International Journal of Photoenergy The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Visible-Light Degradation of Dyes and Phenols over Mesoporous Titania Prepared by Using Anthocyanin from Red Radish as Template Tue, 02 Sep 2014 11:07:50 +0000 Heterogeneous photocatalysis is able to operate effectively to eliminate organic compounds from wastewater in the presence of semiconductor photocatalyst and a light source. Although photosensitization of titania by organic dyes is one of the conventional ways for visible-light utilization of titania, previous studies have not yet addressed the use of natural food coloring agents as templates in the synthesis of mesostructured materials, let alone the simultaneous achievement of highly crystalline mesoscopic framework and visible-light photocatalytic activity. In this work, anthocyanin, a natural pigment from red radish was directly used as template in synthesis of highly crystalline mesoporous titania. The synthesized mesoporous titania samples were characterized by a combination of various physicochemical techniques, such as XRD, SEM, HRTEM, nitrogen adsorption/desorption, and diffuse reflectance UV-Vis. The prepared mesoporous titania photocatalyst exhibited significant activity under visible-light irradiation for the degradation of dyes and phenols due to its red shift of band-gap-absorption onset and visible-light response as a result of the incorporation of surface carbon species. Zhiying Yan, Wenjuan Gong, Yongjuan Chen, Deliang Duan, Junjie Li, Wei Wang, and Jiaqiang Wang Copyright © 2014 Zhiying Yan et al. All rights reserved. Evaluation of Fuzzy Logic Subsets Effects on Maximum Power Point Tracking for Photovoltaic System Tue, 02 Sep 2014 00:00:00 +0000 Photovoltaic system (PV) has nonlinear characteristics which are affected by changing the climate conditions and, in these characteristics, there is an operating point in which the maximum available power of PV is obtained. Fuzzy logic controller (FLC) is the artificial intelligent based maximum power point tracking (MPPT) method for obtaining the maximum power point (MPP). In this method, defining the logical rule and specific range of membership function has the significant effect on achieving the best and desirable results. This paper presents a detailed comparative survey of five general and main fuzzy logic subsets used for FLC technique in DC-DC boost converter. These rules and specific range of membership functions are implemented in the same system and the best fuzzy subset is obtained from the simulation results carried out in MATLAB. The proposed subset is able to track the maximum power point in minimum time with small oscillations and the highest system efficiency (95.7%). This investigation provides valuable results for all users who want to implement the reliable fuzzy logic subset for their works. Shahrooz Hajighorbani, M. A. M. Radzi, M. Z. A. Ab Kadir, S. Shafie, Razieh Khanaki, and M. R. Maghami Copyright © 2014 Shahrooz Hajighorbani et al. All rights reserved. Pyran-Squaraine as Photosensitizers for Dye-Sensitized Solar Cells: DFT/TDDFT Study of the Electronic Structures and Absorption Properties Mon, 01 Sep 2014 12:31:39 +0000 In an effort to provide, assess, and evaluate a theoretical approach which enables designing efficient donor-acceptor dye systems, the electronic structure and optical properties of pyran-squaraine as donor-acceptor dyes used in dye-sensitized solar cells were investigated. Ground state properties have been computed at the B3LYP/6-31+ level of theory. The long-range corrected density functionals CAM-B3LYP, PBEPBE, PBE1PBE (PBE0), and TPSSH with 6-311++ were employed to examine absorption properties of the studied dyes. In an extensive comparison between experimental results and ab initio benchmark calculations, the TPSSH functional with 6-311++ basis set was found to be the most appropriate in describing the electronic properties for the studied pyran and squaraine dyes. Natural transition orbitals (NTO), frontier molecular orbitals (FMO), LUMO, HOMO, and energy gaps, of these dyes, have been analyzed to show their effect on the process of electron injection and dye regeneration. Interaction between HOMO and LUMO of pyran and squaraine dyes was investigated to understand the recombination process and charge-transfer process involving these dyes. Additionally, we performed natural bond orbital (NBO) analysis to investigate the role of charge delocalization and hyperconjugative interactions in the stability of the molecule. Reda M. El-Shishtawy, Shaaban A. Elroby, Abdullah M. Asiri, and Rifaat H. Hilal Copyright © 2014 Reda M. El-Shishtawy et