Pennapa Muthitamongkol

Effect of Silver Nanoparticle Size on Efficiency Enhancement of Dye-Sensitized Solar Cells

Titanium dioxide/silver (TiO2/Ag) composite films were prepared by incorporating Ag in pores of mesoporous TiO2 films using a photoreduction method. The Ag nanoparticle sizes were in a range of 4.36–38.56 nm. The TiO2/Ag composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The TiO2 and TiO2/Ag composite films were then sensitized by immersing in a 0.3 mM N719 dye solution and fabricated for conventional dye-sensitized solar cells (DSCs). J-V characteristics of the TiO2/Ag DSCs showed that the Ag nanoparticle size of 19.16 nm resulted in the short circuit current density and efficiency of 8.12 mA/cm2 and 4.76%.

A Combined Effect of Plasmon Energy Transfer and Recombination Barrier in a Novel TiO2/MgO/Ag Working Electrode for Dye-Sensitized Solar Cells

Novel TiO2/MgO/Ag composite electrodes were applied as working electrodes of dye-sensitized solar cells (DSSCs). The TiO2/MgO/Ag composite films were prepared by dip coating method for MgO thin films and photoreduction method for Ag nanoparticles. The MgO film thicknesses and the Ag nanoparticle sizes were in ranges of 0.08–0.46 nm and 4.4–38.6 nm, respectively. The TiO2/MgO/Ag composite films were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The TiO2/MgO/Ag composite electrodes were sensitized by immersing in a 0.3 mM of N719 dye solution and fabricated for conventional DSSCs. - characteristics of the TiO2/MgO/Ag DSSCs showed that the MgO film thickness of 0.1 nm and the Ag nanoparticle size of 4.4 nm resulted in maximum short circuit current density and efficiency of 8.6 mA/cm2 and 5.2%, respectively. Electrochemical Impedance Spectroscopy showed that such values of short circuit current density and efficiency were optimal values obtained from plasmon energy transfer by 4.4 nm Ag nanoparticles and recombination barrier by the ultrathin MgO film.

Power Factor of Germanium Antimony Tellurium Thin Film on Al2O3 Ceramic Substrate Deposited by Pulsed–DC Magnetron Sputtering

Germanium–Antimony–Telluride (Ge–Sb–Te) has low electrical resistivity and thermal conductivity for good thermoelectric properties. The Ge–Sb–Te thin films were deposited on Al2O3 ceramic substrate by pulsed–dc magnetron sputtering system using a 99.99 % Ge:Sb:Te of 1:1:1 composite target and annealed at 573, 623, 673, and 723 K for 1 hour in vacuum. The phase identification, atomic composition, morphology and film thickness (d), carrier concentration (n), mobility (µ), Seebeck coefficient (S) and electrical resistivity (ρ) of the as–deposited and the annealed samples were investigated by X–ray diffraction (XRD), energy dispersive X–ray spectroscopy (EDX), field–emission scanning electron microscopy (FE–SEM), Hall–effect measurement, steady state method and calculation of from n and µ, respectively. The results demonstrated that the as–deposited Ge–Sb–Te film showed amorphous phase and annealing changed the phase crystalline. Morphologies of annealed Ge–Sb–Te films showed very large grain size and porosity to obtaining good n and µ. The approximately maximum power factor (P) was 4.22×10−4 W m−1 K−2 at annealing temperature of 723 K.

Effects of Magnetic Field on Synthesis and Thermoelectric Properties of NaCoO2

We synthesized polycrystalline sodium cobalt oxide (NaCoO2) by using solid state reaction (SSR) method in a magnetic field. The powder of Na2CO3 and Co3O4 were mixed by ball milling and compacted in a magnetic field. The characterization of microstructure of powder size and crystal structure were analyzed through XRD. Thermoelectric properties and the lattice parameter of NaCoO2 showed little change in magnetic field. The lattice parameters of NaCoO2 are a = 2.8443 Å, b = 2.8443 Å, and c = 10.8091 Å in the hexagonal structure (a = b ≠ c).

