Recent Progress in Pyridine Containing Heterocycles as High Performance Host Materials for Blue PHOLEDs

Phosphorescent Organic Light-Emitting Diodes (PHOLEDs) have an advantage of stability for a lifetime in comparison with the conventional Organic Light-Emitting Diodes (OLEDs). Green and red OLEDs have already achieved success, but for the last decade, blue OLEDs have observed a surge in the attention towards them from academia as well as the industry. There are incessant efforts devoted towards the improvement of external quantum efficiency from 25-30%. The host materials (or host compounds), hole transporting and electron transporting are the preeminent factors for the enhancement of External Quantum Efficiency (EQE). This review aims at highlighting the role of pyridine as an efficient Electron Transporting Material (ETM) for blue PHOLEDs. Pyridine having electron withdrawing nature can serve as valuable host compounds for electron transport material in PHOLEDs of a blue color. The presence of nitrogen atom in pyridine facilitates in lowering HOMO/LUMO energy levels compared to benzene ring and this assists in adding phenyl rings at the periphery of pyridine ring. Keywords: PHOLEDs, phosphorescent organic light-emitting diodes, host materials, blue OLED, pyridine, electron transport material, hole transport material, carbazole, azacarbazole, organic electronics.