Tsong-Pyng Perng

Highly efficient flexible inverted organic solar cells using atomic layer deposited ZnO as electron selective layer

With atomic-layer-deposition grown zinc oxide as the electron selective layer, we developed plastic substrate compatible processing for organic photovoltaic devices and demonstrated flexible inverted organic solar cells on poly(ethylene naphthalate) with a power conversion efficiency of 4.18%.

Electron field emission from Fe-doped TiO2 nanotubes

Titanium dioxide nanotubes were prepared by refluxing TiO2 in 10 M NaOH at 200 °C for 12 h. The light absorption edge was slightly shifted to a longer wavelength when 0.025 mol % of iron was incorporated to TiO2 nanotubes. A turn-on field at 12 V/μm and a maximum current density of 12 mA/cm2 at 19 V/μm was observed for the Fe-doped but not for pure TiO2. The field emission behavior can be correlated with the geometry and electronic states of the nanotubes.

Fabrication of Ag-loaded multi-walled TiO2 nanotube arrays and their photocatalytic activity

TiO2 multi-walled nanotube arrays (MWNTAs) were synthesized by atomic layer deposition (ALD) using anodic aluminum oxide (AAO) as the template. TiO2 and Al2O3 layers were alternately deposited into the AAO pores by ALD. The tube thickness and the gap span were controlled by the ALD cycle numbers of TiO2 and Al2O3, respectively. A MWNT composed of two or three concentric tubes with different diameters was formed after removal of Al2O3. Silver nanoparticles were then deposited on both inner and outer surfaces of the tubes by photochemical reduction. Degradation of methylene blue was carried out to evaluate the photocatalytic activity of bare and silver-loaded TiO2 MWNTAs. It was found that the amount of TiO2, the reaction surface area, the crystalline phase, and silver modification were the factors to determine the photocatalytic activity. The triple-walled MWNTAs showed the best performance, and Ag loading further enhanced the activity.

Correlation of substitutional solid solution with hydrogenation properties of TiFe1−xMx (M=Ni, Co, Al) alloys

The hydrogenation properties of TiFe partially substituted with a small amount of Ni, Co, or Al for Fe were studied. Complete solid solutions were observed for all compositions, but different characteristics of the pressure–composition–temperature (P–C–T) curves were observed. For Ni- and Co-substituted alloys, the shape of the P–C–T curves and the hydrogen storage capacities were very similar to those of pure TiFe. The plateau pressures in the two-phase (α–β) region always remained flat, but decreased drastically as the amount of nickel or cobalt was increased. The different hydrogenation behaviors are explained on the basis of different values of hydride formation enthalpies of TiFe, TiNi, and TiCo. When Fe was partially replaced by Al, a solid solution was also formed, but the sizes of the octahedral sites were changed. The hydrogen storage capacity was decreased and the slope of the plateau pressure increased as the amount of aluminum increased. The change of slope of the plateau pressure is explained and modeled by the various sizes of the octahedral sites.

Effect of the second phase on the initiation of hydrogenation of TiFe1−xMx (M = Cr,Mn) alloys

Abstract The hydrogen absorption characteristics of TiFe partially substituted with a small amount of Cr or Mn for Fe were studied. The morphology of the specimen surface was examined and the phases in the sample were identified. The microscopic composition differences for the individual phases were analyzed. It was observed that the samples required no activation for hydrogenation when a second phase was present. Increasing the amount of the second phase led to a higher activation rate, lower plateau pressure and higher maximum absorption capacity. Homogenization treatment at 900°C reduced the activation rate, but had no effect on the subsequent hydrogenation properties. The effects of substitution and homogenization on the hydrogenation of TiFe were correlated with the quantity and morphology of the second phase.

