OLED technology has come far since the first reported successful demonstration in the late 80s by Van Slyke and Tang [1]. It has, since then, found its way into mainstream technology and remains a competitive research topic in both industry and academia [2]. Thanks to the discovery of thermally activated delayed fluorescence (TADF) [3] OLED technology has received a much needed influx of research worldwide. Today, OLED technology is evolving at a rapid pace yet development of stable, high emission color purity and efficient materials remains center most focus. One of the key components in majority of OLEDs are host materials of emissive layers, due to their ability to prevent excitons from self-quenching via triplet-triplet annihilation, which furthermore improves electroluminescence efficiency [4]. Yi-Mei Huang et al. recently reported a series of di-carbazolyl substituted 1,2-diphenylbenzoimidazole derivatives as hosts for multi colored OLEDs (red, green, blue) with external quantum efficiency up to 31% [5].
In this work we propose two new cyano-substituted 1,2-diphenylbenzoimidazoles with di-tert-butylcarbazole moieties as hosts for OLEDs. The proposed materials were synthesized in a simple two-step, noble metal-free synthesis method. The electrochemical, thermal and photophysical properties will be reported as well as characteristics of OLEDs. External quantum efficiency values ranging from 10% to 13% for green and sky-blue emitting devices were observed.