Triplet–Triplet Annihilation via the Triplet Channel in Crystalline 9,10-Diphenylanthracene

Abstract

Delayed fluorescence resulting from triplet–triplet annihilation in crystalline 9,10-diphenylanthracene was observed by means of steady-state fluorescence measurements under magnetic fields of ≤10 T. At five specific magnetic fields, four peaks and one dip in the magnetic field dependence of fluorescence intensity were observed, proving that exchange-coupled triplet pairs were generated in the course of triplet–triplet annihilation. The dip was in the opposite direction predicted for singlet channel triplet–triplet annihilation. Further analysis using the stochastic Liouville equation confirmed that the closest exchange-coupled triplet pair in crystalline 9,10-diphenylanthracene is quenched via both triplet channel and singlet channel triplet–triplet annihilation.

Efficient Red-to-Blue Triplet–Triplet Annihilation Upconversion Using the C70-Bodipy-Triphenylamine Triad as a Heavy-Atom-Free Triplet Photosensitizer

“…Moreover, f denotes spin-statistical factor, which is an important parameter in the TTA process defined as the probability to obtain a singlet excited state (S 1 ) by the annihilation of two triplet states (T 1 ). According to the spin-statistical law, ,, the f value should equal to 1/9. However, considering that the formation of quintet excited state usually is energetically forbidden, the quintet coupling pair will split back into two T 1 state to participate in further annihilations.…”

Spin-dependent recombination mechanisms for quintet bi-excitons generated through singlet fission

“…These states are called quintets in the spin resonance literature. The strong exchange interaction between the two bound triplet excitons was then confirmed by high magnetic fields experiments showing level anti-crossings between singlet S=0, triplet S=1 and quintet S=2 manifolds of the triplet pair [41][42][43][44][45][46]. Recently S=2 bi-exciton states were observed in several systems, including several reports investigating quintet pairs at room temperature [47][48][49][50][51][52] and their quantum properties can be investigated in detail with double resonance magnetic resonance techniques [53].…”

Photon Upconversion with a Low Threshold Excitation Intensity in Plain Water

“…The low value obtained for the overall TTA-UC quantum yield can be explained by the low triplet yield of PdTPPS 4− , the nonquantitative triplet energy transfer efficiency (78%), and the reabsorption of the DCDPA 2− fluorescence in the 400− 450 nm region by PdTPPS 4− (see Figure S10). In addition, the triplet channel TTA, which is a sort of nonradiative bimolecular elimination and has been recently elucidated in a DPA single crystal, 29 can be another reason for the low quantum yield. Nevertheless, the photochemical characteristics of DCDPA 2− clearly induce the low I th value.…”