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Recently, SnO2-based perovskite solar cells (PSCs) have become more promising than traditional-material-based PSCs because of their simple low-temperature solution approach and low cost; meanwhile, the high-temperature process of mesoporous TiO2-based PSCs still offers a higher power conversion efficiency (PCE). In planar-based PSCs, nonradiative recombination of electron-hole pairs at the SnO2/perovskite interface leads to a loss of potential and a reduced PCE. Here, the SnO2-SDBS electron transport layer (ETL) is employed in PSCs to depress the defects of the SnO2 layer and the grain boundaries of the perovskite film. The surfactant SDBS was used as a wetting agent for SnO2 nanoparticles, to improve dispersibility. In addition, the benzene sulfonic acid group of SDBS attached to the SnO2-SDBS film can control the process of perovskite crystallization, producing a vertically aligned growth and large-grain perovskite layer. Finally, the open-circuit voltage was improved from 1.038 to 1.077 V and the PCE increased from 18.01% to 19.25% in the devices using the SnO2-SDBS ETL. The incorporation of SnO2-SDBS as an ETL paves the way to further performance enhancements of SnO2-based planar PSCs.

Perovskite solar cells have been attracting extensive attention because of their superior photovoltaic performances and lower costs as compared to those of prevailing photovoltaic technologies. There are four main interfaces in perovskite solar cells: flourine-doped tin oxide/electron transport layer, electron transport layer/perovskite layer, perovskite layer/hole transport layer, and hole transport layer/metal electrode. Among them, the interface between the perovskite layer (general formula RPbX3) and electron transport layer significantly affects the power conversion efficiency. In this study, a layer of TiO2, which is the most popular metal oxides used for perovskite solar cells applications, was deposited as the electron transport layer. To enhance the perovskite solar cells performance, surface treatment was performed with TiCl4 (80 mM). To investigate the effect of TiCl4 treatment, ultraviolet-visible spectroscopy was performed on the perovskite film. Atomic force microscopy, X-ray diffraction, scanning electron microscopy and performance of perovskite solar cells have been also evaluated in this paper. The results indicated that the TiCl4 treatment significantly improved the perovskite solar cells performance.

In this letter, we report on the simple process of preparing perovskite oxide SrMnO3 and the studying of the size effect on electrochemical properties for high-performance supercapacitor electrode. The high-crystalline micro-sized and nano-sized perovskite oxide SrMnO3 particles were successfully synthesized by a simple solid-state reaction, followed by a simple size reduction using high-energy ball milling. The electrochemical properties of the SrMnO3 had intriguing results on both sizes of particle, especially when comparing between before and after cycles. After a size reduction, the specific capacitance of the particles increased approximately twofold. Interestingly, the micro-sized SrMnO3 gained ∼500% its initial specific capacitance after 3000 successive cycles due to electrochemical nano-feature activation and oxygen-vacancy production, while the specific capacitance for the nano-sized SrMnO3 remained almost unchanged. Our work suggested a cost-effective and simple technique for high-performance perovskite-based supercapacitor electrodes by achieving the desired performance.

As the BO6 octahedral structure in perovskite oxide is strongly linked with electronic behavior, it is actively studied for various fields such as metal–insulator transition, superconductivity, and...

The ferroelectric material chosen for a solar cell has to absorb as much of the solar spectrum as possible, therefore a low band gap is desirable, but it is rarely known for phase transition temperature on the bandgap engineered ferroelectric materials. The phase transition temperature of a ferroelectric material can be determined by monitoring its dielectric constant with increasing temperature, as the dielectric constant changes abruptly at the phase transition temperature. Here, we inform the measurement of the phase transition temperature of the ferroelectric complex oxide Bi3.25La0.75Ti3O12 as well as cobalt and iron doped Bi3.25La0.75Ti3O12 bulk ceramics for photovoltaic cells based on dielectric monitoring with changing temperature. We synthesized lanthanum-modified bismuth-titanate-based ceramics with various doping concentrations transition metal to Ti. X-ray diffraction analysis revealed that all the compounds crystallized in an orthorhombic structure. Their morphologies and size distributions were observed using scanning electron microscopy. From the ultraviolet-visible spectroscopy absorption spectra of the synthesized powder, bandgaps were checked. An inductance-capacitance-resistance meter was used to obtain the relationship between dielectric responses and the temperature of the targets in a tube furnace. We observed that the dielectric constant increases gradually with increasing temperature, until the transition temperature and subsequently decreases, and we were able to determine the phase transition temperatures of the tested materials. Furthermore, the results revealed that all the doped bismuth titanates keep their phase transition temperatures, which were sufficiently high, to maintain their ferroelectric properties above room temperature.

