Electron injection polymer for polymer light-emitting diodes

Yang, Y.; Pei, Qibing

doi:10.1063/1.359401

Cited by 81 publications

(31 citation statements)

References 24 publications

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“…For example, by using a combination of doped polyaniline and ITO as the transparent anode of a polymer LED with MEH-PPV as the active layer, the operating voltage was lowered and the quantum efficiency increased significantly, compared to devices using ITO alone as the hole-injecting anode [106,107]. This effect was attributed to a higher electronegativity of doped polyaniline as compared to ITO, which then provides a lower barrier to hole injection into MEH-PPV [108].…”

Section: Polyaniline On Indium-tin-oxidementioning

confidence: 99%

Electronic Structure of Surfaces and Interfaces in Conjugated Polymers

Lögdlund¹,

Salaneck

1999

Semiconducting Polymers

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A description of the electronic and chemical structure of polymeric and condensed molecular solid systems is an important ingredient in the field of organic polymeric and molecular materials in modern electronics applications. The investigation of the interaction between conjugated polymer materials and various metals has become an important issue, both for interfacial characteristics as well as for doping-induced effects. Studies on the interface characteristics are of significant importance in the connection with various device applications. Investigations of initial stages of both metal-on-polymer and polymer-on-metal interface formation are of importance in the context of how the interfaces may affect the actual device performance. In other words, when a few isolated atoms of an active metal are applied in some way to a polymer surface, they will react in a very different way compared to the case where an isolated polymer chain is applied in some way to the clean surface of an otherwise three dimensional metal substrate, with or without the presence of an oxide layer [1]. In this context, the single most useful experimental tool has turned out to be photoelectron spectroscopy (PES) [2]. Also, it has been shown that use of the results of appropriate quantum-chemical calculations [3] in interpreting PES data in many cases provides a level of information output which is larger than the sum of the two [4]. In this chapter, the principles involved in the study of the electronic and chemical structure of conjugated polymer surfaces and interfaces are reviewed. Examples of materials system are included which demonstrate information obtainable from photoelectron spectroscopy on both pristine and doped conjugated polymers as well as the modification of the electronic and chemical structure of conjugated systems induced upon interaction with different metals such as aluminum and calcium. Also, the usefulness of the combination of photoelectron spectroscopy and quantum-chemical calculations is demonstrated with some examples. The theoretical models most commonly used are only briefly outlined. More theoretical details are to be found in, for example, Ref. [3].This chapter is organized as follows: the experimental and theoretical techniques are presented briefly in Sections 5.2 and 5.3. In Section 5.4 some materials aspects and concepts are introduced, where trans-polyacetylene is used as an illustrative example. A series of illustrative examples on surfaces and interfaces Semiconducting Polymers: Chemistry, Physics and Engineering. Edited by G. Hadziioannou and P. F. van Hutten

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Section: Polyaniline On Indium-tin-oxidementioning

confidence: 99%

Electronic Structure of Surfaces and Interfaces in Conjugated Polymers

Lögdlund¹,

Salaneck

1999

Semiconducting Polymers

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“…For example, an electron injection and transport layer between the luminescent polymer and the cathode will facilitate electron injection; molecular acceptors such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, PBD, and conjugated polymer acceptors such as cyano-derivatives of PPV have been used with considerable success [4,18,19]. Alternatively, the electron transport material can be directly blended with the active luminescent polymer [20].…”

Section: Introductionmentioning

confidence: 98%

“…On the other hand, some polymers have excellent charge transport properties, but emit different colors of light to the active EL polymer, with the result that LEDs using these polymers as the charge injection and transport layer usually result in emission of unwanted colors, often the combination of transporting layer and EL layer. Examples include: (a) ITO (indium tin oxide)/MEH-PPV/Alq 3 (tris(8-quinolinolato)-aluminum)Mg : Ag LEDs emit green-orange light instead of the red-orange light from MEH-PPV [26], (b) ITO/PPV/CN-PPV/Al LEDs emit red light from CN-PPV instead of the green light from PPV [18,19], and (c) ITO/PPV/Alq 3 /Mg : Ag LEDs emit light from both PPV and Alq 3 , depending upon the thickness of Alq 3 layer [27].…”

Section: Introductionmentioning

confidence: 99%

Poly(1,4-phenylene-1,2-diphenylvinylene) and tris(8-quinolinolato)aluminum bilayer light-emitting diodes

Yang

Pei

1997

Polym. Adv. Technol.

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A bilayer polymer light‐emitting diode has been demonstrated. This bilayer structure is composed of two different materials with nearly identical luminescent spectra, but different band positions. The band structure of one material, poly(1,4‐phenylene‐1,2‐diphenylvinylene), favors hold injection, while the band structure of the other material, tris‐(8‐quinolinolato)aluminum, favors electron injection. Therefore in this device structure, a heterojunction forms at the bilayer interface. Charges injected from the anode and cathode accumulated at this interface and subsequently radiative recombine. Compared with the single‐layer devices made from each of these two materials, the device performance of this bilayer LED is significantly improved owing to this carrier localization. Device quantum efficiency is enhanced by a factor of 20 to reach ⪅1% photons/electron. Unlike some other bilayer systems, there is no color shift of this bilayer structure, because the luminescent spectra are the same for both materials. © 1997 John Wiley & Sons, Ltd.

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“…Aromatic oxadiazole-based compounds have an electron-withdrawing imine nitrogen (C@N) framework and have attracted interest because they have a high electron affinity, which facilitates both electron injection and transport, as well as excellent mechanical, thermal, and thermo-oxidative stabilities [12,13]. Thus, polymers containing an oxadiazole moiety have been widely used in electronic devices such as electron-transporting materials because the presence of the oxadiazole ring in the molecular backbone affects the electronic properties of the resulting polymers [14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%