Tian Wenjing

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 Electroluminescent Diodes Utilizing Blend of Poly (2, 5-Dibutoxyphenylene) in Poly (N-Vinylcarbazole)

Blue emission from polymer blends composed of poly (2,5-dibutoxyphenyiene) (PPP) in a matrix polymer poly (N-vinylcarbazole) (PVK) is reported. The light-emitting layer can be fabricated by spin-coating of PPP-PVK blend solution without subsequent processing or heat treatment. A cell structure of glass substrate /indium-tin-oxide /PPP-PVK blend/aluminum is employed. Blue light emission with a peak position at 448 nm occurs at a bias of about 8 V.

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.

Photoinduced electron transfer of [ Ru (bpy)2 (4,4′‐dcbpy) ]2+ with electron donors

Emission quenching of [Ru(bpy)2(4, 4’-dcbpy)] (PF6)2 (1) by benzenamine,4-[2-[5-[4-[4-dimethylamino]phenyl]-4,5-di-hydro-1-phenyl-1H-pyrazol-3-yl]-ethenyl]-N,N-dimetyl (2) or 1, 5-diphenyl-3-(2-phenothiazine)-2-pyrazoline (3) was observed. Measurements of the emission decay of 1 before and after addition of 2 or 3 by single photon counting technique con-finned the observations. The emission quenching of 1 by 2 or 3 was submitted to Stern-Volmer equation. It was calculated that the quenching rate constants (kq) are 5.5 × 109(mol/L)-1s-1 for 2 and 4.0 × 109(mol/L)-1s-1 for 3, respectively. These results indicated a character of dynamic quenching process. The singlet-state of 2 or 3 was also quenched by 1. The quenching behaviors did not conform to the Stern- Volmer equation and involved both static and dynamic quenching processes. The apparent quenching rate constant (kapp) was calculated to be 3 × 109 (mol/L)-1 for the interaction of excited 2 with 1, and 1.2 × 109 (mol/L)-1 for that of excited 3 wit

X-shape oligo(thiophene)s as donor materials for vacuum-deposited organic photovoltaic cells

The fllms of two x-shape oligo(thiophene)s, 3, 4-dibithienyl-2, 5-dithienylthiophene (7T) and 2, 5-dibithienyl-3, 4ditrithienylthiophene (11T), which are prepared by vacuum evaporation, have been investigated as novel electron donor layers in two-layer photovoltaic cells. UV{Vis absorptions show red-shifted and broadened absorptions of the vacuumevaporated fllms as compared with those of the corresponding solutions and spin-coating fllms, which is beneflcial for photovoltaic properties. X-ray difiraction (XRD) and difierential scanning calorimetry (DSC) measurements show that the vacuum-evaporated fllms are almost amorphous. Two-layer photovoltaic cells have been realized by the thermal evaporation of 7T and 11T as donors and N, N 0 ibis(1-ethylpropyl)-3, 4:9,10-perylene bis(tetracarboxyl diimide) (EPPTC) as an acceptor. An energy conversion e‐ciency (ECE) of 0.18% of the cell based on 7T with an irradiation of white light at 100mw/cm2 has been demonstrated by the measurements of current (I)- voltage (V ) curves of the cells to be higher than the ECE of the reference system based on donor dihexylterthienyl (H3T) that is linear and without fi, fl linkage.

A Label-free Fluorescent Aptasensor for Turn-on Monitoring Ochratoxin A Based on AIE-active Probe and Graphene Oxide

A label-free fluorescent aptasensor for specific and ultrasensitive monitoring ochratoxin A(OTA) was developed using the specific aptamer of OTA(OSA) as recognition element, an aggregation-induced emission(AIE) molecule(a 9,10-distyrylanthracene with two ammonium groups, DSAI) as a fluorescent probe, and graphene oxide(GO) as a quencher. In the absence of OTA, the AIE probe DSAI and OSA complex(DSAI/OSA) is adsorbed on the GO surface, and the fluorescence of DSAI will be quenched efficiently via the fluorescence resonance energy transfer(FRET) from DSAI to GO. Upon the OTA addition, a more stable complex(OSA-OTA) is formed and released from GO. Meanwhile, DSAI and OSA-OTA can form a new complex(DSAI/OSA-OTA), then the fluorescent signal of DSAI recovers gradually. Therefore, by introducing GO and DSAI, the fluorescence signal of DSAI can be easily turned from “off” to “on” after the addition of OTA, and the ultrasensitive detection of OTA by monitoring the change of the fluorescence signal of DSAI can be readily realized. The detection limit of the assay can reach 0.324 nmol/L with a linear detection range of 10—200 nmol/L. And the aptasensor exhibits high selectivity for OTA against other analogues. Moreover, it has been successfully applied for the detection of OTA in red wine samples.