Triplet-triplet extinction coefficients via energy transfer

Bensasson, René V.; Land, Edward J.

doi:10.1039/tf9716701904

Cited by 424 publications

(253 citation statements)

References 0 publications

Supporting

Mentioning

238

Contrasting

Order By: Relevance

“…10 ms was reported from delayed luminescence measurements on polycrystalline Alq 3 at 6 K. 13 This may indicate a marked temperature dependence for the triplet decay, possibly due to triplet hopping to quenching sites at higher temperatures. From the initial absorbances of biphenyl triplet and Alq 3 transient absorptions, and the value ) 27 100 M -1 cm -1 for the biphenyl triplet state, 16 a molar absorption coefficient 510 nm ) 3350 ( 350 M -1 cm -1 was determined for the Alq 3 triplet state, within the range of values reported for triplets of heavy metal quinolates. 11 The triplet state was also studied by laser flash photolysis, exciting an Ar saturated solution of Alq 3 (6.7 × 10 -5 M) in benzene with the third harmonic of a Nd:YAG laser (355 nm).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Characterization of the Triplet State of Tris(8-hydroxyquinoline)aluminium(III) in Benzene Solution

et al. 2003

View full text Add to dashboard Cite

Since Tang and VanSlyke first reported efficient electroluminescence from a device based on tris(8-hydroxyquinoline)aluminium(III) (Alq 3 ) as the luminescent layer, 1 organic light-emitting diodes (OLEDs), based on these materials, are now at the stage where they are being used as monochrome displays. This results from emission from a ligand centered π, π* excited state, formed in the transition of an electron from a highest occupied molecular orbital (MO) lying mainly on the phenoxide ring to a lowest unoccupied MO predominantly on the nitrogen atom. 2 By doping with the appropriate dyes, the emission can be tuned through the visible spectrum, 3,4 leading to the possibility of full color OLED displays. The basic processes involved are reasonably well understood, 5,6 with electroluminescence involving generation of singlet excitons from electron-hole recombination. From spin statistics, theoretical calculations, and experiment, 7 the singlet:triplet exciton ratio is 1:3, limiting the maximum internal OLED efficiency from fluorescent materials to e25%. Nevertheless, by doping with heavy atom-containing complexes, such as platinum(II) octaethylporphyrin (PtOEP), it is possible to capture triplet excitons (or charge carriers) to give electrophosphorescence, increasing internal quantum yields dramatically. 8 Although of interest for display applications, efficient exploitation requires detailed knowledge of the properties of the lowest triplet state of Alq 3 , which is not available. We are reporting here what we believe to be the first detailed characterization of this state.There is relatively little detailed information on Alq 3 photophysics. Various values have been reported for the fluorescence quantum yield 3,9,10 and lifetime, 3,11 and only indirect information exists on the triplet state. 12,13 Attempts to observe phosphorescence have proved unsuccessful, 11,12 although some information has been inferred from data on heavy metal quinolates. 11 We have shown 14 that pulse radiolysis of benzene solutions selectively produces triplet states of conjugated organic polymers by energy transfer from appropriate sensitizers following pulse radiolysis of benzene solutions. The triplet state of Alq 3 is characterized in the same way.Following pulse radiolysis 15 of an Ar saturated solution of Alq 3 (2.25 × 10 -4 M) and biphenyl (0.01 M) in benzene, the absorption of the biphenyl triplet state 16 was observed, with a maximum below 380 nm. This decayed within a few microseconds to be replaced by a new absorption maximum around 510 nm (Figure 1). This is similar to spectra reported by Ballardini et al. 11 for triplet states of various heavy metal 8-quinolinol chelates and is assigned to the Alq 3 triplet state, which decayed by good first-order kinetics with a lifetime τ ) 56.3 ( 0.4 µs. From the analysis of transient diffusion measurements in doped films, 12 a lifetime of 25 ( 15 µs was estimated for this triplet state. In contrast, a value of ca. 10 ms was reported from delayed luminescence measurements on polycrystall...

