Amorphous Metal-Free Room-Temperature Phosphorescent Small Molecules with Multicolor Photoluminescence via a Host–Guest and Dual-Emission Strategy

Abstract

Metal-free room-temperature phosphorescence (RTP) materials offer unprecedented potentials for photoelectric and biochemical materials due to their unique advantages of long lifetime and low toxicity. However, the achievements of phosphorescence at ambient condition so far have been mainly focused on ordered crystal lattice or on embedding into rigid matrices, where the preparation process might bring out poor repeatability and limited application. In this research, a series of amorphous organic small molecular compounds were developed with efficient RTP emission through conveniently modifying phosphor moieties to β-cyclodextrin (β-CD). The hydrogen bonding between the cyclodextrin derivatives immobilizes the phosphors to suppress the nonradiative relaxation and shields phosphors from quenchers, which enables such molecules to emit efficient RTP emission with decent quantum yields. Furthermore, one such cyclodextrin derivative was utilized to construct a host-guest system incorporating a fluorescent guest molecule, exhibiting excellent RTP-fluorescence dual-emission properties and multicolor emission with a wide range from yellow to purple including white-light emission. This innovative and universal strategy opens up new research paths to construct amorphous metal-free small molecular RTP materials and to design organic white-light-emitting materials using a single supramolecular platform.

Single‐Molecular White‐Light Emitters and Their Potential WOLED Applications

“…Recently, pure organic room temperature phosphorescence (RTP) based emitters have attracted much attention as promising candidates for the white‐light emission . In general, the spin‐orbit coupling (SOC) in a pure organic material is too small to afford efficient ISC for the generation of triplet excitons.…”

“…The other is to suppress the nonradiative decay of triplet excitons. Heavy atoms (such as chlorine (Cl), bromine (Br), iodine (I) and deuterium substituents) and heteroatoms (nitrogen (N)) are commonly used to facilitate the effective ISC, which promotes the triplet emission to achieve RTP . There are two approaches to achieve the white‐light emission.…”

Enhanced Room‐Temperature Phosphorescence through Intermolecular Halogen/Hydrogen Bonding

“…Recently,T ian and co-workers reported that efficient RTP from as eries of amorphous organic small-molecule compounds were obtained by modifying different phosphors onto b-cyclodextrin (b-CD). [39] These bromine-containing phosphor molecules were initially inefficient phosphorescence emitters, althoughe fficient RTP luminescence with decent quantum yields was obtained by modifying them onto b-CD. Strong intermolecular hydrogen bonds between the cyclodextrin derivatives restricts the vibration of phosphors and eliminates selfquenching and atmosphericO 2 quenching.…”

A Simple Strategy to Construct Amorphous Metal‐Free Room Temperature Phosphorescent and Multi‐Color Materials

“…An important contribution made by Ma and Tian et al. provides a general and applicable strategy to obtain amorphous organic molecules with efficient RTP emission by simply modifying phosphors onto β‐cyclodextrin (β‐CD) . The nonradiative decay processes and oxygen quenching have been significantly suppressed by the strong intermolecular hydrogen bonding between β‐CD derivatives.…”