Influence of energy gap between charge-transfer and locally excited states on organic long persistence luminescence

Zesen Lin,Kai Wang,Ryota Kabe,Chihaya Adachi

doi:10.1038/s41467-019-14035-y

Abstract

Organic long-persistent luminescence (LPL) is an organic luminescence system that slowly releases stored exciton energy as light. Organic LPL materials have several advantages over inorganic LPL materials in terms of functionality, flexibility, transparency, and solution-processability. However, the molecular selection strategies for the organic LPL system still remain unclear. Here we report that the energy gap between the lowest localized triplet excited state and the lowest singlet charge-transfer excited state in the exciplex system significantly controls the LPL performance. Changes in the LPL duration and spectra properties are systematically investigated for three donor materials having a different energy gap. When the energy level of the lowest localized triplet excited state is much lower than that of the charge-transfer excited state, the system exhibits a short LPL duration and clear two distinct emission features originating from exciplex fluorescence and donor phosphorescence.

Highlights

Organic long-persistent luminescence (LPL) is an organic luminescence system that slowly releases stored exciton energy as light
The organic LPL (OLPL) systems were fabricated by the meltcasting of a mixture containing 1% of an electron donor and 99% of an electron acceptor[7]
The lack of spectral shift and thermally activated delayed fluorescence (TADF) emission in the LPL emission spectrum at 10 K confirms the contribution of TADF to the emission of the DMDTB/PPT system at room temperature. These results clearly indicate the importance of the energy level of 3LED for obtaining efficient LPL emission

Summary

Results

The OLPL systems were fabricated by the meltcasting of a mixture containing 1% of an electron donor and 99% of an electron acceptor[7]. The highest occupied molecular orbital (HOMO) levels of the donors were determined from the first redox peaks of cyclic voltammograms (Supplementary Fig. 2) and the HOMO levels of a

Intermediate state

Discussion

Methods