Ma Yuguang

Influence of the Energy Level Matching on the Performances of Organic/Polymeric Electroluminescent Devices

The performances such as the operating-voltage and the brightness of three types of devices: single-layer device, double-layer device and three-layer device, were examined. It is demonstrated that the I-V characteristics of single-layer device depends not on the applied voltage but instead on the electric-field strength, and the brightness increased by a factor of 50 and the operating-voltage decreased when introducing one electron transporting layer or an electron transporting layer and one hole blocking layer between the light emitting layer and the negative electrode. In fact, it is imperative to match the energy level of each layer in the electroluminescent device in order to improve its comprehensive performances.

Carriers Confinement for Polymer Electroluminescent Devices with Multilayer Structure

The polymer electroluminescence (EL) device with PBD as carriers confinement layer yields bright blue emission having intensity of 300 cd/m2, in same case the device without PBD layer have luminance only 44 cd/m2. The effect of PBD layer on EL characteristic was studied. The results show that only in EL devices with PBD thickness over 30 nm, the holes are completely confined in emitting layer. The luminance over 2000 cd/m2 can be obtained by inserting an electron injecting layer between the negative electrode and PBD to increase the electron injection.

Blue-Green Electroluminescent Diodes Utilizing Tris (8-Quinolinolato)-Aluminum Doped Poly (Vinylcarbazole)

Blue-green electroluminescent diodes utilizing tris (8-quinolinolato)-aluminum doped poly (vinylcarbazole) have been demonstrated. A Schottky-type electroluminescent diode of the polymer film is driven at 20 V and has a peak emission wavelength of 490 nm at room temperature with lifetime up to 4 h.

Photoluminescence and Electroluminescence from Plasma Ploymerized Naphthalene Films

A polymer thin film electroluminescence (EL) device has been prepared by using plasma polymerization technique. Its basic structure consists of an emitting layer of plasma polymerized naphthalene (PPN) which is sandwiched between two metal electrodes. A uniform blue emission is observed under 8-20 V. Some electrical and optical properties of the device are described. The possible explanations for the blue EL from PPN are discussed.

Blue Electroluminescent Devices Using the Dye Doped Polymers as Emitter and the Organic Molecule Film as Hole Blocking Layer

By placing a hole blocking layer between the polymer and the metallic electrode, we have achieved improved efficiencies for blue electroluminescent devices fabricated with poly (N-vinylcarbazole) doped with 1, 1, 4, 4, -tetraphenyl-1, 3-butadiene as the emitter layer and with aluminum and indium/tin-oxide as the electron and hole injecting electrodes. This bilayer device yields bright blue emission having intensity of 300 cd/m2, in same case the devices without hole blocking layer have luminance of only 44 cd/m2.

Photoluminescence and Electroluminescence of Poly p-Phenyl Phenol Prepared by Enzymatic Catalyzed Polymerization

The photoluminescence (PL) peak of poly p-phenyl phenol (PPP) is at about 370-420 nm excited by the light at 350 nm. The absorption band edges and photon emitting peaks of the polymer are found the conjugated lengths dependent on molecular weight of polymer. In the transient luminescence measurement the lifetime of PL decay is determined to be 2.0 ns which is supposed an evidence of polaron excitation recombination. The electroluminescence is observed with aluminum/PPP/indium-tin oxide cell.

THE KINETICS OF METHYL METHACRYLATE POLYMERIZATION INITIATED BY THE VOLATILE PRODUCTS OF A METHYL METHACRYLATE PLASMA

It is found that the volatile products of methyl methacrylate plasma can very actively initiate the polymerization of the monomer to produce ultrahigh molecular weight polymers. This polymerization of MMA occurs by a livlng free radical mechanism with instantaneous initiation and monomer transfer.