Roll-Off Characteristics of Electroluminescence Efficiency of Organic Blue Electrophosphorescence Diodes

Son, Kyung Soo; Yahiro, Masayuki; Imai, Toshiro; Yoshizaki, Hiroki; Nishide, Junichi; Sasabe, Hiroyuki; Adachi, Chihaya

doi:10.1143/jjap.47.7363

Cited by 7 publications

(8 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This effect, known as concentration quenching, is attributed to increased triplet exciton diffusion at high guest concentrations, when transfer between the guests is favored due to shorter distances [5,6]. Furthermore, at high luminance levels, triplet exciton diffusion enhances the IQE loss ("rolloff") that occurs due to triplet-triplet annihilation (TTA) and triplet-polaron quenching (TPQ) [7][8][9][10][11][12][13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Triplet exciton diffusion in metalorganic phosphorescent host-guest systems from first principles

et al. 2019

View full text Add to dashboard Cite

We present an ab initio computational study of triplet exciton diffusion in four phosphorescent emitters commonly used in organic light-emitting diodes (OLEDs). By kinetic Monte Carlo simulations, triplet diffusion lengths are obtained for these emitters in neat films and as a guest in two different hosts. The triplet transfer rates governing the diffusion contain a transfer integral factor that includes both Förster and Dexter contributions and a Franck-Condon weighted density of vibrational states that includes the coupling to all intramolecular vibrations in a fully quantum mechanical way. We find that at guest concentrations around 10 mol% the Förster transfer contribution is most important. At larger concentrations of about 30-40 mol% the Dexter contribution becomes dominant. We show that obtaining the triplet transfer rates by the semiclassical Marcus theory yields diffusion lengths that are too short and that using a simple cubic lattice in combination with the often used Miller-Abrahams rates instead of using a real morphology with the ab initio rates leads to an underestimation of the diffusion lengths due to transfers down in energy that are too slow.

show abstract

Section: Introductionmentioning

confidence: 99%

Triplet exciton diffusion in metalorganic phosphorescent host-guest systems from first principles

et al. 2019

View full text Add to dashboard Cite

show abstract

“…The optical energy gap, as derived from the onset of absorption, is 2.6 eV for P1 (see Figure 1c) and 3.5 eV for PYD-2Cz. 46 With the energy-level data in hand, the conclusion is that an intermolecular charge-transfer (or exciplex) state between the host and guest will not form in the PYD-2Cz:P1 host−guest system. Specifically, we find that the LUMO offset (or electron trap depth) for the PYD-2Cz:P1 host-guest active material is 0.4 eV, whereas the HOMO offset (or hole trap depth) is 0.3 eV.…”

Section: T H Imentioning

confidence: 99%

“…We observe that the PL emission of the PYD-2Cz host (solid purple squares) significantly overlaps the absorption of the P1 guest (open black circles), which demonstrates that a principle requirement for Forster resonance energy transfer (FRET) from PYD-2Cz to P1 is fulfilled. 47 The substantial separation, and the lack of overlap, between the PL spectrum of the emitter P1 (solid cyan circles) and the absorption spectrum of the host PYD-2Cz with an onset at 350 nm 46 signals that the self-absorption within a thin layer of active material should be low.…”

Section: T H Imentioning

confidence: 99%

“…The triplet energy of PYD-2Cz is reported to be 2.93 eV. 46 Because the singlet energy of P1 is 2.6 eV and because the singlet and triplet energies are essentially identical in TADF emitting materials by design, the conclusion is that Dexter energy transfer from PYD-2Cz to P1 should also be an effective population pathway. 48 Figure 1d and Figure S1 present PL spectra of a number of different thin films comprising the P1 polymer.…”

Section: T H Imentioning

confidence: 99%

See 1 more Smart Citation

Polymer Featuring Thermally Activated Delayed Fluorescence as Emitter in Light-Emitting Electrochemical Cells

Lundberg

Wei

et al. 2020

J. Phys. Chem. Lett.

View full text Add to dashboard Cite

Semiconducting polymers that feature thermally activated delayed fluorescence (TADF) can deliver a much desired combination of high-efficiency and metal-free electroluminescence and cost-efficient solution-based fabrication. A TADF polymer is thus a very good fit for the emitting compound in light-emitting electrochemical cells (LECs) because the commonly employed air-stabile and few-layer LEC architecture is well suited for such solution-based fabrication. Herein we report on the first LEC device based on a TADF polymer as the emitting species, which delivers a luminance of 96 cd m –2 at 4 V and a current efficacy of 1.4 cd A –1 and >600 cd m –2 at 6 V, which is competitive with the performance of multilayer organic light-emitting diodes based on the same TADF polymer. We further utilize the established sensitivity of the emission of the TADF polymer to its environment to draw conclusions on the exciton populations in host-guest and host-free TADF LEC devices.

show abstract

“…When studying phosphorescent host-guest systems, important research subjects are the relative roles of quenching by polarons on the host and the guest molecules [17], the relative roles of quenching by hole and electron polarons [18,19], and ultimately the development of molecular-scale understanding of the TPQ mechanism. Triplet-polaron quenching studies typically make use of either photoluminescence (PL) experiments, electroluminescence (EL) experiments or combinations of the two, depending on whether unipolar or bipolar devices are studied [5,[17][18][19][20][21][22][23][24][25]. Correctly disentangling the roles of hole and electron quenching requires the use of unipolar devices, studied using a PL experiment.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic description of the efficiency loss in organic phosphorescent host–guest systems due to triplet-polaron quenching

Ligthart

Nevels

Weijtens

et al. 2021

Organic Electronics

View full text Add to dashboard Cite

published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User

show abstract

Roll-Off Characteristics of Electroluminescence Efficiency of Organic Blue Electrophosphorescence Diodes

Cited by 7 publications

References 9 publications

Triplet exciton diffusion in metalorganic phosphorescent host-guest systems from first principles

Triplet exciton diffusion in metalorganic phosphorescent host-guest systems from first principles

Polymer Featuring Thermally Activated Delayed Fluorescence as Emitter in Light-Emitting Electrochemical Cells

Mechanistic description of the efficiency loss in organic phosphorescent host–guest systems due to triplet-polaron quenching

Contact Info

Product

Resources

About