al. All rights reserved. Experiment Investigation on Electrical and Thermal Performances of a Semitransparent Photovoltaic/Thermal System with Water Cooling Mon, 01 Sep 2014 05:51:05 +0000 Different from the semitransparent building integrated photovoltaic/thermal (BIPV/T) system with air cooling, the semitransparent BIPV/T system with water cooling is rare, especially based on the silicon solar cells. In this paper, a semitransparent photovoltaic/thermal system (SPV/T) with water cooling was set up, which not only would provide the electrical power and hot water, but also could attain the natural illumination for the building. The PV efficiency, thermal efficiency, and exergy analysis were all adopted to illustrate the performance of SPV/T system. The results showed that the PV efficiency and the thermal efficiency were about 11.5% and 39.5%, respectively, on the typical sunny day. Furthermore, the PV and thermal efficiencies fit curves were made to demonstrate the SPV/T performance more comprehensively. The performance analysis indicated that the SPV/T system has a good application prospect for building. Guiqiang Li, Gang Pei, Ming Yang, and Jie Ji Copyright © 2014 Guiqiang Li et al. All rights reserved. Growth and Properties of ZnO:Al on Textured Glass for Thin Film Solar Cells Thu, 28 Aug 2014 15:25:38 +0000 Aluminium induced texturing (AIT) method has been used to texture glass substrates in order to enhance the photon absorption in thin film solar cells. The resultant glass roughness has been analyzed by varying the AIT process parameters and it has been found that the deposition method of Al is a decisive factor in tuning the texture. Two types of textures, a soft (texture E) and a rough texture (texture S), were achieved from the thermally evaporated and sputtered Al layers through AIT process. Aluminium-doped zinc oxide (AZO) layers of different thickness were deposited over both textures and over smooth glass. Haze values above 30% were obtained for texture S + AZO and above 10% for texture E + AZO. The resultant morphologies were free from sharp edges or deep valleys and the transparency and the resistivity values were also good enough to be used as front contact for thin film solar cells. In order to demonstrate the light absorption enhancement in a solar cell device, 200 nm of a-Si:H followed by 300 nm of Ag were grown over the textured and smooth substrates with AZO, and an optical absorption enhancement of 35% for texture E and 53% for texture S was obtained in comparison to the smooth substrate. Marta Lluscà, Aldrin Antony, and Joan Bertomeu Copyright © 2014 Marta Lluscà et al. All rights reserved. Preparation, Characterization, and Photocatalytic Applications of MWCNTs/TiO2 Composite Thu, 28 Aug 2014 15:10:15 +0000 The multiwall carbon nanotubes (MWCNTs)/titanium dioxide (P25) composite in different ratios was prepared using simple evaporation and drying process. The composite was characterized by Raman spectroscopy, X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy, and scanning electron microscopy (SEM). The photocatalytic activity of this composite was investigated using degradation of the Bismarck brown R dye (BBR). An optimal MWCNTs/TiO2 ratio of 0.5% (w/w) was found to achieve the maximum rate of BBR degradation. It was observed that the composite exhibits enhanced photocatalytic activity compared with TiO2. The enhancement in photocatalytic activity performance of the MWCNTs/P25 composite is explained in terms of recombination of photogenerated electron-hole pairs. In addition, MWCNTs act as a dispersing support to control the morphology of TiO2 particles in the MWCNTs/TiO2 composite. Ahmed M. Kamil, Falah H. Hussein, Ahmed F. Halbus, and Detlef W. Bahnemann Copyright © 2014 Ahmed M. Kamil et al. All rights reserved. Bridging Photonics and Optoelectronics Curriculum for the Solar Photovoltaic and LED Industries Thu, 28 Aug 2014 15:05:00 +0000 The gap between learning courses and practical demands has existed in Taiwanese solar photovoltaic and LED industries; therefore, this study attempts to analyze the existing curriculum design of universities. This study collected the current 103 course programs from all optoelectronics-related departments in Taiwanese 36 colleges and universities and sorted these curriculums by three domains of education objectives theory. This theoretical framework was verified on the basis of samples from 150 Taiwanese industrial experts and 354 optoelectronics-related undergraduates and postgraduates. We found that the levels of correlation among the independent variables including cognitive, affective, and skill-based domains and the dependent