Magnetic-Field Dependence of the Electroluminescence of Organic Light-Emitting Diodes: A Competition between Exciton Formation and Spin Mixing

Kersten, S. P.; Schellekens, A. J.; Koopmans, B.; Bobbert, Peter A.

doi:10.1103/physrevlett.106.197402

Cited by 115 publications

(162 citation statements)

References 29 publications

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“…Furthermore, we assume that exchange splitting prevents spin mixing between D and Q trions, similar to S and T excitons. 11 Finally, we note that our analysis can in principle also be used to model trapping of triplet-polaron pairs without significant spin coupling.…”

Section: Fig 3 (Color Online) (A)mentioning

confidence: 99%

“…19,23,30,[36][37][38][39] The only unknown parameter is P T , although it should be on the order of a few percent at large magnetic fields. 11 We can also derive the MC of the HFE with…”

Section: Analytical Calculationsmentioning

confidence: 99%

“…The authors consider the triplet excitons to momentarily capture polarons in states they recently referred to as charged excitons, 21 thereby reducing the polaron transport. Since the formation of triplet excitons as well as their reactions with polarons 12,15 can be considered magnetic-field dependent, 11,22 a change in current can be explained.…”

Section: Introductionmentioning

confidence: 99%

“…This has been used to successfully simulate magnetic-field effects in the electroluminescence of organic semiconductors using a density-matrix approach. 11 A similar theoretical framework has been applied to account for other microscopic mechanisms and their effect on the magnetic-field dependent current, i.e., magnetoconductance (MC). 12 In recent work 13 we have shown that the dominant mechanism for OMAR in a real device depends on the operating conditions and morphology.…”

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: Fig 3 (Color Online) (A)mentioning

confidence: 99%

“…19,23,30,[36][37][38][39] The only unknown parameter is P T , although it should be on the order of a few percent at large magnetic fields. 11 We can also derive the MC of the HFE with…”

Section: Analytical Calculationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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“…Due to their short lifetime and low optical activity, attempts to interrogate CT states directly have brought limited success. Notably, however, recent experiments that probe CT states indirectly via their response to an applied magnetic field have demonstrated the potential to reveal new information about this elusive class of excited states [13][14][15][16][17][18][19][20][21]. Unfortunately, extracting this information is challenging because it is encoded by a complex interplay of electronic and nuclear spin dynamics [15,22,23].…”

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confidence: 99%

A Model of Charge-Transfer Excitons: Diffusion, Spin Dynamics, and Magnetic Field Effects

Lee

Shi

Willard

2016

J. Phys. Chem. Lett.

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In this letter we explore how the microscopic dynamics of charge transfer (CT) excitons are influenced by the presence of an external magnetic field in disordered molecular semiconductors. This influence is driven by the dynamic interplay between the spin and spatial degrees of freedom of the electron-hole pair. To account for this interplay we have developed a numerical framework that combines a traditional model of quantum spin dynamics with a stochastic coarse-grained model of charge transport. This combination provides a general and efficient methodology for simulating the effects of magnetic field on CT state dynamics, therefore providing a basis for revealing the microscopic origin of experimentally observed magnetic field effects. We demonstrate that simulations carried out on our model are capable of reproducing experimental results as well as generating theoretical predictions related to the efficiency of organic electronic materials.1 arXiv:1603.08160v2 [physics.chem-ph] Apr 2016Charge transfer (CT) states play a fundamental role in mediating interconversion between bound electronic excitations and free charge carriers in organic electronic materials.For processes that require this interconversion, such as electroluminescence in organic light emitting diodes (OLEDs) and photocurrent generation in organic photovoltaics (OPVs), low-energy (thermalized) CT states are often implicated as a precursor to efficiency loss pathways [1][2][3][4][5][6][7][8][9][10][11][12]. Despite this, much remains to be understood about the properties of CT states and how they contribute to various energy loss mechanisms. Due to their short lifetime and low optical activity, attempts to interrogate CT states directly have brought limited success. Notably, however, recent experiments that probe CT states indirectly via their response to an applied magnetic field have demonstrated the potential to reveal new information about this elusive class of excited states [13][14][15][16][17][18][19][20][21]. Unfortunately, extracting this information is challenging because it is encoded by a complex interplay of electronic and nuclear spin dynamics [15,22,23]. This interplay is further complicated when the dynamics of the electron-hole spin state (or the specific experimental observable) is coupled to a source of fluctuating microscopic disorder such as charge transport or molecular conformational dynamics [21]. In this letter we focus on disentangling this interplay.The dependence of an experimental observable on an applied magnetic field is generically referred to as the magnetic field effect (MFE). For CT-mediated processes, MFEs require that the observed physical property depends either directly or indirectly on the spin state of the electron-hole pair. For instance, spin selection rules for radiative electron-hole recombination can give rise to a magnetic field-dependent electroluminescence yield [20,[24][25][26]. To understand specifically how CT state properties are influenced by the presence of a magnetic field it is na...

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Recent Advances in Ambipolar Transistors for Functional Applications

Ren

Yang

Zhou

et al. 2019

Adv Funct Materials

169

139

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Ambipolar transistors represent a class of transistors where positive (holes) and negative (electrons) charge carriers both can transport concurrently within the semiconducting channel. The basic switching states of ambipolar transistors are comprised of common off-state and separated on-state mainly impelled by holes or electrons. During the past years, diverse materials are synthesized and utilized for implementing ambipolar charge transport and their further emerging applications comprising ambipolar memory, synaptic, logic, and light-emitting transistors on account of their special bidirectional carrier-transporting characteristic. Within this review, recent developments of ambipolar transistor field involving fundamental principles, interface modifications, selected semiconducting material systems, device structures, ambipolar characteristics, and promising applications are highlighted. The existed challenges and prospective for researching ambipolar transistors in electronics and optoelectronics are also discussed. It is expected that the review and outlook are well timed and instrumental for the rapid progress of academic sector of ambipolar transistors in lighting, display, memory, as well as neuromorphic computing for artificial intelligence.

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Magnetic-Field Dependence of the Electroluminescence of Organic Light-Emitting Diodes: A Competition between Exciton Formation and Spin Mixing

Cited by 115 publications

References 29 publications

Traps and trions as origin of magnetoresistance in organic semiconductors

Traps and trions as origin of magnetoresistance in organic semiconductors

A Model of Charge-Transfer Excitons: Diffusion, Spin Dynamics, and Magnetic Field Effects

Recent Advances in Ambipolar Transistors for Functional Applications

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