A diphenylamino-substituted quinacridone derivative: red fluorescence based on intramolecular charge-transfer transition

Abstract

Quinacridone (QA) derivatives are long-established emitting materials for use in organic light-emitting diodes (OLEDs). However, their role in OLEDs has generally been limited to green/yellow-green emitters. Herein, we report a QA-based red emissive OLED material, NPh₂-QA, constructed through the introduction of two strongly electron-donating diphenylamino groups onto the QA core of green emissive N,N′-dioctyl-substituted QA. The green-to-red change is due to an alteration of the electronic transition responsible for the population of the S₁ state, i.e. from a QA-centered π → π* transition to an intramolecular charge-transfer transition. NPh₂-QA can be easily synthesized and it exhibits efficient red emission, with a fluorescence quantum yield of 0.56 in toluene, as well as good thermal stability, with a decomposition temperature of 444 °C. By adopting NPh₂-QA as a dopant emitter, for the first time, an efficient and bright QA-based red OLED has been realized.