Man-Chung Tang

Dendritic Luminescent Gold(III) Complexes for Highly Efficient Solution-Processable Organic Light-Emitting Devices†

Emission control: carbazole-based dendritic alkynylgold(III) complexes have been evaluated as phosphorescent emitters in organic light-emitting devices. The energy as well as the bathochromic shift of the emissions can be tuned effectively through a control of the dendrimer generation. The optimized devices show high current and external quantum efficiencies of up to 24.0 cd A(-1) and 7.8 %, respectively.

Bipolar gold(III) complexes for solution-processable organic light-emitting devices with a small efficiency roll-off.

A new class of bipolar alkynylgold(III) complexes containing triphenylamine and benzimidazole moieties has been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of solution-processable organic light-emitting devices (OLEDs). The incorporation of methyl groups in the central phenyl unit has been found to rigidify the molecule to reduce nonradiative decay, yielding a high photoluminescence quantum yield of up to 75% in spin-coated thin films. In addition, the realization of highly efficient solution-processable OLEDs with an extremely small external quantum efficiency (EQE) roll-off has been demonstrated. At practical brightness level of 1000 cd m(-2), the optimized devices exhibited a high EQE of up to 10.0% and an extremely small roll-off of less than 1%.

Design Strategy for High-Performance Dendritic Carbazole-Containing Alkynylplatinum(II) Complexes and Their Application in Solution-Processable Organic Light-Emitting Devices

A new class of luminescent dendritic carbazole-containing alkynylplatinum(II) complexes has been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of solution-processable organic light-emitting devices (OLEDs). These complexes exhibit high photoluminescence quantum yields of up to 80% in spin-coated thin films. In addition, the incorporation of carbazole dendrons into the platinum(II) center can significantly suppress intermolecular interactions in solid-state thin films, giving rise to emission spectra that are similar to those found in solution irrespective of dopant concentrations. High-performance solution-processable OLEDs have also been fabricated, with a maximum external quantum efficiency of up to 10.4%, which is comparable to that of the vacuum-deposited devices based on the small-molecule counterpart. This is one of the highest ever reported values for solution-processable devices based on platinum(II) complexes with tridentate ligands.

Saturated Red-Light-Emitting Gold(III) Triphenylamine Dendrimers for Solution-Processable Organic Light-Emitting Devices

A novel isoquinoline-containing C^N^C ligand and its phosphorescent triphenylamine-based alkynylgold(III) dendrimers have been synthesized. These alkynylgold(III) dendrimers serve as phosphorescent dopants in the fabrication of efficient solution-processable organic light-emitting devices (OLEDs). The photophysical, electrochemical, and electroluminescence properties were studied. A saturated red emission with CIE coordinates of (0.64, 0.36) and a high EQE value of 3.62% were achieved. Unlike other red-light-emitting iridium(III) dendrimers, a low turn-on voltage of less than 3 V and a reduced efficiency roll-off at high current densities were observed; this can be accounted for by the enhanced carrier transporting ability and the relatively short lifetimes in the high-generation dendrimers. This class of alkynylgold(III) dendrimers are promising candidates as phosphorescent dopants in the fabrication of solution-processable OLEDs.

Strategy for the Realization of Efficient Solution-Processable Phosphorescent Organic Light-Emitting Devices: Design and Synthesis of Bipolar Alkynylplatinum(II) Complexes

A new class of highly luminescent bipolar alkynylplatinum(II) complexes has been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of solution-processable organic light-emitting devices (OLEDs). Through the incorporation of a delicate balance of electron-donating carbazole moieties and electron-accepting phenylbenzimidazole or oxadiazole moieties into the platinum(II) core, the platinum(II) complexes have been demonstrated to exhibit bipolar charge transport character with high photoluminescence quantum yields of up to 0.75 in thin films. The introduction of meta-linkages into the complexes further helps weaken the donor-acceptor interactions, facilitating better carrier-transporting abilities. More importantly, high-performance solution-processable green-emitting OLEDs with maximum current efficiencies of up to 57.4 cd A-1 and external quantum efficiencies of up to 16.0% have been realized. This is among the best performances for solution-processable phosphorescent OLEDs reported based on platinum(II) complexes as well as bipolar metal complexes.

Sky-Blue-Emitting Dendritic Alkynylgold(III) Complexes for Solution-Processable Organic Light-Emitting Devices

A new class of tridentate ligand-containing cyclometalated gold(III) complexes featuring dendritic alkynyl ligands with carbazole moieties as dendrons and peripheral groups has been synthesized up to the third generation. High-performance solution-processable organic light-emitting devices (OLEDs) with maximum current efficiency of up to 23.7 cd A-1 and external quantum efficiency of up to 6.9% have been realized by a simple spin-coating technique. With the incorporation of bulky carbazole moieties to form higher generation dendrimers, the undesirable excimeric emission could be effectively reduced, allowing the fine-tuning of the emission color toward the blue region. This represents the first successful demonstration of sky-blue-emitting alkynylgold(III) complexes and its application in solution-processable OLEDs.

Versatile Design Strategy for Highly Luminescent Vacuum-Evaporable and Solution-Processable Tridentate Gold(III) Complexes with Monoaryl Auxiliary Ligands and Their Applications for Phosphorescent Organic Light Emitting Devices

A new class of brightly blue-green-emitting arylgold(III) complexes has been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of solution-processable and vacuum-deposited organic light-emitting devices (OLEDs). These arylgold(III) complexes can be readily synthesized by reacting the corresponding arylboronic acids with the gold(III) precursor complexes in a one-pot Suzuki-Miyaura coupling reaction. When compared to the structurally related alkynylgold(III) complex, arylgold(III) complexes 1 and 2 exhibit much higher photoluminescence quantum yields in solution state. High photoluminescence quantum yields are also observed in solid-state thin films. More importantly, the solid-state emission spectra show strong resemblance to those in solution, irrespective of the dopant concentration, leading to significant improvement in the color purity of the OLEDs by suppressing any excimer emission resulting from the π-stacking of the tridentate ligand. High performance solution-processable and vacuum-deposited blue-green-emitting OLEDs have also been realized, with maximum external quantum efficiencies of 7.3% and 14.7%, respectively, representing the first demonstration of efficient blue-green-emitting OLEDs based on cyclometalated arylgold(III) complexes.

A new class of gold(III) complexes with saturated poly(benzyl ether) dendrons for solution-processable blue-green-emitting organic light-emitting devices

A new class of gold(III) complexes with saturated poly(benzyl ether) dendrons has been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of solution-processable organic light-emitting devices (OLEDs). The incorporation of the poly(benzyl ether) dendron into the cyclometalated gold(III) center can effectively perturb the packing of the molecules and minimizes the intermolecular interactions for suppressing excimeric emission. In addition, blue-green-emitting OLEDs can be realized, representing the first example of a blue-green-emitting device based on saturated dendrimer containing alkynylgold(III) complexes. Taking advantage of the diverse and well-developed synthetic routes for saturated dendrons, this work provides a simple means to develop a new class of gold(III) complexes emitting in the blue region.