Synthesis and characterization of new host molecules available as red phosphorescent OLED host material

OLED-based displays have good efficiency with self-emission. This is an environmentally friendly display with low power consumption. In theory, phosphorescent organic light-emitting materials is able to harvest internal... [ view full abstract ]

OLED-based displays have good efficiency with self-emission. This is an environmentally friendly display with low power consumption. In theory, phosphorescent organic light-emitting materials is able to harvest internal quantum efficiency (EQE) close to 100% but fluorescent emitter has low EQE to 25%. Phosphorescent OLED materials are demanding more development with better advantages than fluorescence. The host material plays a key role for good energy transfer to the emitter.

Hetero-aromatic system compounds have been widely used as organic electroluminescent materials. Carbazoles and their derivatives are highly interesting because they have fine optical properties, a low redox potential, and high chemical stability. Dibenzothiophene also has high triplet energy of 3.04 eV and good hole-transporting ability. The quinazoline and 1,3,5-triazine moiety has good electron transport ability due to electron deficiency characteristics. indolizine has good luminescent properties and is likely to be used as an OLED device material. We designed the host material by mixing various hetero-aromatic molecules.

InTri and CzDBTPMB were synthesized as host materials for phosphorescent OLEDs. We used the Spartan 08' program to predict HOMO/LUMO levels and orbital distributions of the host materials. The synthesized host materials were analyzed and confirmed by ¹H NMR, ¹³C NMR, Mass Spectrometer. Also, optical characteristics were examined by UV-Vis spectrophotometer and photoluminescence spectroscopy. The thermal stability of host materials were analyzed by thermo gravimetric analyzer (TGA) and differential scanning calorimeter (DSC).