Bifunctional near-ultraviolet emitting materials based on hybridized local and charge-transfer (HLCT) excited states for efficient electro-fluorescence and phosphorescent OLEDs

Abstract

Near-ultraviolet (NUV) organic light-emitting diodes (OLEDs) have attracted considerable attention due to their practical applications in various cutting-edge fields. However, the design and synthesis of novel molecules that combine high efficiency in non-doped NUV emission with excellent host functionality remains a significant challenge. In this work, a novel structurally simple donor–acceptor (D–A) type NUV emitter MePBODCz with hybridized local and charge transfer (HLCT) characteristics was designed and synthesized. Single-crystal analysis reveals a highly ordered molecular arrangement with regular acceptor arrays that form electron transport channels, resulting in balanced bipolar carrier mobility. Additionally, the twisted molecular conformation gives rise to a high triplet energy level (T₁ = 2.63 eV). As a result, the non-doped NUV OLED based on MePBODCz achieves an electroluminescence peak at 393 nm with a low Commission Internationale de l'Eclairage (CIE) y coordinate of 0.038. Moreover, MePBODCz as a host achieves EQE_max values of 21.52%, 23.67%, and 7.38% for green, yellow, and red phosphorescent OLEDs, respectively. In this study, we present a bifunctional HLCT material that combines efficient non-doped near-ultraviolet electroluminescence with phosphorescent host functionality.