http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2013 , Hindawi Publishing Corporation . All rights reserved. Wed, 22 May 2013 15:53:57 +0000 http://www.hindawi.com/journals/ijp/2013/749167/ Ching-Song Jwo, Sih-Li Chen, Ho Chang, Yu-Shan Su, and Jen-Shiun Chen Copyright © 2013 Ching-Song Jwo et al. All rights reserved. Wed, 22 May 2013 08:11:26 +0000 http://www.hindawi.com/journals/ijp/2013/598753/ The dye-sensitized solar cells (DSSCs) have been fabricated using highly ordered TiO2 nanotube arrays as photoelectrode and natural dyes as photosensitizers. The natural dyes were extracted from the abundant plants in the tropical region, such as Tradescantia zebrina, kapok, and pitaya. The dyes could chemically couple with TiO2 nanotubes and effectively convert visible light into electricity in DSSCs. A power conversion efficiency could be achieved up to 0.3% in the solar cell sensitized by the extracts from kapok with a short-circuit current of 0.86 mA/cm2. Furthermore, the influences of the crystal structure of TiO2 nanotube arrays on the performance of the natural DSSCs were discussed. Na Li, Nengqian Pan, Danhong Li, and Shiwei Lin Copyright © 2013 Na Li et al. All rights reserved. Tue, 21 May 2013 10:46:48 +0000 http://www.hindawi.com/journals/ijp/2013/465837/ Silicon wafer accounts for almost one-half the cost of a photovoltaic (PV) panel. A bifacial silicon solar cell is attractive due to its potential of enhancing power generation from the same silicon wafer in comparison with a conventional monofacial solar cell. The bifacial PV cell is able to capture solar radiation by back surface. This ability requires a suitable reflector appropriately oriented and separated from the cell’s rear surface. In order to optimize the bifacial solar cell performance with respect to an external back surface reflector, diffuse and semimirror reflectors were investigated at various angles and separations from the back surface. A simple bifacial solar panel, consisting of four monocrystalline Si solar cells, was designed and built. Reflection from the rear surface was provided by an extended semimirror and a white-painted diffuse reflector. Maximum power generation was observed at 30° with respect to ground for the semimirror reflector and 10° for diffuse reflector at an optimized reflector-panel separation of 115 mm. Output power enhancement of 20% and 15% from semimirror and diffuse reflectors, respectively, were observed. This loss from diffuse reflector is attributed to scattering of light beyond the rear surface capture cross-section of the bifacial solar panel. P. Ooshaksaraei, K. Sopian, R. Zulkifli, M. A. Alghoul, and Saleem H. Zaidi Copyright © 2013 P. Ooshaksaraei et al. All rights reserved. Sun, 19 May 2013 13:38:52 +0000 http://www.hindawi.com/journals/ijp/2013/616139/ Nitrogen-doped TiO2 powders have been prepared using technical guanidine hydrochloride, titanyl sulfate, and urea as precursors via a mild hydrothermal method under initial pressure of 3MPa, holding for 2h without any postheat treatment for crystallization. The nanocrystalline N-doped TiO2 powders were composed of anatase TiO2 by XRD. The grain size was estimated as about 10 nm, and the BET specific surface area of the powder was measured as 154.7 m2/g. The UV-visible absorption spectra indicated that the absorption edge of the N-doped TiO2 powders had been red shifted into the visible light region. The photocatalytic performance of the synthesized powders was evaluated by degradation of phenol under visible light irradiation. And the effects of the catalyst load and the initial pH value on the photodegradation were also investigated. Junna Xu, Feng Wang, Wenxiu Liu, and Wenbin Cao Copyright © 2013 Junna Xu et al. All rights reserved. Sun, 19 May 2013 11:34:27 +0000 http://www.hindawi.com/journals/ijp/2013/784743/ Nanostructured amorphous carbon (a-C) solar cells were successfully deposited via a self-designed aerosol-assisted chemical vapor deposition (AACVD). The fabricated solar cell with the configuration of Au/p-C/n-Si/Au achieved efficiency () of % for device deposited at 500°C, % for 450°C, and % for 400°C. Photoresponse characteristic was highlighted under illumination (AM 1.5 illuminations: 100 mW/cm2, 25°C), where conductivity increased when the sample was being hit by light. Transmittance spectrum exhibits a large transmittance value (85%) and absorption coefficient value of  cm−1 at the visible range from 390 to 790 nm. The