Ambient White-Light Afterglow Emission Based on Triplet-to-Singlet Förster Resonance Energy Transfer

Abstract

Compared with fluorescent materials, metal-free organic environmental afterglow materials, with larger Stokes shifts, longer lifetimes, higher S/N ratios, and sensitivities, present potential in new applications. However, achieving air stability and long lifetime organic afterglow systems with tunable emission color still remains a challenge. Herein, we have designed and synthesized luminescent copolymers exhibiting afterglow emission with tunability including white-light afterglow with considerable quantum yield [Commission Internationale de l'Eclairage (CIE) coordinates (0.32, 0.33), Φ P = 11%] in the amorphous state through the rarely reported triplet-to-singlet Förster resonance energy transfer (TS-FET). Also, they can emit different colors under UV light, including white-light [CIE coordinates (0.31, 0.33), Φ Pl = 27%]. This strategy was achieved by copolymerizing two simple-structured single-benzene-based compounds with acrylamide (AM) in different ratios. In addition, these materials can also be employed as a safety ink for paper paving the way for long lifetime luminescent material applications.

Relief of excited-state antiaromaticity enables the smallest red emitter

“…1a ) to bring the excitation and emission energy windows to the visible wavelength range. Such single benzene fluorophores (SBFs) have recently gained significant attention due to their unique photophysical properties of strong solid-state emission with large Stokes shifts (3000–8000 cm −1 ) 29 – 35 . While the electronic origin of the large Stokes shifts of SBFs has often been ascribed to the HOMO–LUMO asymmetry implying ICT-type transitions 29 – 32 , it is less clear how the small benzene core can promote significant charge separation.…”

Aromatic Electrophilic Directing for Fluorescence and Room-Temperature Phosphorescence Modulation

“…Organic luminescent molecules are ubiquitously used in laboratory research, − product development, , clinical tests, and energy efficient illumination devices. , As of today, a central challenge in application remains, where the prediction between spectroscopic properties and chemical structures is usually subpar . Furthermore, recent emerging interests in RTP molecules may add a new layer of complexity in the systematic modulation of luminescent materials, given that the triplet emitting (phosphorescent) state could be drastically different in origin compared to the singlet (fluorescent) counterpart. − For example, in a given intramolecular charge-transfer (ICT) system, the lowest singlet excited state typically consists of singly occupied molecular orbitals (SOMOs) delocalized on both donor and acceptor moieties, respectively, thus forming an 1 ICT emitting state, − while the lowest triplet state SOMOs are mostly located on one of the two moieties due to a much larger exchange energy between localized 1 π–π* and 3 π–π* states compared that of the 1 ICT/ 3 ICT states, according to the molecular orbital (MO) theory. As can be seen, molecular luminescence modulation is essentially the manipulation of frontier orbitals that become SOMOs in the excited state. − …”

Triplet-to-singlet exciton transfer in hyperfluorescent OLED materials

“…21 More recently, TTS transfers have also been engineered to develop systems that present long-persistent luminescence. 22,23 In a further example, a donor–acceptor system that displayed both singlet and triplet FRET has also been demonstrated, showing that cooperation between these two exciton transfer channels can be possible. 24…”

“…21 More recently, TTS transfers have also been engineered to develop systems that present long-persistent luminescence. 22,23 In a further example, a donor-acceptor system that displayed both singlet and triplet FRET has also been demonstrated, showing that cooperation between these two exciton transfer channels can be possible. 24 Fundamentally, triplet-to-singlet FRET is only possible if the triplet state in question is not pure, that is, if it mixes with singlet states 25 through spin-orbit coupling.…”