Supachai Ngamsinlapasathian

Partially nanowire-structured TiO2 electrode for dye-sensitized solar cells

Partially nanowire-structured TiO2 was prepared by a hydrothermal processing followed by calcination in air. The hydrogen titanate powder as-synthesized was calcined at 300 °C for 4 h to obtain the partially nanowire-structured TiO2. A dye-sensitized solar cell (DSC) with a film thickness of 5.6 μm, fabricated using the partially nanowire-structured TiO2 showed better performance than using a fully nanowire-structured TiO2 or a conventional equi-axed TiO2 nanopowder. The short-circuit current density (JSC), the open-circuit voltage (VOC), the fill factor (FF) and the overall efficiency (η) are 11.9 mA/cm2, 0.754 V, 0.673 and 6.01 %, respectively. The effects of one-dimensional nanostructure and electron expressway concept are discussed.

TiO2-Anatase Nanowire Dispersed Composite Electrode for Dye-Sensitized Solar Cells

TiO2 anatase nanowires have been prepared by a hydrothermal process followed by post-heat treatment in air. TiO2 nanoparticle/TiO2 nanowire composite electrodes were prepared for dye-sensitized solar cells (DSC) in order to improve light-to-electricity conversion efficiency. The TiO2 NP/TiO2NW composite cells showed higher DSC performance than ordinary nanoparticle cells and fully nanowire cells: efficiency (η = 6.53 % for DSC with 10% nanowire, whereas 5.59% for 0% nanowire, and 2.42% for 100% nanowire.

Addition of TiO2 nanowires in different polymorphs for dye-sensitized solar cells

TiO2 (B) and TiO2 anatase nanowires were prepared at 150 °C for 120 h by a hydrothermal method followed by calcination in air at 400 °C for 2 h and at 700 °C for 2 h for TiO2 (B) and TiO2 anatase, respectively. Although dye-sensitized solar cells (DSC) with fully nanowire electrodes showed a rather low light-to-electricity conversion efficiency of 1.33 % for TiO2 (B) and 2.42% for TiO2 anatase, 10 wt % nanowire-dispersed electrodes in a P-25 TiO2-nanoparticle matrix demonstrated improved efficiency of 6.17 % for TiO2 (B) and 6.53% for TiO2 anatase, these exceeding that of pure P-25 electrodes in this work (η=5.59%). The dominant mechanisms of the improvement at 10 wt% for the two different polymorphs are thought to be different, i.e., a light-scattering and film-thickness increment for the TiO2 (B) system, whereas there is an improved conduction path through the matrix for the TiO2 anatase system.

Positive role of incorporating P-25 TiO2 to mesoporous-assembled TiO2 thin films for improving photocatalytic dye degradation efficiency.

In this work, a simple and effective strategy to improve the photocatalytic dye degradation efficiency of the mesoporous-assembled TiO2 nanoparticle thin films by incorporating small contents of commercial P-25 TiO2 during the thin film preparation was developed. The mesoporous-assembled TiO2 nanoparticles were synthesized by a sol-gel method with the aid of a mesopore-directing surfactant, followed by homogeneously mixing with P-25 TiO2 prior to the thin film coating on glass substrate. The mesoporous-assembled TiO2 film with 5 wt.% P-25 TiO2 incorporation and calcined at 400°C provided an improved photocatalytic Acid Black (AB) dye degradation efficiency. The increase in number of coated layers to the optimum four layers of the aforementioned film was found to further improve the degradation efficiency. The recyclability test of this 5 wt.% P-25 TiO2-incorporated mesoporous-assembled TiO2 film with four coated layers revealed that it can be reused for multiple cycles without a requirement of post-treatment while the degradation efficiency was retained.

Photochemically deposited nano-Ag/sol-gel TiO2-In2O3 mixed oxide mesoporous-assembled nanocrystals for photocatalytic dye degradation.

