Excimers or Emissive On-Chain Defects?

Gaal, Martin; List, Emil; Scherf, Ullrich

doi:10.1021/ma021614m

Cited by 222 publications

(133 citation statements)

References 18 publications

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“…The origin of these emission features has been the subject of hot discussion. Fourier transform infrared (FTIR) spectroscopy has revealed that fluorenone defects, formed on degradation of PFs, are related to the intensity of the low-energy emission band (15,19,(31)(32)(33)(34)(35)(36)(37)(38). The idea that fluorenones could be responsible for the green light emission was substantiated by the synthesis of poly-and oligofluorenes containing a precise number of fluorenone moieties that exhibit green emission, even in dilute solution (24,33,(39)(40)(41).…”

Section: Resultsmentioning

confidence: 99%

Luminescent properties of a novel fluorene organic material

Lou

Qian

et al. 2008

Luminescence

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The photo-physical properties of 6,6′-(9H-fluoren-9,9-diyl)bis(2,3-bis(9,9-dihexyl-9H-fluoren-2-yl)quinoxaline) (BFLBBFLYQ) and its blend doped with N′-biphenyl-N,N′-bis-(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD) were investigated. The absorption, photoluminescence (PL) and electroluminescence (EL) properties of pristine BFLBBFLYQ and blend in solution and spin-coated film are outlined, including a discussion of charge-transfer (CT) exciplex emission of BFLBBFLYQ:TPD blend in the solid state. The luminescent properties of BFLBBFLYQ films using different deposition processes were studied. It was found that the low-energy emission bands at 530-570 nm appeared in the PL spectra of BFLBBFLYQ evaporated films in ultra-high vacuum. Also, the low-energy band was the exclusive emission in the EL spectra of BFLBBFLYQ films.

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Section: Resultsmentioning

confidence: 99%

Luminescent properties of a novel fluorene organic material

Lou

Qian

et al. 2008

Luminescence

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“…After the reaction mixture was refluxed for 2 h, a solution of sodium hydroxide (0.75 g, 18.75 mmol) in a mixture of water (0.5 ml) and methanol (3.75 ml) was added to the solution, and the reaction mixture was stirred for 15 min. After the reaction mixture was poured into an aqueous solution (50 ml) of potassium dihydrogen phosphate (5 …”

Section: M1 M2 P1 P2mentioning

confidence: 99%

“…[1][2][3][4] High thermal and oxidative stabilities are also required for blue-light-emitting polymers because blue-light emissions are associated with high energy gaps and high-electrical field intensities; however, the 9-position of fluorenyl moiety is easily oxidized at high operating temperature, inducing the decline of the color stability of light emission resulting from changes in the emission spectra. [5][6][7] The introduction of bulky aryl moieties into the 9-position of fluorene has been reported to be effective in the inhibition of oxidation, although the low solubilities in common organic solvents raise another problem owing to the increase in the tendency to crystallize. 8 On the other hand, conjugated polymers based on dibenzosilole, in which the vulnerable C-9 carbon in fluorene is replaced by a silicon, have been reported to be new polymeric materials for OLEDs in recent years.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the use of polysiloxane derivatives as polymeric OLED materials seems to be inadequate because of their extremely low T g, 19,20 which allows the formation of aggregates and/or interchain excimers to induce the decline of the color stability of light emission. [5][6][7] This is so even though the other properties of polysiloxanes such as good thermostability and stability against atomic oxygen, 19 which is generated by the irradiation of ultraviolet light to molecular oxygen (O 2 ), would be appropriate for polymeric OLED materials. To raise T g , we achieved the synthesis of fluorene-based polysiloxane derivatives with a bulky spirofluorenyl substituent on the C-9 carbon.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and characterization of poly(tetramethylsilarylenesiloxane) derivatives bearing diphenylfluorene or diphenyldibenzosilole moieties

