International Journal of Photoenergy The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Theoretical Study on Electronic Structure and Optical Performance of Nickel and Nitrogen Codoped Rutile Titanium Dioxide Thu, 24 Jul 2014 12:32:20 +0000 The nickel doped, nitrogen doped and nickel + nitrogen codoped rutile titanium dioxide have been investigated by ab initio calculations based on density functional theory. The electronic structure and optical performance of different ions doping models are researched through the obtained results, which reflects that the band gap of nickel and nitrogen codoped system declines apparently; the decrease of electron-hole pairs separation and charge carriers recombination rate becomes more desirable. Moreover, the optical absorption curves of nitrogen and nickel codoped rutile titanium dioxide demonstrate the higher photoresponse for visible-light than that of nickel or nitrogen single doped. The above results could provide theoretical basis for further developing of titanium dioxide photocatalyst and related experimental studies. Fei Wang, Lei Feng, Dongmei Zhang, Qingguo Tang, Jinsheng Liang, and Dan Feng Copyright © 2014 Fei Wang et al. All rights reserved. A Facile Synthesis of Graphene-WO3 Nanowire Clusters with High Photocatalytic Activity for O2 Evolution Thu, 24 Jul 2014 08:55:40 +0000 In the present work, graphene-WO3 nanowire clusters were synthesized via a facile hydrothermal method. The obtained graphene-WO3 nanowire clusters were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy (DRS) techniques. The photocatalytic oxygen (O2) evolution properties of the as-synthesized samples were investigated by measuring the amount of evolved O2 from water splitting. The graphene-WO3 nanowire clusters exhibited enhanced performance compared to pure WO3 nanowire clusters for O2 evolution. The amount of evolved O2 from water splitting after 8 h for the graphene-WO3 nanowire clusters is ca. 0.345 mmol/L, which is more than 1.9 times as much as that of the pure WO3 nanowire clusters (ca. 0.175 mmol/L). The high photocatalytic activity of the graphene-WO3 nanowire clusters was attributed to a high charge transfer rate in the presence of graphene. M.-J. Zhou, N. Zhang, and Z. H. Hou Copyright © 2014 M.-J. Zhou et al. All rights reserved. A Newton-Based Extremum Seeking MPPT Method for Photovoltaic Systems with Stochastic Perturbations Thu, 24 Jul 2014 00:00:00 +0000 Microcontroller based maximum power point tracking (MPPT) has been the most popular MPPT approach in photovoltaic systems due to its high flexibility and efficiency in different photovoltaic systems. It is well known that PV systems typically operate under a range of uncertain environmental parameters and disturbances, which implies that MPPT controllers generally suffer from some unknown stochastic perturbations. To address this issue, a novel Newton-based stochastic extremum seeking MPPT method is proposed. Treating stochastic perturbations as excitation signals, the proposed MPPT controller has a good tolerance of stochastic perturbations in nature. Different from conventional gradient-based extremum seeking MPPT algorithm, the convergence rate of the proposed controller can be totally user-assignable rather than determined by unknown power map. The stability and convergence of the proposed controller are rigorously proved. We further discuss the effects of partial shading and PV module ageing on the proposed controller. Numerical simulations and experiments are conducted to show the effectiveness of the proposed MPPT algorithm. Heng Li, Jun Peng, Weirong Liu, Zhiwu Huang, and Kuo-Chi Lin Copyright © 2014 Heng Li et al. All rights reserved. A Communication Based Islanding Detection Method for Photovoltaic Distributed Generation Systems Wed, 23 Jul 2014 07:25:06 +0000 PV based distributed generation (DG) systems must have some electrical connection standards while they connected to an electrical grid. One of these electrical conditions and the most important one is unplanned islanding condition. Islanding is a very dangerous condition because it could damage the PV system and related electrical systems and also working people have been at risk in islanding condition. In this application study, a new communication based islanding detection method was introduced for grid tied PV systems. A real time controller was developed with Labview for detecting islanding condition. Developed method is a hybrid method which uses the effective ways of communication based and passive methods. The results obtained from the proposed real time islanding detection method show that proposed method is reliable, robust, and independent from load and inverter. Nondetection zone (NDZ) is almost zero and islanding detection time is approximately 1-2 cycles indicated in experimental results so this time has a significant short response time according to IEEE 929-2000 standard. The proposed method is effective and presents a realistic solution to islanding so it could be implemented