White light emission from a single organic molecule with dual phosphorescence at room temperature

Zikai He,Huili Ma,Jacky W Y Lam,Weijun Zhao,Guodong Liang,Ben Zhong Tang,Zhigang Shuai,Qian Peng

doi:10.1038/s41467-017-00362-5

Abstract

The development of single molecule white light emitters is extremely challenging for pure phosphorescent metal-free system at room temperature. Here we report a single pure organic phosphor, namely 4-chlorobenzoyldibenzothiophene, emitting white room temperature phosphorescence with Commission Internationale de l’Éclair-age coordinates of (0.33, 0.35). Experimental and theoretical investigations reveal that the white light emission is emerged from dual phosphorescence, which emit from the first and second excited triplet states. We also demonstrate the validity of the strategy to achieve metal-free pure phosphorescent single molecule white light emitters by intrasystem mixing dual room temperature phosphorescence arising from the low- and high-lying triplet states.

Highlights

The development of single molecule white light emitters is extremely challenging for pure phosphorescent metal-free system at room temperature
According to the origin of these mixed color bands, they can be divided into three classes including (1) pure fluorescent single molecule white light emitters (SMWLEs) whose emission originates only from singlet excitons, generated in such as monomer/excimer complex[7, 8], excited-state intramolecular proton transfer systems[9, 10], prompt/delayed dual fluorescence[11, 12], and conformation-dependent emission systems[13], etc., (2) hybrid fluorescent/phosphorescent SMWLEs stem from radiative decay of both singlet and triplet excitons[14], and (3) pure phosphorescent SMWLEs that emit only from triplet excitons[3, 15, 16]
The search for pure organic phosphorescent SMWLE remains at the early stage and a challenging research area because pure organic phosphors are scarce and triplet excitons are quenched

Summary

Introduction

The development of single molecule white light emitters is extremely challenging for pure phosphorescent metal-free system at room temperature. The white light emission comes from the mixing of two RTP bands with different wavelengths and lifetimes, which originate from two electronic excited triplet states with different excitation energies and transition orbital features.

Results

Conclusion