Electronic structure and intersystem crossing in 9,10-diphenylanthracene

Photon Upconversion in Supramolecular Gel Matrixes: Spontaneous Accumulation of Light-Harvesting Donor–Acceptor Arrays in Nanofibers and Acquired Air Stability

“…Upon heating from 25 to 80 °C, the UC emission intensity gradually decreased and reached an almost constant value above the gel-to-sol transition temperature (∼45 °C). The molecular diffusion in the higher-temperature solution phase should be high enough to complete the TTET and TTA processes, and the Dexter energy transfer is known to be temperature independent. , Also, the fluorescence quantum yield of DPA is unity independent of the solvent and temperature . From this information, the decrease in UC emission intensity observed for the sol phase is ascribed to the quenching of excited triplet species by dissolved oxygen.…”

“…18,21 Also, the fluorescence quantum yield of DPA is unity independent of the solvent and temperature. 22 From this information, the decrease in UC emission intensity observed for the sol phase is ascribed to the quenching of excited triplet species by dissolved oxygen. To our interest, the UC emission intensity recovered reversibly upon cooling to 25 °C.…”

Trap-State-Induced Becquerel Type of Photoluminescence Decay in DPA-Activated Silicon Nanocrystals

“…Thus, this theoretically predicted decay law can be combined with the measured PL decay , which allows for the determination of the capture cross-section from the measured decay τ This trapping model can be applied to the PL of the DPA-SiNC sample since the attachment of the DPA molecules can be expected to lead to the formation of DPA-related trap states in the NC; see Figure b. This trap state could be connected with the lowest excited DPA level, which is a triplet state and is energetically close to the observed emission (1.77 eV → 700 nm) . As detailed in section 2, the absorption cross-section and the concentration of NCs are known.…”

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

“…3,8,18−26 However, it is not clear whether T-channel TTA takes place in DPA molecules. 6,15,20,21,27 It is known that the intensity of delayed fluorescence produced by TTA can be modulated by the application of an external magnetic field, 2,28 and TTA processes have been studied with magnetic fields in solid states 2,29−33 and in solutions. 19,21,34−38 The effects of a magnetic field on the delayed fluorescence in crystalline DPA were first reported in the 1970s, with three peaks of fluorescence intensity observed when a magnetic field of 0.5−2.5 T was applied; 2 however, the origin of these peaks has not yet been clarified.…”

“…The polycyclic aromatic hydrocarbon 9,10-diphenylanthracene (DPA) is commonly used as an annihilator in TTA-UC systems because of its high fluorescence quantum yield, commercial availability, and ease of handling. ,,− However, it is not clear whether T-channel TTA takes place in DPA molecules. ,,,, It is known that the intensity of delayed fluorescence produced by TTA can be modulated by the application of an external magnetic field, , and TTA processes have been studied with magnetic fields in solid states ,− and in solutions. ,,− The effects of a magnetic field on the delayed fluorescence in crystalline DPA were first reported in the 1970s, with three peaks of fluorescence intensity observed when a magnetic field of 0.5–2.5 T was applied; however, the origin of these peaks has not yet been clarified. , Our group − and others − have reported that in singlet fission materials, dips in the magnetic field dependence of fluorescence arise because of efficient spin-state mixing in the avoided level crossing region (the region where the energies of the two spin states are closest) in exchange-coupled triplet pairs. In our previous reports, − we used term “level crossing”; however, in strict temrs, this should have been “avoided level crossing” because the energy levels of the two spin states avoid crossing in the presence of a spin-state mixing term.…”