Photooxidation of the Evaporated Films of Polycyclic Aromatic Hydrocarbons Studied by X-Ray Photoelectron Spectroscopy

Yamada, Masamichi; Ikemoto, Isao; Kuroda, Haruo

doi:10.1246/bcsj.61.1057

Cited by 80 publications

(76 citation statements)

References 26 publications

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“…459 Such photo oxidation effects are well-known for condensed materials like rubrene and naphthacene as well. 259 As expected, photoinduced reactions with oxygen were already discovered for illumination experiments with UV 460,461 as well as for the visible part of the light. 128,129,462 Many OLED materials, for example, α-NPD and TPD, are known to degrade (changes in their absorption and PL emission characteristics) after UV irradiation (365 nm, 150 W Hg arc lamp) of single layers in air.…”

Section: Photochemical Reactionssupporting

confidence: 58%

Degradation Mechanisms and Reactions in Organic Light-Emitting Devices

et al. 2015

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Section: Photochemical Reactionssupporting

confidence: 58%

Degradation Mechanisms and Reactions in Organic Light-Emitting Devices

et al. 2015

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“…Earlier researchers have shown that illumination increases the oxidation of rubrene thin films. They also used a source of radiation in the UV to visible range 29,30 . After each exposure, the sample was characterized using XPS and UPS spectroscopies.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Oxidation of Rubrene Thin Films: An Electronic Structure Study

et al. 2014

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The performances of organic semiconductor devices are crucially linked with their stability at the ambient atmosphere. The evolution of electronic structures of 20 nm thick rubrene films exposed to ambient environment with time has been studied by UV and X-ray photoemission spectroscopy (UPS and XPS), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and density functional theory (DFT). XPS, NEXAFS data, and DFT calculated values suggest the formation of rubrene-epoxide and rubrene-endoperoxide through reaction of tetracene backbone with oxygen of ambient environment. Angle dependent XPS measurement indicates that the entire probed depth of the films reacts with oxygen by spending only about 120 min in ambient environment. The HOMO peak of pristine rubrene films almost disappears by exposure of 120 min to ambient environment. The evolution of the valence band (occupied states) and NEXAFS (unoccupied states) spectra indicates that the films become more insulating with exposure as the HOMO-LUMO gap increases on oxidation. Oxygen induced chemical reaction completely destroys the delocalized nature of the electron distribution in the tetracene backbone of rubrene. The results are relevant to the performance and reliability of rubrene based devices in the environment.

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“…[15,16] Many pentacene OFETs have achieved mobilities more than 1.0 cm 2 V 21 s 21 , depending on the fabrication conditions. [17][18][19][20][21] Although pentacene has an excellent performance for charge transport, it is sensitive to oxygen and light, and has a poor solubility, [22] which limit its application. Many attempts have been made to improve the stability and charge transport properties of pentacene by substrate modification or functionalization of the molecular structure.…”

Section: Introductionmentioning

confidence: 99%

Theoretical comparative studies on transport properties of pentacene, pentathienoacene, and 6,13‐dichloropentacene

et al. 2015

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Pentacene derivative 6,13-dichloropentacene (DCP) is one of the latest additions to the family of organic semiconductors with a great potential for use in transistors. We carry out a detailed theoretical calculation for DCP, with systematical comparison to pentacene, pentathienoacene (PTA, the thiophene equivalent of pentacene), to gain insights in the theoretical design of organic transport materials. The charge transport parameters and carrier mobilities are investigated from the first-principles calculations, based on the widely used Marcus electron transfer theory and quantum nuclear tunneling model, coupled with random walk simulation. Molecular structure and the crystal packing type are essential to understand the differences in their transport behaviors. With the effect of molecule modification, significant one-dimensional π-stacks are found within the molecular layer in PTA and DCP crystals. The charge transport along the a-axis plays a dominant role for the carrier mobilities in the DCP crystal due to the strong transfer integrals within the a-axis. Pentacene shows a relatively large 3D mobility. This is attributed to the relatively uniform electronic couplings, which thus provides more transport pathways. PTA has a much smaller 3D mobility than pentacene and DCP for the obvious increase of the reorganization energy with the introduction of thiophene. It is found that PTA and DCP exhibit lower HOMO (highest occupied molecular orbital) levels and better environmental stability, indicating the potential applications in organic electronics.

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Photooxidation of the Evaporated Films of Polycyclic Aromatic Hydrocarbons Studied by X-Ray Photoelectron Spectroscopy

Cited by 80 publications

References 26 publications

Degradation Mechanisms and Reactions in Organic Light-Emitting Devices

Degradation Mechanisms and Reactions in Organic Light-Emitting Devices

Oxidation of Rubrene Thin Films: An Electronic Structure Study

Theoretical comparative studies on transport properties of pentacene, pentathienoacene, and 6,13‐dichloropentacene

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