variable employability are all positively related to each other. We also found the currently curriculum design in Taiwanese universities rarely fit into theory of education objectives from the results of multiple regression analysis. Industrial and student’s group also have few consistent ideas on courses within the curriculum. Finally in order to bridge the gap between learning and practical application, the study provides an idea on curriculum design and suggests that curriculum review should be executed by industrial experts to confirm the courses related to the employability. Yu-Shan Su and Han-Chao Chang Copyright © 2014 Yu-Shan Su and Han-Chao Chang. All rights reserved. Study of an Amorphous Silicon Oxide Buffer Layer for p-Type Microcrystalline Silicon Oxide/n-Type Crystalline Silicon Heterojunction Solar Cells and Their Temperature Dependence Thu, 28 Aug 2014 11:34:36 +0000 Intrinsic hydrogenated amorphous silicon oxide (i-a-SiO:H) films were used as front and rear buffer layers in crystalline silicon heterojunction (c-Si-HJ) solar cells. The surface passivity and effective lifetime of these i-a-SiO:H films on an n-type silicon wafer were improved by increasing the CO2/SiH4 ratios in the films. Using i-a-SiO:H as the front and rear buffer layers in c-Si-HJ solar cells was investigated. The front i-a-SiO:H buffer layer thickness and the CO2/SiH4 ratio influenced the open-circuit voltage , fill factor (FF), and temperature coefficient (TC) of the c-Si-HJ solar cells. The highest total area efficiency obtained was 18.5%  mV,  mA/cm2, and . The TC normalized for this c-Si-HJ solar cell efficiency was −0.301%/°C. Taweewat Krajangsang, Apichan Moollakorn, Sorapong Inthisang, Amornrat Limmanee, Kobsak Sriprapha, Nattaphong Boriraksantikul, Tianchai Taratiwat, Nirod Akarapanjavit, and Jaran Sritharathikhun Copyright © 2014 Taweewat Krajangsang et al. All rights reserved. Experiment and Simulation Study on the Amorphous Silicon Photovoltaic Walls Wed, 27 Aug 2014 08:13:04 +0000 Based on comparative study on two amorphous silicon photovoltaic walls (a-Si PV walls), the temperature distribution and the instant power were tested; and with EnergyPlus software, similar models of the walls were built to simulate annual power generation and air conditioning load. On typical sunshine day, the corresponding position temperature of nonventilated PV wall was generally 0.5~1.5°C higher than that of ventilated one, while the power generation was 0.2%~0.4% lower, which was consistent with the simulation results with a difference of 0.41% in annual energy output. As simulation results, in summer, comparing the PV walls with normal wall, the heat per unit area of these two photovoltaic walls was 5.25 kWh/m2 (nonventilated) and 0.67 kWh/m2 (ventilated) higher, respectively. But in winter the heat loss of nonventilated one was smaller, while ventilated PV wall was similar to normal wall. To annual energy consumption of heating and cooling, the building with ventilated PV wall and normal wall was also similar but slightly better than nonventilated one. Therefore, it is inferred that, at low latitudes, such as Zhuhai, China, air gap ventilation is suitable, while the length to thickness ratio of the air gap needs to be taken into account. Wenjie Zhang, Bin Hao, and Nianping Li Copyright © 2014 Wenjie Zhang et al. All rights reserved. J-Aggregates of Amphiphilic Cyanine Dyes for Dye-Sensitized Solar Cells: A Combination between Computational Chemistry and Experimental Device Physics Tue, 26 Aug 2014 08:52:10 +0000 We report on the design and structure principles of 5,5′-6,6′-tetrachloro-1,1′-dioctyl-3,3′-bis-(3-carboxypropyl)-benzimidacarbocyanine (Dye 1). Such metal-free amphiphilic cyanine dyes have many applications in dye-sensitized solar cells. AFM surface topographic investigation of amphiphilic molecules of Dye 1 adsorbed on TiO2 anode reveals the ability of spontaneous self-organization into highly ordered aggregates of fiber-like structure. These aggregates are known to exhibit outstanding optical properties of J-aggregates, namely, efficient exciton coupling and fast exciton energy migration, which are essential for building up artificial light harvesting to the photovoltaic device. A light-to-electricity conversion efficiency of DSSC based on the metal free amphiphilic Dye 1 is , which is about 50% of that based on metal-based N719 Ru-dye (Di-tetrabutylammoniumcis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II)). DFT and TD-DFT studies show that large intramolecular charge transfer takes place from the HOMO to LUMO. HOMO is localized on a part of the molecule with almost no contribution from