Binding energies of triplet excimers in poly(N-vinylcarbazole) solid films from laser-based kinetic spectroscopy between 15 and 55 K

Burkhart, Richard D.; Chakraborty, Dilip K.

doi:10.1021/j100373a049

Cited by 26 publications

(28 citation statements)

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“…producing the broad emission band with maximum at 530 nm is known [13,14] and has been demonstrated above. It is worth to underline that some authors undertake the trials to clear the origin of the emission at 600-750 nm range [9].…”

Section: 3tl Versus Elmentioning

confidence: 82%

“…Chakraborty [13]. It has been explained as a change of photoexcited states in PVK from monomeric triplet states at low temperatures to excimeric ones at higher temperatures.…”

Section: Thermoluminescencementioning

confidence: 99%

“…This emission bands about 590 nm and above 600 nm were attributed to several different mechanisms, such as aggregation, [7,9] electroplex [3,9] or phosphorescence [13,14]. In contrast to PVK, for which photophysical properties were extensively studied since many years, the PVK-PBD system was investigated much less intensively.…”

Section: Introductionmentioning

confidence: 99%

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The nature of trapping sites and recombination centres in PVK and PVK–PBD electroluminescent matrices seen by spectrally resolved thermoluminescence

Glowacki¹,

Szamel²

2010

J. Phys. D: Appl. Phys.

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To cite this version:Ireneusz Glowacki, Zbigniew Szamel. The nature of trapping sites and recombination centres in PVK and PVKPBD electroluminescent matrices seen by spectrally resolved thermoluminescence. with the electroluminescence (EL) spectra has allowed identifying the localized (trapping) sites and the radiative recombination centres present in the investigated matrices. In the neat PVK films deep traps with a depth about 200 meV, related to triplet excimers dominate, while in the PVK-PBD (40 wt %) blend films the traps that are related to triplet exciplexes formed by the carbazole groups and the PBD molecules dominate. Depth of the traps in the PVK-PBD blend is somewhat lower than that in the neat PVK. An analysis of the EL spectra shows that in the PVK and in the PVK-PBD blend the dominant radiative centres are singlet excimers and singlet exciplexes, respectively. However in the neat PVK some contributions of the triplet monomer and the triplet excimer states in the electroluminescence were also detected.

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Section: 3tl Versus Elmentioning

confidence: 82%

“…Chakraborty [13]. It has been explained as a change of photoexcited states in PVK from monomeric triplet states at low temperatures to excimeric ones at higher temperatures.…”

Section: Thermoluminescencementioning

confidence: 99%

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The nature of trapping sites and recombination centres in PVK and PVK–PBD electroluminescent matrices seen by spectrally resolved thermoluminescence

Glowacki¹,

Szamel²

2010

J. Phys. D: Appl. Phys.

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“…centered at 500 nm and delayed by 0.1 ms which belongs to the excimer phosphorescence [15] appears in addition to the fluorescence band (λ ∼ 410 nm) [14].…”

Section: Results and Their Discussionmentioning

confidence: 99%

Luminescence of Zn2L2- and PVC-based organic molecular compositions under photo- and electroexcitation

et al. 2010

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solvate with ethanol} are investigated in solutions, powder, and thin polyvinylcarbazole (PVC) films. The trends in their change versus the nature, aggregate state, and excitation method are established. Electroluminescence (λ mаx = 493 nm) of an ITO/PEDOT/PVC : Zn 2 L 2 /LiF/CaMg/Ag device is excited, and its current-voltage and brightness-voltage characteristics are investigated.Keywords: metalloorganic complex, spectral and luminescent characteristics, electroluminescence.Nowadays organic electroluminescent devices (OELD) are very popular due to numerous applications, in particular, in flat displays. They represent multilayered sandwich structures capable of converting the electric energy into light. The simplified sandwich structures comprise anode/emitting layer/cathode. Their main element is the material of the light-emitting layer. The potential material of the light-emitting layer of the electroluminescent device must have high photoluminescence intensity, thermal stability, and capability of forming thin film coatings (100 nm). From the viewpoint of further commercial production of electroluminescent devices, the material must have low cost and simple procedure of synthesis. In the last decade, the active search is on for new thin-film electroluminescent materials based on metalloorganic coordination compounds. The combination of metal ions and organic ligands in one molecule and the opportunity of purposeful change of the composition and structure of coordination compounds are favorable to the production of molecular materials for OELD with efficient electroluminescence in a wide range of wavelengths on their basis [1, 2]. A special place among organic luminescent materials belonging to different classes is occupied by metal complexes with ligands comprising the C = N azomethine bond and electron-donor oxygen and/or nitrogen atoms. They are distinguished by the ease of production and thermal stability; they are capable to form thin layers and to transport electrons in them. In most cases, thin layers of organic substances of different natures are formed on the anode surface either by the vacuum deposition or centrifuging method. In the latter case, compositions including an electroactive low-molecular organic substance, an electroactive polymer, and a solvent are used. In these emitting layers, the polymeric matrix is a solid solvent for the luminophor. The processes of energy and charge transfer can proceed in the layers. At present, a search for photo-and electrostable luminophor: polymer pairs with high emissivity is urgent.However, it is difficult to develop the OELD with high efficiency and long lifetime combining the two methods of thin-film structure production (centrifuging and thermal vacuum deposition) in one device, since under laboratory conditions, it is often impossible to prevent the interaction of thin-film structures with oxygen and moisture in the