nanostructured a-C thin film deposited at higher temperature possesses lower transmittance due to higher absorption as a result of the higher content of sp2-bonded carbon atoms. From Tauc’s plot, optical band gap () was determined, and decreased as deposition temperature increased (1.2 eV, 1.0 eV, 0.7 eV). On the other hand, FESEM images exhibited a nanostructured sized a-C with the particle size less than 100 nm. To the best of our knowledge, the presence of nanostructured particle of a-C by a self-prepared AACVD has not frequently been reported. A. N. Fadzilah, K. Dayana, and M. Rusop Copyright © 2013 A. N. Fadzilah et al. All rights reserved. Thu, 16 May 2013 18:26:35 +0000 http://www.hindawi.com/journals/ijp/2013/563897/ Large particle sizes having a strong light scattering lead to a significantly decreased surface area and small particle sizes having large surface area lack light-scattering effect. How to combine large and small particle sizes together is an interesting work for achieving higher solar efficiency. In this work, we investigate the solar performance influence of the dye-sensitized solar cells (DSSCs) by the multiple titanium oxide (TiO2) layers with different particle sizes. It was found that the optimal TiO2 thickness depends on the particle sizes of TiO2 layers for achieving the maximum efficiency. The solar efficiency of DSSCs prepared by triple TiO2 layers with different particle sizes is higher than that by double TiO2 layers for the same TiO2 thickness. The choice of particle size in the bottom layer is more important than that in the top layer for achieving higher solar efficiency. The choice of the particle sizes in the middle layer depends on the particle sizes in the bottom and top layers. The mixing of the particle sizes in the middle layer is a good choice for achieving higher solar efficiency. Ming-Jer Jeng, Yi-Lun Wung, Liann-Be Chang, and Lee Chow Copyright © 2013 Ming-Jer Jeng et al. All rights reserved. Thu, 16 May 2013 10:10:04 +0000 http://www.hindawi.com/journals/ijp/2013/130541/ Zinc oxide (ZnO)/titanium dioxide (TiO2) nanorods have been synthesized via a hydrothermal method for ZnO nanorods and an electron-beam deposition for TiO2 nanorods. This work examined the effect of annealing ZnO seed layer on the photocatalytic activity of the ZnO/TiO2 nanorods which was determined from photodecomposition of methylene blue under UV irradiation. The photocatalytic activity of the ZnO/TiO2 nanorods was improved with increasing annealing temperature of the seed layer from 300°C to 500°C. Annealing the seed layer at 500°C showed the best photocatalytic activity resulting from high UV absorption ability, a large surface area with flower structure and copious oxygen defects which promote separation of electron-hole pairs reducing electron recombination. The prepared nanorods were characterized by field emission-scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), photoluminescence (PL), and UV-visible spectroscopy. Woo-Young Kim, Soon-Wook Kim, Dae-Hwang Yoo, Eui Jung Kim, and Sung Hong Hahn Copyright © 2013 Woo-Young Kim et al. All rights reserved. Thu, 16 May 2013 08:59:43 +0000 http://www.hindawi.com/journals/ijp/2013/502576/ This study attempts to enhance broadband absorption in advanced plasmonic circular nanostructures (PCN). Experimental results indicate that the concentric circular metallic gratings can enhance broadband optical absorption, due to the structure geometry and the excitation of surface plasmon mode. The interaction between plasmonic enhancement and the absorption characteristics of the organic materials (P3HT:PCBM and PEDOT:PSS) are also examined. According to those results, the organic material's overall optical absorption can be significantly enhanced by up to ~51% over that of a planar device. Additionally, organic materials are enhanced to a maximum of 65% for PCN grating pitch = 800 nm. As a result of the PCN's enhancement in optical absorption, incorporation of the PCN into P3HT:PCBM-based organic solar cells (OSCs) significantly improved the performance of the solar cells: short-circuit current increased from 10.125 to 12.249 and power conversion efficiency from 3.2% to 4.99%. Furthermore, optimizing the OSCs architectures further improves the performance of the absorption and PCE enhancement. Nan-Fu Chiu, Cheng-Hung Hou, Chih-Jen Cheng, and Feng-Yu Tsai Copyright © 2013 Nan-Fu Chiu et al. All rights reserved. Thu, 16 May 2013 08:58:13 +0000 