the carboxylic moiety. This clearly indicates that the anchoring carboxylic group plays a minor role. M. S. A. Abdel-Mottaleb, Mohamed M. S. Abdel-Mottaleb, Hoda S. Hafez, and Mona Saif Copyright © 2014 M. S. A. Abdel-Mottaleb et al. All rights reserved. Band-Gap Engineering of NaNbO3 for Photocatalytic H2 Evolution with Visible Light Tue, 26 Aug 2014 08:26:52 +0000 A new visible light response photocatalyst has been developed for H2 evolution from methanol solution by elemental doping. With lanthanum and cobalt dopants, the photoabsorption edge of NaNbO3 was effectively shifted to the visible light region. It is also found that the photoabsorption edge is effectively controlled by the dopant concentration. Under visible light irradiation, H2 was successfully generated over the doped NaNbO3 samples and a rate of 12 μmol·h−1 was achieved over (LaCo)0.03(NaNb)0.97O3. Densityfunctional theory calculations show that Co-induced impurity states are formed in the band gap of NaNbO3 and this is considered to be the origin of visible-light absorption upon doping with La and Co. Peng Li, Hideki Abe, and Jinhua Ye Copyright © 2014 Peng Li et al. All rights reserved. Effect of Aging Time and Film Thickness on the Photoelectrochemical Properties of TiO2 Sol-Gel Photoanodes Mon, 25 Aug 2014 08:41:40 +0000 This work has focused on the investigation of a non-aqueous based sol-gel process to produce TiO2 based photoelectrodes for solar water splitting. In particular, the effect of the aging time of the sol and TiO2 film thickness on the photoelectrochemical properties of the photoanodes has been investigated. In order to achieve optimal performances (i.e., photocurrent density up to 570 µA/cm2 and IPCE of 26% at 300 nm), the sol needs to be aged for 3 to 6 h, before being dip-coated to produce the photoanodes. The importance of the aging time can also be appreciated from the optical properties of the TiO2 films; the absorbance threshold of the sol-gel aged for 3–6 h is slightly shifted towards longer wavelenghts in comparison to 0 h aging. Aging is necessary to build up a well-interconnected sol-gel network which finally leads to a photoelectrode with optimized light absorption and electron collection properties. This is also confirmed by the higher IPCE signal of aged photoelectrodes, especially below 340 nm. Among thicknesses considered, there is no apparent significant difference in the photoresponse (photocurrent density and IPCE) of the TiO2 sol-gel films. D. Regonini, A. K. Alves, F. A. Berutti, and F. Clemens Copyright © 2014 D. Regonini et al. All rights reserved. Heterojunction Solar Cells Sun, 24 Aug 2014 10:37:52 +0000 Aung Ko Ko Kyaw, Antonio Otavio T. Patrocinio, Dewei Zhao, and Victor Brus Copyright © 2014 Aung Ko Ko Kyaw et al. All rights reserved. Reactive Power Control of Single-Stage Three-Phase Photovoltaic System during Grid Faults Using Recurrent Fuzzy Cerebellar Model Articulation Neural Network Sun, 24 Aug 2014 09:38:11 +0000 This study presents a new active and reactive power control scheme for a single-stage three-phase grid-connected photovoltaic (PV) system during grid faults. The presented PV system utilizes a single-stage three-phase current-controlled voltage-source inverter to achieve the maximum power point tracking (MPPT) control of the PV panel with the function of low voltage ride through (LVRT). Moreover, a formula based on positive sequence voltage for evaluating the percentage of voltage sag is derived to determine the ratio of the injected reactive current to satisfy the LVRT regulations. To reduce the risk of overcurrent during LVRT operation, a current limit is predefined for the injection of reactive current. Furthermore, the control of active and reactive power is designed using a two-dimensional recurrent fuzzy cerebellar model articulation neural network (2D-RFCMANN). In addition, the online learning laws of 2D-RFCMANN are derived according to gradient descent method with varied learning-rate coefficients for network parameters to assure the convergence of the tracking error. Finally, some experimental tests are realized to validate the effectiveness of the proposed control scheme. Faa-Jeng Lin, Kuang-Chin Lu, and Hsuan-Yu Lee Copyright © 2014 Faa-Jeng Lin et al. All rights reserved. An Improved Matlab-Simulink Model of PV Module considering Ambient Conditions Sun, 24 Aug 2014 00:00:00 +0000 A photovoltaic (PV) model is proposed on Matlab/Simulink environment considering the real atmospheric conditions and this PV model is tested with different PV panels technologies (monocrystalline silicon, polycrystalline silicon, and thin film). The meteorological data of