Dipyrazolopyridine derivatives as bright blue electroluminescent materials

Tao, Yu‐Tai; Balasubramaniam, E.; Danel, A.; Tomasik, Piotr

doi:10.1063/1.1288811

Cited by 103 publications

(74 citation statements)

References 9 publications

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“…[9,10] An alternative approach which overcomes such a problem is to blend two blue-light-emitting organic molecules of different electron affinities, whose interaction gives rise to exciplex states. [11,12] The combination of the exciplex emission with the blue-light emission of the individual donor molecule results in the generation of white light. However, in both of these approaches the purity of the color emission is strongly dependent on the relative concentration of the different molecular species and, generally, on the applied voltage.…”

Section: Methodsmentioning

confidence: 99%

An Ultraviolet Organic Thin‐Film Solid‐State Laser for Biomarker Applications

Schneider

Rabe

Riedl³

et al. 2005

Advanced Materials

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Since the discovery of lasing in organic solid-state thin films many efforts have been devoted to this field.[1±9] Organic lasers offer broad tuning ranges and there are active materials covering almost the whole visible spectrum. However, electrically pumped organic lasing has not been shown so far. One of the challenges unachieved so far has been the realization of organic thin-film solid-state lasing in the ultraviolet wavelength region below 380 nm. Organic materials for ultraviolet organic light-emitting diodes (OLEDs) have been reported.[10±12] Solid-state dyes lasing in that wavelength region have only been reported for doped silica-gel layers not suitable for possible electrical applications. [13,14] Organic lasing in semiconducting thin films has only been shown for wavelengths above 392 nm. [3] In this communication we report on the first thin-film organic semiconductor laser operating in the ultraviolet wavelength region between 377.7 and 395 nm. This is the shortest laser wavelength reported so far for thin-film organic solid-state lasers. The novel spiro-linked material 2,2¢,7,7¢-tetrakis(4-fluorphenyl)spiro-9,9¢-bifluorene was used as the active organic layer in an optically pumped distributed feedback (DFB) structure. The chemical structure is shown in the inset of Figure 1. Spiro-linked materials have been proven to be very stable materials for utilization as charge transport and emitting layers in OLEDs.[15±22] They are also known as candidates for organic solid-state lasers. Amplified spontaneous emission (ASE) has been observed in a variety of spirolinked materials, including spiro-quarterphenyl (Spiro-4U), and spiro-sexiphenyl (Spiro-6U). [18,21,22] In Spiro-4U, an ASE maximum was observed at approximately 390 nm. A very promising application for tunable organic solid-state lasers is the field of tunable laser spectroscopy (TLS). The small size and the availability of organic thin-film solid-state lasers in the whole visible spectrum makes them an inexpensive alternative to conventional gas or dye lasers. The large tuning range of organic lasers allows the easy adjustment of the output wavelength to the particular requirements of the spectroscopic application. In the ultraviolet region alternatives are especially limited. Ultraviolet diode lasers exhibit only small tuning ranges, gas lasers are limited to certain discrete wavelengths, and liquid-based dye lasers are cumbersome in handling. As long as no electrical operation of thin-film organic lasers is demonstrated, they may, due to their low thresholds, be pumped by compact and inexpensive diode pumped microchip lasers.[23] Thus the strong infrastructure requirements of certain gas or liquid-based dye lasers can be avoided. In this report, we prove the capability of organic thin-film UV lasers for spectroscopic applications in the field of TLS. Therefore we measure the photoluminescence spectra of the fluorescence marker dyes Coumarin 6, Coumarin 152, and Rhodamine 6G in solution using our thin-film organic laser as the excitation source. R...

