A degradation study of poly(p-phenylene vinylene) based light emitting diodes

Nguyen, T.P.; Spiesser, M.; Garnier, A.; Kok, Margreet de; Tran, V.H.

doi:10.1016/s0921-5107(99)00026-4

Cited by 14 publications

(9 citation statements)

References 25 publications

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“…In particular, the disappearance of the aliphatic peaks corresponding to the tetrahydrothiophenium ring and the methylene carbon after the polymerization is a sign of the elimination of this residue and the formation of C=C double bonds. In accordance with this, only sp 2 carbons are recorded in the 13 C NMR spectrum of PPV@mpSiO 2 .…”

supporting

confidence: 77%

“…Solid-state MAS 13 C NMR of PPV@mpSiO 2 ( Figure 3) also confirmed the success of the polymerization. In particular, the disappearance of the aliphatic peaks corresponding to the tetrahydrothiophenium ring and the methylene carbon after the polymerization is a sign of the elimination of this residue and the formation of C=C double bonds.…”

supporting

confidence: 52%

“…Characterization techniques: Solid-state 13 C NMR spectra were recorded by using a Varian 400 MHz at a spinning rate of 5.5 kHz. Ground-state diffuse reflectance UV/Vis spectra were recorded by using a Cary 5G using a praying mantis accessory for solids and using BaSO 4 as standard.…”

mentioning

confidence: 99%

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Monomers That Form Conducting Polymers as Structure‐Directing Agents: Synthesis of Microporous Molecular Sieves Encapsulating Poly‐para‐phenylenevinylene

Atienzar

Díaz–Cabañas

Moliner

et al. 2007

Chemistry A European J

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We have developed a novel concept that uses monomers required for making conducting polymers as organic structure-directing agents, for the synthesis of microporous molecular sieves. We show that these monomers facilitate the formation of crystalline and amorphous molecular sieves depending on the synthesis procedure. The monomers filling the pores of the silicates can be polymerized under certain conditions, resulting in a polymer immobilized and protected inside the matrix. The concept was exemplified with para-phenylenemethylene-bis(1-tetrahydrothiophenium) and para-phenylenemethylene-bis(trimethylammonium) that were used to template microporous molecular sieves and subsequently to obtain poly-para-phenylenevinylene (PPV) inside the matrix. The organic self-assembled organic-inorganic material was extensively characterized and the implication on electrical conductivity is presented.

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supporting

confidence: 77%

supporting

confidence: 52%

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Monomers That Form Conducting Polymers as Structure‐Directing Agents: Synthesis of Microporous Molecular Sieves Encapsulating Poly‐para‐phenylenevinylene

Atienzar

Díaz–Cabañas

Moliner

et al. 2007

Chemistry A European J

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“…[2][3][4][5][6] OLEDs are amorphous thin solid film heterojunction devices constructed by vacuum evaporation of the transport layers onto a supporting electrode.…”

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confidence: 99%

Impact of Particulate Contaminants on the Current Leakage Defect in OLED Devices

Nagai

2007

J. Electrochem. Soc.

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Using focused ion beam and scanning electron microscopy, we investigated the effect of particulate contaminants on current leakage defects in organic light-emitting diode devices ͑200 nm thick organic layer͒. Flaked particles from sputtering targets and resist-related particles were investigated as examples of particulate contaminants. Three types of defects were identified corresponding to the dimensions and locations of the particulate contaminants. Large particles ͑Ͼ3 m in height͒ on the substrate formed short-circuit-type defects. They prevented an organic layer from being deposited on the anode, resulting in localized exposure of the anode surface. The cathode contacted the anode at these locations. Small particles ͑0.5-1.0 m in height and 1.0-3.0 m in length͒ on the substrate caused localized thinning at the places where the organic layer was deposited on the particles. This localized thinning of the organic layer apparently increased the Fowler-Nordheim tunneling current and the resultant avalanche multiplication, leading to leakage current. Very minute particles of lithium-oxide ͑Li 2 O͒ ͑0.03-0.05 m in diameter͒ in the cathode buffer layer caused current leakage. The local electric field concentration due to these minute particles and the resultant carrier injection is the possible cause of current leakage.Following the initial report, by Tang and Van Slyke, 1 organic light-emitting diodes ͑OLEDs͒ have attracted much attention for their potential use in next-generation display technologies. [2][3][4][5][6] OLEDs are amorphous thin solid film heterojunction devices constructed by vacuum evaporation of the transport layers onto a supporting electrode.Although they promise excellent device performance, OLED devices are difficult to manufacture and are subject to dark spot and current leakage defects. Dark spots are attributed to moisture and oxygen penetration. Device design ͑glass encapsulation, thin film passivation, etc.͒ has been the main approach to controlling them. 7 Current leakage defects are caused mainly by foreign particulate contaminants. Reducing these defects requires controlling particulate contamination over the entire fabrication process.Since the distance between the anode and cathode electrodes in OLED devices is very short, 100-200 nm, particulate contaminants left in the devices can easily cause current leakage defects. Even a single current leakage defect can prevent proper functioning of the device. In contrast to their thicknesses, conventional OLED panels have large surface areas. This means that particulate contaminants must be eliminated over a wide area, which makes it difficult to control current leakage defects in OLED devices.Despite the importance of controlling current leakage defects in OLED devices, there have been relatively few reports on their sources and mechanism. 8,9 In this study, we investigated the effect of particulate contamination on current leakage using focused ion beam ͑FIB͒ and scanning electron microscopy ͑SEM͒. As typical particulate contaminants formed ...