Istanbul—the location of the study—such as irradiance, cell temperature, and wind speed are taken into account in the proposed model for each technology. Eventually, the power outputs of the PV module under real atmospheric conditions are measured for resistive loading and these powers are compared with the results of proposed PV model. As a result of the comparison, it is shown that the proposed model is more compatible for monocrystal silicon and thin-film modules; however, it does not show a good correlation with polycrystalline silicon PV module. R. Ayaz, I. Nakir, and M. Tanrioven Copyright © 2014 R. Ayaz et al. All rights reserved. Optical and Structural Characterization of Nickel Coatings for Solar Collector Receivers Thu, 21 Aug 2014 00:00:00 +0000 The development of spectrally selective materials is gaining an increasing role in solar thermal technology. The ideal spectrally selective solar absorber requires high absorbance at the solar spectrum wavelengths and low emittance at the wavelengths of thermal spectrum. Selective coating represents a promising route to improve the receiver efficiency for parabolic trough collectors (PTCs). In this work, we describe an intermediate step in the fabrication of black-chrome based solar absorbers, namely, the fabrication and characterization of nickel coatings on stainless steel substrates. Microstructural characteristics of nickel surfaces are known to favorably affect further black chrome deposition. Moreover, the high reflectivity of nickel in the thermal infrared wavelength region can be advantageously exploited for reducing thermal emission losses. Thus, this report investigates structural features and optical properties of the nickel surfaces, correlating them to coating thickness and deposition process, in the perspective to assess optimal conditions for solar absorber applications. Stefano Pratesi, Elisa Sani, and Maurizio De Lucia Copyright © 2014 Stefano Pratesi et al. All rights reserved. A Hybrid MCDM Model for Improving GIS-Based Solar Farms Site Selection Wed, 20 Aug 2014 07:29:42 +0000 The purpose of this research is to establish a decision model for improving the performance of solar farms. To investigate the interdependent interrelationship and influential weights among criteria for solar farms site selection, a hybrid MCDM model including decision-making trial and evaluation laboratory (DEMATEL) and DEMATEL-based analytic network process (DANP) based on geographical information systems (GIS) is utilized. The empirical results display that there are interdependence and self-effect relationships among criteria via DEMATEL technique. According to the influential network relation map (INRM), the dimension that administrators of solar energy industry should improve first when enhancing the performance of solar farms is orography. In the ten criteria, solar radiation is the most important criterion impacting solar farms site selection, followed by average temperature and distance to villages. Chao-Rong Chen, Chi-Chen Huang, and Hung-Jia Tsuei Copyright © 2014 Chao-Rong Chen et al. All rights reserved. Innovative Solar Tracking Concept by Rotating Prism Array Wed, 20 Aug 2014 00:00:00 +0000 Solar energy has become one of the most promising renewable energies and is the most widely used nowadays. In order to achieve an optimum performance, both photovoltaic and solar thermal applications are required to track the position of the sun throughout the day and year in the most effective way possible to avoid a high negative impact on the system efficiency. The present paper attempts to describe a novel semipassive solar tracking concentrator (SPSTC) in which, in order to track the sun, two independent arrays of polymethyl methacrylate (PMMA) prisms are implemented to refract sunlight by rotating said prisms, thus being able to redirect solar radiation as desired. The first set is responsible for eliminating one of the directional components of the solar radiation; the task is achieved by rotating the prisms within the array at a specific angle. The second set deals with another of the sunlight’s directional components, transforming its direction into a completely perpendicular pattern to the array. Having downward vertical radiation makes it possible to implement a stationary Fresnel lens to concentrate the solar radiation for any application desired. The system is designed and validated using simulation software to prove the feasibility of the concept. Héctor García, Carlos Ramírez, and Noel León Copyright © 2014 Héctor García et al. All rights reserved. Investigation on Thermal Degradation Process of Polymer Solar Cells Based on Blend of