http://www.hindawi.com/journals/ijp/2013/807931/ We report on enhanced performance of N719-sensitized TiO2 solar cells (DSCs) incorporating size and photoelectron diffusion-controlled TiO2 as sensitizer-matched light-scatter layers on conventional nanocrystalline TiO2 electrodes. The double-layered N719/TiO2 composite electrode with a high dye-loading capacity exhibits the diffused reflectance of more than 50% in the range of  = 650–800 nm, even when the films are coupled with the titania nanocrystalline underlayer in the device. As a result, the increased near-infrared light-harvesting produces a high light-to-electricity conversion efficiency of over 9% mainly due to the significant increase of . Such an optical effect of the NIR-light scattering TiO2 electrodes will be beneficial when the sensitizers with low molar extinction coefficients, such as N719, are introduced in the device. Ke-Jian Jiang, Jin-Ming Zhou, Kazuhiro Manseki, Qi-Sheng Liu, Jin-Hua Huang, Yan-lin Song, and Shozo Yanagida Copyright © 2013 Ke-Jian Jiang et al. All rights reserved. Tue, 14 May 2013 19:06:35 +0000 http://www.hindawi.com/journals/ijp/2013/435017/ Ferrioxalate is a visible light-responsive photocatalyst. The solar ferrioxalate/ process has high degradation efficiency because ferrioxalate is able to absorb light strongly at longer wavelength and generates hydroxyl radical with high quantum yield. Degradation of pesticide chlorothalonil in aqueous solution by ferrioxalate/ under solar irradiation was examined. The optimum operating conditions for treatment of a 300 mg/L chlorothalonil aqueous solution were obtained by using the central composite design of the response surface methodology. Under the optimum operating conditions (/COD molar ratio 2.75, /Fe3+ molar ratio 75, /C2H2O4 molar ratio 37.5, reaction time 90 min, and pH 3), COD, NH3-N, and TOC removal of 75.71, 47.11, and 54.33%, respectively, was achieved and the biodegradability (BOD5/COD ratio) improved from zero to 0.42. Model prediction and actual removal were in close agreement (<4% error). The solar ferrioxalate/H2O2 process is effective in pretreatment of the chlorothalonil aqueous solution for biological treatment. Malay Chaudhuri, Hafizi Zuhali, and Augustine Chioma Affam Copyright © 2013 Malay Chaudhuri et al. All rights reserved. Mon, 13 May 2013 13:46:30 +0000 http://www.hindawi.com/journals/ijp/2013/567426/ The photoelectrocatalytic performance of benzoic acid on TiO2 nanotube array electrodes was investigated. A thin-cell was used to discuss the effect of the bias voltage, illumination intensity, and electrolyte concentration on the photoelectrocatalytic degradation efficiency of benzoic acid. The photogenerated current-time (I-t) profiles were found to be related to the adsorption and the degradation process. The relationship between the initial concentration and the photocurrent peaks () fits the Langmuir-type adsorption model, thus confirming that the adsorption of benzoic acid on TiO2 nanotube arrays (TNAs) was single monolayer adsorption. At low concentrations, the I-t profiles simply decay after the initial transient peak due to the sufficient holes on the TNAs which would oxidize the benzoic acid quickly. However, the I-t profiles varied with increasing benzoic acid concentrations because the rate of diffusion in the bulk solution and the degradation of the intermediate products affect the photoelectrocatalysis on the electrode surface. Hongchong Chen, Jinhua Li, Quanpeng Chen, Di Li, and Baoxue Zhou Copyright © 2013 Hongchong Chen et al. All rights reserved. Sun, 12 May 2013 09:45:30 +0000 http://www.hindawi.com/journals/ijp/2013/245195/ The fabrication of large-grain 1.25 μm thick polycrystalline silicon (poly-Si) films via two-stage aluminum-induced crystallization (AIC) for application in thin-film solar cells is reported. The induced 250 nm thick poly-Si film in the first stage is used as the seed layer for the crystallization of a 1 μm thick amorphous silicon (a-Si) film in the second stage. The annealing temperatures in the two stages are both 500°C. The effect of annealing time (15, 30, 60, and 120 minutes) in the second stage on the crystallization of a-Si film is investigated using X-ray diffraction (XRD), scanning electron microscopy, and Raman spectroscopy. XRD and Raman results confirm that the induced poly-Si films are induced by the proposed process. Hsiao-Yeh Chu, Min-Hang Weng, and Chen Lin Copyright © 2013 Hsiao-Yeh Chu et