Triplet excitons in diphenylbutadiene and diphenylhexatriene single crystals by zero-field delayed fluorescence ODMR

1994 ◽  
Vol 225 (1-3) ◽  
pp. 124-130 ◽  
Author(s):  
Y. Teki ◽  
J.U. von Schütz ◽  
H. Wachtel ◽  
V. Weiss ◽  
H.C. Wolf
Keyword(s):  
Single Crystals ◽  
Delayed Fluorescence ◽  
Zero Field ◽  
Triplet Excitons

scholarly journals Mobile and Trapped Triplet States in Single Crystals of Charge Transfer Complexes

1974 ◽  
Vol 29 (8) ◽  
pp. 1216-1228 ◽  
Author(s):  
H. Möhwald ◽  
E. Sackmann
Keyword(s):  
Charge Transfer ◽  
Delayed Fluorescence ◽  
Charge Transfer Complexes ◽  
Zero Field ◽  
Triplet States ◽  
Zero Field Splitting ◽  
Triplet Energy ◽  
Molecular Arrangement ◽  
Ct Complexes ◽  
Triplet Excitons

Homogeneously doped crystals of charge transfer (CT-) complexes were grown by incorporating aromatic guest donors in host CT-crystals. The host crystals contained 1,2.4,5-tetracyanobenzene (TCNB) as acceptor and deuterated aromatic electron donors. By using such doped crystals CT complexes in a well defined configuration may be studied. The triplet states of the guest complexes were used as ESR spectroscopic probes in order to determine the molecular arrangement in the host lattice. The zero-field-splitting (ZFS) parameters, D and E, of the triplet energy traps were determined and the degree of electron derealization in the triplet state was calculated from these values. In some cases a very strong guest host interaction (multicomplex formation) was established. A method for the determination of CT-triplet energies is described (accuracy 200 cm-1) . The phosphorescence spectrum of the anthracene-TCNB complex was obtained from the delayed emission spectra of different anthracene doped CT-crystals. The vibronic structure is identical to that of anthracene, while the O-O-band of the complex is blue shifted by 600 cm-1. It is shown that the undoped anthracene-TCNB crystal exhibits P-type delayed fluorescence and that the triplet exciton diffusion in this crystal is nearly temperature independent. In the undoped biphenyl-TCNB crystal E-type delayed fluorescence originating from the thermal depopulation of the mobile triplet excitons is established. The remarkable differences of the two types of triplet excitons are interpreted in terms of the different polarity in the triplet states of the two CT-crystals.

Ein Modell zur verzögerten Fluoreszenz von Anthracen/Tetracen Kristallen

1974 ◽  
Vol 29 (10) ◽  
pp. 1461-1466 ◽  
Author(s):  
H. Wolff
Keyword(s):  
Energy Transfer ◽  
Simple Model ◽  
Single Crystals ◽  
Transfer Rate ◽  
Diffusion Constant ◽  
Host Lattice ◽  
Delayed Fluorescence ◽  
Guest Molecules ◽  
Decay Times ◽  
Triplet Excitons

Abstract Spectra and decay-times of delayed fluorescence in anthracene single crystals doped with tetracene at concentrations ranging between 3·10-10 to 3·10-5 were measured (T = 300°K). The dependence of the relative intensities and the decay-times on the concentration is explained by a simple model: The triplet-excitons of the host-lattice are captured by triplet traps localized in the nearest neighbourhood of the guest molecules. Than, the energy either goes to the tetracene, or thermally stimulated back into the triplet exciton band. The energy transfer of singlet excitons is taken into the considerations. The differential-equations describing the model are approximative^ solved. The solutions are compared with the experimental results. From the measurements a transfer rate K= (1.1 ± 0.4) · 104 for singlet excitons is derived, corresponding to a velocity constant of ks = 5.5 · 1011 s-1 (at p = 0.7 ± 0.07). The transfer of triplet excitons is governt by the constant k = 2 · 1011 s-1 . This corresponds a diffusion constant of triplet excitons D= (1.25 ± 0.2) · 104 cm2 s-1 . The lifetime of the tetracene triplet state within the antracene lattice is found to be τ = ( 1.09 ± 0.1) · 10-3 s.

