Harnessing TADF in iridium(III) complexes for nearly 20% external quantum efficiency in solution-processed OLEDs
Year: 2026
Type: preprint
Abstract: Our work presents three new di-iridium(III) complexes Ir-H, Ir-F, and Ir-CN displaying strong thermally activated delayed fluorescence (TADF) behaviour. These complexes were obtained by variating the group R = H, F, CN at the 5-position on the pyrimidine-based bridging ligand. Our Ir(III) complexes emit green to orange photoluminescence in polystyrene film, with λPL in the range from 529 nm for Ir-H to 583 nm for Ir-CN and with unity photoluminescence quantum yield. They display clear negative solvatochromism in solution, in line with the metal-to-ligand charge-transfer (MLCT) nature of their excited states. Their TADF performance has been established in a temperature-dependent experiment with the ΔE S-T ranging 30-46 meV with the lowest value reported for orange emitter Ir-CN. Our work is complemented with a detailed computational study and modelling. We report the record high solution-processed organic light-emitting diode (OLED) external quantum efficiency (EQE) of 19.5% recorded for emitter Ir-F at luminance of 1000 cd m -2 . This remarkable achievement presents the highest EQE figure for any iridium(III) complex for which TADF has been reported and double the previous record. The low efficiency roll-off of this device is a result of extremely short PL lifetimes τ PL ~300 ns and high radiative decay rate constants k r ~3×10 6 s -1 of the Ir(III) TADF emitters.
Source: ChemRxiv
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7211879770