al. All rights reserved. Thu, 09 May 2013 14:44:57 +0000 http://www.hindawi.com/journals/ijp/2013/413507/ One-dimensional SrTiO3/TiO2−xNx nanostructures were prepared by the hydrothermal method and investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) measurements. The photocatalytic activities of the prepared samples were evaluated by photodegrading the methylene blue (MB) solution. According to the characterizations, the intermediate product of SrTiO3/titanate nanotubes was presented after hydrothermal processing of the TiO2−xNx nanoparticles with the mixed solution of NaOH and Sr(NO3)2. The final product of SrTiO3/TiO2−xNx nanorods was obtained after calcining the intermediate. As compared to the TiO2−xNx nanoparticles, the absorption performance of SrTiO3/titanate nanotubes or SrTiO3/TiO2−xNx nanorods was depressed, instead of improving it. The mechanisms of the absorption property changes were discussed. The SrTiO3/TiO2−xNx nanorods presented better photocatalytic activity than the TiO2−xNx nanoparticles or nanorods. However, due to overmuch adsorption, the SrTiO3/titanate nanotubes gave ordinary photocatalytic performances. Huarong Zhang, Miao Guashuai, Ma Xingping, and Wang Bei Copyright © 2013 Huarong Zhang et al. All rights reserved. Thu, 09 May 2013 08:44:31 +0000 http://www.hindawi.com/journals/ijp/2013/348171/ Titanium dioxide nanotube (TNT) arrays were prepared in electrolytes containing fluoride by anodic oxidation. Different preparation parameters were investigated in order to evaluate their effects on length and inner diameter of nanotube, including weight ratio of glycerol to water, anodization voltage, electrolysis time, bath temperature, and electrolyte solution pH. The well defined and highly ordered TNT arrays were formed in electrolyte containing 40, and 20% water. The inner diameter of TNT was observed to increase as anodization voltage increased across the range of 10–40 V. The length of TNT was affected simultaneously by both anodization voltage and electrolysis time. The inner diameter and length depend on bath temperature below 60°C. The morphology of TNT was well defined and highly ordered only at electrolyte solution pH of 6 across the pH range of 2–10. Photocatalysis of methylene blue showed that reaction rate constants by TNT films were higher than P-25 films at comparable thickness. Reaction rate constants by TNT films increased as film thickness increased, but the enhancement was retarded when the length of TNT reached 2200 nm which appeared to be the limited penetration of incident UV light. Wen-Yu Wang and Bo-Ruei Chen Copyright © 2013 Wen-Yu Wang and Bo-Ruei Chen. All rights reserved. Wed, 08 May 2013 16:34:57 +0000 http://www.hindawi.com/journals/ijp/2013/639843/ High efficiency white organic light emission devices were demonstrated with phosphor material dye bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2′]iridium (acetylacetonate) and ultrathin layer structure. The ultra thin layer be composed of 4,4′-bis[N-1-naphthyl-N-phenyl-amino]biphenyl (NPB) or 4,4′-N,N′-dicarbazole-biphenyl : NPB mixed layer with blue light emission. The emission spectra of devices could be adjusted by different phosphor doping concentrations and ultra thin layer structure. Warm white light emitting device could be obtained with 5 wt% doping concentration and power efficiency of 9.93 lm/W at 5 V. Pure white light with Commission Internationale de l'Eclairage (CIE) coordinates of (0.33, 0.30) and external quantum efficiency of 4.49% could be achieved with ultra thin layer device structure and 3 wt% phosphor doped device. Jun Wang and Weizhi Li Copyright © 2013 Jun Wang and Weizhi Li. All rights reserved. Tue, 07 May 2013 13:40:25 +0000 http://www.hindawi.com/journals/ijp/2013/129621/ CdS-sensitized TiO2 nanotube arrays have been fabricated using the method of successive ionic layer adsorption and reaction and used as a photoanode for quantum-dot-sensitized solar cells. Before being coated with CdS, the surface of TiO2 nanotube arrays was treated with TiCl4, nitric acid (HNO3), potassium hydroxide (KOH), and methyltrimethoxysilane (MTMS), respectively, for the purpose of reducing the interface transfer resistance of quantum-dot-sensitized solar cells. The surfaces of the modified samples represented the characteristics of superhydrophilic and hydrophobic which directly affect the power conversion efficiency of the solar cells. The results showed that surface modification resulted