Boosting the Quantum Efficiency of Ultralong Organic Phosphorescence up to 52 % via Intramolecular Halogen Bonding

Abstract

Ultralong organic phosphorescence (UOP) has attracted increasing attention due to its potential applications in optoelectronics, bioelectronics, and security protection. However, achieving UOP with high quantum efficiency (QE) over 20 % is still full of challenges due to intersystem crossing (ISC) and fast non‐radiative transitions in organic molecules. Here, we present a novel strategy to enhance the QE of UOP materials by modulating intramolecular halogen bonding via structural isomerism. The QE of CzS2Br reaches up to 52.10 %, which is the highest afterglow efficiency reported so far. The crucial reason for the extraordinary QE is intramolecular halogen bonding, which can not only effectively enhance ISC by promoting spin–orbit coupling, but also greatly confine motions of excited molecules to restrict non‐radiative pathways. This work provides a reasonable strategy to develop highly efficient UOP materials for practical applications.

Bridging the Void: Halogen Bonding and Aromatic Interactions to Program Luminescence and Electronic Properties of π-Conjugated Materials in the Solid State

“…In a similar design, Yang and co-workers demonstrated an intramolecular XB phosphorescence enhancement in a series of carbazolesubstituted bromodiphenylsulfone regioisomers with variable Br substitution (Figure 2b). 54 Although all compounds displayed yellow phosphorescence with long lifetimes (up to 180 ms at 77 K), phosphorescence QE varied from 6% up to a remarkably high 52% as a function of positional isomerism, where large gains in QE were attributed to intramolecular XB between sulfones and bromine atoms inhibiting nonradiative decay of ortho isomers. In 2017, Xue and co-workers described how intermolecular π-type XB between bromine substituents and carbazole arenes in a set of bromophenoxy-carbazoles also enhanced phosphorescence, which Fateminia et al and other researchers elaborated the same year to prepare redphosphorescent nanocrystals for imaging breast cancer cells.…”

Progress and Perspective of Solid-State Organic Fluorophores for Biomedical Applications

“…Initially, AIE probes were mainly used to detect some primary biological species such as metal ions and small molecules. , However, owing to the advances in fluorescent imaging techniques, they have been further used for cell imaging . Recently, owing to the extensive fabrication of NIR-I (650–900 nm) and NIR-II (1000–1700 nm) AIE-based SSOFs, , several SSOF-based organic reagents have been reported for in vivo imaging, sensing, and imaging-guided therapy. , Additionally, inspired by the increasing number of SSOFs, solid-state luminescent materials that exhibit strong room temperature phosphorescence and thermally activated delayed fluorescence have been developed. − …”

Multistage Stimulus‐Responsive Room Temperature Phosphorescence Based on Host–Guest Doping Systems

“…[4] In recent years, the preparation and application of pure organic RTP materials have made great progress, especially the single-component system. [5] Though accessing to and from the triplet state is a forbidden process for organic luminogens and once thought to be too inefficient to be realized at room temperature, recent advances have vastly increased ISC efficiency by enhancing spin-orbit coupling (SOC) with the use of heteroatoms, [6] heavy atoms, [7] and multimers. [8] However, most of them rely on special crystal structures [9] with certain maintaining difficulties in cultivation and practical applications, which greatly limits actual application scenarios.…”