Perovskite solar cells (PSCs) represent the third generation of solar cells that comprise a semiconductor electrode, a counter electrode, and an electrolyte. Perovskite solar cells (PSCs) have been comprehensively researched and led to an impressive improvement in a short period of time as cheaper alternatives to silicon solar cells due to their high energy-conversion efficiency and low production cost. Tin oxide (SnO2) has attracted attention as a promising candidate for electron transport material of perovskite solar cells, because it can be easily processed by low annealing temperature and solution processing method. However, in the fabrication of SnO2 electron transfer layer (ETL) via the conventional solution method, it is greatly difficult to increase the size of the substrate by the solution treatment method or to commercialize it. In this work, we report the photovoltaic characteristics of SnO2 based electron transport layer for perovskite solar cells (PSCs) fabricated by the thermal-evaporation processing method. The deposited SnO2 layer with the thermal evaporator is known to be not crystallographically stable. To solve this problem, we performed the annealing process at relatively low temperature (below 200 °C). As a result, we could confirm the optimum annealing temperature and we could demonstrate PSCs with thermally deposited SnO2 as the compact electron transport layer through a low-temperature annealing process. It would contribute to new opportunities in commercialization and development of perovskite solar cells.

In the proposed method, we could complete the synthesis with only 3 h of thermal treatment, which is relatively fast in comparison to the previously reported procedure, without an expensive gascontrolled chamber system. The compound comprises Re2O3 and NiO3 powders that were mixed thoroughly in a stoichiometric ratio in a ball mill for 24 h and then dried in an oven at a 100 °C. The powder mixture was quickly calcined at various temperature for at least 3 h in an oxygen gas flow compared to conventional annealing method. After calcination at 1100 °C, the detected XRD peaks matched well with peaks of the standard ABO3 perovskite structure. Moreover, EDX and FT-IR spectral analysis results confirmed that the mixture had formed stoichiometry ReNiO3. All prepared samples comprised plate-like grains with a random orientation, and their average particle size was in the range of 1 to 3 μm calculated from FE-SEM images.

Understanding metal-to-insulator phase transitions in solids has been a keystone not only for discovering novel physical phenomena in condensed matter physics but also for achieving scientific breakthroughs in materials science. In this work, we demonstrate that the transport properties (i.e., resistivity and transition temperature) in the metal-to-insulator transitions of perovskite nickelates are tunable via the epitaxial heterojunctions of LaNiO3 and NdNiO3 thin films. A mismatch in the oxygen coordination environment and interfacial octahedral coupling at the oxide heterointerface allows us to realize an exotic phase that is unattainable in the parent compound. With oxygen vacancy formation for strain accommodation, the topmost LaNiO3 layer in LaNiO3/NdNiO3 bilayer thin films is structurally engineered and it electrically undergoes a metal-to-insulator transition that does not appear in metallic LaNiO3. Modification of the NdNiO3 template layer thickness provides an additional knob for tailoring the tilting angles of corner-connected NiO6 octahedra and the linked transport characteristics further. Our approaches can be harnessed to tune physical properties in complex oxides and to realize exotic physical phenomena through oxide thin-film heterostructuring.