in the reduction of the surface tension, which played a significant role in the connectivity of CdS and TiO2 nanotube arrays. In addition, the solar cells based on CdS/TiO2 electrode treated by HNO3 achieved a maximum power conversion efficiency of 0.17%, which was 42% higher than the reference sample without any modification. Danhong Li, Nengqian Pan, Jianjun Liao, Xiankun Cao, and Shiwei Lin Copyright © 2013 Danhong Li et al. All rights reserved. Tue, 07 May 2013 11:48:01 +0000 http://www.hindawi.com/journals/ijp/2013/563170/ Granular ZnO nanostructures of single-crystalline wurtzite hexagonal phases were synthesized by a facile and low-cost chemical method in aqueous condition. The average size of ZnO nanograin increased with reflux time, and it significantly affected the open circuit potential while the short circuit current density was not changed much. The overall energy conversion efficiency was 1.82% with the smaller grain size of ca. 250 nm when it was used as photoelectrode of DSSCs. The positive shifting of the Fermi energy () and low density of surface states (DOS) were consistent with the reduction of the recombination of excited electron with electrolyte for smaller grains. Md. Mahbubur Rahman, Narayan Chandra Deb Nath, Kwang-Mo Noh, Jaecheon Kim, and Jae-Joon Lee Copyright © 2013 Md. Mahbubur Rahman et al. All rights reserved. Tue, 07 May 2013 11:39:45 +0000 http://www.hindawi.com/journals/ijp/2013/268723/ The synergistic effect of nitrogen content and calcinations temperature on the N-doped TiO2 catalysts prepared by sol-gel method was investigated. The phase and structure, chemical state, optical properties, and surface area/pore distribution of N-doped TiO2 were characterized using X-ray diffraction spectrometer, high-resolution transmission electron microscope, X-ray photoelectron spectroscopy, UV-vis diffusion reflectance spectroscopy, and Brunauer-Emmett-Teller specific surface area. Finding showed that the photocatalytic activity of N-doped TiO2 was greatly enhanced compared to pure TiO2 under visible irradiation. N dopants could retard the transformation from anatase to rutile phase. Namely, N-doping effect is attributed to the anatase phase stabilization. The results showed nitrogen atoms were incorporated into the interstitial positions of the TiO2 lattice. Ethylene was used to evaluate the photocatalytic activity of samples under visible-light illumination. The results suggested good anatase crystallization, smaller particle size, and larger surface are beneficial for photocatalytic activity of N-doped TiO2. The N-doped TiO2 catalyst prepared with ammonia to titanium isopropoxide molar ratio of 2.0 and calcinated at 400°C showed the best photocatalytic ability. Yao-Tung Lin, Chih-Huang Weng, Hui-Jan Hsu, Yu-Hao Lin, and Ching-Chang Shiesh Copyright © 2013 Yao-Tung Lin et al. All rights reserved. Tue, 30 Apr 2013 11:42:47 +0000 http://www.hindawi.com/journals/ijp/2013/893850/ We report results of density functional theory (DFT) calculations of a metal-free dye, 5-(4-sulfophenylazo)salicylic acid disodium salt, known as Mordant Yellow 10 (MY-10), used as sensitizer for TiO2 dye-sensitized solar cells (DSSCs). Given the need to better understand the behavior of the dyes adsorbed on the TiO2 nanoparticle, we studied various single and double deprotonated forms of the dye bound to a TiO2 cluster, taking advantage of the presence of the carboxyl, hydroxyl, and sulfonic groups as possible anchors. We discuss various binding configurations to the TiO2 substrate and the charge transfer from the pigment to the oxide by means of DFT calculations. In agreement with other reports, we find that the carboxyl group tends to bind in bidentate bridging configurations. The salicylate uses both the carboxyl and hydroxyl substituent groups for either a tridentate binding to adjacent Ti(IV) ions or a bidentate Ti-O binding together with an O-H-O binding, due to the rotation of the carboxyl group out of the plane of the dye. The sulfonic group prefers a tridentate binding. We analyze the propensity for electron transfer of the various dyes and find that for MY-10, as a function of the anchor group, the DSSC performance decreases in the order hydroxyl + carboxyl > carboxyl > sulfonate. Corneliu I. Oprea, Petre Panait, Jeanina Lungu, Daniela Stamate, Anca Dumbravă, Fanica Cimpoesu, and Mihai A. Gîrţu Copyright © 2013 Corneliu I. Oprea et al. All rights reserved. Tue, 30 Apr 2013 10:18:53 +0000 http://www.hindawi.com/journals/ijp/2013/690165/ Cu2ZnSnS4 (CZTS) thin films were deposited using the cosputtering technique. The growth parameters, such as working pressure, target powers, and postannealing atmosphere, were optimized for CZTS films deposition. A comparative study between post annealing using sulfur vapor in a quartz tube furnace and sulfurization chamber using H2S gas was carried out to optimize the kesterite Cu2ZnSnS4 phase. 