Elongation of Triplet Lifetime Caused by Intramolecular Energy Hopping in Diphenylanthracene Dyads Oriented to Undergo Efficient Triplet–Triplet Annihilation Upconversion

Abstract

Triplet-triplet annihilation (TTA)-assisted photon upconversion (TTA-UC) in three dyads (DPA-Cn-DPA), comprised of two diphenylanthracene (DPA) moieties connected by nonconjugated C1, C2, and C3 linkages (Cn), has been investigated. The performance of these dyads as energy acceptors in the presence of the energy donor platinum octaethylporphyrin are characterized by longer triplet lifetimes (tT) and different TTA rate constants than those of the parent DPA. The larger tT of the linked systems, caused by "Intramolecular Energy Hopping" in the triplet dyad 3 DPA*-Cn-DPA, results in a low threshold intensity, a key characteristic of efficient TTA-UC.

High‐Performance Deep‐Blue OLEDs Harnessing Triplet–Triplet Annihilation Under Low Dopant Concentration

“…This molecular conformation corresponds to a distance between the two phenyl groups around 8.3 Å and a distance between the C9 and C9′ position of the DPA groups is 9.9 and 10.2 Å for PAPF and PAPE ( Figure S2, Supporting Information ) , respectively. As reported by Ikeda et al, [16a] the molecules exhibiting different emission behaviors from the DPA chromophore such as reducing threshold intensity and increasing TTA rate with the distance of two DPA groups ranging from 8.3 to 12.3 Å. Note that TTA requiring the Dexter type energy transfer, which is efficient when the distance between the two triplet species 3 DPA* is smaller than 10 Å.…”

“…[ 15 ] Furthermore, Ikeda et al clearly showed that the critical factor ( I th) for judging the efficiency of TTA‐UC was lower for the σ‐spacer linked DPA dimer with a sufficiently close interchromophore distance as compared to that of the DPA monomer and concluded that intra‐TTA was operative. [ 16 ] Fundamentally, the distance between annihilators is not the only factor that affects intra‐TTA behavior. The relative configuration between chromophores is of great importance as well.…”

Efficient Triplet–Triplet Annihilation Upconversion in Solution and Hydrogel Enabled by an S-T Absorption Os(II) Complex Dyad with an Elongated Triplet Lifetime

“…A triplet energy donor (photosensitizer) and energy acceptor (triplet annihilator/emitter) are key components in typical TTA-UC systems. , Owing to highly efficient intersystem crossing by strong spin-orbit coupling (SOC), photosensitizers typically employ transition metals (Pt, Pd, Ru, and Ir) or heavy atoms (I and Br) to populate triplet excitons. − In recent years, some pure organic photosensitizers have also been developed for TTA-UC including thermally activated delayed fluorescence materials, fullerene (C 60 and C 70 ) derivatives, and spin-orbit charge transfer intersystem crossing molecules. − Nonetheless, the absorption bands of most photosensitizers are mainly distributed in the visible region, and TTA-UC pairs that are able to convert light from deep-red (>650 nm)/near-infrared (NIR) to visible region remain scarce (Table S1). …”

Triplet–Triplet Annihilation Photopolymerization for High-Resolution 3D Printing

“…The well-studied system of palladium­(II) octaethylporphine (PdOEP) and 9,10-diphenylanthracene (DPA) was selected from a library of a few dozen TTA pairs as it has been shown to upconvert even in nonideal conditions such as in polymer matrices. , Palladium stabilizes the triplet state of the porphyrin molecule and increases its lifetime to 50–250 μs, which enables TTA at low light intensities. Typical DPA triplet lifetimes are long, at ∼0.1–1 ms, leading to a reasonably high probability of TTA occurring. , The photoinitiator, Irgacure 2100 (I2100), was selected because its absorbance overlaps with the emission of DPA and because its liquid nature facilitates homogeneous mixing. Ethoxylated trimethylopropane triacrylate (ETPTA) was selected as the monomer to reach gelation quickly during 3D printing.…”