Highly Efficient Room‐Temperature Phosphorescence Promoted via Intramolecular‐Space Heavy‐Atom Effect

Abstract

Purely organic room‐temperature phosphorescence (RTP) materials have attracted increasing attention due to their unique photophysical properties and widespread optoelectrical applications, but the pursuit of high quantum yield is still a continual struggle for RTP emission under ambient conditions. Here, a series of novel RTP molecules (26CIM, 246CIM, 24CIM, and 25CIM) are developed on the basis of indole luminophore, in which a carbonyl group bridges indole and chloro‐substituted phenyl group. The structural isomerism is systematically regulated toward enhancing the intramolecular‐space heavy‐atom effect, thus promoting the spin–orbit coupling and intersystem crossing for high RTP efficiency. While rationally modulating the intramolecular‐space heavy‐atom effect, the phosphorescence efficiency is dramatically increased by 16‐fold from 2.9% (24CIM) to 48.9% (26CIM). Basically, the fully occupied chlorine atoms at the positions 2 and 6 can effectively favor the stronger intramolecular H…Cl effect, and the tight lock coupling with anti‐parallel stacking in 26CIM further boosts RTP emission synergistically. The experimental findings along with deeper theoretical insights elucidate the structure–performance relationship clearly, and further suggest a general strategy for rationally constructing high‐efficiency RTP materials.

Carbon Dot/Al2O3 Nanocomposites with an Enhanced Lifetime, Phosphorescence Quantum Efficiency, and Stability for Anticounterfeiting Applications

“…RTP materials enable visual observation of long-lived emissions from seconds to several hours. 5,6 However, the present RTP materials are mainly traditional inorganic compounds, 7 organic compounds, 8,9 or organometallic complexes, 10,11 which more or less suffer from complicated preparation, poor processability, high cost, and heavy metal toxicity. Carbon dots (CDs), as a class of metalfree luminescent nanomaterials, exhibit some excellent characteristics, such as stable chemical properties, 12 low toxicity, 13,14 and tunable photoluminescence.…”

“…Room-temperature phosphorescence (RTP) materials have received tremendous interest in the past several decades, owing to their many promising applications in optoelectronic devices, information encryption/anticounterfeiting, bioimaging, sensing, and so on. RTP materials enable visual observation of long-lived emissions from seconds to several hours. , However, the present RTP materials are mainly traditional inorganic compounds, organic compounds, , or organometallic complexes, , which more or less suffer from complicated preparation, poor processability, high cost, and heavy metal toxicity. Carbon dots (CDs), as a class of metal-free luminescent nanomaterials, exhibit some excellent characteristics, such as stable chemical properties, low toxicity, , and tunable photoluminescence .…”

“…The introduction of heavy atoms and heteroatoms (N, O, S, P, and so on) has been proven to efficiently facilitate the ISC of CDs. Great efforts have been devoted to stabilizing the triplet excited states of CDs through the constriction of CDs in organic or inorganic matrices, ,− including silica gels, zeolites, poly­(vinyl alcohol), polyurethane, and boric acid, In many cases, hydrogen bonds, covalent bonds, or structural confinement were utilized to stabilize the triplets of CDs. For example, Liu et al proposed a thermally activated delayed fluorescence material with a relatively long lifetime of 350 ms by the in situ confinement of CDs in zeolitic matrices during hydrothermal/solvothermal crystallization .…”

Two new Cd-based metal–organic frameworks for afterglow detection of Fe3+ and NH3

“…Typically, the introduction of heavy atoms and/or heteroatoms effectively enhances spin–orbit coupling (SOC) and promotes intersystem crossing (ISC), consequently increasing the production of triplet excitons. 21,22 Through structural hardening, clustering, cross-linking, and other techniques, a more rigid environment can be created to restrict molecular vibrations and stabilize triplet excitons. 23–25 These measures effectively enhance the afterglow performance of the material.…”

Recent advances in the design of afterglow materials: mechanisms, structural regulation strategies and applications

“…), heavy atoms, etc. 65–68 Matrix protection is a common method to suppress NRTs and protect T 1 from being quenched by the external environment, such as oxygen and humidity. 7,69–71 Based on the above two strategies, many high-performance organic molecule-based RTP materials have been reported.…”