Increase of charge carriers density and reduction of Hall mobilities in oxygen-plasma treated indium–tin–oxide anodes

Kim, Jinhyun; Cacialli, Franco; Cola, A.; Gigli, Giuseppe; Cingolani, R.

doi:10.1063/1.124263

Cited by 94 publications

(64 citation statements)

References 20 publications

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“…Thin-film PL efficiency was measured in air with the aid of an integrating sphere and using a He-Cd laser or UV excitation at 3.82 eV. Light-emitting devices consisted of thin films of PEDOT:PSS spun from water (0.02 g mL À1 ) solutions onto pre-etched, oxygen-plasma-treated ITO substrates [37,38] and annealed at 200 8C for 15 min in nitrogen. Then the emissive polymers were spun from a THF solution (2% by weight) onto the PEDOT:PSS substrates in nitrogen.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and Optoelectronic Properties of Nonpolar Polyrotaxane Insulated Molecular Wires with High Solubility in Organic Solvents

Frampton

Sforazzini

Brovelli

et al. 2008

Adv Funct Materials

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Hydrophilic polyanionic conjugated polyrotaxanes are readily synthesized in water by Suzuki coupling, but their high polarity and ionic nature limit the potential applications of these materials. Here, we demonstrate three methods for transforming these polar polyelectrolytes into nonpolar lipophilic insulated molecular wires. A water‐soluble polyfluorene‐alt‐biphenylene β‐cyclodextrin (CD) polyrotaxane was converted into nonpolar derivatives by methylation of the carboxylic acid groups with diazomethane and conversion of the hydroxyl groups of the CDs to benzyl ethers, trihexylsilyl ethers, benzoyl esters, and butanoate esters to yield polyrotaxanes that are soluble in organic solvents such as chloroform and cyclohexane. Elemental analysis, NMR spectroscopy, and gel permeation chromatography (GPC) data support the proposed structures of the organic‐soluble polyrotaxanes. The extents of reaction of the polyrotaxane CD hydroxyl groups were 55% for trihexylsilyl chloride/imidazole; 81% for benzyl chloride/sodium hydride; 72% for benzoyl chloride/pyridine/4‐dimethylaminopyridine; and 98% butanoic anhydride/pyridine/4‐dimethylaminopyridine. Alkylation, silylation, and esterification increase the bulk of the encapsulating sheath, preventing interstrand aggregation, increasing the photoluminescence efficiency in the solid state and simplifying the time‐resolved fluorescence decay. The organic‐soluble polyrotaxanes were processed into polymer light‐emitting diodes (PLEDs) from solution in nonpolar organic solvents, thereby excluding ionic impurities from the active layer.

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Section: Methodsmentioning

confidence: 99%

Synthesis and Optoelectronic Properties of Nonpolar Polyrotaxane Insulated Molecular Wires with High Solubility in Organic Solvents

Frampton

Sforazzini

Brovelli

et al. 2008

Adv Funct Materials

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“…By treating ITO anodes with oxygen plasma the surface energy can be increased, which not only raises the ITO work function, but also leads to greater adhesion with subsequently deposited polymer layers. [26,27] This leads to reduced interfacial stress and a more-efficient electrical contact, with concomitant improvement in charge-carrier injection and OLED performance. Such effects would also be highly desirable in the case of VPP PEDOT anodes.…”

mentioning

confidence: 97%

Fabrication of Highly Conductive Poly(3,4‐ethylenedioxythiophene) Films by Vapor Phase Polymerization and Their Application in Efficient Organic Light‐Emitting Diodes

