2026/07/13 by Wenrui Wang, Hassan Hafeez, Sen Wu +4 · 1 voice
Engineering · Materials Science · #Organic Light-Emitting Diodes Research #Luminescence and Fluorescent Materials #Organic Electronics and Photovoltaics
paper · doi:10.1002/anie.9957319
openalex publication_date 2026/07/13 · openalex created_date 2026/07/14 · openalex updated_date 2026/07/15
ABSTRACT One of the key factors affecting the stability and efficiency roll‐off of organic light‐emitting diodes is the rate constant of reverse intersystem crossing ( k RISC ), which is itself influenced by both the magnitude of the singlet‐triplet energy gap (Δ E ST ) and spin‐orbit coupling (SOC) matrix elements. Most MR‐TADF emitters possess relatively large Δ E ST and small SOC. With the goal of designing an MR‐TADF compound having a small Δ E ST and strong SOC that emits in the deep blue region, here we report a heavy atom‐free boron‐nitrogen‐carbonyl hybrid MR‐TADF emitter, DDOBDiKTa , which emits at λ PL of 438 nm in toluene with a narrow full width at half maximum (FWHM) of 33 nm. DDOBDiKTa has a Φ PL of 70% and a Δ E ST of 0.05 eV in 5 wt% doped films in 26DCzPPy. Remarkably, without any heavy atoms, this emitter shows fast prompt, τ p , and delayed, τ d , fluorescence lifetimes of 2.3 ns and 1.48 µs, respectively, leading to a k RISC of 1.98 ×10 6 s −1 in 26DCzPPy. This is one of the fastest k RISC values among reported MR‐TADF emitters that have no heavy atoms. The OLED showed EQE max /EQE 10000 of 23.0%/10%, demonstrating unusually mild efficiency roll‐off for a blue device.