High Performance Organic Narrowband Emitters for Stable Blue OLEDs

Constricted by electron spin statistics, the maximum internal quantum efficiency of 100% can be achieved in organic light-emitting diodes (OLEDs) by utilizing purely organic thermally activated delayed fluorescence (TADF) materials. However, due to strong charge transfer, they exhibit broad emission with a full-width-at-half maximum (FWHM) > 70 nm.

Recently, multiresonant TADF (MR-TADF) emitters, a sub-class of TADF materials based on alternating boron and nitrogen atoms embedded into polycyclic aromatic hydrocarbon scaffolds, are attracting much interest in OLEDs. Their key attributes include a narrow FWHM, high photoluminescence quantum yield, and unprecedented color purity.

Even though these MR materials have advantages in color purity over conventional TADF materials, their device stability is weak and results in a poor operational lifetime (LT) due to the large singlet-triplet energy gap, delayed fluorescence lifetime, and too slow rate of reverse intersystem crossing (RISC).

Especially, narrowband blue OLEDs LT (<100h) is still inferior to the conventional TADF OLEDs. The HONESTY project seeks to address the above issues by rationally designing organic narrowband novel TADF emitters.

Our designs comprised four types (a combination of boron and non-boron) targeting a high RISC rate, leading to highly stable narrowband blue OLEDs with long LT.

Among the four types, one design includes yet unexplored rigid tellurium-based acceptor decorated with high triplet energy donors, which is keen for new TADF scaffolds.

The rigidity of all chemical components with slightly twisted confirmation and aryl groups on donors will work coherently to furnish highly stable OLEDs with suppressed efficiency roll-off, improved device stability, and long LT.

Overall, the HONESTY proposal is anticipated to provide a breakthrough in stable blue narrowband TADF-OLEDs with the supervision of Karolis Kazlauskas, a physics expert in stable OLEDs working at Vilnius University, Lithuania.