New Phenanthro[9,10-d]oxazole-Based Fluorophores with Hybridized Local and Charge-Transfer Characteristics for Highly Efficient Blue Non-Doped OLEDs with Negligible Efficiency Roll-Off.

It is vital to develop highly efficient non-doped blue organic light-emitting diodes (OLEDs) with high color purity and low-efficiency roll-off for applications in display and lighting. Herein, two blue D-A fluorophores TPA-PO and TPA-DPO are designed and synthesized, in which phenanthro[9,10-d]oxazole (PO) acts as the acceptor and triphenylamine as the donor. TPA-PO and TPA-DPO display good thermal stability and efficient luminescence efficiency in neat film. Results based on photophysical property and theoretical calculation demonstrate that TPA-PO and TPA-DPO possess the hybridized local and charge-transfer (HLCT) feature, which can utilize the triplet exciton to achieve highly efficient electroluminance (EL). The non-doped OLEDs with TPA-PO/TPA-DPO as pure emissive layer show the uniform EL emission peak at 468 nm, corresponding to CIE coordinates of (0.168, 0.187) and (0.167, 0.167), respectively. The TPA-DPO-based non-doped OLEDs provide the maximum external quantum efficiency (EQE) of 7.99 % and high exciton utility efficiency of 48.4 %~72.6 %. Moreover, the TPA-DPO-based device exhibits low-efficiency roll-off, still maintaining the EQE of 6.03 % at the high luminance of 5000 cd m-2. Those findings state clearly that PO is a promising building block of blue fluorophore with a potential HLCT feature to be applied in non-doped OLEDs.

Synthesis, photophysical, electrochemical and electroluminescent properties of a novel iridium(III) complex based on 2-phenylbenzo[d]oxazole derivative.

A new phosphorescent iridium (III) complex based on 2-(4-tert-butylphenyl)-5-methylbenzo[d]oxazole as main ligand, i.e. bis(2-(4-tert-butylphenyl)-5-methylbenzo[d]oxazole-N,C(2'))iridium(acetylacetonate) [(tmbo)2Ir(acac)], was synthesized for organic light-emitting diodes (OLEDs), and its photophysical, electrochemical and electroluminescent properties were investigated. The complex displayed strong phosphorescence emission, high decomposition temperature, short phosphorescent lifetime and reversible redox electrochemical behavior. The OLEDs based on (tmbo)2Ir(acac) as dopant emitter exhibited maximum luminance efficiency of 26.1cdA(-1) and high luminance of 16,445 cd m(-2). Interestingly, highly doped device based on (tmbo)2Ir(acac) showed high efficiency with negligible roll-off under a wide range of driving current density, which was mainly attributed to the effect of bulky steric hindrance of multi-methyl groups on this complex and its short phosphorescent lifetime.

3-(4-Meth-oxy-phen-yl)pyrido[2,3-b]pyrazine.

In the title mol-ecule, C(14)H(11)N(3)O, the benzene ring is twisted by 14.0 (2)° from the plane through the fused ring system. In the crystal, π-π inter-actions [centroid-centroid distances = 3.609 (1), 3.639 (1) and 3.735 (1) Å] form stacks of mol-ecules propagating along the b axis. The crystal packing is further stabilized by weak inter-molecular C-H⋯O and C-H⋯N hydrogen bonds.

4-[4,5-Bis(pyridin-2-yl)-1H-imidazol-2-yl]phenol monohydrate.

In the title hydrate, C(19)H(14)N(4)O·H(2)O, the dihedral angle between the two pyridine rings is 38.0 (2)°. The dihedral angle between the imidazole and benzene rings is 25.3 (2)°. The crystal structure is stabilized by inter-molecular O-H⋯O, O-H⋯N and N-H⋯O hydrogen bonds.

cis-Bis[2-(1,3-benzothia-zol-2-yl)-1-(4-fluoro-phen-yl)ethen-yl](pentane-2,4-dionato-κO,O')iridium(III).

In the title compound, [Ir(C(15)H(9)FNS)(2)(C(5)H(7)O(2))], the Ir atom is hexa-coordinated by three chelating ligands, with two cyclo-metalated 2-(1,3-benzothia-zol-2-yl)-1-(4-fluoro-phen-yl)ethenyl ligands showing N,C-bidentate coordination and an O,O'-bidenate pentane-2,4-dionate anion, thereby forming a distorted octa-hedral enviroment.