Carbene-metal-amide type photoemitters based on CF3-substituted carbazolate ligands show sky-blue to deep-blue photoluminescence from charge-transfer excited states. They are suitable for incorporation into organic light-emitting diodes (OLEDs) by thermal vapour deposition techniques, either embedded within a high-triplet-energy host, or used host-free. We report high-efficiency OLEDs with emission ranging from yellow to blue (Commission Internationale de l'\'Eclairage (CIE) coordinates from [0.35, 0.53] to [0.17, 0.17]). The latter show a peak electroluminescence external quantum efficiency (EQE) of 20.9 % in a polar host. We observe that the relative energies of CT and 3LE states influence the performance of deep-blue emission from carbene-metal-amide materials. We report prototype host-free blue devices with peak external quantum efficiency of 17.3 %, which maintain high performance at brightness levels of 100 cd m−2.
@article{arxiv.1908.03074,
title = {Highly Efficient Blue Host-Free and Host-Guest Organic Light-Emitting Diodes Based on Carbene-Metal-Amides},
author = {Patrick J. Conaghan and Campbell S. B. Matthews and Florian Chotard and Saul T. E. Jones and Neil C. Greenham and Manfred Bochmann and Dan Credgington and Alexander S. Romanov},
journal= {arXiv preprint arXiv:1908.03074},
year = {2020}
}