Theoretical Study on Thermally Activated Delayed Fluorescence Emitters in White Organic Light-Emitting Diodes: Emission Mechanism and Molecular Design

Employing dual-emission thermally activated delayed fluorescence (TADF) molecules to fabricate single emitters in highly efficient white organic light-emitting diodes (WOLEDs) is still a challenge. In this work, a systematic study on the luminescence mechanism of three TADF molecules with blue-orange dual emission is performed. It is found that the quasi-axial (ax) conformer is responsible for blue normal fluorescence (NF), while the quasi-equatorial (eq) conformer is responsible for orange TADF. In addition, the upconversion for the TADF molecules happens from the first triplet state (T