In this study, Co-doped TiO2 was prepared successfully using a solvothermal method with trimesic acid (H3BTC) as an organic framework to form the Co-doped Ti metal–organic framework (Co-doped Ti-MOF). By thermally decomposing the Co-doped Ti-MOF in air, the framework template was removed, and porous Co-doped TiO2 was obtained. The crystal structure of the material was analyzed using X-ray diffraction. The morphology was examined using scanning electron microscopy (SEM) and focused ion beam SEM. The large specific surface area was determined to be 135.95 m2 g–1 using Brunauer–Emmett–Teller theory. Fourier transform infrared spectroscopy verified the presence of Ti–O–Ti and Co–O vibrations in the as-prepared sample. Furthermore, the results of UV–vis spectroscopy showed that doping with Co remarkably improved the absorption ability of Ti-MOF toward the visible-light region with a band gap energy of 2.38 eV (λ = 502 nm). Steady-state photoluminescence and electrochemical impedance spectroscopy were conducted to illustrate the improvement of electron transfer in the doped material further. The optimum power conversion efficiency of solar cells using 1 wt % Co-doped TiO2 as an electron transport layer was found to be 15.75%, while that of solar cells using commercial dyesol TiO2 is only 14.42%.

Recently, single-crystal silicon solar cells have achieved efficiencies of 25%. However, their production is energy-demanding and relatively expensive. Therefore, photovoltaic cells based on organic- inorganic hybrid perovskites have attracted considerable attention owing to their high conversion efficiencies, simple preparation, and potentially low production costs. In this study, we investigated the effect of Fe3+ doped into a compact and mesoporous layer of TiO₂ on the efficiency of the resultant perovskite solar cell (PSC). The efficiencies achieved for PSCs with Fe3+/TiO₂ were higher than those for cells with pure TiO₂ nanoparticles. The samples were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy, and current-voltage measurements. The photoelectrode PSC exhibited a high light-to-electric-energy conversion efficiency under a simulated solar light irradiation of 100 mW/cm² (AM 1.5). Our results suggest that Fe3+ nanoparticles in the TiO₂ layer may contribute to the performance improvement of the PSC.

Piezoelectric nanogenerators (PNGs) have been studied as renewable energy sources. PNGs consisting of organic piezoelectric materials such as poly(vinylidene fluoride) (PVDF) containing oxide complex powder have attracted much attention for their stretchable and high-performance energy conversion. In this study, we prepared a PNG combined with PVDF and lanthanum-modified bismuth titanate (Bi4−XLaXTi3O12, BLT) ceramics as representative ferroelectric materials. The inserted BLT powder was treated by high-speed ball milling and its particle size reduced to the nanoscale. We also investigated the effect of particle size on the energy-harvesting performance of PNG without polling. As a result, nano-sized powder has a much larger surface area than micro-sized powder and is uniformly distributed inside the PNG. Moreover, nano-sized powder-mixed PNG generated higher power energy (> 4 times) than the PNG inserted micro-sized powder.

The electron transport layer (ETL) of organic–inorganic perovskite solar cells plays an important role in their power conversion efficiency (PCE). In this study, TiO2 hollow nanospheres with a diameter of 150 nm were prepared by a facile synthesis method. The synthesized TiO2 hollow nanospheres had a highly porous structure with a surface area of 85.23 m2g−1, which is significantly higher than commercial TiO2 (P25) (54.32 m2g−1), indicating that they can form an ideal mesoporous layer for Formamidinium iodide-based perovskite solar cells (PSCs). In addition, the nanospheres achieved a remarkable perovskite performance, and the average PCE increased from 12.87% to 14.27% with a short circuit current density of 22.36 mAcm−2, an open voltage of 0.95 V, and a fill factor of 0.65. The scanning electron microscopy images revealed that the enhanced PCE could be due to the improved carrier collection and transport properties of the nanosphere, which enabled efficient filtration of perovskite into the TiO2 mesoporous ETL. The TiO2 hollow nanospheres fabricated in this study show high potential as a high-quality ETL material for efficient (FAPbI3)0.97(MAPbBr3)0.03-based PSCs.

Multifunctional nanoparticles with a core/shell structure of Fe3O4/mSiO2/ZrO2 were prepared using two-step solution processes. First, magnetite (Fe3O4) core nanoparticles were prepared using the so...