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“…Dark spots are known to be the major degradation of OLED devices and moisture is largely responsible for these dark spots. [1][2][3][4][5][6] When making OLEDs directly onto CF substrates, passivation films are required to prevent this remaining moisture from reaching the OLEDs. In the manufacturing process, particulate contaminants often make pinholes in the passivation films to conduct moisture into the OLEDs, leading to dark spots.…”

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confidence: 99%

Defects of Passivation Films for Color-Filter-Based OLED Devices

Nagai¹

2007

J. Electrochem. Soc.

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The color filter ͑CF͒-based organic light-emitting diode ͑OLED͒ devices suffer dark spots due to remaining moisture in the CFs. A passivation film is thus used to prevent this remaining moisture from reaching the OLED. The characteristics of defects in passivation films and their effects on dark spot formation in OLED devices were investigated. The structure of the sample devices were CF ͑1.5 m͒/over coat ͑OC͒ ͑1.5 m͒/SiO 2 passivation film by sputtering ͑100 nm͒/indium-tin-oxide ͑ITO͒ anode ͑100 nm͒/OLED/Al cathode ͑200 nm͒, fabricated on glass substrates. The defects of passivation films caused dark spots in the OLED devices. These defects can be classified as particulate and nonparticulate. The particulate defects can be further classified as typical pinhole defects resulting from large particles ͑micrometer order size͒ and as defects with a characteristic explosive shape resulting from small particles ͑submicrometer order͒. The explosive degradation of the films may be due to the gasification of localized moisture. Nonparticulate defects consist of microvoids formed at the OC-passivation film interface. The surface treatments, such as "light-ashing" and "ion-cleaning" done on the OC surface are largely responsible for these microvoids.Organic light-emitting diodes ͑OLEDs͒ have attracted much attention for a new display technology. A lifetime, a long pending problem, has been already demonstrated longer than 10,000 hours. Products using them, such as small display panels for in-car audio systems and mobile phones, have reached the market. The basic research on the mechanism for OLEDs has been finished and their development is in the final stage, just ahead of manufacturing.The production cost of OLEDs has become an important consideration. One of the most costly processes in the OLED fabrication is their color patterning process. Vacuum evaporated patterning for red-green-blue ͑RGB͒ using shadow-masks has been conventionally proposed to develop full color OLED panels. However, this method has a serious problem of high cost of shadow-masks. Recently, color filter ͑CF͒-based OLED devices have attracted attention, where CFs are used with a white OLED to attain full color function. Because this method requires no shadow-masks, it has a potential to reduce production cost significantly. Conventionally, CFs are prepared in aqueous solutions and then coated on glass substrates followed by patterning. CF-based OLED devices involve a problem of dark spots due to remaining moisture in the CF layer. Dark spots are known to be the major degradation of OLED devices and moisture is largely responsible for these dark spots.

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A degradation study of poly(p-phenylene vinylene) based light emitting diodes

Cited by 14 publications

References 25 publications

Monomers That Form Conducting Polymers as Structure‐Directing Agents: Synthesis of Microporous Molecular Sieves Encapsulating Poly‐para‐phenylenevinylene

Monomers That Form Conducting Polymers as Structure‐Directing Agents: Synthesis of Microporous Molecular Sieves Encapsulating Poly‐para‐phenylenevinylene

Impact of Particulate Contaminants on the Current Leakage Defect in OLED Devices

Defects of Passivation Films for Color-Filter-Based OLED Devices

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