Suppression of Charge Transfer States in Aryl-Substituted 9,9′-Bianthryl Derivatives

Abstract

Recently, various 9,9′-bianthryl (BA) compounds demonstrated promising performances in blue OLEDs as charge transport and emissive materials. However, the emission of 9,9′-bianthryl is of dual character where the highly emissive excitonic locally excited state (LE) is accompanied by the internal charge transfer process (ICT), which induces a significant reduction of the radiative decay rate as well as low emission quantum yield. In this work, we address the possibility to control the ICT process in 9,9′-bianthryl compounds as well as the proportion of LE state emission by introducing conjugated aromatic substitutions parallel and perpendicular to the short axis of the molecular backbone. By employing time-resolved fluorescence and ultrafast pump-probe spectroscopy techniques, we analyze the impact of aromatic substituents on solvation reactions. Results on the initial charge transfer (CT) state formation time and selective excitation in the vicinity of the lowest absorption band reveal evidence of an enha...