Charge injection and transport in single-layer organic light-emitting diodes

Crone, B. K.; Campbell, I. H.; Davids, P. S.; Smith, D. L.

doi:10.1063/1.122706

Cited by 78 publications

(44 citation statements)

References 16 publications

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“…Diodes made with several metals of varying work function ͓Al͑4.2 eV͒, Ag͑4.3 eV͒, Cu͑4.5 eV͔͒ were tested. In all cases, the current flow of holes that was contact limited 8 changed to bulk limited when PEDOT͑PSS͒ was used in between the anode metal and MEH-PPV. We choose to study copper metal due to the good stability and ease of patterning.…”

confidence: 99%

Polymer diodes with high rectification

Roman¹,

Berggren²,

Inganäs³

1999

Applied Physics Letters

102

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Polymer diodes made using a bilayer of doped poly(3,4-ethylenedioxythiophene) and a semiconducting polymer in a sandwich structure with two low-work-function metals are reported. The conducting polymer layer acted as a modifier of the injection properties of the low-work-function metal, allowing easy hole injection. Upon insertion of the conducting polymer layer, the contact-limited current flow became bulk limited. With this anode, the fabrication of diodes with a rectification ratio of seven orders of magnitude was possible. We present patterned microdiodes made with crossing of 10 μm lines, showing similar performance as the mm-size diode.

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confidence: 99%

Polymer diodes with high rectification

Roman¹,

Berggren²,

Inganäs³

1999

Applied Physics Letters

102

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“…[25,26] In addition, these four layers are able to block a diffusion of active metal atoms, such as Cs or Ca, into PFO to form quenching centers during device fabrication. [17,18] Note that we also prepared a device with the structure, ITO/ PEDOT/PFO/Cs 2 CO 3 (spin coating)/Cs 2 CO 3 /Ca/Al, in which the Cs 2 CO 3 was spin-coated from its dilute solution in 2-ethoxyethanol is the same way as that in the previous report.…”

mentioning

confidence: 97%

“…In addition to the modifications of electrodes, many efforts have been attempted to reduce an imbalance in hole and electron fluxes and a possible quenching by cathode by introducing a hole blocking layer (which was also claimed as an electron transport layer), [12,13] since in conjugated polymers hole mobility is often larger than electron mobility leading to a recombination zone very close to the cathode. [17,18] Hirayama et al [12] and Tseng et al [13] inserted a layer of polyfluorenebased copolymer between MEH-PPV and Ca cathode and a layer of 1,3,5-tris(N-phenylbenzimidazol-2-yl) benzene (TPBI) between PFO and Ca cathode as hole blocking layer leading to the improved current efficiency from 1.0 to 3.6 cd A À1 and 0.61 to 1.45 cd A…”

mentioning

confidence: 99%

Design of Hole Blocking Layer with Electron Transport Channels for High Performance Polymer Light‐Emitting Diodes

Hsiao

Chen

2008

Advanced Materials

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A novel dual‐functional composite layer composed of a high ionization potential nonconjugated polymer or conjugated molecular material and an inorganic salt of a low work function metal is demonstrated. The composite provides superior hole blocking along with promising electron transport capability and results in good device performance for two model electroluminescent polymers, PFO and MEH‐PPV.

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“…On taking this first effect into account and also considering a current flow due to thermionic emission (j th ), the overall current flow through (J D ) of ITO/MEH-PPV/Al devices, which was assumed to be dominated by holes, was well described by Davids et al [81,84]:…”

Section: Field-induced Injectionmentioning

confidence: 99%

Solid‐State Aspects of Conjugated Semiconductors

Graupner

Tasch

Leising

1999

Semiconducting Polymers

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Conjugated semiconductors can exhibit energy bandgaps of 1 eV up to several eVs depending on the choice of the (1) building blocks, (2) the number of such building blocks, and (3) their precise arrangement with respect to each other. Therefore, they cover the region of narrow bandgap materials which absorb and emit light in the infrared region (a) and show reasonable charge transport properties. However, via the visible region (b), they even extend to the ultraviolet spectral range (c), performing like inorganic wide bandgap materials. This versatility and several other advantages such as mechanical flexibility, very high photoluminescence quantum yields (PL QY), easy production of large areas outweigh the intrinsic instability of conjugated molecules to photo-oxidation. Except for applications where long-term stability is not required [1], a proper encapsulation has to be used to introduce conjugated semiconductors for technical applications; such an encapsulation is for example intrinsic to applications such as capacitors and batteries [2].This chapter is organized as follows: after a brief introduction into the class of conjugated semiconductors we will discuss the solid state properties needed in order to achieve the functionalities required for efficient device operation, based on this class of materials. Very different degrees of short and long range order can be obtained in conjugated semiconductors; we will describe them and discuss their consequences on macroscopic properties of films of these materials. Since the properties of the excited states in conjugated semiconductors are both a highly relevant question of fundamental research and essential for applications we will treat the field of excited states spectroscopy in a separate section. This section will be followed by a treatise of device aspects of light emitting devices made from conjugated molecules. Before concluding we will briefly discuss the photophysics of excitation energy transfer and the properties of highly emissive conjugated systems under high excitation densities.

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Charge injection and transport in single-layer organic light-emitting diodes

Cited by 78 publications

References 16 publications

Polymer diodes with high rectification

Polymer diodes with high rectification

Design of Hole Blocking Layer with Electron Transport Channels for High Performance Polymer Light‐Emitting Diodes

Solid‐State Aspects of Conjugated Semiconductors

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