Magnetic field effects on emission and current in Alq3-based electroluminescent diodes

Kalinowski, J.; Cocchi, M.; Virgili, D.; Marco, P. Di; Fattori, V.

doi:10.1016/j.cplett.2003.09.086

Cited by 323 publications

(311 citation statements)

References 17 publications

(23 reference statements)

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“…The discovery of a large intrinsic magneto-resistance in organic thin films and light emitting diodes triggered a novel interest in spin processes in carbon based semiconductors although this topic was already debated at length in the past [1][2][3][4][5]. Nowadays, the study of organic magneto-resistance (OMAR) is of great importance in the framework of organic spintronics and it introduces a new scenario of possible applications [6,7].…”

Section: Introductionmentioning

confidence: 99%

Pulsed magnetic resonance of Alq3 OLED detected by electroluminescence

Comandè

Ansermet

2013

Synthetic Metals

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The aim of the present work is to investigate the nature of spin dependent processes in an organic light emitting diode based on a ITO/ α-NPD/Alq3 structure. The electroluminescence time response of the sample is monitored while the OLED is exposed to a high power resonant microwave pulse. Measurements are carried out at room temperature. The time scale of the induced transition is found to be independent of the bias voltage. It is shown, by way of a simulation, that this behavior appears inconsistent with models which attribute a change in the electroluminescence to a variation in charge mobility. Spin dependent processes directly related to a change in the rate of charge recombination play therefore a relevant role in Alq 3 light emitting diodes.

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Section: Introductionmentioning

confidence: 99%

Pulsed magnetic resonance of Alq3 OLED detected by electroluminescence

Comandè

Ansermet

2013

Synthetic Metals

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“…1(a) inset] is a common active molecular layer used in organic light emitting devices (OLED), due to its efficient electro-luminescence (EL) emission and high electron mobility [1][2][3] . It is thus not surprising that magnetic field effects (MFE) in Alq 3 -based OLED devices such as magnetoelectroluminescence (MEL) and magneto-conductance (MC) have been extensively studied in the last few years [4][5][6][7][8][9][10] . As a result, several basic models were originally proposed to explain the obtained magnetic-field effect response, MFE(B).…”

Section: Introductionmentioning

confidence: 99%

Isotope effect in the spin response of aluminum tris(8-hydroxyquinoline) based devices

Nguyen

Basel

et al. 2012

Phys. Rev. B

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We studied the spin response of various magnetic field effects and magneto-transport in both protonated and deuterated aluminum tris(8-hydroxyquinoline) [Alq 3 ]-based organic light emitting diodes and spin-valve devices. Both conductivity-detected magnetic resonance in diodes and magneto-resistance in spin valves show substantial isotope dependence pointing to the importance of the hyperfine interaction (HFI) in the spin response of spin ½ charge polarons in Alq 3 . In addition the low field (B<20 mT) magneto-electroluminescence (MEL) response is also isotope sensitive, showing that HFI-induced spin mixing of polaron-pairs spin sublevels dominates this response too. However, the magneto-conductance (MC) response was found to be much less sensitive to isotope exchange at low fields, in agreement with previous studies. The disparity between the isotope sensitivity of MC and MEL responses in Alq 3 indicates that the HFI in the MC response is overwhelmed by an isotope independent spin mixing mechanism. We propose that collisions of spin ½ carriers -with triplet species such as polaron pairs may be the main spin mixing mechanism in the low field MC response in Alq 3 diodes.

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“…In that case, ionization of a donor can take place at thermal conditions by hopping of an electron from the donor to a neighboring host site. With the unionized donor being a spin singlet, the combination of the free electron and the ionized donor, both having spin 1 2 , will initially also be a spin singlet. However, the different hyperfine fields at the positions of the free electron and ionized donor mixes in triplet character, which reduces the recombination rate back to the singlet state of the unionized donor.…”

Section: Modelmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10] The precise mechanisms behind these effects are still debated, but agreement is arising that the effects are caused by the magnetic-field sensitivity of spin-selective reactions between spin-carrying electronic excitations (electrons, holes, triplet excitons). Striking analogies exist with mechanisms known in the field of spin chemistry.…”

Section: Introductionmentioning

confidence: 99%

“…The largest magnetoresistance occurs when k hop is much smaller than ω hf , and this "slow-hopping" case is the case we consider from now on. The observation of large magnetic field effects in organic semiconductors [1][2][3][4][5][6][7][8][9][10] indicates that the hopping rate can indeed be smaller than or at least comparable to the hyperfine precession frequency. Because coherent effects between eigenstates of the spin Hamiltonian vanish in the limit of slow hopping, we only need to consider the occupancy of the (localized) spin eigenstates and hopping between these states.…”

Section: Modelmentioning

confidence: 99%

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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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Magnetic field effects on emission and current in Alq3-based electroluminescent diodes

Cited by 323 publications

References 17 publications

Pulsed magnetic resonance of Alq3 OLED detected by electroluminescence

Pulsed magnetic resonance of Alq3 OLED detected by electroluminescence

Isotope effect in the spin response of aluminum tris(8-hydroxyquinoline) based devices

Route towards huge magnetoresistance in doped polymers

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