Daniel Ping-Kuen Tsang

High-efficiency green organic light-emitting devices utilizing phosphorescent bis-cyclometalated alkynylgold(III) complexes

A new phosphorescent material of cyclometalated alkynylgold(III) complex, [Au(2,5-F(2)C(6)H(3)-C∧N∧C)(C≡C-C(6)H(4)N(C(6)H(5))(2)-p)] (1) (2,5-F(2)C(6)H(3)-HC∧N∧CH = 2,6-diphenyl-4-(2,5-difluorophenyl)pyridine), has been synthesized, characterized, and its device performance investigated. This luminescent gold(III) complex was found to exhibit rich PL and EL properties and has been utilized as phosphorescent dopants of OLEDs. At an optimized dopant concentration of 4%, a device with a maximum external quantum efficiency (EQE) of 11.5%, corresponding to a current efficiency of 37.4 cd/A and a power efficiency of 26.2 lm/W, has been obtained. Such a high EQE is comparable to that of Ir(ppy)(3)-based devices. The present work suggests that the alkynylgold(III) complex is a promising phosphorescent material in terms of both efficiency and thermal stability, with the additional advantages of its relatively inexpensive cost and low toxicity.

A luminescent cyclometalated platinum(II) complex and its green organic light emitting device with high device performance

A luminescent cyclometalated platinum(II) complex has been demonstrated to show green electrophosphorescence in multilayer organic light-emitting devices (OLEDs) using a dual emissive layer with high current and external quantum efficiencies of 38.9 cd A(-1) and 11.5%, respectively.

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%.

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.

Synthesis of Unsymmetric Bipyridine–PtII–Alkynyl Complexes through Post‐Click Reaction with Emission Enhancement Characteristics and Their Applications as Phosphorescent Organic Light‐Emitting Diodes

Two unsymmetric bipyridine-platinum(II)-alkynyl complexes have been synthesised by a post-click reaction. These metal complexes are found to exhibit emission enhancement properties. The photoluminescence quantum yield can be significantly increased from 0.03 in solution to 0.72 in solid-state thin films. Efficient solution-processable organic light-emitting diodes have been fabricated by utilizing these complexes as phosphorescent dopants. A high external quantum efficiency of up to 5.8% has been achieved.

Organic Photovoltaic Devices Based on a New Class of Oligothienylenevinylene Derivatives as Donor Materials

A new class of donor-acceptor-containing oligothienylenevinylenes with a triphenylamine donor and a dicyanovinyl group as acceptor has been synthesized and characterized. By extending the oligothiophene backbone, both the optical bandgaps and the charge-transport properties can be tuned. These oligothienylenevinylene derivatives show intense charge-transfer absorption bands that cover the entire visible spectrum, with low optical bandgaps of approximately 1.64 eV. In addition, electrochemical studies reveal that these compounds possess relatively large ionization potentials of approximately 5.5 eV. On the basis of these newly developed dicyanovinyl-substituted chromophores as donor materials and C(60) as acceptor material, bilayer organic photovoltaic devices have been fabricated, with the best device showing a high power conversion efficiency (PCE) of 2.0%, with an open-circuit voltage of 0.68 V and a fill factor of 0.60 after thermal annealing. The obvious morphology change with the formation of small domains in thin films and the reduction of series resistance are believed to be responsible for the dramatic performance improvement upon thermal annealing.

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.