Anomalous room temperature magnetoresistance in organic semiconductors

Prigodin, V. N.; Bergeson, Jeremy D.; Lincoln, Derek M.; Epstein, Arthur J.

doi:10.1016/j.synthmet.2006.04.010

Cited by 308 publications

(329 citation statements)

References 15 publications

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“…The magnetic-field dependence of the current density J (B) is then calculated with MC(B) = [J (B) − J (0)]/J (0). In order to separate the LFE and HFE, we fit the resulting MC with the sum of two empirical "non-Lorentzian" fitting functions: 2 , which incorporates the amplitudes a LFE and a HFE and widths B LFE and B HFE for the LFE and HFE, respectively. For each specific material the widths are taken independent of the bias voltage, allowing us to focus on the V dependency of the amplitude of the magnetic-field effects.…”

Section: Resultsmentioning

confidence: 99%

“…1-9 All contemporary models explaining OMAR rely on magneticfield dependent reactions of the spin carrying particles. One competing model proposes reactions between polaronic electron and hole pairs, 2 whereas another relies on the reaction between triplet excitons and (trapped) polarons. 3,4 Conversely, the reactions of equal charges are described by a third (bipolaron) model.…”

Section: Introductionmentioning

confidence: 99%

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Traps and trions as origin of magnetoresistance in organic semiconductors

et al. 2013

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The large effect of a small magnetic field on the current, magnetoconductance (MC), in organic semiconductors-so-called organic magnetoresistance-has puzzled the field of organic spintronics during the last decade. Although the microscopic mechanisms regarding spin mixing are well understood by now, it is still unknown which pairs of spin carrying particles are influencing the current in such a drastic manner. Here, a model for the MC is presented based on the spin selective formation of metastable trions from triplet exciton-polaron pairs. Additionally, the magnetic-field and voltage dependence of the MC are experimentally investigated in materials showing large effects. Using a combination of analytical and numerical calculations, it is shown that the MC is perfectly described by a process in which trions are created at polaron trap sites.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Traps and trions as origin of magnetoresistance in organic semiconductors

et al. 2013

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“…This evidence suggests that the spin dependent process under examination directly affects the recombination rate and is independent of space charge reaction time which is bias dependent. Models that directly influence the recombination rate need to be taken into account [8,16]. It should be noted that both electron and hole mobilities explicitly appear in the Langevin expression for the recombination rate (Eqn.…”

Section: Simulations and Discussionmentioning

confidence: 99%

“…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]. Spin dependent charge recombination, spin blocking bipolaron formation and triplet-polaron scattering were proposed as possible explanations [8][9][10]. Furthermore, experimental evidence showed that trapping centers may be related to OMAR, suggesting that more mechanisms may participate to the magnetoresistance [11].…”

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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“…[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%

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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Anomalous room temperature magnetoresistance in organic semiconductors

Cited by 308 publications

References 15 publications

Traps and trions as origin of magnetoresistance in organic semiconductors

Traps and trions as origin of magnetoresistance in organic semiconductors

Pulsed magnetic resonance of Alq3 OLED detected by electroluminescence

Route towards huge magnetoresistance in doped polymers

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