion on the characteristics of OLEDs. Partially mixing the interface improved the current efficiencies due to suppressed triplet-polaron quenching at the interface. Controlling and understanding the interfacial structures of the miultilayers will be more important to improve the OLED characteristics.

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“…Sharp and defined interfaces are required for the high efficiency of the device. 10 Undefined interfaces lead to a loss of the function separation 11 and a shift of the area for electron-hole recombination. The low film thicknesses in organic electronics applications and the high requirements for the quality of the interfaces demand extremely precise coating techniques.…”

Section: Introductionmentioning

confidence: 99%

Formation of blade and slot die coated small molecule multilayers for OLED applications studied theoretically and by XPS depth profiling

et al. 2016

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Slot die coaters especially designed for low material consumption and doctor blades were used to process small molecule solutions for organic light-emitting diodes (OLEDs). Optimum process parameters were developed for the large-scale coating techniques to generate stable single and multiple layers only a few nanometers thick. Achieving a multilayer architecture for solution-processed OLEDs is the most challenging step. X-ray photoelectron spectroscopy sputter depth profiling was performed to determine defined interfaces between coated organic layers. Commercially available small molecules NPB (N,N’-Di(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4,4’-diamine) and BAlq (Bis(8-hdroxy-2methylquinoline)-(4-phenylphenoxy)aluminum), originally developed for vacuum deposition, were used as hole, respectively electron transport material. Defined double-layers were processed with both scalable coating methods using the orthogonal solvent approach. The use of non-orthogonal solvents resulted in complete intermixing of the material. The results are explained by calculations of solubilities and simulating drying and diffusion kinetics of the small molecule solutions.

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Diffusion – the Hidden Menace in Organic Optoelectronic Devices

Cited by 38 publications

References 48 publications

Adhesion and degradation of organic and hybrid organic-inorganic light-emitting devices

Adhesion and degradation of organic and hybrid organic-inorganic light-emitting devices

Molecular Interdiffusion between Stacked Layers by Solution and Thermal Annealing Processes in Organic Light Emitting Devices

Formation of blade and slot die coated small molecule multilayers for OLED applications studied theoretically and by XPS depth profiling

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