Over the past few decades, silicon-based solar cells have been used in the photovoltaic (PV) industry because of the abundance of silicon material and the mature fabrication process. However, as more electrical devices with wearable and portable functions are required, silicon-based PV solar cells have been developed to create solar cells that are flexible, lightweight, and thin. Unlike flexible PV systems (inorganic and organic), the drawbacks of silicon-based solar cells are that they are difficult to fabricate as flexible solar cells. However, new technologies have emerged for flexible solar cells with silicon. In this paper, we describe the basic energy-conversion mechanism from light and introduce various silicon-based manufacturing technologies for flexible solar cells. In addition, for high energy-conversion efficiency, we deal with various technologies (process, structure, and materials).

The use of composites such as hydroxyapatite (HA)/TiO2 in bioapplications has attracted increasing attention in recent years. Herein, for the enhancement wetting ability and biocompatibility, the HA/TiO2 composite was subjected to different treatments to improve nanoparticle (NP) distribution and surface energy with an aim of mitigating nanotoxicity concerns. The treatments included ultrasonication, high-temperature annealing, and addition of a dispersant and surfactant, sodium dodecylbenzenesulfonate (SDBS). Contact angle measurement tests revealed the effect of SDBS addition on the distribution of TiO2 NPs on the HA surface: a decrease in the contact angle and, thus, an increase in the wetting ability of the HA/TiO2 composite were observed. The combination of annealing and SDBS addition treatments allowed for guest TiO2 particles to be uniformly distributed on the surface of the host HA particles, showing a rapid conversion from a hydrophobic to superhydrophilic property. In vitro investigation suggested that the cell viabilities of annealed HA/TiO2, SDBS-added HA/TiO2, and SDBS-added and annealed HA/TiO2 reached 89.7%, 94.7%, and 95.8%, respectively, while those of HA and untreated HA/TiO2 were 80.3% and 86.9%, respectively. The modified composites exhibited lower cytotoxicities than the unmodified systems (HA and HA/TiO2). Furthermore, the cell adhesion behavior of the composites was confirmed through actin-4′,6-Diamidino-2-phenylindole (DAPI) staining, which showed negligible changes in the cytoskeleton architecture of the cells. This study confirmed that a modified HA/TiO2 composite has potential for bioapplications.

For the previous few decades, the photovoltaic (PV) market was dominated by silicon-based solar cells. However, it will transition to PV technology based on flexible solar cells recently because of increasing demand for devices with high flexibility, lightweight, conformability, and bendability. In this review, flexible PVs based on silicone developed using the emerging technology are introduced. The technological limitations of traditional solar cells have been overcome, which will give rise to the new paradigm of solar energy conversion systems and flexible electronic devices. In this review, in terms of flexible PVs, we focus on the materials (substrate and electrode), cell processing techniques, and module fabrication for flexible solar cells beyond silicon.

Bismuth vanadate (BiVO4) has attracted significant attention as a promising photoanode material for hydrogen production via photoelectrochemical (PEC) water splitting because of its narrow optical band gap and suitable band edge positions for water oxidation. However, the actual photoactivity of BiVO4 is considerably limited by its poor electron transport and slow water oxidation kinetics. Although several studies have been carried out to improve its photo-efficiency via the enhancement of electron transport and water oxidation kinetics, only a few studies have reported the growth of epitaxial BiVO4 to explore the fundamental properties of BiVO4 for PEC water splitting because extremely flat epitaxial films exhibit poor photo-efficiency because of their low surface-active area. However, studies of epitaxial BiVO4 still have the potential to provide new routes for improving its photo-efficiency. In this study, the growth of epitaxial BiVO4 is investigated using a thin γ-WO3 template layer deposited on a SrTiO3(001) substrate covered by a SrRuO3 (SRO) bottom electrode using pulsed laser deposition. Consequently, at 1.23 V vs. the RHE (reversible hydrogen electrode), the photocurrent density of epitaxial BiVO4 on the γ-WO3 template layer (2.20 mA cm−2) is approximately 10 times that of bare BiVO4, related to the effective charge transfer by the γ-WO3 intermediate layers and the subsequent increase in the surface-active area of epitaxial BiVO4. These results strongly suggest that epitaxial BiVO4 grown using a template layer can be a cornerstone for the in-depth understanding of the fundamental properties of BiVO4 for PEC water splitting.

