A New Host Material for Electrophosphorescent Devices

Significance

The authors present a facile synthesis of TFTPA, and demonstrate its utility as a host material for iridium-based phosphorescent light-emitting diodes (LEDs). TFTPA is found to have superior properties to both CBP and mCP in terms of its high glass transition temperature (T _g = 186 °C) and large (estimated) triplet energy gap (2.89 eV). Additionally, due to the steric bulk of the TFTPA structure, bimolecular interactions of the phosphors is minimized resulting in some of the highest reported efficiencies in electrophosphorescent devices.

Comment

The long lifetimes of phosphors allows for self-quenching via triplet-triplet annihilation. As such the phosphorescent emitters are usually placed in host material such as CBP or mCP, to minimize bimolecular interactions between the phosphors. The material described here (TFTPA) compares favorably to CBP for green and (especially) red phosphorescence while, unlike CBP, it possesses a large enough triplet energy gap to accommodate blue phosphors and does so admirably. While not a conceptual leap, this work has many practical advantages, the host material is made in a single step from commercial materials, it is purified by sublimation and does not require any metal catalysts. Due to its availability and promising characteristics as a host material it is likely that this scaffold will be the subject of further study in the field of phosphorescent LEDs.