easily to grid tied PV systems and could be used in real system applications. Gökay Bayrak and Mehmet Cebeci Copyright © 2014 Gökay Bayrak and Mehmet Cebeci. All rights reserved. Electron Correlation Effects on the Longitudinal Polarizabilities and Second Hyperpolarizabilities of Polyenes: A Finite Field Study Wed, 23 Jul 2014 00:00:00 +0000 We carry out ab initio calculations, based on finite-field scheme, of the longitudinal polarizabilities () and second hyperpolarizabilities () of conjugated polyenes, and study the effects of electron correlation, with second-order Moller-Plesset perturbation theory and coupled cluster with singles and doubles method. Calculations with density functional theory are also made to compare with wave-function based methods. Our study shows that electron correlation reduces linear longitudinal polarizability and enhances longitudinal second hyperpolarizability for short polyenes, but the effects decrease as the chain increases; choosing appropriate basis sets is important when quantitative results are required. Qingxu Li, Xianju Zhou, and Shiwei Yin Copyright © 2014 Qingxu Li et al. All rights reserved. Development of Hydrogenated Microcrystalline Silicon-Germanium Alloys for Improving Long-Wavelength Absorption in Si-Based Thin-Film Solar Cells Tue, 22 Jul 2014 11:58:30 +0000 Hydrogenated microcrystalline silicon-germanium (μc-:H) alloys were developed for application in Si-based thin-film solar cells. The effects of the germane concentration and the hydrogen ratio on the μc-:H alloys and the corresponding single-junction thin-film solar cells were studied. The behaviors of Ge incorporation in a-:H and μc-:H were also compared. Similar to a-:H, the preferential Ge incorporation was observed in μc-:H. Moreover, a higher significantly promoted Ge incorporation for a-:H, while the Ge content was not affected by in μc-:H growth. Furthermore, to eliminate the crystallization effect, the 0.9 μm thick absorbers with a similar crystalline volume fraction were applied. With the increasing , the accompanied increase in Ge content of μc-:H narrowed the bandgap and markedly enhanced the long-wavelength absorption. However, the bias-dependent EQE measurement revealed that too much Ge incorporation in absorber deteriorated carrier collection and cell performance. With the optimization of and , the single-junction μc-:H cell achieved an efficiency of 5.48%, corresponding to the crystalline volume fraction of 50.5% and Ge content of 13.2 at.%. Compared to μc-Si:H cell, the external quantum efficiency at 800 nm had a relative increase by 33.1%. Yen-Tang Huang, Hung-Jung Hsu, Shin-Wei Liang, Cheng-Hang Hsu, and Chuang-Chuang Tsai Copyright © 2014 Yen-Tang Huang et al. All rights reserved. Synthesis and Characterization of CZTS Thin Films by Sol-Gel Method without Sulfurization Tue, 22 Jul 2014 07:02:40 +0000 One process of layer-by-layer sol-gel deposition without sulfurization was developed. The CZTS films with 1.2 μm and the sulfur ratio of ~48% were prepared and their characteristics were measured. The as-deposited and annealed films are of Kesterite structure. The as-deposited films do not present obvious electric conduction type. However, the annealed 9-LAY-ANN film is p-type conduction and has sheet resistance of 4.08 kΩ/□ and resistivity of 4.896 × 10−1 Ω·cm. The optic energy gap is 1.50 eV for as-deposited films and is 1.46 eV after being annealed. The region deposited by using Lo-Con solution is more compact than that by the Hi-Con solution from SEM morphology images. Xiaoqi Yu, Aobo Ren, Fogen Wang, Ci Wang, Jingquan Zhang, Wenwu Wang, Lili Wu, Wei Li, Guanggen Zeng, and Lianghuan Feng Copyright © 2014 Xiaoqi Yu et al. All rights reserved. Stimulative Effects of Low Intensity He-Ne Laser Irradiation on the Proliferative Potential and Cell-Cycle Progression of Myoblasts in Culture Mon, 21 Jul 2014 08:23:43 +0000 Low intensity laser irradiation (LILI) was found to promote the regeneration of skeletal muscle in vivo but the cellular mechanisms are not fully understood. Myoblasts, normally quiescent and inactivated in adult skeletal muscle, are a type of myogenic progenitor cells and considered as the major candidates responsible for muscle regeneration. The aim of the present study was to study the effect of LILI on the growth potential and cell-cycle progression of the cultured myoblasts. Primary myoblasts isolated from rat hind legs were cultured in nutrient-deficient medium for 36 hours and then irradiated by helium-neon laser at a certain energy density. Immunohistochemical and flow cytometric analysis revealed that laser irradiation could increase the expression of cellular proliferation marker and the amount of cell subpopulations in the proliferative phase as compared with the nonirradiated control group. Meanwhile, the expressions of cell-cycle regulatory proteins in the laser-treated myoblasts were markedly upregulated as compared to the unirradiated cells, indicating that LILI could promote the reentry of quiescent myoblasts