Dye-sensitized solar cells (DSSCs) based on titanium dioxide (TiO2) have been extensively studied because they constitute promising low-cost alternatives to their conventional semiconductor-based counterparts. However, much of the effort aimed at achieving high conversion efficiencies has focused on dye and liquid electrolytes. In this work, we report the photovoltaic characteristics of DSSCs fabricated by mixing TiO2 with Fe-doped bismuth lanthanum titanate (Fe-BLT). These nanosized Fe-BLT powders were prepared by using a high-energy ball-milling process. In addition, we used a UV radiation-ozone (UV-O3) treatment to change the surface wettability of TiO2 from hydrophobic to hydrophilic and thereby prevented the easy separation of the Fe-BLT-mixed TiO2 from the fluorine-doped tin-oxide (FTO) coating glass.

In recent years, perovskite solar cells (PSCs) have attracted considerable research attention owing to their ease of fabrication, high photovoltaic performance, and reasonable cost compared to conventional photovoltaic devices. These PSCs consist of four main interfaces between the conductive oxide such as fluorine-doped tin oxide and indium tin oxide, compact titanium dioxide electrode (cp-TiO2) layer, mesoporous titanium dioxide electrode (mp-TiO2) layer, perovskite layer, hole transporting layer, and metallic electrode. Among these interfaces, the electron transporting layer and perovskite layers such as cp-TiO2 and mp-TiO2 play a significant role in blocking holes and transporting electrons, which is important for realizing high power conversion efficiency (PCE). Various approaches have been employed to modify TiO2 to improve PCE. In this study, the effect of chemical surface activation on the TiO2 electrode via lithium bis(trifluoromethane)sulfonimide treatment were investigated, and the performances of the PSCs were evaluated. The experimental results help understand the effect of surface activation on the PSCs.

The regeneration of bone defects caused by periodontal disease or trauma is an important goal. Porous hydroxyapatite (HA) is an osteoconductive graft material. However, the hydrophobic properties of HA can be a disadvantage in the initial healing process. HA can be coated with TiO2 to improve its hydrophilicity, and ultraviolet irradiation (UV) can further increase the hydrophilicity by photofunctionalization. This study was designed to evaluate the effect of 5% TiO2-coated HA on rabbit calvarial defects and compare it with that of photofunctionalization on new bone in the early stage. The following four study groups were established, negative control, HA, TiO2-coated HA, and TiO2-coated HA with UV. The animals were sacrificed and the defects were assessed by radiography as well as histologic and histomorphometric analyses. At 2 and 8 weeks postoperatively, the TiO2-coated HA with UV group and TiO2-coated HA group showed significantly higher percentages of new bone than the control group (p &lt, 0.05). UV irradiation increased the extent of new bone formation, and there was a significant difference between the TiO2-coated HA group and TiO2-coated HA with UV group. The combination of TiO2/HA and UV irradiation in bone regeneration appears to induce a favorable response.

Recently, ferroelectric materials, such as La-substituted bismuth titanate (Bi3.25La0.75Ti3O12, BLT), have attracted interest for their potential applications in nano-electronics and nano-optoelectronics. On the other hand, the wide band gap of BLT has limited its opto-electronics applications. To solve this wide band gap problem in complex oxides, Fe doped BLT (Bi3.25La0.75FeTi2O12, Fe-BLT) could result in a dramatic decrease in the band gap without breaking its crystallographic symmetry. To fabricate the opto-electric devices, a bulk ceramic target was synthesized using Fe-BLT for thin film growth. To determine the optimal temperature, the pellets were sintered at different temperatures ranging from 700°C–1100°C for 2.5 hours. This study found that Fe-BLT target can be sintered at 1000°C without an impurity phase with comparable density and hardness to a target sintered at higher temperatures.

