Solid-State, Near-Infrared to Visible Photon Upconversion via Triplet–Triplet Annihilation of a Binary System Fabricated by Solution Casting

Abstract

Herein, triplet–triplet annihilation upconversion (TTA-UC) from near-infrared (NIR, 785 nm) to visible (yellow, centered at 570 nm) regions has been demonstrated in the binary solid of condensed chromophores. Microparticles of the binary solid comprising rubrene as a matrix (emitter) and π-extended Pd-porphyrin as a dopant (sensitizer) in a mole ratio of 1000:1 were obtained by solution casting. Excitation intensity dependence and quantum yield (QY) of the upconverted emission were characterized for individual particles under a microscope and revealed a low threshold intensity (∼100 mW/cm2) as compared to the solution and moderate UC-QY (∼0.5%) in the NIR range. The factors contributing to the UC-QY were investigated by time-resolved and steady-state spectroscopies. It was found that the intersystem crossing of the sensitizer, triplet energy transfer, and TTA occurred efficiently in the binary solid, and the fluorescence QY of the emitter governed the UC-QY.

Triplet–triplet annihilation based near infrared to visible molecular photon upconversion

“…29). 43 Interestingly, the film was formed after simple drying of the THF solution of chromophores. Although, 100% sensitizer to annihilator TET, was reported, UC quantum yield was recorded low due to singlet fission promoted fluorescence quenching of rubrene and back energy transfer to the sensitizer in the solid state.…”

“…Although, 100% sensitizer to annihilator TET, was reported, UC quantum yield was recorded low due to singlet fission promoted fluorescence quenching of rubrene and back energy transfer to the sensitizer in the solid state. 43 To address the issue of singlet fission (SF), induced fluorescence quenching of rubrene, Kazlauskas's research group synthesized t-butyl substituted rubrene (t-butyl-rubrene) as shown in Fig. 30.…”

“…The scale bars are 50 mm, l ex = 785 nm. (c) UC emission spectrum of a single microparticle under aerated conditions at the intensity of 7 W cm À2 at the sample position (black solid curve filled with yellow, with a 785 nm notch filter) and normal fluorescence from rubrene neat solid excited at 532 nm (red dotted) 43. Reproduced with permission from ref 43…”

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

“…These results clearly show that IUC is governed by concentration of the triplet species with the 3 DPA* moiety, not by the prepared concentration of the ground state DPA. Employment of Kamada fitting function shown in eqn 5, [35][36][37] !" = #$ $1 +…”

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

“…I TH / mW cm -2 1 2 mM) containing PtOEP (0.05 mM). Kamada fitting function (eqn 5) [35][36][37] was employed.…”