Excited state relaxation paths in 9,9′-bianthryl and 9-carbazolyl-anthracene: a sub-ps transient absorption study

Jurczok, Martin; Plaza, Pascal; Martin, Monique M.; Meyer, Yves; Rettig, Wolfgang

doi:10.1016/s0301-0104(99)00386-9

Cited by 43 publications

(74 citation statements)

References 29 publications

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“…Immediately following photoexcitation, 9,9′-bianthryl undergoes rapid, unhindered conformational relaxation on sub-picosecond time scales. [ 12 ] Our observation of singlet fi ssion in DP-Mes with comparable rates suggests that nuclear relaxation and tripletpair formation may be coupled, as they are in TIPS-pentacene fi lms. [ 25 ] An important distinction between the molecules is the later evolution in polar media.…”

Section: Discussionmentioning

confidence: 63%

“…We consider these spectra to refl ect a combination of solvent stabilization of the excited state and conformational relaxation into a nonorthogonal equilibrium geometry. [ 10,12,17 ] The latter effect is prevented in rigid polystyrene matrix, and indeed we can detect no long-lived emission in such fi lms (see below). Given the rapid prompt PL decay, these measurements of delayed fl uorescence require either that a sub-population of molecules is unable to undergo this initial decay or that a similar emissive species is regenerated on long time scales.…”

Section: Prompt and Delayed Photoluminescencementioning

confidence: 61%

“…The same confi guration was identifi ed previously in a structurally related anthracene dimer (9,9′-bianthryl). [10][11][12] However, the absorption spectra reveal that dimerization has important photophysical effects in spite of this orthogonal structure. DP-Mes exhibits a clear vibronic progression similar to most soluble pentacene derivatives, but with a lower 0-1/0-0 peak ratio than P-Mes (0.5 vs 0.6, Figure 1 d).…”

Section: Energetic Structurementioning

confidence: 99%

See 2 more Smart Citations

Tuneable Singlet Exciton Fission and Triplet–Triplet Annihilation in an Orthogonal Pentacene Dimer

Lukman

Musser

Chen

et al. 2015

Adv Funct Materials

192

270

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5452 wileyonlinelibrary.com proceed on ultrafast (≈100 fs) time scales, allowing it to out-compete other decay channels and achieve high effi ciencies. [ 3 ] The essential condition for effi cient SEF is the energetic alignment of the singlet and triplet states, such that 2 E (T 1 ) ≤ E (S 1 ). A recent combined theoretical and experimental study of SEF rates in a range of acene solids has demonstrated that the rate of SEF is also greatly affected by the strength of intermolecular coupling within the fi lm. [ 4 ] In the canonical system, pentacene, triplet pair formation is exothermic and the intermolecular coupling is strong, resulting in SEF with an 80 fs time constant and nearly 200% yield. [ 5 ] Though most experimental studies of SEF have involved crystalline, polycrystalline or amorphous solids, the most basic unit capable of SEF is a pair of chromophores. Indeed, it was recently demonstrated in concentrated solutions of TIPS-pentacene that singlet fi ssion can proceed at high efficiency through bimolecular diffusional interactions. [ 6 ] However, early attempts to directly control the interaction between chromophores through the use of covalent dimers have not been as successful. The most notable systems in this regard are tetracene and 1,3-diphenylisobenzofuran. These materials are found to exhibit effi cient SEF in the solid state, but their covalent dimers achieved triplet yields of only a few percent. In both of these studies, [ 7 ] the two SEF chromophores were joined by a range of linkers to modify the strength of the electronic coupling between them, with the aim of tuning the rate and effi ciency of SEF. The impact was subtle, and it thus remains unclear why covalent dimers have proved ineffi cient to date. Current models suggest that dimers should be asymmetric or contain signifi cant cofacial interaction between chromophores to attain high triplet yields. [ 2,8 ] Interestingly, a recent study of pentacene dimers separated by a phenyl spacer unit achieved triplet yields above 100% in spite of using the same symmetric bonding motifs of the earlier tetracene dimers. [ 9 ] In this work, we report highly effi cient intramolecular SEF in a new type of covalent dimer, with triplet yields of up to 192 ± 3%. The molecule used in this study, 13,13′-bis(mesityl)-6,6′-dipentacenyl (DP-Mes, Figure 1 a), consists of two pentacenes directly bonded through a single C C bond with two bulky mesityl groups at the meso -positions. The geometry of the dimer, with two nearly orthogonal pentacene cores, is unlike Tuneable Singlet Exciton Fission and Triplet-Triplet Annihilation in an Orthogonal Pentacene DimerSteven Lukman , Andrew J. Musser , Kai Chen , Stavros Athanasopoulos , Chaw K. Yong , Zebing Zeng , Qun Ye , Chunyan Chi , Justin M. Hodgkiss , Jishan Wu , * Richard H. Friend , and Neil C. Greenham * Fast and highly effi cient intramolecular singlet exciton fi ssion in a pentacene dimer, consisting of two covalently attached, nearly orthogonal pentacene units is reported. Fission to triplet excitons from...