into the cell division cycle. These results suggest that LILI at certain fluences could promote their proliferation, thus contributing to the skeletal muscle regeneration following trauma and myopathic diseases. Cui-Ping Zhang, Shao-Dan Li, Yan Chen, Yan-Ming Jiang, Peng Chen, Chang-Zhen Wang, Xiao-Bing Fu, Hong-Xiang Kang, Ben-Jian Shen, and Jie Liang Copyright © 2014 Cui-Ping Zhang et al. All rights reserved. An Alternative Approach for Improving Performance of Organic Photovoltaics by Light-Enhanced Annealing Mon, 21 Jul 2014 07:49:08 +0000 This work proposes an approach for improving the performance of poly(3-hexylthiophene) (P3HT-) based organic photovoltaics (OPVs). P3HT-based bulk heterojunction (BHJ) film can absorb the energy from 532 nm laser light and be transformed into favorable morphology. A combination of traditional thermal annealing and laser annealing improved device performance, with a slight increase in fill factor and a significant improvement in short-circuit current density. Better crystallization and a higher degree of molecular order in the thermal/laser coannealed P3HT-based BHJ film were observed through X-ray diffraction and Raman spectroscopy. En-Ping Yao, Chiu-Sheng Ho, Chang Yu, E-Ling Huang, Ying-Nan Lai, and Wei-Chou Hsu Copyright © 2014 En-Ping Yao et al. All rights reserved. Improving Light Extraction of Organic Light-Emitting Devices by Attaching Nanostructures with Self-Assembled Photonic Crystal Patterns Sun, 20 Jul 2014 12:16:05 +0000 A single-monolayered hexagonal self-assembled photonic crystal (PC) pattern fabricated onto polyethylene terephthalate (PET) films by using simple nanosphere lithography (NSL) method has been demonstrated in this research work. The patterned nanostructures acted as a scattering medium to extract the trapped photons from substrate mode of optical-electronic device for improving the overall external quantum efficiency of the organic light-emitting diodes (OLEDs). With an optimum latex concentration, the distribution of self-assembled polystyrene (PS) nanosphere patterns on PET films can be easily controlled by adjusting the rotation speed of spin-coater. After attaching the PS nanosphere array brightness enhancement film (BEF) sheet as a photonic crystal pattern onto the device, the luminous intensity of OLEDs in the normal viewing direction is 161% higher than the one without any BEF attachment. The electroluminescent (EL) spectrum of OLEDs with PS patterned BEF attachment also showed minor color offset and superior color stabilization characteristics, and thus it possessed the potential applications in all kinds of display technology and solid-state optical-electronic devices. Kai-Yu Peng and Da-Hua Wei Copyright © 2014 Kai-Yu Peng and Da-Hua Wei. All rights reserved. Photoirradiation Caused Controllable Wettability Switching of Sputtered Highly Aligned c-Axis-Oriented Zinc Oxide Columnar Films Sun, 20 Jul 2014 00:00:00 +0000 This study presents the microstructure morphology and UV photoirradiation coupling effects of the c-axis-oriented zinc oxide (ZnO) columnar films. Highly aligned c-axis-oriented films have been deposited onto glass substrates at room temperature by radio-frequency (RF) magnetron sputtering without introducing any oxygen source under different sputtering powers ranging from 50 to 150 W. Self-assembled ZnO columnar structures that were successfully obtained belong to wurtzite structure, and the corresponding columnar structures and crystalline orientation were confirmed by the FE-SEM and XRD, respectively. All the ZnO columnar films exhibit good transparency with a visible light averaged transmittance over 82%. According to water contact angle (CA) measurement, ZnO columnar films exhibit hydrophobic behavior. After exposing to photoirradiation under ultraviolet (UV) environment, all the ZnO samples showed remarkable transition from hydrophobic to superhydrophilic surfaces and could return to their original hydrophobicity after being placed in the dark. It is demonstrated that the controllable wettability of ZnO columnar films under changing between the UV photoirradiation and dark storage is due to the surface charges accumulation and discharging processes. As a result, this study could provide important applications for many fields such as ZnO-based hybrid sensors/solar cells functional devices with photoirradiation disinfection surfaces accompanied with reversible wettability switches. P. W. Chi, C. W. Su, B. H. Jhuo, and D. H. Wei Copyright © 2014 P. W. Chi et al. All rights reserved. Effect of Mn Doping on Properties of CdS Quantum Dot-Sensitized Solar Cells Thu, 17 Jul 2014 12:12:55 +0000 Quantum dot-sensitized solar cells (QDSSCs) have received extensive attention in recent years due to their higher theoretical conversion efficiency and lower production costs. However, the photoelectric conversion efficiency of QDSSCs is still lower than the DSSCs because of the severe recombination of electrons of quantum dots conduction band. In order to improve the photoelectric