Hydrogenation of TiFe by high-energy ball milling

The hydrogenation properties of TiFe, TiFe2 and pure Ti during high-energy ball milling in hydrogen atmosphere were studied. By ball milling, TiFe could absorb hydrogen without activation treatment. For Ti powder, a single phase TiH1.924 was formed. In addition, TiFe2 could also be hydrided by ball milling in hydrogen, which was ascribed to decomposition to form TiFeHx, TiH1.924, and Fe. Based on the hydrogenation properties of Ti, TiFe, and TiFe2 during dynamic ball milling and the thermal stability of the milled powders, it is proposed that the reactions in the milling of TiFe in hydrogen involve four steps: (1) fresh surfaces created by collision with the balls; (2) absorption of hydrogen by the powder; (3) oversaturation of hydrogen in the powder; (4) decomposition of TiFeHx to TiH1.924 and Fe.

Tris-(8-hydroxyquinoline) aluminum nanoparticles prepared by vapor condensation

Tris-(8-hydroxyquinoline) aluminum (AlQ3) spherical nanoparticles of the average size varying from 50 to 500 nm were synthesized by vapor condensation. The surface of the nanoparticles is quite sleek and smooth like that of pearls. The x-ray diffraction patterns reveal that the nanoparticles have an amorphous structure. The chemical bonding of AlQ3 is preserved in the nanoparticles even after evaporation at 410 °C. The photoluminescence spectra of the nanoparticles show a broadened peak varying from 4500 to 7000 A, with the maximum intensity at about 5380 A. The maximum intensity increases as the particle size decreases, owing to the large specific surface area.Tris-(8-hydroxyquinoline) aluminum (AlQ3) spherical nanoparticles of the average size varying from 50 to 500 nm were synthesized by vapor condensation. The surface of the nanoparticles is quite sleek and smooth like that of pearls. The x-ray diffraction patterns reveal that the nanoparticles have an amorphous structure. The chemical bonding of AlQ3 is preserved in the nanoparticles even after evaporation at 410 °C. The photoluminescence spectra of the nanoparticles show a broadened peak varying from 4500 to 7000 A, with the maximum intensity at about 5380 A. The maximum intensity increases as the particle size decreases, owing to the large specific surface area.

In situ observation of combustion to form TiN during ball milling Ti in nitrogen

Mechanical milling of Ti powder in nitrogen by a high-energy ball mill was performed. The pressure was monitored in situ. Initially, nitrogen was dissolved in Ti to form a solid solution. Under suitable conditions, when the nitrogen content had reached 32 at. %, the nitrogen pressure drastically dropped and instant formation of TiN took place. The TiN was formed by means of self-catalytic combustion, which was triggered by the high impact energy and the large clean surface of the fine Ti particles.

Fabrication of tin dioxide nanowires with ultrahigh gas sensitivity by atomic layer deposition of platinum

Gas-sensing properties of SnO2 nanowires were investigated before and after their surface functionalization by the atomic layer deposition (ALD) of Pt nanoparticles. The morphology, size, and concentration of Pt particles on SnO2 nanowires can be controlled by varying the number of ALD reaction cycles, and therefore, the gas-sensing properties of the nanowires can be altered via the Pt catalyst effect and the modification of Schottky barrier junctions on the nanowire surface in the vicinity of Pt nanoparticles. The Pt-decorated SnO2 nanowires obtained after 200 ALD reaction cycles exhibited an ultrahigh gas sensitivity (S = Ig/Ia) of ∼8400 to 500 ppm ethanol vapor at 200 °C. This provides an efficient route for strongly enhancing the gas sensitivity of semiconducting nanostructures and fabricating gas sensors that are highly sensitive and responsive.

Electrochemical Hydrogenation of Crystalline Co Powder

The electrochemical hydrogenation properties of two boron-free crystalline Co powder samples were investigated. They exhibited almost the same maximum discharge capacities with 2-h charging, 415 and 428 mAh/g (corresponding to CoH 0.91 and CoH 0.93 ) for samples A and B, respectively. The high discharge capacity of Co powder was attributed to hydrogenation of Co and phase transition between the phases of hexagonal close-packed and face centered cubic.