NOVEL HOST MATERIALS FOR STABLE BLUE THERMALLY ACTIVATED DELAYED FLUORESCENCE OLEDS

Organic light-emitting diode (OLED) technology has been established in the display sector due to its ease of fabrication and high energy efficiency. Current OLED displays employ low-efficiency fluorescent or expensive heavy metal-containing phosphorescent emitters. In recent years, thermally activated delayed fluorescence (TADF) materials have emerged as a promising alternative to currently utilized purely organic emitters, achieving 100% internal quantum efficiency [1]. However, developing stable and efficient blue OLEDs presents challenges due to high-energy exciton transitions, leading to increased degradation pathways. Host materials are vital in optimizing device performance by facilitating efficient energy transfer and suppressing undesirable intermolecular interactions. Therefore, engineering a proper host material for the emissive layer of blue TADF OLEDs is an essential step for the advancement of this technology.

In this work, we introduce and investigate three novel carbazole-based OLED host materials (Fig. 1). New molecules were designed to avoid relatively weak C-N bonds, which are known for exhibiting one of the lowest bond dissociation energies in a typical structure [2,3]. Additionally, cyano substituents were added to enhance electron transfer character. Photophysical and electrochemical studies of novel hosts, as well as the performance of blue OLED devices, are presented. Novel hosts exhibit significantly high singlet and triplet excited state energies and ambipolar charge transfer properties, enabling their successful utilization in OLED fabrication.