In recent years, there has been increasing interest in the bandgap engineering of ferroelectric oxides to improve absorbance of the solar spectrum, which is governed by their band gap. To enhance the photovoltaic efficiency by tuning the optical bandgap of complex oxides, an attempt was recently made to reduce the optical band gap of iron doping of lanthanum-modified Bi4Ti3O12-based oxides (Fe-BLT) using oxygen vacancy doping. To study the tunability of the optical band gap from the generation of oxygen vacancies, the thermal treatment time and temperature were controlled during heat treatment under a vacuum environment. The structural, optical properties of the synthesized podwers were examined by X-ray diffraction, scanning electron microscopy, and ultraviolet-visible spectroscopy. Typically, an oxygen vacancy in a complex oxide can alter their structure very easily. On the other hand, the ultraviolet-visible absorption spectra of iron-doped bismuth titanate ceramics under optimal conditions (12 h, 800 °C) showed a decrease in optical bandgap from 2.02 eV to 1.8 eV without a corresponding change in their crystallographic structure. This study suggests that optimal control of the thermal treatment time and temperature critically effects the optical band gap of complex oxides.

Achieving wide band gap tunability in ferroelectric perovskite oxides is desirable for the development of photovoltaic device applications and solar cells. To tune the wide band gap of perovskite oxides, ferroelectric iron doped BLT thin films (BLFT) on SrTiO3 substrates were fabricated by RF sputtering with simple control of the oxygen content. The structural and optical properties were analyzed by X-ray diffraction, scanning electron microscopy and ultraviolet-visible absorption spectroscopy. As the oxygen content in the mixed Ar+O2 atmosphere was increased from 0% to 50%, the optical band gap of the thin films were decreased from 2.8 eV to 2.64 eV. The BLFT film deposited at an Ar/O2 ratio of 1/1 exhibited a significantly lower optical band gap than the other samples. This simple sputtering approach to controlling the band gap with a simple method can provide a new candidate tool for manipulating optoelectronics devices.

Gallium-aluminum doped zinc oxide (GAZO) thin film is evaluated as an alternative to ITO for use as transparent electrodes for display devices. GAZO transparent conducting thin films were deposited using a facing targets sputtering (FTS) system with a hetero-targets. The FTS system can generate high plasma density, suppress the bombardment of high-energy particles to the substrate, and reduce the working pressure and substrate temperature. The average transmittance achieved with these films was as high as 80% in the visible range. Using a working pressure of 0.4 Pa, the lowest resistivity achieved with the deposited film was 5.342 × 10−4 Ω·cm.

Dye-sensitized solar cells (DSSCs) have been intensively studied since their discovery in 1991. DSSCs have been extensively researched over the past decades as cheaper alternatives to silicon solar cells due to their high energy-conversion efficiency and their low production cost. However, some problems need to be solved in order to enhance the efficiency of DSSCs. In particular, the electron recombination that occurs due to the contact between the transparent conductive oxide (TCO) and a redox electrolyte is one of the main limiting factors of efficiency. In this work, we report for the first time the improvement of the photovoltaic characteristics of DSSCs by doping TiO2 with Al2O3. DSSCs were constructed using composite particles of Al2O3-doped TiO2 and TiO2 nanoparticles. The DSSCs using Al2O3 showed the maximum conversion efficiency of 6.29% due to effective electron transport. DSSCs based on Al2O3-doped TiO2 films showed better photovoltaic performance than cells fabricated with only TiO2 nanoparticles. This result is attributed to the prevention of electron recombination between electrons in the TiO2 conduction band with holes in the dye or the electrolyte. There mechanism is suggested based on impedance results, which indicated improved electron transport at the TiO2/dye/electrolyte interface.

The wide band gap of complex oxides is one of the major obstacles limiting their use in photovoltaic cells. To tune the band gap of complex oxides, this study examined the effects of chemical/oxygen vacancy doping on Bi4Ti3O12 based oxides synthesized using a solid reaction method. The structural, optical and electrical properties of the synthesized powers were determined by x-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy, and resistant measurements. Both types of doping, chemical doping and oxygen doping, could affect the tunability of the band gap. On the other hand, the decrease in band gap from oxygen vacancy doping was much more significant in the chemical doped sample than in the sample without chemical doping. Two stage doping, which combined chemical and oxygen vacancy doping, of La doped bismuth titanate reduced the band gap of La doped bismuth titanate from 2.75eV to 1.2eV without breaking symmetry.