et al. 2007

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The discovery of organic electroluminescence (EL) in manufacturable small molecule [1] and p-conjugated polymer [2] thin-film format has led to the commercialization of organic light-emitting diode (OLED) technology and the development of many other novel semiconductor devices. One of the key goals for research in this field is high-performance, fully plastic electronic devices, but before such technology can be realized, organic electrode materials with conductivities and stabilities comparable to standard inorganic materials must be developed. Indium tin oxide (ITO) is the present industry standard transparent inorganic anode material for rigid devices, such as optical displays and solar cells. Attempts have also been made at implementing ITO in an emerging generation of flexible devices, but it is not an ideal choice owing to its inherent brittleness and susceptibility to conductivity changes after bending. [3][4][5] When this is considered alongside the ever-increasing cost of indium, it is clear that there is a pressing need to develop organic-based electrode materials for both flexible and rigid substrate devices. Here, we report the synthesis and optoelectronic properties of highly conductive (≤ 1180 S cm -1 ) poly(3,4-ethylenedioxythiophene) (PEDOT) films prepared by vapor phase polymerization (VPP). We focus on their application in ITO-free OLEDs as a patternable organic anode material. We describe devices fabricated on glass and flexible plastic substrates with efficiencies (16.8 and 9.8 lm W PEDOT is an especially promising organic electrode material. Though insoluble in all common solvents, PEDOT films exhibit a number of desirable properties in the oxidized state, including high conductivity, good stability, and high thin-film transparency. [6,7] It is possible to circumvent the low solubility of PEDOT using a water-soluble polyelectrolyte such as poly(styrene sulfonic acid) (PSSA) during polymerization in water, yielding a PEDOT-PSS aqueous composite with good film-forming properties. [8,9] However, the conductivity of a PEDOT-PSS film is typically no more than ca. 10 S cm -1 , well below the level typical of ITO (ca. 4000 S cm -1 ). Researchers have explored several methods for raising the conductivity, including the addition of a range of secondary dopants.

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“…On other hand, the sheet resistance of ITO anodes treated by the oxygen plasma and the SCCO 2 /H 2 O 2 were 4.5 X/square and 4.5-4.8 X/square, as compared with 5 X/square of the as-cleaned ITO anode. The oxygen plasma and SCCO 2 /H 2 O 2 treatments can both improve the sheet resistance of the ITO samples through removing surface contaminants and increasing oxygen vacancies on the ITO surfaces [19]. Figure 3 shows the deconvoluted XPS O 1 s spectra of the as-cleaned ITO surface and the ITO surfaces treated with the oxygen plasma and the SCCO 2 /H 2 O 2 fluid at 4000 psi for 15 min.…”

Section: Methodsmentioning

confidence: 98%

Aging of ITO anodes treated by supercritical CO2/H2O2 fluids for OLEDs

Tien

Chen

Chuang

et al. 2015

J Mater Sci: Mater Electron

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The aging behaviors of indium tin oxide (ITO) anodes treated by supercritical CO 2 /H 2 O 2 (SCCO 2 /H 2 O 2 ) fluids were investigated. As the SCCO 2 /H 2 O 2 -treated ITO anodes were aged, the contact angle and surface energy were analyzed and compared with those of the ITO anodes treated by oxygen plasma. The SCCO 2 /H 2 O 2 pretreatment yielded a stable polar component of the ITO surfaces after 48 h of aging. The energy reduction in the polar component of the oxygen-plasma-treated ITO due to aging was 20 %, as compared with the 1.1 % decrease in ITO treated with the SCCO 2 /H 2 O 2 fluids at 4000 psi for 15 min. The X-ray photoelectron spectroscopy analysis revealed that the oxygen content of the ITO surfaces with the SCCO 2 /H 2 O 2 pretreatment was significantly higher than that of the ITO treated by oxygen plasma. This could result from the formation of hydroxyl products that functioned as a stable buffer layer against further contamination during aging. In addition, the correlated dependence of the OLED performance on the aged ITO anodes was also studied. The OLEDs with the SCCO 2 /H 2 O 2 pretreatment showed an improved degradation of I-V characteristics and brightness in comparison with those of the devices treated with oxygen plasma after aging the treated ITO anodes for 6 and 12 h. The obtained results suggested that the ITO anodes treated by the SCCO 2 /H 2 O 2 fluids exhibited a stable surface chemistry and could be useful for OLED applications.

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Increase of charge carriers density and reduction of Hall mobilities in oxygen-plasma treated indium–tin–oxide anodes

Cited by 94 publications

References 20 publications

Synthesis and Optoelectronic Properties of Nonpolar Polyrotaxane Insulated Molecular Wires with High Solubility in Organic Solvents

Synthesis and Optoelectronic Properties of Nonpolar Polyrotaxane Insulated Molecular Wires with High Solubility in Organic Solvents

Fabrication of Highly Conductive Poly(3,4‐ethylenedioxythiophene) Films by Vapor Phase Polymerization and Their Application in Efficient Organic Light‐Emitting Diodes

Aging of ITO anodes treated by supercritical CO2/H2O2 fluids for OLEDs

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