We have demonstrated that fabrication and characterization of nanocomposite polymer light emitting devices with metal Zinc Oxide (ZnO) nanoparticles and 2,3-dibutoxy-1,4-poly(phenylenevinylene) (DBPPV). The current and luminance characteristics of devices with ZnO nanoparticles are much better than those of device with pure DBPPV. Optimized maximum luminance efficiencies of DBPPV–ZnO (3:1 wt%) before annealing (1.78 cd/A) and after annealing (2.45 cd/A) having a brightness 643 and 776 cd/m2at a current density of 36.16 and 31.67 mA/cm2are observed, respectively. Current density–voltage and brightness–voltage characteristics indicate that addition of ZnO nanoparticles can facilitate electrical injection and charge transport. The thermal annealing is thought to result in the formation of an interfacial layer between emissive polymer film and cathode.

A wide hysteresis width characteristic (memory window) was observed in the organic thin film transistors (OTFTs) using poly(2-hydroxyethyl methacrylate) (PHEMA)-based polymer multilayers. In this study, a strong memory effect was also found in the pentacene-based OTFTs and the electric characteristics were improved by introducing PHEMA/poly(methyl methacrylate) (PMMA)/PHEMA trilayer to replace the conventional PHEMA monolayer or PMMA/PHEMA and PHEMA/PMMA bilayer as the dielectric layers of OTFTs. The memory effect was originated from the electron trapping and slow polarization of the dielectrics. The hydroxyl (-OH) groups inside the polymer dielectric were the main charge storage sites of the electrons. This charge-storage phenomenon could lead to a wide flat-band voltage shift (memory window, △VFB = 22 V) which is essential for the OTFTs’ memory-related applications. Moreover, the fabricated transistors also exhibited significant switchable channel current due to the charge-storage and slow charge relaxation.

We demonstrate the fabrication and characterization of high efficacy tetrachromatic white light-emitting diodes based on polymer and colloidal quantum dots (QDs). With a certain amount of yellowish green-emitting 2,3-dibutoxy-1,4-poly(phenylene vinylene) (DBPPV) and red-emitting CdSe/ZnS QD composite attached to an InGaN blue chip, stable and pure white light with CIE-1931 chromaticity coordinates of (0.325, 0.342), a correlated color temperature of 5800 K, and a color rendering index of 75 can be obtained. The luminous flux and efficacy of the device operated at 20 mA are 0.55 lm and 330 lm/W, respectively. In this device configuration, the emission of QDs is due not only to the radiative energy transfer from InGaN QWs and DBPPV but also to the Förster energy transfer of excitons in adjacent DBPPV chains. Based on a theoretical calculation, a high efficiency up to 32% is possible.

This work presents a fast purification system that involves a vertical quartz tube and vacuum sublimation for separation without dilution. This system produced re-crystallized 1,4-di(pyren-1-yl)benzene (DPB) in a few hours following the synthesis of pyrene derivatives with a mole yield ratio of 1,4-di(pyrene-1yl)benzene to 1-phenylpyrene (1PP) of 5:1. Differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) were utilized to identify the products. Finally, the lifetimes of pyrene derivatives DPB and 1PP were determined by exponential regression to be 10.0 ± 0.14 and 3.3 ± 0.15 ns, respectively. From the lifetime measurements, the purity of the photo-responsive materials could be easily determined. To prevent red-shift of electro-luminescence (EL) spectra by the energy transfer mechanism, it has acquired to elect transfer layers for pure electroluminescence. A co-catalytic reaction reduced the amount of impurities and eliminated the need for the use of a solvent in the purification step. CHEMICAL SOCIETYFig. 3. (a) Scheme of photon-path of lifetime measurement, (b) Exponential fitting curve for lifetime t value of purified sample evaporated at 350 o C, mixing material (DPB: 1PP = 1:1) at 350 o C and the product evaporated at 330 o C were 10.0 ± 0.14, 3.3 ± 0.15 and 3.3 ± 0.08 ns, respectively.

Color-tunable light-emitting diodes with a polymer homojunction structure have been demonstrated. The homojunction structure consisted of two emissive layers, and poly(9,9-dioctylfluorene) (PFO) was used as the host material in both emissive layers. One emissive layer was composed of a blend of blue-emitting PFO and its green-emitting copolymer, and the other one was composed of a blend of green-emitting PFO copolymer and red-emitting poly[2-methoxy-5(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEHPPV). In device characterization, when the injection current was increased, partial electrons could easily pass through the second emissive layer and flow into the first emissive layer near the anode, because there was no potential barrier existing in the homojunction. Therefore, the emission color of our devices could be tuned as orange, yellow, white, and cyan by adjusting the injection current or bias voltage.