Red Emitters for OLEDs

Red Emitters for OLEDs

Author: Angewandte Chemie International Edition

Molecules with thermally activated delayed fluorescence (TADF) can be used in, e.g., organic light-emitting diodes (OLEDs). Blue and green TADF OLEDs have achieved high external quantum efficiencies (EQEs). However, red or near-infrared (NIR) TADF emitters have lagged behind the green and blue ones due to their narrow energy gaps. These often lead to substantial energy loss through non-radiative decay.

Xiao-Hong Zhang, Soochow University, Suzhou, Jiangsu, P. R. China, Chun-Sing Lee, City University of Hong Kong, Hong Kong SAR, and colleagues have developed two efficient red TADF compounds,  BPPZ‐PXZ and mDPBPZ‐PXZ (pictured). The molecules combine rigid planar phenoxazine segments (pictured on the bottom) with large heterocyclic aromatic hydrocarbon segments. Both compounds were synthesized via a 3‐(10H‐phenoxazin‐10‐yl)phenanthrene‐9,10‐dione intermediate, which was obtained from 3‐bromophenanthrene‐9,10‐dione and phenoxazine via a Buchwald–Hartwig cross‐coupling reaction.

Both TADF molecules obtained near 100 % photoluminescence quantum yields in films doped with 4,4′‐di(9H‐carbazol‐9‐yl)‐1,1′‐biphenyl (CBP). OLEDs based on BPPZ‐PXZ achieved EQEs of 25.2 %—the highest efficiency among reported red TADF OLEDs.


 

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