PBDTTT-C and BM Tue, 19 Aug 2014 11:41:04 +0000 The effects of thermal treatment on the photovoltaic performance of conventional and inverted polymer solar cells (PSCs) based on the combination of poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b;4,5-b′]dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thie-no[3,4-b]thiophene))-2,6-diyl] (PBDTTT-C) and [6,6]-phenyl C70-butyric acid methyl ester (PC70BM) are investigated. The transient photoconductivity, the absorption spectra, and the transmission electron microscopy (TEM) images have been employed to study the thermal degradation of the inverted PSCs. The degradation is attributed to the inefficient charge generation and imbalance in charge-carrier transport, which is closely associated with the morphological evolution of the active layer with prolonged heating time. Yu Ning, Longfeng Lv, Yunzhang Lu, Aiwei Tang, Yufeng Hu, Zhidong Lou, Feng Teng, and Yanbing Hou Copyright © 2014 Yu Ning et al. All rights reserved. Cadmium Sulfide Nanoparticles Synthesized by Microwave Heating for Hybrid Solar Cell Applications Tue, 19 Aug 2014 08:27:30 +0000 Cadmium sulfide nanoparticles (CdS-n) are excellent electron acceptor for hybrid solar cell applications. However, the particle size and properties of the CdS-n products depend largely on the synthesis methodologies. In this work, CdS-n were synthetized by microwave heating using thioacetamide (TA) or thiourea (TU) as sulfur sources. The obtained CdS-n(TA) showed a random distribution of hexagonal particles and contained TA residues. The latter could originate the charge carrier recombination process and cause a low photovoltage (, 0.3 V) in the hybrid solar cells formed by the inorganic particles and poly(3-hexylthiophene) (P3HT). Under similar synthesis conditions, in contrast, CdS-n synthesized with TU consisted of spherical particles with similar size and contained carbonyl groups at their surface. CdS-n(TU) could be well dispersed in the nonpolar P3HT solution, leading to a of about 0.6–0.8 V in the resulting CdS-n(TU) : P3HT solar cells. The results of this work suggest that the reactant sources in microwave methods can affect the physicochemical properties of the obtained inorganic semiconductor nanoparticles, which finally influenced the photovoltaic performance of related hybrid solar cells. Claudia Martínez-Alonso, Carlos A. Rodríguez-Castañeda, Paola Moreno-Romero, C. Selene Coria-Monroy, and Hailin Hu Copyright © 2014 Claudia Martínez-Alonso et al. All rights reserved. Sensitization of Perovskite Strontium Stannate SrSnO3 towards Visible-Light Absorption by Doping Mon, 18 Aug 2014 11:19:33 +0000 Perovskite strontium stannate SrSnO3 is a promising photocatalyst. However, its band gap is too large for efficient solar energy conversion. In order to sensitize SrSnO3 toward visible-light activities, the effects of doping with various selected cations and anions are investigated by using hybrid density functional calculations. Results show that doping can result in dopant level to conduction band transitions which lie lower in energy compared to the original band gap transition. Therefore, it is expected that doping SrSnO3 can induce visible-light absorption. Hungru Chen and Naoto Umezawa Copyright © 2014 Hungru Chen and Naoto Umezawa. All rights reserved. Integrating Photovoltaic Systems in Power System: Power Quality Impacts and Optimal Planning Challenges Sun, 17 Aug 2014 12:49:01 +0000 This paper is an overview of some of the main issues in photovoltaic based distributed generation (PVDG). A discussion of the harmonic distortion produced by PVDG units is presented. The maximum permissible penetration level of PVDG in distribution system is also considered. The general procedures of optimal planning for PVDG placement and sizing are also explained in this paper. The result of this review shows that there are different challenges for integrating PVDG in the power systems. One of these challenges is integrated system reliability whereas the amount of power produced by renewable energy source is consistent. Thus, the high penetration of PVDG into grid can decrease the reliability of the power system network. On the other hand, power quality is considered one of the challenges of PVDG whereas the high penetration of PVDGs can lead to more harmonic propagation into the power system network. In addition to that, voltage fluctuation of the integrated PVDG and reverse power flow are two important challenges to this technology. Finally, protection of power system with integrated PVDG is one of the most critical challenges to this technology as the current protection schemes are designed for