# Simultaneous delayed fluorescence and phosphorescence in organic luminescent material employing multiple excited states

## TL;DR

This paper explores a new organic material that emits light in three ways at room temperature, offering insights for better light-emitting materials.

## Contribution

The study introduces a model emitter with three emission components enabled by a second triplet state, T2.

## Key findings

- The material shows prompt fluorescence, delayed fluorescence, and phosphorescence with distinct time scales.
- A second triplet state facilitates simultaneous emission processes in the material.
- Tuning excited state energies allows for efficient phosphorescence with over 30% quantum yield.

## Abstract

Triplet dynamics play a key role in room temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF). In this work, we report a model emitter with three emission components: prompt fluorescence (PF) in nanoseconds, delayed fluorescence in microseconds, and RTP in milliseconds, with the emission spectrum ranging from ultraviolet to deep blue. We experimentally and theoretically verify that a second triplet excited state, T2, below the singlet state S1 is involved in facilitating simultaneous PF, TADF, and RTP in the model emitter. The reverse intersystem crossing (rISC) from T2 to S1 contributes to the TADF, while the radiative transition from T1 to the ground state is the origin of the long-lived RTP. By transferring the energy of multiple excited states to a series of conventional fluorescence emitters, a multi-color emissive system covering the entire visible wavelength range has been realized, with the photoluminescence decay ranging from 10−9 s to 10−1 s. By slightly tuning the energy difference between these excited states in the model molecule, a highly efficient organic luminescent material with only PF and RTP emission has been obtained with an RTP quantum yield above 30%. This work provides insights into the key role of higher-lying triplet states in the development of efficient TADF and RTP materials.