Why Triage the Materials with Low Luminescence Quantum Efficiency: The Use of 35Cbz4BzCN as a Universal Host for Organic Light Emitting Diode through Effective Triplet Energy Transfer

2021 ◽  
Author(s):  
Yi-Mei Huang ◽  
Tse-Ying Chen ◽  
Deng-Gao Chen ◽  
Hsuan-Chi Liang ◽  
Cheng-Ham Wu ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Delayed Fluorescence ◽  
Triplet Energy ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Thermally Activated ◽  
Triplet Energy Transfer ◽  
Triplet Lifetime ◽  
Triplet Excitons

35Cbz4BzCN, a novel universal host with long triplet lifetime, has been developed. The triplet excitons in 35Cbz4BzCN can be effectively harvested by phosphorescence and thermally activated delayed fluorescence emitters. In...

scholarly journals P∩N Bridged Cu(I) Dimers Featuring Both TADF and Phosphorescence. From Overview towards Detailed Case Study of the Excited Singlet and Triplet States

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3415
Author(s):  
Thomas Hofbeck ◽  
Thomas A. Niehaus ◽  
Michel Fleck ◽  
Uwe Monkowius ◽  
Hartmut Yersin
Keyword(s):  
Quantum Yield ◽  
Decay Time ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Photo Luminescence ◽  
Delayed Fluorescence ◽  
Spin Lattice Relaxation ◽  
Zero Field ◽  
Triplet States ◽  
Spin Lattice

We present an overview over eight brightly luminescent Cu(I) dimers of the type Cu2X2(P∩N)3 with X = Cl, Br, I and P∩N = 2-diphenylphosphino-pyridine (Ph2Ppy), 2-diphenylphosphino-pyrimidine (Ph2Ppym), 1-diphenylphosphino-isoquinoline (Ph2Piqn) including three new crystal structures (Cu2Br2(Ph2Ppy)3 1-Br, Cu2I2(Ph2Ppym)3 2-I and Cu2I2(Ph2Piqn)3 3-I). However, we mainly focus on their photo-luminescence properties. All compounds exhibit combined thermally activated delayed fluorescence (TADF) and phosphorescence at ambient temperature. Emission color, decay time and quantum yield vary over large ranges. For deeper characterization, we select Cu2I2(Ph2Ppy)3, 1-I, showing a quantum yield of 81%. DFT and SOC-TDDFT calculations provide insight into the electronic structures of the singlet S1 and triplet T1 states. Both stem from metal+iodide-to-ligand charge transfer transitions. Evaluation of the emission decay dynamics, measured from 1.2 ≤ T ≤ 300 K, gives ∆E(S1-T1) = 380 cm−1 (47 meV), a transition rate of k(S1→S0) = 2.25 × 106 s−1 (445 ns), T1 zero-field splittings, transition rates from the triplet substates and spin-lattice relaxation times. We also discuss the interplay of S1-TADF and T1-phosphorescence. The combined emission paths shorten the overall decay time. For OLED applications, utilization of both singlet and triplet harvesting can be highly favorable for improvement of the device performance.

Delayed Fluorescence from Carbon Nanotubes through Singlet Oxygen-Sensitized Triplet Excitons

2020 ◽  
Vol 142 (50) ◽  
pp. 21189-21196
Author(s):  
Ching-Wei Lin ◽  
Sergei M. Bachilo ◽  
R. Bruce Weisman
Keyword(s):  
Carbon Nanotubes ◽  
Singlet Oxygen ◽  
Delayed Fluorescence ◽  
Triplet Excitons

scholarly journals Thermally assisted delayed fluorescence (TADF): fluorescence delayed is fluorescence denied

2020 ◽  
Vol 7 (5) ◽  
pp. 1210-1217 ◽  
Author(s):  
Daniel Sylvinson Muthiah Ravinson ◽  
Mark E. Thompson
Keyword(s):  
Delayed Fluorescence ◽  
Triplet Excitons

Thermally assisted delayed fluorescence (TADF) allows for efficient collection of both singlet and triplet excitons with both emitting through the singlet channel.  TADF opens the door to photo- and electroluminescence efficiencies close to 100%.

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