10 min annealing at 530°C in the furnace in sulfur vapor eliminated all the secondary phases and formed kesterite Cu2ZnSnS4. The diffusion of sulfur in the film during the annealing process enhanced the crystallinity of the film. The kesterite Cu2ZnSnS4 phase was confirmed by X-ray diffraction, Raman scattering, and optical measurements. The film showed phonon peaks corresponding to the kesterite CZTS, high-absorption coefficient (1.1 × 105 cm−1), and desired optical direct band gap (1.5 eV). Arun Khalkar, Kwang-Soo Lim, Seong-Man Yu, Shashikant P. Patole, and Ji-Beom Yoo Copyright © 2013 Arun Khalkar et al. All rights reserved. Tue, 30 Apr 2013 09:50:10 +0000 http://www.hindawi.com/journals/ijp/2013/406158/ Phosphotungstic acid (HPW)-impregnated yeast hybrid microspheres were prepared by impregnation-adsorption technique through tuning pH of the aqueous yeast suspensions. The obtained products were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), thermogravimetry-differential scanning calorimetry (TG-DSC), and ultraviolet-visible spectrophotometry (UV-Vis), respectively. FE-SEM and EDS ascertain that the HPW has been effectively introduced onto the surface of yeast, and the resulting samples retain ellipsoid shape, with the uniform size (length 4.5 ± 0.2 μm, width 3.0 ± 0.3 μm) and good monodispersion. XRD pattern indicates that the main crystal structure of as-synthesized HPW@yeast microsphere is Keggin structure. TG-DTA states that the HPW in composites has better thermal stability than pure HPW. Fourier transform infrared spectroscopy (FT-IR) elucidates that the functional groups or chemical bonds inherited from the pristine yeast cell were critical to the assembling of the composites. UV-Vis shows that the obtained samples have a good responding to UV light. The settling ability indicates that the hybrid microspheres possess an excellent suspension performance. In the test of catalytic activity, the HPW@yeast microsphere exhibits a high photocatalytic activity for the decoloration of Methylene blue and Congo red dye aqueous solutions, and there are a few activity losses after four cycles of uses. Lan Chen and Bo Bai Copyright © 2013 Lan Chen and Bo Bai. All rights reserved. Mon, 29 Apr 2013 14:35:26 +0000 http://www.hindawi.com/journals/ijp/2013/718596/ This paper presents a method for determining optimal sizes of PV array, wind turbine, diesel generator, and storage battery installed in a building integrated system. The objective of the proposed optimization is to design the system that can supply a building load demand at minimum cost and maximum availability. The mathematical models for the system components as well as meteorological variables such as solar energy, temperature, and wind speed are employed for this purpose. Moreover, the results showed that the optimum sizing ratios (the daily energy generated by the source to the daily energy demand) for the PV array, wind turbine, diesel generator, and battery for a system located in Sohar, Oman, are 0.737, 0.46, 0.22, and 0.17, respectively. A case study represented by a system consisting of 30 kWp PV array (36%), 18 kWp wind farm (55%), and 5 kVA diesel generator (9%) is presented. This system is supposed to power a 200 kWh/day load demand. It is found that the generated energy share of the PV array, wind farm, and diesel generator is 36%, 55%, and 9%, respectively, while the cost of energy is 0.17 USD/kWh. Hussein A. Kazem and Tamer Khatib Copyright © 2013 Hussein A. Kazem and Tamer Khatib. All rights reserved. Mon, 29 Apr 2013 10:22:18 +0000 http://www.hindawi.com/journals/ijp/2013/650281/ An ultrafiltration (UF) membrane process was employed to treat the secondary effluent discharged from a manufacturing of thin film transistor-liquid crystal display (TFT-LCD) in this study. A bench-scale system was performed to evaluate the fouling removal of a UF membrane with coated titanium dioxide (TiO2) nanoparticles under UV irradiation. The operating pressure and feed temperature were controlled at 300 KN/m2 