Imai

Kihara

Kimoto

et al. 2010

Polym J

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Poly(tetramethylsilarylenesiloxane) derivatives having diphenylfluorene (P1) or diphenyldibenzosilole (P2) moieties were prepared via polycondensation of the corresponding disilanol monomers, that is, 2,7-bis(dimethylhydroxysilyl)-9,9-diphenylfluorene (M1) and 2,7-bis(dimethylhydroxysilyl)-9,9-diphenyldibenzosilole (M2), respectively. P1 and P2 exhibited good solubility in common organic solvents. The glass transition temperatures (T g s) of P1 and P2 were determined by differential scanning calorimetry to be 125 and 119 1C, respectively. The melting temperature (T m ) of P1 was observed at 276 1C; however, the T m of P2 was not observed, indicating that the introduction of a dibenzosilole moiety decreased the crystallization tendency. The temperatures at 5% weight loss (T d5 s) of P1 and P2 were 539 and 520 1C, respectively, suggesting good thermostability of P1 and P2. Bathochromic and hyperchromic effects were observed in the absorption and fluorescence spectra by introducing a dimethylsilyl substituent onto diphenylfluorene and diphenyldibenzosilole skeletons. The replacement of diphenylfluorene by the corresponding diphenyldibenzosilole also led to bathochromic shifts. The fluorescence quantum yield (U F ) of P1 was lower than that of M1, probably because of the formation of aggregates; however, the U F of P2 was higher than that of M2, indicating a decrease in the tendency toward aggregation using a dibenzosilole skeleton.

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“…However, a disadvantage of PFs is that these polymers show green emissions induced by excimer/aggregate formation 1,2 and/or keto defects induced by the oxidation of C-9 of the fluorene ring. [3][4][5] Such drawbacks in the performances of blue-emitting PF derivatives limit the practical applications of the polymers. To make stable and pure blue- 8,9 quinoxaline, 10 quinoline, 11 or alkoxy 12 groups into the main chain or side chain.…”

Section: Introductionmentioning

confidence: 99%

Electroluminescent copolymers based on dihexylfluorene and 2‐{2,6‐bis[2‐(4‐diphenylaminophenyl)vinyl]pyran‐4‐ylidene}malononitrile units

Kim

You

Lee

2006

J. Polym. Sci. A Polym. Chem.

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A series of statistical copolymers (poly[(9,9-di-nhexylfluorene)-co-2-{2,6-bis-[2-(4-diphenylaminophenyl)vinyl]pyran-4-ylidene}malononitrile) were synthesized by the Suzuki coupling reaction. The copolymers showed absorption bands at 379 and 483-489 nm, which were attributed to the oligofluorene segments and the segments containing 2-[2,6-bis(2-{4-[(4-bromophenyl)phenylamino] phenyl}vinyl)pyran-4-ylidene]malo nonitrile (3), respectively. The absorption band around 483-489 nm increased with the feed ratio of 3. The photoluminescence (PL) spectra of the copolymers showed emission bands at 420 and 573-620 nm.As the feed ratio of 3 increased, the PL emission in the longer wavelength region redshifted, and the intensity increased as well. The electroluminescence (EL) spectrum of the copolymers showed a very weak emission at 420 nm. The PL and EL emission colors redshifted dramatically with the increase in the feed ratio of 3. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels of the model compound (2-{2,6-bis[2-(4-diphenylaminophenyl)vinyl] pyran-4-ylidene}malononitrile) were determined to be À5.34 and À3.14 eV, respectively. It was concluded that energy transfer took place from the oligofluorene blocks to the segments containing 3 and that direct charge trapping occurred in the segments containing 3 during the EL operation. The Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of the copolymer (x ¼ 0.63, y ¼ 0.37) containing 10 mol % 3 were very close to those (x ¼ 0.67, y ¼ 0.33) for National Television System Committee (NTSC) red with a maximum photometric power efficiency of 0.27 cd/A.

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Excimers or Emissive On-Chain Defects?

Cited by 222 publications

References 18 publications

Luminescent properties of a novel fluorene organic material

Luminescent properties of a novel fluorene organic material

Synthesis and characterization of poly(tetramethylsilarylenesiloxane) derivatives bearing diphenylfluorene or diphenyldibenzosilole moieties

Electroluminescent copolymers based on dihexylfluorene and 2‐{2,6‐bis[2‐(4‐diphenylaminophenyl)vinyl]pyran‐4‐ylidene}malononitrile units

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