Deep-Blue and Fast Delayed Fluorescence from Carbene-Metal-Amides for Highly Efficient and Stable Organic Light-Emitting Diodes.

Abstract

Linear gold complexes of the "carbene-metal-amide" (CMA) type are prepared with a rigid benzoguanidine amide donor and various carbene ligands. These complexes emit in the deep-blue range at 424 and 466nm with 100% quantum yields in all media. The deep-blue thermally activated delayed fluorescence (TADF) originates from a charge transfer state (CT) with an excited state lifetime as low as 213ns, resulting in fast radiative rates of 4.7 × 106 s-1. The high thermal and photo-stability of these CMA materials enabled us to fabricate highly energy efficient organic light-emitting diodes (OLED) in host-guest architectures. We report deep-blue OLED devices with electroluminescence at 416nm and 457nm with practical external quantum efficiencies of up to 23% at 100cd m-2 with excellent colour coordinates CIE (x; y) = 0.16; 0.07 and 0.17; 0.18. The operating stability of these OLEDs is the longest reported to date (LT50 = 1 hour) for deep-blue CMA emitters, indicating a high promise for further development of blue OLED devices. Our findings inform the molecular design strategy and correlation between delayed luminescence with high radiative rates and CMA OLED device operating stability. This article is protected by copyright. All rights reserved.