XPS and sputtering study of the Alq3/electrode interfaces in organic light emitting diodes

Nguyen, T.P.; Ip, J.; Jolinat, Pascale; Destruel, P.

doi:10.1016/s0169-4332(00)00826-6

Cited by 48 publications

(30 citation statements)

References 27 publications

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“…189 Nguyen et al was able to measure the content of indium across a complete degraded OLED, consisting of an ITO|Alq 3 (100 nm)| Al stack. 183 Indium atoms are known to quench the luminescence in the active area. This was shown by Lee et al by intentional doping experiments on Alq 3 -emission layers in OLEDs.…”

Section: Diffusion and Driftmentioning

confidence: 99%

“…237 Nguyen et al were able to examine the ITO decomposition, where they could show dissolution of In and Sn and a further migration/diffusion into the organic layer from an ITO|Alq 3 hetero stack during device degradation. 183 Such a decomposition of ITO is sometimes accompanied by a volcano or dome-like structure forming at its surface, where In-rich regions are detectable. 448 Another mechanism can be observed for cathode materials.…”

Section: Electrochemical Reactionsmentioning

confidence: 99%

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Degradation Mechanisms and Reactions in Organic Light-Emitting Devices

et al. 2015

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Section: Diffusion and Driftmentioning

confidence: 99%

Section: Electrochemical Reactionsmentioning

confidence: 99%

Degradation Mechanisms and Reactions in Organic Light-Emitting Devices

et al. 2015

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“…This result is consistent with the data published in the literature on an ultra-thin Al film that was thermally evaporated on a polymer surface under similar conditions. [11][12][13] The deconvolution of the Al 2p peak from the HY-PPV/PEGDE25/Al50 surface reveals the presence of two additional peaks -one at 75.4 eV, which corresponds to the oxide species, and the other one at 72.5 eV. The latter peak is at a position that is typically assigned to C-O-Al or C-Al bonds, [11,43,44] supporting the formation of carbide-like species revealed by the C 1s spectra in Figure 3c and d.…”

Section: Full Papermentioning

confidence: 99%

“…[7][8][9] However, the surface of Al, which intrinsically has a very large amount of non-bonding orbitals (dangling bonds) or surface states, is very active, oxidizing immediately when exposed to the atmosphere and tending to react with organic materials during vacuum thermal evaporation. [10,11] Additionally, the release of energy of Al followed by the condensation of metallic vapor on the substrate of organic/polymer film at room temperature breaks chemical bonds. Changes in the polymer configuration affect the overall performance of the devices and have stimulated the interest of many researchers.…”

Section: Introductionmentioning

confidence: 99%

Organic‐Oxide Cathode Buffer Layer in Fabricating High‐Performance Polymer Light‐Emitting Diodes

Lee

Huang

Pakhomov

et al. 2008

Adv Funct Materials

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Spin‐casting or thermal evaporation in vacuum of a salt‐free, neutral, organic‐oxide ultra‐thin film as a buffer layer with an aluminum (Al) cathode has become an alternative approach for fabricating high‐performance organic and polymer light‐emitting diodes (O/PLEDs). [Guo et al., Appl. Phys. Lett. 2006, 88, 113501 and Appl. Phys. Lett. 2006, 89, 053507] The electroluminescence efficiency of phenyl‐substituted poly(para‐phenylene vinylene) copolymer‐based PLEDs is 0.16 cd A−1 when Al is used as the device cathode, but is approximately two orders of magnitude higher, 14.53 cd A−1, when an organic oxide/Al composite cathode is used. The polymer/metal junction in PLEDs with and without depositing an ultra‐thin organic oxide interlayer is studied by X‐ray photoelectron spectroscopy. Experimental results indicate that the deposition of an Al electrode causes the oxidation at the surface of the light‐emissive polymer layer. Introducing an organic‐oxide cathode buffer layer suppresses the oxidation and the diffusion of the Al atoms into the functional polymer layer. The formation of a carbide‐like (negative carbon) thin layer, which accompanies interfacial interactions, is critical to the injection of electrons through the Al cathode. The balanced charge injection is responsible for the substantially improved device performance. This process is specific to the organic oxide/Al interface, as revealed by a comparison with similar device configurations that have Ag as the electrode, in which no significant interaction in the interface is observed.

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“…[4][5][6] The metal atoms also tend to react with conjugated molecules near the contact interface to break the conjugated length and cause localized defect states. [7][8][9] These largely degrade the device performance and limit the application of organic electronic devices.…”

Section: Introductionmentioning

confidence: 99%

The Roles of Poly(Ethylene Oxide) Electrode Buffers in Efficient Polymer Photovoltaics

Jeng

Lin

Hsu

et al. 2011

Advanced Energy Materials

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The role of poly(ethylene oxide) polymer is investigated as an effective buffer with Al electrodes to markedly improve the electrode interface and enhance the open‐circuit voltage (VOC) and the power conversion efficiency (PCE, η) of poly(3‐hexylthiophene) (P3HT):[6,6]‐phenyl C61‐butyric acid methyl ester (PCBM)‐based bulk‐heterojunction (BHJ) solar cells. A unique process is developed by thermally co‐evaporating the poly(ethylene glycol) dimethyl ether (PEGDE, Mn ca. 2000) polymer with Al metal simultaneously at different ratios in vacuum (10−6 Torr) to prepare the electrode buffers. The instant formation of a carbide‐like junction at the ethylene oxide/Al interface during the thermal evaporation is of essential importance to the extraction of electrons through the Al electrode. The performance of P3HT:PCBM‐based solar cells can be optimized by modulating the co‐evaporation ratios of the PEGDE polymer with Al metal due to the changes in the work functions of the electrodes. The VOC and η for devices fabricated with Al electrode are 0.44 V and 1.64%, respectively, and significantly improve to 0.58 V and 4.00% when applying the PEGDE:Al(2:1)/Al electrode. This research leads to a novel electrode design – free of salts, additives, complicated syntheses, and having tunable work function – for fabricating high‐performance photovoltaic cells.

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XPS and sputtering study of the Alq3/electrode interfaces in organic light emitting diodes

Cited by 48 publications

References 27 publications

Degradation Mechanisms and Reactions in Organic Light-Emitting Devices

Degradation Mechanisms and Reactions in Organic Light-Emitting Devices

Organic‐Oxide Cathode Buffer Layer in Fabricating High‐Performance Polymer Light‐Emitting Diodes

The Roles of Poly(Ethylene Oxide) Electrode Buffers in Efficient Polymer Photovoltaics

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