Microstructure and Thermoelectric Properties of Na0.5CoO2

The polycrystalline of sodium cobalt oxide (Na0.5CoO2) was synthesized by solid state reaction method and sintering method. The microstructure was composed of powder size and crystal structure. The Seebeck coefficient and electrical resistivity are measured. We found that the concentration of sodium ions sandwiched between two neighboring CoO2 layers played a crucial role in transport properties. The results showed small particle size, single phase and orthorhombic structure. The Seebeck coefficient of Na0.5CoO2 increased as the temperature increased. The electrical resistivity was decreased as temperature decreased from the range 300-500 K.

Transparent conductive nanocolumnar AZO film coating by glancing angle deposition technique

In this work, we deposited nanocolumnar aluminum doped zinc oxide (AZO) film by glancing angle deposition (GLAD) to produce transparent conductive oxide (TCO) film with omnidirectional antireflecti...

Effect of Strong Correlation of Mg2+-doped into Cr3+ Sites of CuCrO2 on Thermoelectric Properties

This study aims to investigate the strong correlation effect of spin and charge carriers for the Mg2+-substituted into Cr3+ sites of CuCrO2 delafossite on thermoelectric properties. The CuCr0.98Mg0.02O2 sample was synthesized by a solid state reaction. The starting powder CuO, Cr2O3 and MgO were ball milled with poly vinyl alcohol solution for 24 h. The ball milled powder was pressed and sintered in air atmosphere at temperature 1050 C for 6 h. The crystal structure was characterized by XRD, TGA, XPS and the thermoelectric properties were measured at high temperature. The XRD displayed peaks of the pure phase CuCrO2 structure as hexagonal delafossite-type structure space group: Rm. The Seebeck coefficient of the samples displayed positive sign as p-type (hole) conductor. The XPS results displayed Mg2+, Cu1+, Cr3+ and Cr4+ ion states. The Mg2+ induced mixed-valance Cr3+/Cr4+ states resulting in enhanced Seebeck coefficient due to a strong correlation of the spin-entropy. The experimental results of Seebeck value were close to calculated results by the extended Heikes formula confirming of the strong correlation effect. In addition, the Mg-doped CuCrO2 resulted in increased electrical conductivity and reduced thermal conductivity with increasing temperature. These indicate that the Mg2+-substituted for Cr3+ of CuCrO2 delafossite enhance the thermoelectric properties.

Characterization P-Ca3Co4O9 and N-CaMnO3

We present characterization and thermoelectric properties of oxide thermoelectric materials of P-Ca3Co4O9 and N-CaMnO3 synthesized by solid state reaction method and sintering in air. The crystalline structure was measured by x-ray diffraction (XRD) and confirmed by transmission electron microscope (TEM). The powder size and gran size of P-Ca3Co4O9 and N-CaMnO3 were observed by scanning electron microscope (SEM). The electrical resistivity and Seebeck coefficient are measured. It was found that, the P-Ca3Co4O9shows the point symmetry groups in three dimensions require of monoclinic system and N-CaMnO3 shows cubic system corresponding with TEM results. The powder size and grain size were obtained mean values of 1-3 µm. The electrical resistivity and Seebeck coefficient were obtained for P-Ca3Co4O9and for N-CaMnO3 at 360 K.

Characterization of Zn0.96Al0.02Ga0.02O Thermoelectric Material

Crystal structure of Zn0.96Al0.02Ga0.02O was analyzed by X-Ray diffraction (XRD) technique and the microstructure was observed by scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD results showed single phase and hexagonal structure a = b = 3.24982 Å, and c = 5.20661 Å. The SEM and TEM results showed the grain size of material arrangement changed after sintering and TEM diffraction pattern confirmed hexagonal crystal structure of Zn0.96Al0.02Ga0.02O after sintering.