Lanthanum-modified bismuth-titanate powders (BLT) were synthesized using a solid reaction method at various calcination temperatures for 2.5 h under an ambient environment. The evolutions of the structural and the optical properties were analyzed by using X-ray diffraction and ultravioletvisible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurements. The analysis showed that the samples calcined at 700 °C crystallized in an orthorhombic structure with an optimal chemical ratio. The samples calcined at temperature below 500 °C resulted in the α-Bi2O3 phase. The structure and the optical bandgap of the sample calcined at 600 °C showed a decrease in the optical bandgap due to the incomplete formation of an orthorhombic BLT structure. The samples calcined at high temperatures exhibited expansion of the unit-cell volume as compared to the optimal samples. In those samples, Bi vacancies due to the high temperature annealing were responsible for changes in the UV PL profile. The relative intensity of the higher energy part (green) in the PL spectra increased with increasing calcination temperature, even though the origin of the shift in the PL spectra might be different at each temperature.

The replacement of oxide semiconducting TiO2 nano particles with one dimensional TiO2 nanotubes (TNTs) has been used for improving the electron transport in the dye-sensitized solar cells (DSSCs). Although use of one dimensional structure provides the enhanced photoelectrical performance, it tends to reduce the adsorption of dye on the TiO2 surface due to decrease of surface area. To overcome this problem, we investigate the effects of TiCl4 treatment on DSSCs which were constructed with composite films made of TiO2 nanoparticles and TNTs. To find optimum condition of TNTs concentration in TiO2 composites film, series of DSSCs with different TNTs concentration were made. In this optimum condition (DSSCs with 10 wt% of TNT), the effects of post treatment are compared for different TiCl4 concentrations. The results show that the DSSCs using a TiCl4 (90 mM) post treatment shows a maximum conversion efficiency of 7.83% due to effective electron transport and enhanced adsorption of dye on TiO2 surface.

La oxide is known to be the best promoter among reducible metal oxides for acetylene hydrogenation. However, it requires high-temperature reduction, which is not feasible in commercial processes. To maintain the enhanced catalytic performance by La oxide addition while lowering the reduction temperature for application in commercial process, we added Ti oxide as a second promoter, which has a higher reducibility than La oxide. The Ti oxide is added to the Pd surface, which has been partially covered by La oxide, and maintains the modified geometric and electronic structures of the Pd catalyst induced by the high-temperature-reduced La oxide even after low-temperature reduction, as confirmed by H2 chemisorption and X-ray photoelectron spectroscopy. Surprisingly, Ti oxide further modifies the electronic structure of Pd, even for low-temperature reduction, due to its high reducibility, leading to higher ethylene selectivity than when La oxide is used exclusively. We also confirmed that a similar additive effect also applies to other metal oxides, i.e., Nb2O5.

In this study, we focused on the changes on the perovskite layer by annealing. A two-step annealing process, which changes the temperature and time in the annealing process of the perovskite film, is important to obtain a more efficient solar cell. The perovskite synthesis proceeds rapidly, but a significant amount of lead iodide residue remains. Additional annealing is needed to reduce the lead iodide residue that causes degradation in efficiency. A solar cell with an average efficiency of 14.3% and a maximum efficiency of 14.58% was fabricated when it was annealed at 150 °C for 10 min and further annealed at 120 °C for 40 min. In addition, when the TiO2 layer was irradiated with UV light at 185 and 254 nm for 20 min, a perovskite solar cell with an average efficiency of 14.8% and a maximum efficiency of 15.04% was obtained.