and 25°C, respectively. It was found that the optimum operating conditions were attained with TiO2 concentrations of 10 wt% for both 5 KD and 10 KD MWCO. Continuous UV irradiation of 5 KD MWCO improved the permeate flux rate from 45.0% to 59.5% after 4 hours of operation. SEM-EDS analysis also showed that the photocatalytic effect had reduced the average thickness of cake fouling on the membrane from 6.40 μm to 2.70 μm for 5 KD MWCO and from 6.70 μm to 3.1 μm for 10 KD MWCO. In addition, the membrane contact angle was reduced from 54° to 44°. The photocatalytic properties of TiO2 apparently increased the hydrophilicity of the membrane surface, thereby reducing membrane fouling. S. H. You and C. T. Wu Copyright © 2013 S. H. You and C. T. Wu. All rights reserved. Wed, 24 Apr 2013 09:31:39 +0000 http://www.hindawi.com/journals/ijp/2013/260319/ This paper presents a sky luminance model for the tropics. The model is mathematically expressed as a multiplication of two functions. These are , which is a function of the zenith angle of a sky element and solar zenith angle, and , which is a function of the angle between the sky element and the sun. To obtain the analytical forms of these functions, the sky luminance data collected at Nakhon Pathom (13.82°N, 100.04°E), Thailand, during a four-year period were analyzed. Additionally, satellite-derived cloud index at the position of the sky luminance measurements during the same period was estimated. Based on values of the cloud index, the skies were classified into 10 types, from clear to overcast skies. By using appropriate grouping and mathematical operation of the sky luminance data, the values of the two functions were obtained and then fitted with empirical equations. The multiplication of these equations gives the final form of the sky luminance model. To validate the model, it was used to calculate the relative sky luminance at other three sites in the tropics. It was found that values of relative sky luminance calculated from the model and those obtained from the measurements were in reasonable agreement. Serm Janjai Copyright © 2013 Serm Janjai. All rights reserved. Wed, 24 Apr 2013 09:10:30 +0000 http://www.hindawi.com/journals/ijp/2013/831765/ A highly efficient hybrid white organic light-emitting diode (HWOLED) has been demonstrated with a mixed interlayer between fluorescent blue and phosphorescent yellow-emitting layers. The device structure is simplified by using a controllable fluorescence-mixed interlayer-phosphorescence emission layer structure. The electroluminance (EL) performance can be modulated easily by adjusting the ratio of the hole-predominated material to the electron-predominated material in the interlayer. It is found that the HWOLED with a ratio of 3 : 2 exhibits a current efficiency of 34 cd/A and a power efficiency of 29 lm/W at 1000 cd/m2 with warm white Commission Internationale de l’Eclairage (CIE1931) coordinates of (0.4273, 0.4439). The improved efficiency and adaptive CIE coordinates are attributed to the controllable mixed interlayer with enhanced charge carrier transport, optimized excitons distribution, and improved harvestings of singlet and triplet excitons. Chun-Hong Gao, Xiao-Bo Shi, Dong-Ying Zhou, Lei Zhang, Zhao-Kui Wang, and Liang-Sheng Liao Copyright © 2013 Chun-Hong Gao et al. All rights reserved. Sun, 21 Apr 2013 11:12:40 +0000 http://www.hindawi.com/journals/ijp/2013/839301/ A novel pixel driving circuit for active-matrix organic light-emitting diode (AMOLED) displays with low-temperature polycrystalline-silicon thin-film transistors (LTPS-TFTs) is studied. The proposed compensation pixel circuit is driven by voltage programming scheme, which is composed of five TFTs and one capacitor, and has been certified to provide uniform output current by the Automatic Integrated Circuit Modeling Simulation Program with Integrated Circuit Emphasis (AIM-SPICE) simulator. The results of simulation show excellent performance, such as the low average error rate of OLED current variation (<0.5%) and the low average nonuniformity of OLED current variation (<0.8%) while the shift of threshold voltage of the driving poly-Si TFT and the OLED are both in the worst case ( V for TFT and  V for OLED). The proposed pixel circuit shows high immunity to the threshold voltage deviation of both the driving poly-Si TFT and the OLED. Ching-Lin Fan, Fan-Ping Tseng, Hui-Lung Lai, Bo-Jhang Sun, Kuang-Chi Chao, and Yi-Chiung Chen Copyright © 