unidirectional not bidirectional power flow pattern. Aida Fazliana Abdul Kadir, Tamer Khatib, and Wilfried Elmenreich Copyright © 2014 Aida Fazliana Abdul Kadir et al. All rights reserved. SiO2 Antireflection Coatings Fabricated by Electron-Beam Evaporation for Black Monocrystalline Silicon Solar Cells Sun, 17 Aug 2014 00:00:00 +0000 In this work we prepared double-layer antireflection coatings (DARC) by using the SiO2/SiNx:H heterostructure design. SiO2 thin films were deposited by electron-beam evaporation on the conventional solar cell with SiNx:H single-layer antireflection coatings (SARC), while to avoid the coverage of SiO2 on the front side busbars, a steel mask was utilized as the shelter. The thickness of the SiNx:H as bottom layer was fixed at 80 nm, and the varied thicknesses of the SiO2 as top layer were 105 nm and 122 nm. The results show that the SiO2/SiNx:H DARC have a much lower reflectance and higher external quantum efficiency (EQE) in short wavelengths compared with the SiNx:H SARC. A higher energy conversion efficiency of 17.80% was obtained for solar cells with SiO2 (105 nm)/SiNx:H (80 nm) DARC, an absolute conversion efficiency increase of 0.32% compared with the conventional single SiNx:H-coated cells. Minghua Li, Hui Shen, Lin Zhuang, Daming Chen, and Xinghua Liang Copyright © 2014 Minghua Li et al. All rights reserved. Materials, Designs, Fabrications, and Applications of Organic Electronic Devices Thu, 14 Aug 2014 05:46:59 +0000 Jwo-Huei Jou, Ramunas Lygaitis, K. R. Justin Thomas, and Liang-Sheng Liao Copyright © 2014 Jwo-Huei Jou et al. All rights reserved. An Improved Method for Sizing Standalone Photovoltaic Systems Using Generalized Regression Neural Network Mon, 11 Aug 2014 08:08:54 +0000 In this research an improved approach for sizing standalone PV system (SAPV) is presented. This work is an improved work developed previously by the authors. The previous work is based on the analytical method which faced some concerns regarding the difficulty of finding the model’s coefficients. Therefore, the proposed approach in this research is based on a combination of an analytical method and a machine learning approach for a generalized artificial neural network (GRNN). The GRNN assists to predict the optimal size of a PV system using the geographical coordinates of the targeted site instead of using mathematical formulas. Employing the GRNN facilitates the use of a previously developed method by the authors and avoids some of its drawbacks. The approach has been tested using data from five Malaysian sites. According to the results, the proposed method can be efficiently used for SAPV sizing whereas the proposed GRNN based model predicts the sizing curves of the PV system accurately with a prediction error of 0.6%. Moreover, hourly meteorological and load demand data are used in this research in order to consider the uncertainty of the solar energy and the load demand. Tamer Khatib and Wilfried Elmenreich Copyright © 2014 Tamer Khatib and Wilfried Elmenreich. All rights reserved. Investigation of Thermal Instability of Additive-Based High-Efficiency Organic Photovoltaics Sun, 10 Aug 2014 12:57:39 +0000 Most photovoltaics operate at high temperature under sunlight. In this work, the thermal instability of diiodooctane-based high-efficiency bulk heterojunction (BHJ) organic photovoltaics (OPVs) is studied. The BHJ layers were heated to various temperatures to investigate the changes in their physical properties using atomic force microscopy phase images. The mobilities of the carriers were characterized at various temperatures using the space-charge-limited current method, and the carrier lifetime was calculated by applying impedance spectroscopy to the simulated equivalent circuit of the OPV devices. En-Ping Yao, Yi-Jhe Tsai, and Wei-Chou Hsu Copyright © 2014 En-Ping Yao et al. All rights reserved. Low Temperature (180°C) Growth of Smooth Surface Germanium Epilayers on Silicon Substrates Using Electron Cyclotron Resonance Chemical Vapor Deposition Sun, 10 Aug 2014 08:44:28 +0000 This paper describes a new method to grow thin germanium (Ge) epilayers (40 nm) on c-Si substrates at a low growth temperature of 180°C using electron cyclotron resonance chemical vapor deposition (ECR-CVD) process. The full width at half maximum (FWHM) of the Ge (004) in X-ray diffraction pattern and the compressive stain in a Ge epilayer of 683 arcsec and 0.12% can be achieved. Moreover, the Ge/Si interface is observed by transmission electron microscopy to demonstrate the epitaxial growth of Ge on Si and the surface roughness is 0.342 nm. The thin-thickness and smooth surface of Ge epilayer grown on