Recent Advances in Materials with Room‐Temperature Phosphorescence: Photophysics for Triplet Exciton Stabilization

Abstract

Room‐temperature phosphorescence (RTP), which has a much longer emission lifetime than fluorescence, often enables unique material characteristics and fabrication of state‐of‐the‐art optoelectronic devices that cannot be realized using conventional fluorescent materials. The triplet exciton characteristics related to the appearance of efficient RTP also often provide intrinsic intra‐ and inter‐molecular physical information about the materials. This article reviews recently reported aromatic materials that present RTP characteristics. Various aromatic materials with RTP characteristics are classified in terms of their radiative rates and radiationless rates from the lowest triplet excited state (T1) while taking the presence and absence of heavy atoms and charge transfer characteristics at T1 into consideration. Statistical arrangements based on physical factors of RTP materials indicate that the recent appearance of RTP in various metal‐free aromatic structures is related to a large reduction in quenching caused by strong intermolecular interaction between the aromatics and the surrounding materials; additionally, intrinsic factors of the aromatics including the radiative rate and the nonradiative rate caused by intramolecular vibration are still not well controlled. Intrinsic control of these rates is important for overall control of the RTP yield and lifetime for potential material applications. Finally, recent applications using the RTP characteristics are highlighted.

Room‐Temperature Phosphorescence in Pure Organic Materials: Halogen Bonding Switching Effects

“…The ambient RTP efficiency of S‐2I/I−Ph−NH 2 hgDCs is up to 15.96 % (Table ). As known to us, despite the fact that extensive progress has been achieved in green or yellow‐green emissive ORTP materials, red‐light emitters still remain among the most wanted for the use in full‐color displays and biological imaging without the interference of short‐wavelength autofluorescence . However, very few purely organic materials exhibit efficient red RTP under ambient conditions and 15.96 % is a record‐high value in red ORTP crystals with emission maximum reaching 611 nm …”

Extrinsic Heavy Metal Atom Effect on the Solid‐State Room Temperature Phosphorescence of Cyclic Triimidazole

“…Long lived room temperature phosphorescence (RTP) from solid‐state materials represents a relatively new issue in the development of AIE functional compounds with applications in data security technologies, temperature monitoring, sensing and bio‐imaging . The presence of a solid state afterglow emission can be found in inorganic phosphors but is extremely rare in organometallic compounds due to the small lifetimes of their triplet excitons.…”

Polymorphic Pure Organic Luminogens with Through‐Space Conjugation and Persistent Room‐Temperature Phosphorescence

“…Meanwhile, when compared to their inorganic or organometallic counterparts, pure organic RTP luminogens benefit from their good biocompatibility, appreciable processability, wide variety, and so on . Despite dramatic advances having been achieved in the development of such p ‐RTP luminogens, solutions to some fundamental issues, such as a universal molecular design strategy and the effective modulation of the photophysical processes and the emission mechanism, remain in their infancy. To address these issues, it is of crucial importance to develop diverse p ‐RTP luminogens and to summarize their general underlying principles.…”