Electrical characteristics of light-emitting diode based on poly(p-phenylenevinylene) derivatives: CzEH-PPV and OxdEH-PPV

Kang, Hyung Seok; Kim, K.H; Kim, M.S; Park, K.T; Kim, K.M; Lee, T.H; Lee, C.Y; Joo, Jinsoo; Lee, D.W; Hong, Young Rae; Kim, Kyounghyun; Lee, G.J; Jin, Jung‐Il

doi:10.1016/s0379-6779(02)00126-1

Cited by 21 publications

(3 citation statements)

References 28 publications

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“…Many previous studies had employed an LED device-like structure having two electrodes with different work functions, which made charge injection more likely. ,,, Likewise, an AC rather than DC voltage was applied to the cell. This minimizes the accumulation of trapped charges at the sample−electrode interface because of the constantly switching polarity. ,− We note that in some cases present in the literature charge injection has occurred even in cases where AC fields were applied. ,, The presence of free charges was inferred by the fact that the polymer emission intensity increased or decreased depending on the polarity of the charge injected into the material. In contrast, the quenching we observe is independent of the polarity of the applied AC field.…”

Section: Resultsmentioning

confidence: 95%

“…In EMF, the effect of an electric field on the integrated fluorescence spectrum is measured directly rather than indirectly as is provided by the zeroth derivative component of the line shape analysis. Though DC fields are commonly used, AC fields have been utilized as well. ,− In the case of AC fields, the intensity changes in response to the root mean squared amplitude of the AC field, regardless of its polarity. By measuring the quench induced by an AC field, we can substantiate the quenching efficiencies derived from the fit to the EF spectrum.…”

Section: Resultsmentioning

confidence: 99%

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Electric Field Effects on Internal Conversion: An Alternative Mechanism for Field-Induced Fluorescence Quenching of MEH-PPV and Its Oligomers in the Low Concentration Limit

et al. 2007

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In a previously published study (J. Phys. Chem. B 2006, 110, 7732−7742), we reported field-induced fluorescence quenching in both poly[2-methoxy,5-(2‘-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and several model oligomers in solvent glass matrices at high dilution (<0.1% by weight). The observed quenching is not readily explained by field-induced exciton dissociation or by the presence of free charges, two mechanisms that have been invoked to explain this phenomenon by previous authors. A model is developed here that ascribes the observed fluorescence quench in dilute samples to an energetic shift of the relaxed excited state caused by the electric field resulting in increased nonradiative relaxation. To determine whether the relevant nonradiative pathway is intersystem crossing or internal conversion, analytical expressions are derived for each of these two mechanisms. Only the expression derived for the Stark effect on the rate of internal conversion quantitatively predicts the magnitude of quench observed in MEH-PPV and in the oligomeric species.

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Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

Electric Field Effects on Internal Conversion: An Alternative Mechanism for Field-Induced Fluorescence Quenching of MEH-PPV and Its Oligomers in the Low Concentration Limit

et al. 2007

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“…It is deemed that the quasi-Fermi level locates in the trap distribution and the current is limited by trapped charges in TCL conduction. 16 In BFO based thin films, the possible trap center is Fe ions (Fe 2+ ). 15 When doping with Cr 3+ ions, the concentration of oxygen vacancies may be reduced and the distribution of the shallow traps which are above the Fermi level may be correspondingly decreased.…”

Section: Resultsmentioning

confidence: 99%

The study of BiCrxFe1−xO3 thin films synthesized by sol–gel technique

Zhang

Cheng

2010

Journal of the European Ceramic Society

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Blue‐light‐emitting poly(arylene ethynylenes) containing alternating sequences of biphenylene or fluorenediyl and p‐phenylene moieties linked through triple bonds

Joo

Jeong

Ko³

et al. 2006

J of Applied Polymer Sci

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ABSTRACT:Two new poly(arylene ethynylenes) were synthesized by the reaction of 1,4-diethynyl-2.5-dioctylbenzene either with 4,4Ј-diiodo-3,3Ј-dimethyl-1,1Ј-biphenyl or 2,7-diiodo-9,9-dioctylfluorene via the Sonogashira reaction, and their photoluminescence (PL) and electroluminescence (EL) properties were studied. The new poly(arylene ethynylenes) were poly [(3,3Ј-, both of which were blue-light emitters. PPEBE not only emitted better blue light than PPEFE, but it also performed better in EL than the latter when the light-emitting diode devices were constructed with the configuration indium-tin oxide/poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonic acid) (50 nm)/polymer (80 nm)/ Ca:Al. The device constructed with PPEBE exhibited an external quantum efficiency of 0.29 cd/A and a maximum brightness of about 560 cd/m 2 , with its EL spectrum showing emitting light maxima at ϭ 445 and 472 nm. The device with PPEFE exhibited an efficiency of 0.10 cd/A and a maximum brightness of about 270 cd/m 2 , with its EL spectrum showing an emitting light maximum at ϭ 473 nm. Hole mobility ( h ) and electron mobility ( e ) of the polymers were determined by the time-of-flight method. Both polymers showed faster h values. PPEBE revealed a h of 2.0 ϫ 10 Ϫ4 cm 2 /V⅐s at an electric field of 1.9 ϫ 10 5 V/cm and a e of 7.0 ϫ 10 Ϫ5 cm 2 /V⅐s at an electric field of 1.9 ϫ 10 5 V/cm. In contrast, the mobilities of the both carriers were slower for PPEFE, and its h (8.0 ϫ 10 Ϫ6 cm 2 /V⅐s at an electric field of 1.7 ϫ 10 6 V/cm) was 120 times its e (6.5 ϫ 10 Ϫ8 cm 2 /V⅐s at an electric field of 8.6 ϫ 10 5 V/cm). The much better balance in the carriers' mobilities appeared to be the major reason for the better device performance of PPEBE than PPEFE. Their highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels were also a little different from each other.

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Electrical characteristics of light-emitting diode based on poly(p-phenylenevinylene) derivatives: CzEH-PPV and OxdEH-PPV

Cited by 21 publications

References 28 publications

Electric Field Effects on Internal Conversion: An Alternative Mechanism for Field-Induced Fluorescence Quenching of MEH-PPV and Its Oligomers in the Low Concentration Limit

Electric Field Effects on Internal Conversion: An Alternative Mechanism for Field-Induced Fluorescence Quenching of MEH-PPV and Its Oligomers in the Low Concentration Limit

The study of BiCrxFe1−xO3 thin films synthesized by sol–gel technique

Blue‐light‐emitting poly(arylene ethynylenes) containing alternating sequences of biphenylene or fluorenediyl and p‐phenylene moieties linked through triple bonds

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