Blue electroluminescence of a novel Zn^(2+)–β-diketone complex with a carbazole moiety

In this letter, a novel zinc complex of Zn（ECTFBD）2 was synthesized by an environment-friendly grinding technique in high yield. Its structure was confirmed by 1H NMR, MS and EA. HECTFBD is 1-（9-ethyl-9H- carbazol-3-yl）-4,4,4-trifluorobutane-l,3-dione. Zn（ECTFBD）2-based light-emitting devices were fabricated. The architecture of the devices was ITO/PEDOT （40 nm）/100 wt% PVK： 40 wt% OXD-7： x wt% Zn（ECTFBD）2 （85 nm）/CsF （1.5 nm）/Al （100 rim）, where x = 1, 5, and 10 （relative to the mass of PVK and OXD-7）. The three devices displayed blue emissions with peaks at 450, 458, and 460 nm, respectively. A maximum luminous efficiency of 0.86 cd/A and a luminance of 228 cd/m2 were achieved by the 1 wt% doped device. So, we demonstrated further that Zn2＋-β-diketone complexes can be effectively severed as a class of new electroluminescent materials. In addition, the thermal stability of Zn（ECTFBD）2 was tested and the UV-vis and photoluminescent behaviors of Zn（ECTFBD）2 in CH2CI2 were investigated.

Synthesis of Pyrazolines Used as Blue Organic Electroluminescence Materials

Three kinds of pyrazolines were designed and synthesized. Their structures were elucidated by IR, (HNMR)-H-1, MS, UV and elemental analysis. Their luminescent properties were determined, which indicated that they had strong blue fluorescent properties. One of them was designed to have good film formation. All the three kinds of pyrazolines can be used as blue organic electroluminescence materials (OELMs).

Synthesis of a Novel Blue- light- emitting Polymer Material Bearing Coumarin Pendants

A novel blue luminescent polymer bearing coumarin pendants was prepared. Its luminescent properties were determined indicating that it had strong blue fluorescent properties and good film formation ability. This novel polymer can be used as a blue organic electroluminescent material (OELM) in organic electroluminescent devices.

A New Distyrylarylene Derivative Used as Blue Light Emitter in Organic Electroluminescent Device

A new blue electroluminescent material, distyrylarylene(DSA) derivative, 4,4' bis[2,2 (1 naphthyl,phenyl)vinyl] 1,1' biphenyl(NPVBi) is designed and synthesized. The DSA derivative shows better thermal stability because of its high glass transition temperature. A blue organic light emitting diode(OLED) with the structure ITO/TPD/NPVBi/Alq/LiF/Al is studied. The electroluminescent(EL) spectrum of the OLED exhibits that light emission originates from NPVBi with a peak at 460 nm, its Commission Internationale de l'Eclairage(CIE) color coordinates are x=0.16, y=0.15, and showing independence of CIE color coordinates on current density. The new DSA derivative is expectable as a new candidate for blue light emitter in OLEDs.

A Stable Blue Organic Electroluminescent Material

In order to compare two kinds of blue electroluminescent materials, we have investigated two kinds of blue OLEDs with the similar structrue ITO/CuPc/NPB/JBEM: perylene/Alq/Mg:Ag [device(J)] and ITO/CuPc/NPB/DPVBi: perylene/Alq/Mg:Ag [device(D)]. The difference of luminance and efficiency was not obvious for the two devices. However, there was remarkable difference for their lifetime. The device(J) achieved longer half lifetime of 1035 h at initial luminance of 100 cd/m 2, and that of device(D) was only 255 h. According to their energy level diagrams , the difference of their stability may originate from different host materials in the two devices. It may be attributed to the better thermal stability of JBEM molecules than that of DPVBi. It is shown that JBEM may be a promising blue organic electroluminescent material with great stability.

Role of chloride on the instability of blue emitting mixed‑halide perovskites

Although perovskite light-emitting diodes(PeLEDs)have seen unprecedented development in device efciency over the past decade,they sufer signifcantly from poor operational stability.This is especially true for blue PeLEDs,whose operational lifetime remains orders of magnitude behind their green and red counterparts.Here,we systematically investigate this efciency-stability discrepancy in a series of green-to blue-emitting PeLEDs based on mixed Br/Cl-perovskites.We fnd that chloride incorporation,while having only a limited impact on efciency,detrimentally afects device stability even in small amounts.Device lifetime drops exponentially with increasing Cl-content,accompanied by an increased rate of change in electrical properties during operation.We ascribe this phenomenon to an increased mobility of halogen ions in the mixed-halide lattice due to an increased chemically and structurally disordered landscape with reduced migration barriers.Our results indicate that the stability enhancement for PeLEDs might require diferent strategies from those used for improving efciency.