The wide band gap of complex oxides is one of the major obstacles limiting their use in photovoltaic cells. To tune the bandgap of complex oxides, nano-sized bismuth titanate-based powders were synthesized by conventional solid reaction method. X-ray diffraction patterns confirmed that all powders were crystallized in an orthorhombic structure. The photoluminescence signal shows that there was no contribution to the optical bandgap from unwanted oxygen vacancy. The UV-vis absorption spectra of LaCo-BiT powder showed that the optical bandgap drastically decreased from 3.1eV to 2.5eV, while those of of BiT and La-BiT showed change in the optical bandgap. From these observations, we could experimentally confirm that cobalt atoms were responsible for the modification of the electronic structure in BiT-based oxides. This approach to controlling the bandgap could be applied to other complex oxides materials, such as other types of Aurivillius phase materials for use in emerging oxide optoelectronic and energy applications.

Thin film coatings on the windows ofautomobiles and buildings are used to filter out heat waveswhile retaining high transparency for visible light, thussignificantly increasing air conditioning efficiency in summerand heating efficiency in winter. A variety of thin filmcoating materials and technologies have been studied inacademia and industry including rare-earth hexaborides

Nanoscale control of the metal-insulator transition at the interface between LaAlO(3) and SrTiO(3) provides a pathway for reconfigurable, oxide-based nanoelectronics. Four-terminal transport measurements of LaAlO(3)/SrTiO(3) nanowires at room temperature (T = 300 K) reveal an equivalent 2D Hall mobility greatly surpassing that of bulk SrTiO(3) and approaching that of n-type Si nanowires of comparable dimensions. This large enhancement of mobility is relevant for room-temperature device applications.

Indium Zinc Tin Oxide (IZTO) thin-films for OLED (organic light-emitting diode) anodes were prepared through a Facing Target Sputtering (FTS) system under various sputtering conditions. The FTS system has several advantages such as hetero-sputtering, low working pressure, and high plasma density. When two sheets of targets are installed on an FTS system, one of the targets is IZO (In2O3 90wt%, ZnO 10 wt%) and the other target is ITO (In2O3 90wt%, SnO2 10wt%). As-deposited IZTO thin-films were investigated by a UV/VIS spectrometer, an X-ray diffractometer (XRD), a Hall-Effect measurement system, and an atomic force microscope (AFM). The properties of the OLEDs were measured through a J-I-V measurement system. The IZTO thin-films that were deposited on glass substrate showed an average transmittance of over 80% in a visible range except for IZTO thin-film that was deposited under an O2 gas flow rate of 0.1 [sccm].

Gallium-Aluminum doped Zinc Oxide (Ga-Al doped ZnO) thin films prepared on glass substrates by using facing targets sputtering methods. Electrical, structural and optical properties of Ga-Al doped ZnO thin film with various thicknesses were studied in detail. Crystal structure of the Ga-Al doped films was hexagonal wurtzite. Increased thickness of Ga-Al doped ZnO thin film, the resistivity decreased and crystallity improved. As the results, The resistivity of Ga-Al doped ZnO thin films with thickness of 500 nm exhibited 4.17×10–4 Ω.cm and average optical transmittance of all thin films showed above 85% in the visible range.

Highly conducting Al doped ZnO(AZO)/Cu/AZO triple multilayer thin films were deposited on polyethersulfonesusbtrate at room temperature. We investigated the structural, electrical, optical, and mechanical properties of triple multilayers as a function thickness of Cu layers. The triple multilayer with flexible substrate had advantages such as low sheet resistance and stable mechanical properties as compared with single oxide layer. From the results, sheet resistance value of AZO(50 nm)/Cu(9 nm)/AZO(50 nm) multilayer was 12 Ω/□, and average optical transmittance(380–770 nm) value of multilayer was 80%. Moreover the triple multilayer showed mechanical flexural strength properties than single-layered AZO thin films during bending test due to the existence of ductile Cu metal layer.

In this study, transparent conductive films (TCO) of ZnO:Ga (GZO) were deposited by facing target sputtering to explore the effect of post-annealing on the structural, electrical and optical properties of the films. As deposited films have been annealed to each different temperature condition in various atmosphere environments (air, N2, Vacuum N2). In the result, in air atmosphere condition, ZnO:Ga films have lost their characteristics as TCO films, because rapid oxidation occurred over 300°C. But in other atmosphere condition, contacting with oxygen is reduced more, as rapid rise of resistivity has been prevented.