Recent Advances in Emitter Design for High Efficiency OLEDs

Electron pairs with aligned spin give rise to triplet states that are often non-emissive, with radiative decay lifetimes in the range of microseconds or longer. These properties contrast to singlet excited states with anti-aligned electron spin pairs, having lifetimes in the picosecond-nanosecond range. In Organic Light Emitting Diodes (OLEDs), random recombination of electrons and holes results in 75% formation of triplet excitons, severely limiting achievable efficiencies.

Recently, Thermally Activated Delayed Fluorescence (TADF) has emerged as a way to harvest triplet states for emission in OLEDs. While TADF can achieving high-efficiencies and even deep-blue emission, it is also highly demanding in terms of host material properties and molecular design. Recent work to better understand the TADF process and apply it to OLEDs will be presented.