2013 Ching-Lin Fan et al. All rights reserved. Sun, 21 Apr 2013 09:51:54 +0000 http://www.hindawi.com/journals/ijp/2013/346818/ Organic small material lead phthalocyanine (PbPc) nanocolumns were prepared via glancing angle deposition (GLAD) on indium tin oxide (ITO) coated glass substrates. Organic electron acceptor materials fullerene (C60) was evaporated onto the nanocolumn PbPc thin films to prepare heterojunction structure ITO/PbPc/C60/Bphen/Al organic photovoltaic cells (OPVs). It is worthwhile to mention that C60 molecules firstly fill the voids between PbPc nanocolumns and then form impact C60 layer. The interpenetrating electron donor/acceptor structure effectively enhances interface between electron donor and electron acceptor, which is beneficial to exciton dissociation. The short circuit current density (Jsc) of organic photovoltaic devices (OPVs) based on PbPc nanocolumn was increased from 1.19 mA/cm2 to 1.74 mA/cm2, which should be attributed to the increase of interface between donor and acceptor. The effect of illumination intensity on the performance of OPVs was investigated by controlling the distance between light source and sample, and the Jsc of two kind of OPVs was increased along with the increase of illumination intensity. Yang Liu, Fujun Zhang, and Jian Wang Copyright © 2013 Yang Liu et al. All rights reserved. Tue, 16 Apr 2013 17:53:45 +0000 http://www.hindawi.com/journals/ijp/2013/726872/ High-purity anatase TiO2 nanoparticles were prepared using an improved sol-hydrothermal method. The as-prepared sample was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and UV-vis diffuse reflectance spectra. TEM results showed that the average particle size of all TiO2 particles was calculated to be () nm. The XRD analysis indicated that the present sample was fully crystallized and appeared to be highly phase-pure anatase. The BET analysis showed that the as-prepared sample had a very large specific surface area of 186.25 m2/g. The photocatalytic performance of TiO2 nanoparticles was evaluated by photocatalytic degradation of X-3B and X-BR solutions. The degradation results revealed that the as-prepared TiO2 showed slightly higher photocatalytic activities than P25. Whereas, the as-synthesized TiO2 can settle down and be separated easily after the photocatalytic reaction finishes. Xiuzhen Wei, Guangfeng Zhu, Jinfeng Fang, and Jinyuan Chen Copyright © 2013 Xiuzhen Wei et al. All rights reserved. Tue, 16 Apr 2013 11:58:10 +0000 http://www.hindawi.com/journals/ijp/2013/191340/ The photocatalytic degradation of methyl violet using TiSiW12O40/TiO2 as a novel eco-friendly catalyst under simulated natural light irradiation was investigated. The physical characterizations were carried out by TG/DTA, FT-IR, XRD, and UV-visible spectra. The effects of the initial methyl violet concentration, the solution pH, and catalyst dosage on the photocatalytic degradation rate of methyl violet were also examined. The results demonstrated that at optimal condition (initial concentration of methyl violet is 20 mg/L, catalyst dosage is 0.3 g, and the pH is 5.5), the degradation rate of methyl violet is as high as 82.4% after 3 h under simulated natural light irradiation. The reaction of photocatalysis for methyl violet can be expressed as first-order kinetic model. Shuijin Yang, Yulin Xu, Yongkui Huang, Guohui Zhou, Zhiyuan Yang, Yun Yang, and Guohong Wang Copyright © 2013 Shuijin Yang et al. All rights reserved. Sun, 14 Apr 2013 16:18:17 +0000 http://www.hindawi.com/journals/ijp/2013/527948/ An extremum seeking control (ESC) scheme is proposed for maximum power point tracking (MPPT) in photovoltaic power generation systems. The robustness of the proposed scheme toward irradiance changes is enhanced by implementing the ESC scheme using a sliding mode control (SMC) law. In the proposed approach, the chattering phenomenon caused by high frequency switching is suppressed by means of a sliding layer concept. Moreover, in implementing the proposed controller, the optimal value of the gain constant is determined using a particle swarm optimization (PSO) algorithm. The experimental and simulation results show that the proposed PSO-based sliding mode ESC (SMESC) control scheme yields a better transient response, steady-state stability, and robustness than traditional MPPT schemes based on gradient detection methods. Her-Terng Yau, Chih-Jer Lin, and Chen-Han Wu Copyright © 2013 Her-Terng Yau et al. All rights reserved.