Si in this study is suitable to be a virtual substrate for developing the low cost and high efficiency III-V/Si tandem solar cells in our opinion. Furthermore, the low temperature process can not only decrease costs but can also reduce the restriction of high temperature processes on device manufacturing. Teng-Hsiang Chang, Chiao Chang, Yen-Ho Chu, Chien-Chieh Lee, Jenq-Yang Chang, I-Chen Chen, and Tomi T. Li Copyright © 2014 Teng-Hsiang Chang et al. All rights reserved. Photophysical Properties of Pheophorbide-a Derivatives and Their Photodynamic Therapeutic Effects on a Tumor Cell Line In Vitro Sun, 10 Aug 2014 08:42:47 +0000 Pheophorbide-a derivatives have been reported to be potential photosensitizers for photodynamic therapy (PDT). In this study, photophysics of pheophorbide-a derivatives (PaDs) were investigated along with their photodynamic tumoricidal effect in vitro. PaDs were modified by changing the coil length and/or making the hydroxyl group (–OH) substitutions. Their photophysical properties were studied by steady-state and time-resolved spectroscopic methods. The photodynamic tumoricidal effect was evaluated in the mouse breast cancer cell line (EMT6). Lifetime and quantum yield of fluorescence and quantum yields of triplet state and singlet oxygen were studied to determine the dynamic energy flow. The coil length of the substituted alkyl group did not significantly affect the spectroscopic properties. However, the substitution with the hydroxyl group increased the quantum yields of the triplet state and the singlet oxygen due to the enhanced intersystem crossing. In order to check the application possibility as a photodynamic therapy agent, the PaDs with hydroxyl group were studied for the cellular affinity and the photodynamic tumoricidal effect of EMT6. The results showed that the cellular affinity and the photodynamic tumoricidal effect of PaDs with the hydroxyl group depended on the coil-length of the substituted alkyl group. Kang-Kyun Wang, Jing Li, Bong-Jin Kim, Jeong-Hyun Lee, Hee-Won Shin, Si-Hwan Ko, Won-Young Lee, Chang-Hee Lee, Seok Hoon Jung, and Yong-Rok Kim Copyright © 2014 Kang-Kyun Wang et al. All rights reserved. Estimation of Monthly Sunshine Duration in Turkey Using Artificial Neural Networks Sun, 10 Aug 2014 08:35:44 +0000 This paper introduces an artificial neural network (ANN) approach for estimating monthly mean daily values of global sunshine duration (SD) for Turkey. Three different ANN models, namely, GRNN, MLP, and RBF, were used in the estimation processes. A climatic variable (cloud cover) and two geographical variables (day length and month) were used as input parameters in order to obtain monthly mean SD as output. The datasets of 34 stations which spread across Turkey were split into two parts. First part covering 21 years (1980–2000) was used for training and second part covering last six years (2001–2006) was used for testing. Statistical indicators have shown that, GRNN and MLP models produced better results than the RBF model and can be used safely for the estimation of monthly mean SD. H. M. Kandirmaz, K. Kaba, and M. Avci Copyright © 2014 H. M. Kandirmaz et al. All rights reserved. Effect of Different Deposition Power of In2O3 Target on the Characteristics of IGZO Thin Films Using the Cosputtering Method Sun, 10 Aug 2014 06:25:10 +0000 The (In, Ga, Zn)Ox (IGZO) thin films were deposited on glass substrates using cosputtering method in radio frequency magnetron sputtering system. Zn2Ga2O5 (Ga2O3-2 ZnO, GZO) and In2O3 ceramics were used as targets and dual guns were used to deposit the IGZO thin films. Deposition power of GZO target was 80 W and deposition power of pure In2O3 target was changed from 70 W to 100 W, and the deposition time was 30 min. The effect of deposition power of In2O3 target on the crystalline, surface, electrical, and optical properties of the IGZO thin films was investigated at room temperature in a pure Ar atmosphere. The cosputtered IGZO thin films showed a very smooth and featureless surface and an amorphous structure regardless of the deposition power of In2O3 target due to the room temperature sputtering process. However, the cosputtered IGZO thin films exhibited transparent electrode properties because they had high transmittance ratio and low resistivity. The value variations in the optical band gap values of the IGZO thin film were evaluated from the plots of . We would also show that the deposition power of In2O3 target would have a large effect on mobility and value of the IGZO thin films. Shang-Chao Hung, Kin-Tak Lam, Cheng-Fu Yang, and Yu-Jhen Liou Copyright © 2014 Shang-Chao Hung et al. All rights reserved.