Bipolar Deep-Blue Host for High-Performance Multicolor OLEDs by Peripheral Auxiliary Group Strategy

Developing a multifunctional bipolar deep-blue organic fluorophore acting as an emitter and host for long-wavelength emissive phosphors simultaneously is important and urgently needed for organic light-emitting diodes (OLEDs) in the application of full-color displays. However, it remains a big challenge to resolve the contradictions between the inherent wide band gap of deep-blue materials and charge carrier injection/transporting, luminescence efficiency, and thermal stability. In this work, we proposed a peripheral auxiliary group strategy to construct the multifunctional bipolar dibenzothiophene-phenanthroimidazole-based materials (PPISCF and PPISPhCz), realizing the goal of killing two birds with one stone: the thermal stability and fluorescence efficiency can be improved greatly while maintaining deep-blue emission and bipolar transporting abilities effectively. By comparison, phenylcarbazole-modified PPISPhCz shows a high glass transition temperature of 192 °C, as well as high and balanced electron–hole transporting properties. Consequently, the PPISPhCz-based nondoped device shows the color coordinates of (0.157, 0.077) and an external quantum efficiency (EQE) up to 5.34%. Using PPISPhCz as a host for green, yellow, and red phosphors, the OLEDs show the maximum EQEs of 18.90, 21.97, and 23.52%, respectively. Meanwhile, the fluorescent/phosphorescent hybrid white OLED with PPISPhCz as an emitter and host exhibits an excellent power efficiency and EQE of 74.72 lm W –1 and 23.77%, respectively. This study offers a viable strategy to blossom multifunctional deep-blue host materials by a peripheral auxiliary group, which is instrumental in creating simple and high-performance full-color OLEDs.