Persistent room temperature phosphorescence (RTP) from pure organic luminogens can be rationally realized based on the crystallization-induced phosphorescence phenomenon and severe crystallization. A perfect crystal with dense molecular packing and effective inter-molecular interactions isolates the triplet excitons from quenching sites and significantly blocks the high-energy vibrational dissipation, thus yielding long-lasting RTP.

Intrinsic emission from nonconjugated polymers has attracted considerable attention owing to its fundamental importance and intensive applications in diverse fields. The emission mechanism, however, is still in debate. Herein, nonconjugated polyacrylonitrile (PAN) molecules are found to be virtually nonluminescent in dilute solutions, while being highly emissive when concentrated or aggregated as nanosuspensions, solid powders, and films, exhibiting distinct aggregation-induced emission (AIE) characteristics. Moreover, triplet emissions of delayed fluorescence and room temperature phosphorescence are detected from the solid powders. Such unique emission of nonconjugated PAN is ascribed to the formation of cyano clusters, which act as the exact chromophores. In these clusters, through space electronic interactions, namely overlap of π and lone pair (n) electrons among cyano groups extend the conjugation and meanwhile rigidify the molecular conformations, thus offering remarkable emission upon irradiation. The AIE phenomenon can also be well rationalized by the formation of cyano clusters together with conformation rigidification. And the triplet emissions shall be originated from the n-π* transition owing to the presence of lone pairs. It is believed that such clustering-triggered emission mechanism is instructive for further development of unorthodox luminogens.

Crystallization-induced dual emission (fluorescence and phosphorescence) is observed in a group of pure organic aromatic acids and esters.

Efficient room temperature phosphorescence is observed in natural compounds and polymers such as starch, cellulose, bovine serum albumin (BSA), and some other carbohydrates. Whereas being practically nonluminescent in solutions and TLC plates, they emit bright phosphorescence in the crystalline states with lifetime up to microseconds, exhibiting crystallization-induced phosphorescence (CIP) characteristics. The CIP of these natural products without any conventional chromophores offers a new platform for the exploration of conceptually novel luminogens. room temperature phosphorescence, natural products, cellulose, starch, bovine serum albumin

Emissive electron donor–acceptor (D–A) conjugates have a wide variety of applications in biophotonics, two-photon absorption materials, organic lasers, long wavelength emitters, and so forth. However, it is still a challenge to synthesize high solid-state efficiency D–A structured emitters due to the notorious aggregation-caused quenching (ACQ) effect. Though some D–A systems are reported to show aggregation-induced emission (AIE) behaviors, most are only selectively AIE-active in highly polar solvents, showing decreased solid-sate emission efficiencies compared to those in nonpolar solvents. Here we report the triphenylamine (TPA) and 2,3,3-triphenylacrylonitrile (TPAN) based D–A architectures, namely, TPA3TPAN and DTPA4TPAN. Decoration of arylamines with TPAN changes their emission behaviors from ACQ to AIE, making resulting TPA3TPAN and DTPA4TPAN nonluminescent in common solvents but highly emissive when aggregated as nanoparticles, solid powders, and thin films owing to their highly twisted configurations. Both compounds also display a bathochromic effect due to their intramolecular charge transfer (ICT) attribute. Combined ICT and AIE features render TPA3TPAN and DTPA4TPAN intense solid yellow emitters with quantum efficiencies of 33.2% and 38.2%, respectively. They are also thermally and morphologically stable, with decomposition and glass transition temperatures (T d/T g) being 365/127 and 377/141 °C, respectively. Multilayer electroluminescence (EL) devices are constructed, which emit yellow EL with maximum luminance, current, power, and external quantum efficiencies up to 3101 cd/m2, 6.16 cd/A, 2.64 lm/W, and 2.18%, respectively. These results indicate that it is promising to fabricate high efficiency AIE-ICT luminogens with tunable emissions through rational combination and modulation of propeller-like donors and/or acceptors, thus paving the way for their biophotonic and optoelectronic applications.