Magneto‐Electroluminescence as a Tool to Discern the Origin of Delayed Fluorescence: Reverse Intersystem Crossing or Triplet–Triplet Annihilation?

Chen, Ping; Xiong, Zuhong; Peng, Qiming; Bai, Jing; Zhang, Shitong; Li, Feng

doi:10.1002/adom.201300422

Cited by 81 publications

(64 citation statements)

References 48 publications

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“…This value was consistent with the reported B 0 for ISC252627. At a current density of 5 mA/cm 2 , the MEL of the ISC process in exciton-based devices is generally ~6%, while the MEL in TADF devices is only ~1.5%.…”

Section: Resultssupporting

confidence: 90%

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Guest concentration, bias current, and temperature-dependent sign inversion of magneto-electroluminescence in thermally activated delayed fluorescence devices

Deng

Jia

Chen

et al. 2017

Sci Rep

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Non-emissive triplet excited states in devices that undergo thermally activated delayed fluorescence (TADF) can be up-converted to singlet excited states via reverse intersystem crossing (RISC), which leads to an enhanced electroluminescence efficiency. Exciton-based fluorescence devices always exhibit a positive magneto-electroluminescence (MEL) because intersystem crossing (ISC) can be suppressed effectively by an external magnetic field. Conversely, TADF devices should exhibit a negative MEL because RISC is suppressed by the external magnetic field. Intriguingly, we observed a positive MEL in TADF devices. Moreover, the sign of the MEL was either positive or negative, and depended on experimental conditions, including doping concentration, current density and temperature. The MEL observed from our TADF devices demonstrated that ISC in the host material and RISC in the guest material coexisted. These competing processes were affected by the experimental conditions, which led to the sign change of the MEL. This work gives important insight into the energy transfer processes and the evolution of excited states in TADF devices.

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Section: Resultssupporting

confidence: 90%

“…Generally, the MEL in exciton-based OLEDs is positive with a full width at half maximum (FWHM) of several mT because the intersystem crossing (ISC) of polaron pairs is suppressed by the B 23. Conversely, a negative MEL is observed in TADF-based OLEDs because any RISC from CTs is suppressed by the B , which has been described in the literature252627.…”

mentioning

confidence: 93%

Guest concentration, bias current, and temperature-dependent sign inversion of magneto-electroluminescence in thermally activated delayed fluorescence devices

Deng

Jia

Chen

et al. 2017

Sci Rep

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“…In general, three experimental techniques are employed to identify whether TF process contributes to the triplet harvesting in OLEDs: 1) The luminance-current behaviors of an OLED [16]; 2) The time-resolved PL and/or EL spectra of the material and/or device [3,17]; and 3) The mageto-EL (MEL) behaviors of an OLED [18]. Theoretically, if TF process contributes to the efficiency of an OLED, a super-linear luminance-current behavior should be observed [16].…”

Section: Tf Mechanism and Evidence Of Tf Processes In Foledsmentioning

confidence: 99%

“…Note that this device showed nearly negligible efficiency roll-off in a remarkably broad range of current density from 0.1 to 100 mA cm -2 . Another experimental technique capable of identifying the presence of TTA process in OLEDs is MEL [18]. Both Bussmann [25] and Xiong [26] have reported their observations of significant TTA-related high magnetic field effect on EL, which could be enhanced at lower temperatures and higher current densities.…”

Section: Early Observations Of Tta Process In Oledsmentioning

confidence: 99%

Triplet fusion delayed fluorescence materials for OLEDs

Luo

Huang

2016

Chinese Chemical Letters

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“…Thus, intermolecular excited states would have stronger ISC than intramolecular excited states and have a thermally excited reverse ISC (RISC) process. 20 Exciplexes, excitons, and electroplexes can coexistent in a D-A system by choosing proper donors and acceptors. This makes it possible to study MC in a system with multiple emissive states and to then explore the internal processes inside the system.…”

mentioning

confidence: 99%

Anomalous temperature dependent magneto-conductance in organic light-emitting diodes with multiple emissive states

Zhao

Jia

Huang

et al. 2015

Applied Physics Letters

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The temperature dependence of the magneto-conductance (MC) in organic electron donor-acceptor hybrid and layer heterojunction diodes was studied. The MC value increased with temperature in layer heterojunction and in 10 wt. % hybrid devices. An anomalous decrease of the MC with temperature was observed in 25 wt. %–50 wt. % hybrid devices. Further increasing donor concentration to 75 wt. %, the MC again increased with temperature. The endothermic exciplex-exciton energy transfer and the change in electroplex/exciton ratio caused by change in charge transport with temperature may account for these phenomena. Comparative studies of the temperature evolutions of the IV curves and the electroluminescence and photoluminescence spectra back our hypothesis.

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Magneto‐Electroluminescence as a Tool to Discern the Origin of Delayed Fluorescence: Reverse Intersystem Crossing or Triplet–Triplet Annihilation?

Cited by 81 publications

References 48 publications

Guest concentration, bias current, and temperature-dependent sign inversion of magneto-electroluminescence in thermally activated delayed fluorescence devices

Guest concentration, bias current, and temperature-dependent sign inversion of magneto-electroluminescence in thermally activated delayed fluorescence devices

Triplet fusion delayed fluorescence materials for OLEDs

Anomalous temperature dependent magneto-conductance in organic light-emitting diodes with multiple emissive states

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