This work focused on the improvement of the photocatalytic activity for Congo Red (CR) azo dye degradation of mesoporous-assembled 0.95 TiO2-0.05 In2O3 mixed oxide photocatalyst (with a TiO2-to-In2O3 molar ratio of 0.95:0.05) by loading with Ag nanoparticles. The mesoporous-assembled 0.95TiO2-0.05In2O3 mixed oxide photocatalyst was synthesized by a hydrolytic sol-gel method with the aid of a structure-directing surfactant, prior to loading with various Ag contents (0.5-2 wt.%) by a photochemical deposition method. The optimum Ag loading content was found to be 1.5 wt.%, exhibiting a great increase in photocatalytic CR dye degradation activity. The 1.5 wt.% Ag-loaded 0.95TiO2-0.05In2O3 mixed oxide photocatalyst was further applied for the CR dye degradation in the presence of water hardness. Different types (Ca2+ and Ca2+ -Mg2+ mixture) and concentrations (200 and 500 mg/l) of water hardness were investigated. The results showed that the water hardness reduced the photocatalytic CR dye degradation activity, particularly for the extremely hard water with 500 mg/l of Ca2+ -Mg2+ mixture. The adjustment of initial solution pH of the CR dye-containing hard water to an appropriate value was found to improve the photocatalytic CR dye degradation activity under the identical reaction conditions.

Hydrothermal Synthesis of Nanorods/Nanoparticles TiO 2 for Photocatalytic Activity and Dye-sensitized Solar Cell Applications

Nanorods/nanoparticles TiO 2 with mesoporous structure were synthesized by hydrothermal method at 150 °C for 20 h. The samples characterized by XRD, SEM, TEM, SAED, HRTEM, and BET surface area. The nanorods had diameter about 10-20 nm and the lengths of 100-200 nm, the nanoparticles had diameter about 5-10 nm. The prepared material had average pore diameter about 7-12 nm. The BET surface area and pore volume of the sample are about 203 m 2 /g and 0.655 cm 3 /g, respectively. The nanorods/nanoparticles TiO 2 with mesoporous structure showed higher photocatalytic activity (I 3 − concentration) than the nanorods TiO 2 , nanofibers TiO 2 , mesoporous TiO 2 , and commercial TiO 2 (ST-01, P-25, JRC-01, and JRC-03). The solar energy conversion efficiency (η) of the cell using nanorods/nanoparticles TiO 2 with mesoporous structure was about 7.12 % with Jsc of 13.97 mA/cm 2 , Voc of 0.73 V and ff of 0.70; while η of the cell using P-25 reached 5.82 % with Jsc of 12.74 mA/cm 2 , Voc of 0.704 V and ff of 0.649.

Effects of Substrates on Dye-Sensitized Solar Cell Performance Using Nanocrystalline TiO2

The effects of conducting glasses on photovoltatic properties of dye-sensitized solar cells using nanocrystalline TiO2 were studied. The ITO substrate showed low ability to withstand heat during the sintering process, leading to an increase in sheet resistance. The heat stability of ITO conducting glass was improved by depositing metal oxide such as ATO, AZO, and SnO2, on ITO layer. The IPCE spectra of thin MP-TiO2 cell were higher than that of thick P25 cell in the region between 400-475 nm but lower than that of thick P25 cell in the red region, because the thickness of MP-TiO2 film was not enough to scatter the light leading to low absorbed spectra in red region. IPCE spectra can be improved by using the cell made from blend MP-TiO2 with P25. The efficiency of the MP-TiO2+P25 cells using ITO/SnO2 conducting substrate remarkably increased comparing with that of the cells using ITO.

The Enhancement of Dye-Sensitized Solar cell Performance by Tio2-Based Mixed Metal Oxide Nanostructured Electrodes

The TiO2-based mixed metal oxides were synthesized by surfactant assisted templating method. The XRD results indicated that the addition of small amount of other metal oxides into nanostructured TiO2, the structure of the mixed oxide still maintains an anatase type of TiO2.The role of added metal was based on the crystal growth inhibiter, which leads to smaller grain size when compared to the sole metal oxide. Among TiO2-based mixed metal oxides, the cells fabricated from TiZr5 showed the highest efficiency of 5.13%