Boosting the efficiency of organic persistent room-temperature phosphorescence by intramolecular triplet-triplet energy transfer

Weijun Zhao,Wenbin Huang,Nan Jiang,Ben Zhong Tang,Tsz Shing Cheung,Jacky W Y Lam,Zikai He,Xuepeng Zhang

doi:10.1038/s41467-019-09561-8

Abstract

Persistent luminescence is a fascinating phenomenon with exceptional applications. However, the development of organic materials capable of persistent luminescence, such as organic persistent room-temperature phosphorescence, lags behind for their normally low efficiency. Moreover, enhancing the phosphorescence efficiency of organic luminophores often results in short lifetime, which sets an irreconcilable obstacle. Here we report a strategy to boost the efficiency of phosphorescence by intramolecular triplet-triplet energy transfer. Incorpotation of (bromo)dibenzofuran or (bromo)dibenzothiophene to carbazole has boosted the intersystem crossing and provided an intramolecular triplet-state bridge to offer a near quantitative exothermic triplet–triplet energy transfer to repopulate the lowest triplet-state of carbazole. All these factors work together to contribute the efficient phosphorescence. The generation and transfer of triplet excitons within a single molecule is revealed by low-temperature spectra, energy level and lifetime investigations. The strategy developed here will enable the development of efficient phosphorescent materials for potential high-tech applications.

Highlights

Persistent luminescence is a fascinating phenomenon with exceptional applications
The heavy atom effect, El-Sayed’s rule and energy gap principle simultaneously contribute to high kP and knr and efficient reverse intersystem crossing (ISC) process to result in short lifetime
For proof-ofconcept, carbazole was selected as the photo-absorption chromophore and the luminophore where the lowest singlet (S1) and triplet (T1) states are located with bromodibenzofuran as the ISC facilitator

Summary

Introduction

Persistent luminescence is a fascinating phenomenon with exceptional applications. the development of organic materials capable of persistent luminescence, such as organic persistent room-temperature phosphorescence, lags behind for their normally low efficiency. The efficient TTET process occurs when the two exchanging parts locate at a short distance (especially within one molecule with a distance of

Methods

Results

Conclusion