High‐Performance Blue Electroluminescence Devices Based on Linear Gold(I) Complexes as Ultrafast Triplet Exciton Harvesters

Abstract

Achieving large external quantum efficiencies, narrow bandwidths, and a long operational lifetime at high brightness remains the largest hurdle to developing organic blue‐emitting devices. Here, a material strategy is demonstrated that can meet these conditions. The strategy is based on linear heteroleptic Au(I) complex exciton harvesters and multiresonance thermally activated delayed fluorescence (MR‐TADF) emitters. The organic electroluminescence devices produce blue emission with Commission Internationale de l'Eclairage chromaticity coordinates of (0.108, 0.160), a narrow full‐width at half‐maximum value of 20 nm, and a maximum external quantum efficiency (EQE) as high as 30.2%. Notably, the EQE value remains 22.2% at 2000 cd m−2, whereas conventional control devices with an organic exciton harvester suffer from huge roll‐offs in quantum efficiency. An additional benefit of the device is a one‐order‐of‐magnitude improvement in its operational lifetime compared with that of the control device. Finally, the investigations reveal that the improvements are attributable to the unique ability of the Au(I) complexes for ultrafast triplet exciton harvest. In addition, the Au(I) complexes can facilitate Förster energy transfer to the MR‐TADF emitter, with effective suppression of hazardous triplet–triplet Dexter energy transfer. It is believed that the research is helpful in commercializing high‐efficiency and stable blue electroluminescence devices.

Bis-tridentate Ir(III) Phosphors and Blue Hyperphosphorescence with Suppressed Efficiency Roll-Off at High Brightness

“…Table . Such an observation has been documented in many phosphorescent OLEDs involving a variety of transition-metal dopant phosphors. − Moreover, the Irtb1 -based device presented a much-suppressed efficiency roll-off at a high brightness between 100 and 1000 cd/m 2 . This phenomenon can be rationalized by the ascending trend of radiative lifetimes in doped DPEPO thin films (0.71 μs for Irtb1 to 1.21 μs for Irtb2b and to 1.49 μs for Irtb2a ), where the shortened radiative lifetime is favorable for mitigating the efficiency roll-off.…”

A Rising Star: Luminescent Carbene‐Metal‐Amide Complexes

“…Recently, You and co-workers fabricated MR-TADF OLEDs using Au(I)-CMA sensitizers. [45] The sensitized device achieved over 30 % EQE at maximum and over 20 % EQE at 1000 nits, while the non-sensitized device suffered from serious efficiency roll-off. In this term, the combination of the CMA sensitizer and the MR-TADF emitter pave a new avenue for realizing high-efficiency and narrowband OLEDs.…”

Carbazole‐Decorated Organoboron Emitters with Low‐Lying HOMO Levels for Solution‐Processed Narrowband Blue Hyperfluorescence OLED Devices

“…[29] The hyperfluorescence is formed by adding a conventional TADF material with high reverse intersystem crossing (RISC) rate in the emissive layer as the sensitizer, which could obviously improve the efficiency of MR-TADF devices by accelerating the triplet exciton upconversion for avoiding exciton annihilation events of long-lived triplets, [29,33,44,45] such as triplet-triplet and triplet-polaron interactions. Based on a well-known MR-TADF molecule of ν-DABNA as the terminal emitter, [22,44,[46][47][48][49][50][51][52] vacuum-deposited pure blue hyperfluorescence devices with extremely high EQE of 43.9 % have been reported by developing a two-donor TADF sensitizer to precisely control the complicated energy transfer processes. [22] As for solution-processed pure blue hyperfluorescence devices, Che et al achieves a breakthrough by using a gold(III)-TADF complex Au-1 to sensitize the same terminal emitter of ν-DABNA.…”