Solution-processed dendrimer-based bis-tridentate iridium() complexes with red, green, and blue phosphorescence for white OLEDs
We have synthesised blue ( D-Blue ), green ( D-Green ), and red ( D-Red ) emissive solution-processable dendrimers featuring a bis-tridentate iridium( iii ) complex core for incorporation into monochrome and white organic light-emitting diodes (WOLEDs). The iridium( iii ) complex cores have a common...
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Veröffentlicht in: | Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2024-03, Vol.12 (13), p.4751-4761 |
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Sprache: | eng |
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Zusammenfassung: | We have synthesised blue (
D-Blue
), green (
D-Green
), and red (
D-Red
) emissive solution-processable dendrimers featuring a bis-tridentate iridium(
iii
) complex core for incorporation into monochrome and white organic light-emitting diodes (WOLEDs). The iridium(
iii
) complex cores have a common dendronised bis[imidazolyl]phenyl ligand and different ancillary ligands to control the emission colour. The dendronised bis[imidazolyl]phenyl ligand has three first-generation biphenyl dendrons with
t
-butyl surface groups attached, with two of the dendrons projecting over the core of the dendrimer. The three dendrimers,
D-Blue
,
D-Green
, and
D-Red
had similar solution photoluminescence quantum yields (PLQYs) of around 75%. The neat film PLQYs were decreased relative to those in solution due to intermolecular interchromophore interactions. Blending the dendrimers at a concentration of 1 mol% with tris(4-carbazoyl-9-ylphenyl)amine (TCTA) increased the PLQYs but not to the level measured in solution (at best around 50% of the value), which was ascribed to the dendrimers and TCTA not forming a blend film in which the guest was evenly distributed in the host. Neat film monochrome three-layer devices had modest performance with maximum external quantum efficiencies (EQEs) of between 1.6% (red emission) and 5.3% (green emission). When the dendrimers were blended into TCTA at a concentration of 1 mol% the maximum EQEs of the monochrome OLEDs increased to 5.0%, 12%, and 8.3% for blue, green, and red emission, respectively. Host-free WOLEDs composed of a blend of
D-Blue
(95%),
D-Green
(2.5%), and
D-Red
(2.5%) in a single emissive layer had an EQE of 5.4%, which was higher than expected based on the monochrome device performance and was ascribed to
D-Blue
acting as a host for the emissive
D-Green
and
D-Red
. The optimised WOLED with the three dendrimers at a combined concentration of 1.0 mol% in TCTA had an EQE of 9.3%. Both the host-free and host-containing WOLED devices emitted a warm white.
Blue, green, and red emitting solution-processable first-generation dendrimers featuring bis-tridentate iridium(
iii
) complex cores are blended in a single emissive layer to provide organic light-emitting diodes that emit a warm white light. |
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ISSN: | 2050-7526 2050-7534 |
DOI: | 10.1039/d4tc00351a |