Highly Efficient Organic Devices Based on Electrically Doped Transport Layers

Walzer, Karsten; Maennig, B.; Pfeiffer, Martin; Leo, Karl

doi:10.1021/cr050156n

Cited by 1,489 publications

(1,269 citation statements)

References 201 publications

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“…At 3 V, the different field dependence of the recombination rate as obtained when using the functions h 4 or h 2 is not yet very important. However, at 10 V the difference is much larger.…”

Section: A Symmetric Oledsmentioning

confidence: 99%

“…The functioning of organic light-emitting diodes ͑OLEDs͒ as energy efficient and stable light sources [1][2][3] depends strongly on the shape of the recombination profile, i.e., on the dependence of the recombination rate on the position within the active semiconducting single-layer or multilayer material. For example, the shape of the recombination profile determines the wavelength-dependent light outcoupling efficiency, as a result of microcavity effects such as waveguiding and exciton quenching at the metallic electrodes.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effects of disorder on the current density and recombination profile in organic light-emitting diodes

Coehoorn

Mensfoort

2009

Phys. Rev. B

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“…At 3 V, the different field dependence of the recombination rate as obtained when using the functions h 4 or h 2 is not yet very important. However, at 10 V the difference is much larger.…”

Section: A Symmetric Oledsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of disorder on the current density and recombination profile in organic light-emitting diodes

Coehoorn

Mensfoort

2009

Phys. Rev. B

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“…As an example, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) (Figure 1a) with an EA of 5.24 eV [3] was shown early on to be an effective p-type dopant in host materials such as metal phthalocyanines (IE ≈ 5.20-5.35 eV) and N,N,N′,N′-tetrakis(4-Methoxy-phenyl) benzidine (MeO-TPD) (IE = 5.10 eV). [5] However, its efficiency drops considerably in host materials with IE larger than 5.40 eV. [5][6][7] Since large band gap hole transport materials (HTM) with higher IE are ubiquitous in many organic devices, [8,9] strongly oxidizing molecular dopants with larger EA, such as F6-TCNNQ films prepared on different substrates by thermal deposition as well as spin coating, to measure F6-TCNNQ films with different morphologies [Section S1, Supporting Information].…”

Section: Introductionmentioning

confidence: 99%

“…[5] However, its efficiency drops considerably in host materials with IE larger than 5.40 eV. [5][6][7] Since large band gap hole transport materials (HTM) with higher IE are ubiquitous in many organic devices, [8,9] strongly oxidizing molecular dopants with larger EA, such as F6-TCNNQ films prepared on different substrates by thermal deposition as well as spin coating, to measure F6-TCNNQ films with different morphologies [Section S1, Supporting Information]. The LUMO and unoccupied states of the films are shown in Figure 2a.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the High Electron Affinity Molecular Dopant F6‐TCNNQ for Hole‐Transport Materials

Zhang

Kahn

2017

Adv Funct Materials

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2,2′-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6-TCNNQ) is investigated as a molecular p-type dopant in two hole-transport materials, 2,2′,7,7′-tetrakis(N,N-diphenylamino)-9,9-spirobifluorene (Spiro-TAD) and tris(4-carbazoyl-9-ylphenyl)amine (TCTA). The electron affinity of F6-TCNNQ is determined to be 5.60 eV, one of the strongest organic molecular oxidizing agents used to date in organic electronics. p-Doping is found to be effective in Spiro-TAD (ionization energy = 5.46 eV) but not in TCTA (ionization energy = 5.85 eV). Optical absorption measurements demonstrate that charge transfer is the predominant doping mechanism in Spiro-TAD:F6-TCNNQ. The hostdopant interaction also leads to a significant alteration of the host film morphology. Finally, transport measurements done on Spiro-TAD:F6-TCNNQ as a function of dopant concentration and temperature, and using a highly doped contact layer to ensure negligible hole injection barrier, lead to an accurate measurement of the film conductivity and hole-hopping activation energy.

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“…An example is F 4 -TCNQ:ZnPc (tetrafluorotetracyanoquinodimethane:zinc phthalocyanine), which is used as hole-injection material in organic light-emitting diodes. 28 In this system the LUMO energy of the acceptor (F 4 -TCNQ) and the HOMO energy of the host (ZnPc) are nearly identical. The conduction in these systems is not one dimensional, so that the blocking effects discussed above will not be optimal.…”

Section: Realization Of Suitable Systemsmentioning

confidence: 82%

Route towards huge magnetoresistance in doped polymers

Kersten¹,

Meskers²,

Bobbert³

2012

Phys. Rev. B

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Room-temperature magnetoresistance of the order of 10% has been observed in organic semiconductors. We predict that even larger magnetoresistance can be realized in suitably synthesized doped conjugated polymers. In such polymers, ionization of dopants creates free charges that recombine with a rate governed by a competition between an applied magnetic field and random hyperfine fields. This leads to a spin-blocking effect that depends on the magnetic field. We show that the combined effects of spin blocking and charge blocking, the fact that two free charges cannot occupy the same site, lead to a magnetoresistance of almost two orders of magnitude. This magnetoresistance occurs even at vanishing electric field and is therefore a quasiequilibrium effect. The influences of the dopant strength, energetic disorder, and interchain hopping are investigated. We find that the dopant strength and energetic disorder have only little influence on the magnetoresistance. Interchain hopping strongly decreases the magnetoresistance because it can lift spin-blocking and charge-blocking configurations that occur in strictly one-dimensional transport. We provide suggestions for realization of polymers that should show this magnetoresistance.

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Highly Efficient Organic Devices Based on Electrically Doped Transport Layers

Cited by 1,489 publications

References 201 publications

Effects of disorder on the current density and recombination profile in organic light-emitting diodes

Effects of disorder on the current density and recombination profile in organic light-emitting diodes

Investigation of the High Electron Affinity Molecular Dopant F6‐TCNNQ for Hole‐Transport Materials

Route towards huge magnetoresistance in doped polymers

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