Chien-Jung Huang

Surface plasma resonant effect of gold nanoparticles on the photoelectrodes of dye-sensitized solar cells

In this study, we prepared different shapes of gold nanoparticles by seed-mediated growth method and applied them on the photoelectrodes of dye-sensitized solar cells (DSSCs) to study the surface plasma resonant (SPR) effect of gold nanoparticles on the photoelectrodes of dye-sensitized solar cells. The analyses of field emission scanning electron microscopy show that the average diameter of the spherical gold nanoparticles is 45 nm, the average length and width of the short gold nanorods were 55 and 22 nm, respectively, and the average length and width of the long gold nanorods were 55 and 14 nm, respectively. The aspect ratio of the short and long gold nanorods was about 2.5 and 4, respectively. The results of ultraviolet–visible absorption spectra show that the absorption wavelength is about 540 nm for spherical gold nanoparticles, and the absorption of the gold nanorods reveals two peaks. One is about 510 to 520 nm, and the other is about 670 and 710 nm for the short and long gold nanorods, respectively. The best conversion efficiency of the dye-sensitized solar cells with spherical gold nanoparticles and short and long gold nanorods added in is 6.77%, 7.08%, and 7.29%, respectively, and is higher than that of the cells without gold nanoparticles, which is 6.21%. This result indicates that the effect of gold nanoparticles on the photoelectrodes can increase the conductivity and reduce the recombination of charges in the photoelectrodes, resulting in the increase of conversion efficiency for DSSCs. In addition, the long gold nanorods have stronger SPR effect than the spherical gold nanoparticles and short gold nanorods at long wavelength. This may be the reason for the higher conversion efficiency of DSSCs with long gold nanorods than those of the cells with spherical gold nanoparticles and short gold nanorods.

Enhancement and quenching of fluorescence by silver nanoparticles in organic light-emitting diodes

The influence of silver nanoparticles (SNPs) on the performance of organic light-emitting diodes (OLEDs) is investigated in this study. The SNPs are introduced between the electron-transport layers bymeans of thermal evaporation. SNPs are found to have the surface plasmon resonance at wavelength 525 nm when the mean particle size of SNPs is 34 nm. The optimized OLED, in terms of the spacing between the emitting layer and SNPs, is found to have the maximum luminance 2.4 times higher than that in the OLED without SNPs. The energy transfer between exciton and surface plasmons with the different spacing distances has been studied.

Effect of TiO2 nanotubes with TiCl4 treatment on the photoelectrode of dye-sensitized solar cells

In this study, we used the electrochemical anodization to prepare TiO2 nanotube arrays and applied them on the photoelectrode of dye-sensitized solar cells. In the field emission scanning electron microscopy analysis, the lengths of TiO2 nanotube arrays prepared by electrochemical anodization can be obtained with approximately 10 to 30 μm. After titanium tetrachloride (TiCl4) treatment, the walls of TiO2 nanotubes were coated with TiO2 nanoparticles. XRD patterns showed that the oxygen-annealed TiO2 nanotubes have a better anatase phase. The conversion efficiency with different lengths of TiO2 nanotube photoelectrodes is 3.21%, 4.35%, and 4.34% with 10, 20, and 30 μm, respectively. After TiCl4 treatment, the efficiency of TiO2 nanotube photoelectrode for dye-sensitized solar cell can be improved up to 6.58%. In the analysis of electrochemical impedance spectroscopy, the value of Rk (charge transfer resistance related to recombination of electrons) decreases from 26.1 to 17.4 Ω when TiO2 nanotubes were treated with TiCl4. These results indicate that TiO2 nanotubes treated with TiCl4 can increase the surface area of TiO2 nanotubes, resulting in the increase of dye adsorption and have great help for the increase of the conversion efficiency of DSSCs.

Synthesis of Crooked Gold Nanocrystals by Electrochemical Technique

In this article, we demonstrate the synthesis of crooked gold nanocrystals (CGNCs) by an electrochemical technique using micelle templates formed by two surfactants with different amounts of isopropanol solvent, the primary surfactant being hexadecyltrimethylammonium bromide (C16TABr) and the cosurfactant being tetradodecylammonium bromide (TC12ABr). To investigate the influence of isopropanol solvent on the CGNCs, the amount of isopropanol was varied in the range from 50 to 300 µL. It was found that the aspect ratios (γ) of CGNCs were in the range from 1.06 to 1.46, and the UV–vis optical absorption measurement revealed a pronounced redshift of the surface plasmon band from 532 to 560 nm. The CGNCs were composed of many large gold grains with small gold nuclei, and it was determined that several grains are present within each of the CGNCs using a dark-field transmission electron microscopy (TEM) image. It is suggested that the CGNCs have a polycrystalline structure. The CGNCs have been determined to be pure gold with a face-centered cubic (fcc) structure by electron diffraction (ED) analysis.