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Section: Discussionmentioning

confidence: 63%

Section: Prompt and Delayed Photoluminescencementioning

confidence: 61%

Section: Energetic Structurementioning

confidence: 99%

See 1 more Smart Citation

Tuneable Singlet Exciton Fission and Triplet–Triplet Annihilation in an Orthogonal Pentacene Dimer

Lukman

Musser

Chen

et al. 2015

Adv Funct Materials

192

270

View full text Add to dashboard Cite

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“…In the analogous anthracene dimer 9,9′-bianthryl the equilibrium geometry for the Frenkel-excitonic singlet state has a ∼70° dihedral angle between acenes2842. The CT state, on the other hand, is most stabilized near the orthogonal geometry.…”

Section: Discussionmentioning

confidence: 99%

Tuning the role of charge-transfer states in intramolecular singlet exciton fission through side-group engineering

et al. 2016

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Understanding the mechanism of singlet exciton fission, in which a singlet exciton separates into a pair of triplet excitons, is crucial to the development of new chromophores for efficient fission-sensitized solar cells. The challenge of controlling molecular packing and energy levels in the solid state precludes clear determination of the singlet fission pathway. Here, we circumvent this difficulty by utilizing covalent dimers of pentacene with two types of side groups. We report rapid and efficient intramolecular singlet fission in both molecules, in one case via a virtual charge-transfer state and in the other via a distinct charge-transfer intermediate. The singlet fission pathway is governed by the energy gap between singlet and charge-transfer states, which change dynamically with molecular geometry but are primarily set by the side group. These results clearly establish the role of charge-transfer states in singlet fission and highlight the importance of solubilizing groups to optimize excited-state photophysics.

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“…12 BA is a well-known system whose excited state behaviour and dynamical processes have been studied extensively in a range of conventional solvents. [13][14][15][16][17][18][19][20][21] The interest in BA is mainly due to the fact that this pre-twisted molecule with mutually perpendicular anthracene rings in the ground state undergoes symmetry breaking upon excitation and its flourescence spectra show distinct charge transfer (CT) character, especially in polar solvents. [13][14][15] In nonpolar solvents the first excited state (S 1 ) is predominantly a locally excited (LE) state with very little or no CT character, 14-16 whereas, in highly polar solvents a CT state, which is formed rapidly from the LE state, is the emitting state.…”

Section: Introductionmentioning

confidence: 99%

Excited state dynamics of 9,9′-bianthryl in room temperature ionic liquids as revealed by picosecond time-resolved fluorescence study

et al. 2009

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Picosecond time-resolved fluorescence measurements have been carried out on 9,9′-bianthryl in three imidazolium ionic liquids to probe the excited state dynamics. In the early time-scale, the fluorescence spectra of bianthryl have been found to consist of emission from both locally excited (LE) and charge transfer (CT) states. The LE → CT relaxation time, as estimated from the decay of the fluorescence intensity of the LE emission, is found to vary between 230 and 390 ps, while the average solvent relaxation time, as estimated from the analysis of time-dependent fluorescence Stokes shift, is found to vary between 620 ps and 1840 ps, depending on the viscosity of the ionic liquids. The results confirm that while in conventional less viscous solvents the CT formation kinetics of bianthryl occurs simultaneously with the solvation dynamics, in ionic liquids the two processes mostly occur in different time scales.

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Excited state relaxation paths in 9,9′-bianthryl and 9-carbazolyl-anthracene: a sub-ps transient absorption study

Cited by 43 publications

References 29 publications

Tuneable Singlet Exciton Fission and Triplet–Triplet Annihilation in an Orthogonal Pentacene Dimer

Tuneable Singlet Exciton Fission and Triplet–Triplet Annihilation in an Orthogonal Pentacene Dimer

Tuning the role of charge-transfer states in intramolecular singlet exciton fission through side-group engineering

Excited state dynamics of 9,9′-bianthryl in room temperature ionic liquids as revealed by picosecond time-resolved fluorescence study

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