Achieving Persistent, Efficient, and Robust Room‐Temperature Phosphorescence from Pure Organics for Versatile Applications

Abstract

Persistent room-temperature phosphorescence (p-RTP) has drawn extensive attention due to its unique photophysical processes and promising applications in organic light-emitting diodes (OLEDs), [1] biological areas, [2] chemical sensors, [3] optics, [4] and anticounterfeiting technology. [5] Currently, p-RTP systems, however, are normally restricted to inorganic compounds. [6] As promising alternatives, pure organic p-RTP luminogens take advantages of low cost, wide variety, environmental friendliness, good biocompatibility, appreciable stability, and good processability, [7] allowing a wide range of optoelectronic and biological applications. [2] The triplet excitons of organic luminogens, however, are prone to nonradiative relaxations through vibrational stretching and external quenching (i.e., O 2 ), making it difficult to achieve efficient p-RTP. [8] To overcome such barriers, generally, two attempts are endeavored: one is to boost the spin-orbital coupling (SOC) and subsequently promote the intersystem crossing (ISC) processes through incorporation of heavy atoms, [9] heteroatoms, [10] or aromatic carbonyls; [11] the other is to stabilize the triplet excitons in a rigid environment by suppressing nonradiative decay pathways to activate the RTP emission, [12] such as crystal formation, [13] embedding into rigid hosts, [14] polymer assistance, [15] and metal-organic framework (MOF) coordination. [16] Despite exciting advancements have been made in the past few years, fabrication of efficient and robust p-RTP still remains a challenge. First, the p-RTP efficiency (Φ p ) of reported phosphors with the lifetime (〈τ〉 p ) of several hundred milliseconds are generally below 5%, [11a,13a] and moreover, robust p-RTP at complex and changing environments is rare, even though it is essential for diverse applications in data recording, encryption, anticounterfeiting, and bioimaging. [17] For example, when applied in molecular imaging, owing to their long-lasting nature, p-RTP materials can eliminate the need for light irradiation and circumvent the troublesome interference of nanosecond tissue autofluorescence, thus permitting much clearer and more reliable bioimaging with high signal-to-noise ratios. Current methodologies toward biomedical applications, however, mainly adopt nanocrystallization or top-down nanoparticle Pure organic persistent room-temperature phosphorescence (p-RTP) under ambient conditions is attractive but challenging due to the slow intersystem crossing process and susceptibility of triplet excitons. Fabrication of pure organic RTP luminogens with simultaneously high efficiency and ultralong lifetime still remains a daunting job, owing to their conflicting requirements for the T 1 nature of (n,π*) and (π,π*) characteristics, respectively. Herein, a group of amide-based derivatives with efficient p-RTP is developed through the incorporation of spin-orbital-coupling-promoting groups of carbonyl and aromatic π units, giving impressive p-RTP with lifetime and efficiency of up to 710.6 ms and 10.2%,...

Manipulating the Ultralong Organic Phosphorescence of Small Molecular Crystals

“…Aromatic carbonyl group : Owing to weak SOC and intense nonradiative transitions, it is a formidable challenge to obtain UOP with high efficiency in purely organic materials . As proposed, effective SOC occurs when the orbitals effectively overlap, determined by the orbital angular momentum operator, such as transitions from 1 (n, π*) or 1 (π, π*) to 3 (π, π*) or 3 (n, π*) ( Figure ).…”

Quinoline-containing diarylethenes: bridging between turn-on fluorescence, RGB switching and room temperature phosphorescence

“…Host-guest interactions, molecular assembly and polymerization have been utilized to achieve this goal, [31][32][33][34][35][36][37][38] however small molecules that show phosphorescence in the amorphous state have rarely been reported in the literature and most are highly halogenated. 8,[39][40][41][42] To tackle these challenges, we decided to employ DAEs as building blocks for RTP materials. Not only does this provide new scope for molecular design of RTP materials, but it also enables the study of structureproperty relationships between two well-known photochemical and photophysical phenomena: photochromism and RTP.…”

All‐Organic, Temporally Pure White Afterglow in Amorphous Films Using Complementary Blue and Greenish‐Yellow Ultralong Room Temperature Phosphors

“…This fascinating emission phenomenon has great potential in unique applications, such as in night-vision lighting, signage, or displays as a sustainable energy source, in bioimaging to eliminate autofluorescence from cell components and in security protection. [1][2][3][4][5][6][7][8] However, until recently, the afterglow emission could be realized only with rare-earth element doped inorganic phosphors which suffers from heavy-metal toxicity and poor processability. [9] In this respect, the recent success with organic phosphors exhibiting ultralong room temperature phosphorescence (URTP) provides a promising alternative with solution singlet-triplet gap and hence would be a daunting task.…”