Recent Progress in Pure Organic Room Temperature Phosphorescence of Small Molecular Host–Guest Systems

Organic room temperature phosphorescence (RTP) materials have been used in high resolution imaging and anticounterfeiting due to their long lifetime of phosphorescence ability to avoid interference from autofluorescence and excitation light. An important factor when considering phosphorescence is the high constant of the intersystem crossing (ISC) process. It is of great importance to develop novel pure organic RTP materials via precise manipulation of the ISC process and nonradiative decay rate. Encapsulation of a luminophore in the host matrix can avoid phosphorescence quenching caused by the presence of water and oxygen, while increasing intermolecular interaction to suppress nonradiative decay. Compared with polymeric and supramolecular host matrixes, organic small molecular host matrixes can provide possible molecular orbitals to facilitate the ISC process and enhance RTP emission. Herein, recent progress made in organic RTP materials using small molecular host matrixes and their mechanisms in realizing RTP emission are summarized. The design principles as well as possible applications of pure organic RTP materials based on the host–guest system are also revealed. Finally, future prospects on pure organic RTP materials involving small molecular host–guest systems are proposed.