Monte Carlo simulation of electron behaviour in a magnetic hollow-cathode discharge

Li, Jun; Chen, Qingming; Xu, Qiang-Hua; Li, Zaiguang

doi:10.1088/0022-3727/27/12/010

Cited by 8 publications

(7 citation statements)

References 13 publications

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“…[ 35 ] With increasing c D from 10 wt% to 30 wt%, there was a monotonic increase of the hole current in the HODs, which was attributed to the trapping state‐assisted hole transport of dopants because of their shallower HOMO level (5.4 eV) than that of TSPO1 (6.7 eV). [ 36 ] By contrast, a decrease of the electron current was observed with c D increasing from 0 to 20 wt% in the EODs, implying a large carrier scattering effect [ 36b,37 ] of dopants under the electron transport condition, which is consistent with their energy level alignment (i.e., a shallower LUMO of 2.09–2.11 eV for the emitters than that of TSPO1, 2.5 eV). With a further increase of the c D to 30 wt%, an increase of the electron current was observed.…”

Section: Resultsmentioning

confidence: 79%

Bulky Iridium NHC Complexes for Bright, Efficient Deep‐Blue OLEDs

Mackenzie

Zhang

Cordes

et al. 2022

Advanced Optical Materials

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Central to the performance of commercialized green and red OLEDs is the organometallic phosphorescent emitter, [2] which is responsible for the conversion of electrical energy into light with near unity internal quantum efficiency (IQE), as these complexes show simultaneously high photoluminescence quantum yields (Φ PL ) and can efficiently harvest both singlet and triplet excitons to produce light in the device. However, the blue sub-pixel in OLEDs presently uses an organic fluorophore as there do not exist phosphorescent OLEDs that are sufficiently stable or bright for commercial use, and few reported examples of phosphorescent emitters that are close to the BT.2020 industry standard for blue, [3] defined as CIE coordinates of (0.131, 0.046). [4] Among the most promising phosphorescent blue emitters are iridium(III) complexes with cyclometallating N-heterocyclic carbene (NHC) ligands. In these complexes the strongly σ-donating and weakly π-accepting NHC contributes to greatly destabilize the LUMO of the Ir(C^C) 3 complex and thus increase the energy of the emissive triplet state. Luminescent Ir(C^C) 3 complexes were first reported by Thompson and co-workers in 2005; [3a,5] however, in these early examples [fac-Ir(pmi) 3 and fac-Ir(pmb) 3 ] the photo luminescence quantum yields, Φ PL , were very low, and the complexes emitted in the near UV. A step change in the photophysical properties of Ir(C^C) 3 complex occurred in 2016 where Forrest and co-workers reported a bright, blue complex, mer-Ir(pmp) 3 , (λ PL = 465 nm, Φ PL = 78% in degassed 2-MeTHF) and the OLEDs showed unprecedentedly high maximum external quantum efficiencies (EQE max = 14.4%) and blue electroluminescence [CIE = (0.16, 0.15)], (Figure 1). [6] Since this publication, there has been a growing number of blueemitting Ir(C^C) 3 complexes reported and used as emitters in OLEDs, [3b,7] the diversity of iridium(III) NHC complexes has recently been reviewed. [8] A detracting feature of many phosphorescent iridium complexes is the presence of thermally accessible 3 MC excited states. Their population leads to increased nonradiative decay and degradation of the complex induced by the lengthening of the Irligand bonds resulting in deligation. [10] The strongly coordinating and σ-donating NHC ligands in Ir(C^C) 3 complexes possess a much larger octahedral splitting gap, destabilizing Four new deep-blue-emitting iridium(III) NHC complexes containing sterically demanding ligands are synthesized. The four complexes show bright, deep-blue emission, with emission maxima between 420 and 427 nm in both acetonitrile solution and 30 wt% doped films in TSPO1; the two meridional isomers showing photoluminescence quantum yields, Φ PL , in doped films of 80% and 89%. The two meridional isomers are used to assess the impact of emitters containing bulky, sterically demanding ligands on the performance of organic light-emitting diodes (OLEDs). OLEDs employing a stepped doping profile with mer-Ir(tfpi_tmBn) 3 as the emitter produce the highest performing devices in this...

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Section: Resultsmentioning

confidence: 79%

Bulky Iridium NHC Complexes for Bright, Efficient Deep‐Blue OLEDs

Mackenzie

Zhang

Cordes

et al. 2022

Advanced Optical Materials

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“…These simulations and the simulation of electrons' motion in a cylindrical hollow cathode discharge [15] have utilized the null-collision technique to increase the computational speed [12,16]. Direct integration of equations ( 1) and ( 2) was used to trace the electron trajectories in the presence of magnetic field in planeparallel [17] and cylindrical [18] hollow cathode discharges.…”

Section: Methods Of Simulationmentioning

confidence: 99%

Monte Carlo analysis of the electrons' motion in a segmented hollow cathode discharge

Rózsa

Tobin

1996

J. Phys. D: Appl. Phys.

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We have investigated the motion of electrons in a new, high voltage segmented hollow cathode discharge, which is known to be an efficient pumping source for charge-transfer excited UV metal ion lasers. We have studied the spatial distribution of ion production, electron energy distributions, statistics of electron avalanches, the fraction of oscillating electrons, and the distribution of the fast electrons' current on the anode surface in a helium discharge having four electrode segments. We have found that the ion production is strongly peaked in the centre of the discharge due to the focusing cathode geometry. The effect of magnetic field on the characteristics of the discharge was also studied. With increasing magnetic field the peak of the spatial distribution of ionization was split into two regions of high ionization rate. Furthermore, due to the magnetic field, at fixed discharge current the number of high-energy electrons absorbed on the anode increased considerably, and a higher number of primary electrons were absorbed by the anode without making any ionization. At constant discharge voltage the fraction of oscillating electrons was found to decrease, due to the applied longitudinal magnetic field. The magnetic field dependence of the spatial distribution of ion production, the energy distribution of electrons absorbed by the anode and the fraction of oscillating electrons at different discharge conditions were also studied in a discharge having six electrode segments.

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“…The cross sections of these elementary processes were taken from [19], and the handling of the collisions in the MC simulation from [20].…”

Section: Theoretical Descriptionmentioning

confidence: 99%

Proof and analysis of the pendulum motion of beam electrons in a hollow cathode discharge

Stockhausen

Kock

2001

J. Phys. D: Appl. Phys.

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The pendulum motion of electrons in a hollow cathode discharge accelerated in the cathode fall is demonstrated with the use of a femtosecond laser pulse and the so-called fast optogalvanic effect. The signals are described quantitatively using a Monte Carlo model for various pressure and current levels. As a result the discharge can be described by the model from start-up to high-current operation.

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Monte Carlo simulation of electron behaviour in a magnetic hollow-cathode discharge

Cited by 8 publications

References 13 publications

Bulky Iridium NHC Complexes for Bright, Efficient Deep‐Blue OLEDs

Bulky Iridium NHC Complexes for Bright, Efficient Deep‐Blue OLEDs

Monte Carlo analysis of the electrons' motion in a segmented hollow cathode discharge

Proof and analysis of the pendulum motion of beam electrons in a hollow cathode discharge

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