show abstract

mentioning

confidence: 99%

“…Following pulse radiolysis 15 of an Ar saturated solution of Alq 3 (2.25 × 10 -4 M) and biphenyl (0.01 M) in benzene, the absorption of the biphenyl triplet state 16 was observed, with a maximum below 380 nm. This decayed within a few microseconds to be replaced by a new absorption maximum around 510 nm ( Figure 1).…”

mentioning

confidence: 99%

Characterization of the Triplet State of Tris(8-hydroxyquinoline)aluminium(III) in Benzene Solution

et al. 2003

View full text Add to dashboard Cite

show abstract

“…The yield of PhSO • was measured in comparison with the triplet-triplet absorption of anthracene in degassed cyclohexane with these parameters: Φ T ) 0.71 and T (422.5 nm) ) 6.47 × 10 4 M -1 cm -1 . [66][67][68] The optical density at the excitation wavelength and the energy of laser pulse (7 mJ) were equal for solution of sulfoxide and anthracene. These data, together with the decay rate constants, are presented in Table 1.…”

Section: Chartmentioning

confidence: 99%

Generation and Decay of Aryl Sulfinyl and Sulfenyl Radicals: A Transient Absorption and Computational Study

et al. 1997

View full text Add to dashboard Cite

Absorption spectra and extinction coefficients of phenylsulfinyl and phenylsulfenyl (thiyl) radicals are determined by nanosecond laser photolysis in various solvents. Direct observation and characterization of arylsulfinyl radicals from the photolysis of several aromatic sulfoxides provides the strongest evidence to date for R-cleavage as the predominant primary photochemical process for these compounds. The absorption spectrum of phenylsulfinyl, with λ max ) 300 and 450 nm and ) 1.1 × 10 4 and 1.3 × 10 3 M -1 cm -1 , is practically independent of solvent. Quantum yields of free sulfinyl radicals range from 0.09 to 0.18 in various solvents. Recombination rate constants very near diffusion control indicate that there is a large spin-orbital coupling in the radical pair. Rate constants for the reactions of arylsulfinyl radicals with stable nitroxide radicals are among the fastest known, but reactivity with O 2 is very modest. Computations indicate that the singly occupied molecular orbital is a π* orbital largely localized on the sulfur and oxygen atoms.

show abstract

“…One possible mechanism would be through higher excited states of the triplet. Transient state absorption spectroscopy of Alq 3 has shown triplet absorption at a wavelength of ϳ510 nm, 11,12 which is coincident with the singlet emission wavelength of Alq 3 . It is therefore possible that, given the very high concentration of singlet recombination in our samples, the triplet to singlet interchange could be through an intermediate higher energy triplet state, which would overcome the problem of the energy barrier; this is illustrated in Fig.…”

Section: Resultsmentioning

confidence: 99%

Measurement of the intersystem crossing rate in aluminum tris(8-hydroxyquinoline) and its modulation by an applied magnetic field

Zhang

Song

Kreouzis

et al. 2009

Journal of Applied Physics

View full text Add to dashboard Cite

Measurement of the intersystem crossing rate in aluminum tris(8-hydroxyquinoline) and its modulation by an applied magnetic field The rate constant for intersystem crossing in aluminum tris͑8-hydroxyquinoline͒ was measured using the time dependence of the luminescence under high excitation intensity and modeling using a rate equation approach. Under high illumination levels intersystem crossing results in the transfer of singlets into triplets, which due to their long lifetime effectively remove molecules from participating in photoluminescence. The intersystem crossing rate was found to be ϳ2.2 ϫ 10 4 s −1 at 80 K. The presence of a magnetic field was found to increase the rate constant by ϳ10% with applied fields of ϳ100 mT.

show abstract

Triplet-triplet extinction coefficients via energy transfer

Cited by 424 publications

References 0 publications

Characterization of the Triplet State of Tris(8-hydroxyquinoline)aluminium(III) in Benzene Solution

Characterization of the Triplet State of Tris(8-hydroxyquinoline)aluminium(III) in Benzene Solution

Generation and Decay of Aryl Sulfinyl and Sulfenyl Radicals: A Transient Absorption and Computational Study

Measurement of the intersystem crossing rate in aluminum tris(8-hydroxyquinoline) and its modulation by an applied magnetic field

Contact Info

Product

Resources

About