Ultraviolet photodetectors based on MgZnO thin films

In this work, Ti/Au Ohmic contacts to both Mg0.24Zn0.76O and ZnO film-based metal-semiconductor-metal (MSM) photodetectors (PDs) were fabricated on glass substrates for comparative analysis. The transmittance spectra measured around the optical energy gap revealed that Mg0.24Zn0.76O films have a larger optical energy gap (3.54 eV) than ZnO films (3.25 eV). Mg0.24Zn0.76O MSM-structured ultraviolet (UV) PDs show a much higher UV-to-visible rejection ratio of 2.78×103 than those made of ZnO films. This can be attributed to the low dark current (0.08 pA) of the Mg0.24Zn0.76O UV PDs and the small full width at half maximum (0.34°) of the Mg0.24Zn0.76O (002) x-ray diffraction peak, indicating better crystal quality than that of ZnO. With an applied bias of 5 V and illuminations at 350 and 380 nm, the Mg0.24Zn0.76O and ZnO film-based MSM PDs exhibited responsivities of 0.4 and 0.32 A/W, respectively.

Fabrication of Circular Polarization Antenna on PEI/BSTZ Composite Substrate for the Application of UHF-RFID Reader

The dielectric characteristics of poly(ether imide) (PEI)/(Ba 0.8 Sr 0.2 )(Ti 0.9 Zr 0 . 1 )O 3 (BSTZ) composites are developed. A circular polarization (CP) antenna with a simple structure is designed on a PEI/BSTZ composite substrate for the applications of ultrahigh frequency (UHF) band radio-frequency identification (RFID) readers. Two rectangular stubs on the proposed circular patch of RFID antennas are used to tune the impedance matching effect and to improve the axial ratio performance. The proposed CP antennas are successfully fabricated on the PEI/BSTZ composite substrates, and an antenna with a similar structure is also fabricated on the FR4 substrate for comparison. In this study, we demonstrate that the CP antenna fabricated on the PEI/BSTZ substrate has better characteristics and is smaller than that fabricated on the FR4 substrate. The antenna fabricated on the PEI/BSTZ composite substrate also has a larger impedance bandwidth and a smaller axial ratio than the antennas fabricated on the FR4 substrate.

Characterization of YAG Phosphor by Electrophoretic Deposition Technique

In our experiments, by varying the concentration of YAG phosphor, the deposition thickness of YAG phosphor plate can be controlled approximately 16 to 40 micrometer under a bias voltage of 200 V. By combining the blue LED light and the above EPD YAG phosphor plate, the white light with a correlated colour temperature (CCT) can be achieved and varied from 3800 K to 6000 K. In the conventional dispense package, the larger CCT variation was always found and varied from 80 K to 1500 K which is related to the packing density. However, in our EPD YAG case, the uniform white light was achieved easily, i.e. that is the lower CCT variation. In addition, the external extraction efficiency was also found higher than the tradition white LED.

Thin Copper Seed Layers in Interconnect Metallization Using the Electroless Plating Process

In this paper, we present a process for growing a Cu seed layer on a Ta/SiO2/Si substrate using an electroless plating (ELP) process at an extremely low temperature (~30°C). In this process, the activation treatment of the Ta/SiO2/Si substrate was carried out by immersion in a PdCl2/HCl solution prior to electroless Cu deposition. The optimum activation time for the substrate was clearly observed to be 7 min. The Cu seed layer was uniformly and smoothly deposited using a CuSO4 concentration of 30 mM for 80 s with an average roughness of 14 nm under a thin film of 50 nm thickness. The grain size of the Cu seed layer was 34 nm. After annealing in hydrogen ambience at 250–350°C, the average roughness of the Cu seed layer was reduced to 4 nm. A proposed mechanism for the ELP of Cu seed layers on Ta/SiO2/Si substrates is also presented.

The Effects of Dilute Sulfuric Acid on Sheet Resistance and Transmittance in Poly(3,4-thylenedioxythiophene): Poly(styrenesulfonate) Films

The conductivity of poly(3,4-thylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) films by adding various molar concentrations of sulfuric acid (H 2SO 4) was improved and studied in this paper. The sheet resistance of the doped PEDOT: PSS film was enhanced with increasing the ratio of H 2SO 4, but it drops after the maximum sheet resistance. The reason for this phenomenon is resulting from the fact that the H 2SO 4 preferentially react with the sorbitol which is so-called the pinacol rearrangement. The nonconductive anions of some PSS − were substituted by the conductive anions of hydrogen sulfate (HS ) when the residual H 2SO 4 reacted with PSS. In addition to the substitution reaction, PEDOT chains were increasingly aggregated with increasing the ratio of H 2SO 4. After doped H 2SO 4, the sheet resistance of H 2SO 4-doped PEDOT: PSS film is improved nearly 36%; the surface roughness is reduced from 1.268 nm to 0.822 nm and the transmittance is up to 91.9% in the visible wavelength range from 400 to 700 nm.

Growth Of ZnO Nanorods by Hydrotherothermal Method Under Different Temperatures

In this study, the aqueous solution method was employed to synthesize one-dimensional well-aligned ZnO nano-array on ITO glass substrate. We can find that the dimension of ZnO nanorod will changes with different growth temperature. X-ray diffraction patterns show that the nanorods are high-quality crystals growing along [001] direction with a high consistent orientation perpendicular to the substrate while the growth temperature is equal to 80. SEM images show that the average diameters of ZnO nanorods are about 60-90 nm by changing growth temperature. The smallest diameter of ZnO nanorods is observed while the growth temperature is equal to 75 degc. The UV/Vis spectra analyses show the absorption peaks appear at 330 nm, 370 nm and 390 nm while growth temperature increases from 65 degc to 85 degc.