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“…According to the literature [21], the fluorescence band belongs to emission of a pair of carbazolyl groups that only partially overlap each other. The phosphorescence spectrum structure is related to luminescence of shallow traps for triplet excitons localized on carbazolyl groups [22,23]. Above 40 K, the emission structure disappears and the phosphorescence spectrum consists of a broad featureless band that appears as a shoulder at ≈500-510 nm (Fig.…”

mentioning

confidence: 99%

Luminescence of carbazolyl-containing polymers doped with iridium chelates

Skryshevskiĭ

2008

J Appl Spectrosc

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dopant phosphorescence emissions. The balance between basic colors is adjusted by the variation of triplet-emitter dopant concentrations. Spin-allowed singlet-singlet energy transfer from the host to iridium chelate dopants by the Forster mechanism is the dominant process in PVC. Spin-forbidden triplet-singlet transfer by the Forster mechanism from the host to the dopant occurs at low temperatures in 3,6-DBrPEPC due to strong spin-orbit coupling induced by the heavy bromine atoms. Spin-allowed transfer from the same host's triplet excited state to the iridium chelate occurs via electron exchange at high temperatures.Introduction. Light-emitting and transport layers in organic electroluminescent diodes are fabricated from lowmolecular-weight organic compounds and conducting polymers. Layers of low-molecular-weight compounds are prepared by vacuum deposition [1]. Film-forming conducting polymers are interesting mainly because layers can be deposited directly from solutions by coating and by highly technical methods such as jet [2] and stencil [3] printing. This decreases significantly the cost of items, especially during preparation of large planar panels. A method for preparing aqueous suspensions of conducting polymers for deposition of several functional layers has been developed [4] and enables damage by solvent of the already formed layers to be avoided when depositing a new layer.Electroluminescent devices for white light are highly interesting for practical purposes, in particular, for backlighting of liquid-crystalline displays and as light sources. Because organic compounds that emit white light are unknown, it can be produced by mixing in the appropriate ratio the three basic colors red, green, and blue. Therefore, devices with two or three active layers [5, 6] that emit light of different color and structures with several pixels that emit the basic colors and are deposited on a common substrate [7] have been developed. However, these methods are relatively complicated and expensive. Furthermore, it is difficult to control the balance of basic colors to produce pure white light. Several methods have been proposed so that a device would have only one active emitting polymeric layer, which could substantially lower the cost of the item. Of these, the most promising is the use of host conducting polymers that emit blue or shorter wavelength light into which fluorescent or phosphorescent dopants are introduced [8-12].Spin statistics predict [13,14] that three times more triplet excitons than singlet ones are formed upon recombination of charge carriers injected from electrodes. Intersystem transitions that are forbidden by spin-selection rules occur through spin-orbit coupling that mixes singlet and triplet states. Therefore, addition of a dopant containing a heavy metal atom with strong spin-orbit coupling to the emitting layer was proposed [13,14]. As a result, the phosphorescence quantum yield increases greatly in this molecule, called a "triplet emitter" [15,16]. Organic complexes of platinum [13,14,17,18...

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Binding energies of triplet excimers in poly(N-vinylcarbazole) solid films from laser-based kinetic spectroscopy between 15 and 55 K

Cited by 26 publications

References 0 publications

The nature of trapping sites and recombination centres in PVK and PVK–PBD electroluminescent matrices seen by spectrally resolved thermoluminescence

The nature of trapping sites and recombination centres in PVK and PVK–PBD electroluminescent matrices seen by spectrally resolved thermoluminescence

Luminescence of Zn2L2- and PVC-based organic molecular compositions under photo- and electroexcitation

Luminescence of carbazolyl-containing polymers doped with iridium chelates

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