Carbazolylgold(iii) complexes with thermally activated delayed fluorescence switched on by ligand manipulation as high efficiency organic light-emitting devices with small efficiency roll-offs. Issue 34 (19th August 2022)

• Record Type: Journal Article
• Authors: Wong, Chun-Yin; Tang, Man-Chung; Li, Lok-Kwan; Leung, Ming-Yi; Tang, Wai-Kit; Lai, Shiu-Lun; Cheung, Wai-Lung; Ng, Maggie; Chan, Mei-Yee; Yam, Vivian Wing-Wah
• Is Part Of: Chemical science. Volume 13:Issue 34(2022)
• Page Start: 10129
• Page End: 10140
• Publication Date: 2022-08-19
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d2sc03037c
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Switch on of TADF can be achieved by tuning the excited state energy levels via ligand manipulation of the carbazolylgold(iii ) C^C^N complexes. The resulting OLEDs show maximum EQEs of over 11% and efficiency roll-offs of down to less than 1%. Abstract : A series of carbazolyl ligands has been designed and synthesized through the integration of various electron-donating and electron-accepting motifs, including electron-donating 4-(diphenylamino)aryl and electron-accepting cyano and diphenylphosphine oxide moieties, for the development of a new class of gold(iii ) complexes, where the energies of their triplet intraligand and ligand-to-ligand charge transfer excited states can be manipulated for the activation of thermally activated delayed fluorescence (TADF). Upon excitation, these complexes show high photoluminescence quantum yields of up to 80% in solid-state thin films, with short excited state lifetimes down to 1 μs. Vacuum-deposited and solution-processed organic light-emitting devices based on these complexes demonstrate promising electroluminescence (EL) performance with maximum external quantum efficiencies of 15.0% and 11.7%, respectively, and notably small efficiency roll-off values of less than 1% at the practical luminance brightness level of 1000 cd m −2 . These distinct EL performances are believed to be due to the occurrence of multichannel radiative decay pathways via both phosphorescence and TADF that significantly shorten the emission lifetimes and hence reduce the occurrence of the detrimental triplet–triplet annihilation in the gold(iii ) complexes.