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Section: Methodsmentioning

confidence: 99%

An Ultraviolet Organic Thin‐Film Solid‐State Laser for Biomarker Applications

Schneider

Rabe

Riedl³

et al. 2005

Advanced Materials

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“…Usually bathocuproine (BCP) [13,19,22,48,49] and (biphenyloxolatoaluminum(III) bis[2-methylquinolinato(phenylphenolate)] (BAlq) [65,73] are used as HBL or exciton-blocking layers. Other compounds, such as fluorinated phenylenes [51] and oxadiazole, as well as triazolecontaining molecules such as the trimer of N-arylbenzimidazoles (TPBi), [74,75] 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD), [24] 3-phenyl-4-(1¢-naphthyl)-5-phenyl-1,2,4-triazole (TAZ), [76,77] 1,8-naphthalimides, [78] polyquinolines, [79] or carbon nanotubes doped in PPV [80] were also found to be useful as HBLs. In the last step, depositing a cathode completes the assembly of the device.…”

Section: Small-molecule Oledsmentioning

confidence: 99%

New Trends in the Use of Transition Metal–Ligand Complexes for Applications in Electroluminescent Devices

Langeveld²,

2005

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The advantage of using phosphorescent transition metal–ligand complexes in optoelectronic applications such as organic light‐emitting diodes (OLEDs) and light‐emitting electrochemical cells (LECs) are described and evaluated. Additionally, different device constructions utilizing phosphorescent transition‐metal complexes like iridium(III) mixed‐ligand complexes and ruthenium(II) systems are reviewed and specified. Diverse host materials in which the phosphorescent emitters can be placed are discussed, such as small organic molecules and a few polymeric systems, and alternative processing technologies are briefly compared. Recent developments in the synthesis of iridium(III) triplet emitters are discussed. Different device architectures require different kinds of metal–ligand complexes. The different synthetic routes leading to charged and non‐charged complexes are briefly discussed.

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“…6c). Apparently, the passage of holes into the electron-transport layer (ETL) is more difficult in configuration I because the HOMO energy gap between btza and TPBI (HOMO = 6.20 eV) [21] is [a] The measured values are given in the order of devices I, II, and IV. L max , maximum luminance; L, luminance; V on , turn-on voltage; V, voltage; g ext,max , maximum external quantum efficiency; g p,max , maximum power efficiency; g c,max , maximum current efficiency; g ext , external quantum efficiency; g p , power efficiency; g c , current efficiency taken at a current density of 100 mA.…”

Section: Full Papermentioning

confidence: 99%

Color Tuning in Benzo[1,2,5]thiadiazole‐Based Small Molecules by Amino Conjugation/Deconjugation: Bright Red‐Light‐Emitting Diodes

Thomas

Lin²,

Velusamy

et al. 2004

Adv Funct Materials

332

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Bipolar compounds (referred to in general as btza) containing a benzo[1,2,5]thiadiazole core and peripheral diarylamines and/or 4‐tert‐butylphenyl moieties have been synthesized via palladium‐catalyzed cross‐coupling reactions of 4,7‐dibromobenzo[1,2,5]thiadiazole with appropriate stannyl compounds. These compounds are fluorescent and the emission color ranges from green to red. The fluorescence of the compounds originates from a charge‐transfer process and exhibits solvatochromism. These red‐light‐emitting materials are amorphous and devices of different configurations were fabricated: I) ITO/btza/TPBI/Mg:Ag; II) ITO/btza/Alq3/Mg:Ag; III) ITO/btza/Mg:Ag (where ITO = indium tin oxide, TPBI = 1,3,5‐tris(N‐phenylbezimidazol‐2‐yl)benzene, and Alq3 = tris(8‐hydroxyquinoline)aluminum). The performance of some of the red‐light‐emitting devices appears to be very promising.

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Dipyrazolopyridine derivatives as bright blue electroluminescent materials

Cited by 103 publications

References 9 publications

An Ultraviolet Organic Thin‐Film Solid‐State Laser for Biomarker Applications

An Ultraviolet Organic Thin‐Film Solid‐State Laser for Biomarker Applications

New Trends in the Use of Transition Metal–Ligand Complexes for Applications in Electroluminescent Devices

Color Tuning in Benzo[1,2,5]thiadiazole‐Based Small Molecules by Amino Conjugation/Deconjugation: Bright Red‐Light‐Emitting Diodes

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