Abstract: Bulk-heterojunction solar cells were fabricated based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) on an indium tin oxide (ITO) coated flexible polyethylene terephthalate (PET) substrate. Performance improvements of the flexible solar cells by optimizing post thermal annealing conditions are reported. The solar cells annealed at 150 oC showed the minimal deformation of the PET substrate, and the resulted conversion efficiency was 1.35% under the light irradiation conditions of the Superscript textAM1.5 simulated solar intensity of 100 mW/cm2.
Abstract: Polythiophene derivatives, poly(2,2′:5′,2″:5″,2″′:5″′,2″″-quinquethiophene) (P5T), poly (2,3,4,5-tetrathiopenyl-thiophene) (PX5T) and poly(1,3,5-tristhienyl-benzene) (P3TB), were prepared via the electropolymerization. The electrochromic properties of polythiophene derivative films were investigated. The results showed that P5T, PX5T and P3TB films exhibited reversible, clear colour change in liquid electrolyte on electrochemical doping and dedoping. Moreover, solid state electrochromic device, indium tin oxide (ITO)/polythiophene derivative films/conducting gel /ITO, were fabricated with polythiophene derivative films as the active electrochromic layer. The color change of polythiophene derivative films based on gel electrolyte on electrochemical doping and dedoping were similar with the color change based on liquid electrolyte.
Abstract: A novel chromophore molecule (HEPNBT) was synthesized by diazo-coupling reaction. The polyurethane (HEPU) was obtained from chromophore molecule HEPNBT, NJ-220 and isophorone diisocyanate (IPDI). The structures of HEPNBT and HEPU were characterized using the Fourier transform infrared and UV-visible spectroscopy. The refractive index (n) of HEPU was determined at different temperature and wavelength (532nm, 650nm and 850nm) using attenuated total reflection (ATR) technique, and the thermo-optic coefficient (dn/dT) was -4.149×10-4 °C-1(532nm), -7.954×10-4°C-1 (650nm) and -6.71Superscript text4×10-4°C-1 (850nm), resSuperscript textpectively. Using the CCD digital imaging devices, transmission loss of HEPU was measured and the value was 0.238 dB/cm. The results show that the obtained HEPU has a certain significance to the development of new types of digital thermo-optic switch material.
Abstract: By the control of the reducing atmospheres in the one-pot combustion reactions, Eu2+, Eu3+ and Dy3+ co-activated strontium aluminate oxide were synthesized. X-ray diffraction confirmed the formation of monoclinic SrAl2O4 nanocrystals. The photoluminescence spectra of the phosphors were measured. It is found that three sharp emissions at 483, 570 and 615 nm were superimposed onto the broad green emission band at about 520 nm. The origins of the broad green luminescent band, the sharp blue at 483 nm, and sharp yellow emissions at 570 nm and the sharp red emissions at 615 nm can be attributed to the 4f65d1→4f7 transitions of Eu2+ ions, the 4F9/2→6H15/2 transition of Dy3+ ions, the 4F9/2→6H13/2 transition of Dy3+ ions, and the 5D0–7F2 transition of Eu3+ ions in the SrAl2O4 nanocrystals, respectively. The results indicate that the white light emitting phosphors are possible by tuning the relative molar percentages of Eu2+, Eu3+ and Dy3+ in the phosphors.
Abstract: In this thesis, Zn films were deposited on silicon substrates by high-speed galvanization, and then were treated in Muffle Resistance Furnace at 700°Cin an open-air environment. Polycrystalline ZnO films covered with ZnO nanorods were grown. Its morphologies were studied by SEM and its crystal structures were studied by XRD．Its photoluminescence spectrum was also measured．And possible mechanisms of the growth and the photoluminescence of ZnO nanorods were proposed to explain the experimental result．
Abstract: The synthesis of ZnO nanocrystals is carried out in alkaline alcoholic solution of zinc acetate dihydrate by sol-gel method. Effects of thermal annealing in nitrogen on photoluminescence (PL) properties of the sol-gel derived ZnO nanocrystals were investigated by PL spectroscopy. With increasing annealing temperature in nitrogen, UV emissions of the ZnO nanocrystals red-shifted from 378 nm to 388 nm while deep-level luminescent bands ranging from 450 to 700 nm with three emission centers at about 502 nm, 538 nm and 602 nm are enhanced, and the green luminescent band gains its intensity at the expense of the yellow and orange luminescent bands. Our results have demonstrated that the origin yellow-green color PL was tuned towards the cyan color PL with increasing the thermal annealing temperature in nitrogen from 344 oC to 813 oC.
Abstract: ZnO films covered with microrods were grown on silicon and porous silicon through electrochemical deposition with silicon or porous silicon as cathode, a platinum wire as anode, and zinc chloride solution of 0.05mol/L as electrolyte. The morphologies by SEM and the crystal structures by XRD were studied. The photoluminescence spectra were also measured. And the mechanisms of the growth and the photoluminescence of the ZnO thin films were analyzed and compared. Studies showed that the luminous intensity of ZnO thin films is different under different conditions, but its peak is located between 370-385nm, luminous intensity of the ZnO film deposited on porous silicon and then annealed is weaker.
Abstract: ZnTe nanocrystals were synthesized in NaOH solution by hydrothermal method and they were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and micro-Raman spectroscopy. The results indicate that the ZnTe nanocrystals were crystallized in cubic zincblende structure and their morphologies and sizes are polyhedron and diversified, respectively. The Raman results show that different scattering occurred from the ZnTe nanocrystals depending different excitation wavelengths. According to theories related to band-gap and Raman scattering, the excitation wavelength-dependent Raman scattering from the ZnTe nanocrystals was analyzed.
Abstract: Zinc oxide (ZnO) was synthesized by solid-liquid reaction of raw Zn particles in water. The synthesized ZnO were characterized with X-ray diffraction (XRD), scanning electronic microscopy (SEM) and photoluminescence (PL) spectrophotometer. The XRD pattern confirmed that the formation of ZnO with wurtzite structure and ZnOOH crystals. The SEM study clearly exhibited a honeycomb-shaped structure of the Zn/ZnO/ZnOOH composites. Room-temperature PL spectra have been observed a very weak UV emission at 376 nm and a very strong yellow-green emission at 538 nm. Furthermore, a possible mechanism of the water-assisted conversion of ZnO from metallic Zn particles was discussed.