conversion efficiency of QDSSCs, impurity element Mn2+ is doped into the precursor solution of cadmium sulfide (CdS). By optimizing the experimental parameters, the photoelectric conversion efficiency of QDSSCs can be greatly improved. For the deposition of a fixed number of six times, the photoelectric conversion efficiency shows the maximum value (1.51%) at the doped ratio of 1 : 10. Tianxing Li, Xiaoping Zou, and Hongquan Zhou Copyright © 2014 Tianxing Li et al. All rights reserved. Effects of Low-Level Laser Therapy and Eccentric Exercises in the Treatment of Patellar Tendinopathy Wed, 16 Jul 2014 10:54:14 +0000 The study aims to investigate if low-level laser therapy (LLLT) combined with eccentric exercises could more effectively treat patellar tendinopathy than LLLT alone and eccentric exercises alone. Twenty-one patients with patellar tendinopathy were randomized to three groups: laser alone, exercise alone, or laser plus exercise, with seven in each group. Laser irradiations were administered at the inferior pole of the patella and the two acupoints of Extra 36 (Xiyan) with the intensity of 1592 mW/cm2. Eccentric training program consisted of three sets of 15 repetitions of unilateral squat on level ground. All patients received six treatments per week for four weeks. Knee pain and function and quadriceps muscle strength and endurance were evaluated at baseline and the end of treatment. After the 4-week intervention, all groups showed significant improvements in all the outcomes (). The laser + exercise group had significantly greater improvements in all the outcomes than the other two groups (), except nonsignificant difference in pain relief between the laser + exercise group and the laser group. In conclusion, LLLT combined with eccentric exercises is superior to LLLT alone and eccentric exercises alone to reduce pain and improve function in patients with patellar tendinopathy. Xiao-Guang Liu, Lin Cheng, and Ji-Mei Song Copyright © 2014 Xiao-Guang Liu et al. All rights reserved. Development of Thin Film Amorphous Silicon Tandem Junction Based Photocathodes Providing High Open-Circuit Voltages for Hydrogen Production Wed, 16 Jul 2014 10:20:48 +0000 Hydrogenated amorphous silicon thin film tandem solar cells (a-Si:H/a-Si:H) have been developed with focus on high open-circuit voltages for the direct application as photocathodes in photoelectrochemical water splitting devices. By temperature variation during deposition of the intrinsic a-Si:H absorber layers the band gap energy of a-Si:H absorber layers, correlating with the hydrogen content of the material, can be adjusted and combined in a way that a-Si:H/a-Si:H tandem solar cells provide open-circuit voltages up to 1.87 V. The applicability of the tandem solar cells as photocathodes was investigated in a photoelectrochemical cell (PEC) measurement set-up. With platinum as a catalyst, the a-Si:H/a-Si:H based photocathodes exhibit a high photocurrent onset potential of 1.76 V versus the reversible hydrogen electrode (RHE) and a photocurrent of 5.3 mA/cm2 at 0 V versus RHE (under halogen lamp illumination). Our results provide evidence that a direct application of thin film silicon based photocathodes fulfills the main thermodynamic requirements to generate hydrogen. Furthermore, the presented approach may provide an efficient and low-cost route to solar hydrogen production. F. Urbain, K. Wilken, V. Smirnov, O. Astakhov, A. Lambertz, J.-P. Becker, U. Rau, J. Ziegler, B. Kaiser, W. Jaegermann, and F. Finger Copyright © 2014 F. Urbain et al. All rights reserved. Optimal Demand Response of Smart Home with PV Generators Wed, 16 Jul 2014 08:19:19 +0000 Demand response (DR) is used mainly to help to schedule a customer’s power utilization based on the electricity price that is announced by the power distribution company so that both demand and supply can optimally benefit. The work proposes a users’ load model and the interior point method for optimal scheduling with elastic power utilization to minimize power price. The interior point method has the advantages of rapid convergence and robustness. Customers can not only use PV generators and battery sets as backup power sources, but also benefit from green energy. As revealed by the results herein, the use of elastic power utilization time intervals enables customers to pay less power price. Chao-Rong Chen and Ming-Jen Lan Copyright © 2014 Chao-Rong Chen and Ming-Jen Lan. All rights reserved. Enabling Lambertian-Like Warm White Organic Light-Emitting Diodes with a Yellow Phosphor Embedded Flexible Film Wed, 16 Jul 2014 07:24:48 +0000 We demonstrate in this report a new constructive method of fabricating white organic light-emitting devices (OLEDs) with a flexible plastic film embedded with yellow phosphor. The flexible film is composed of polydimethylsiloxane (PDMS) and fabricated by using spin coating followed by peeling technology. From the results, the resultant electroluminescent spectrum shows the white OLED to have chromatic coordinates of 0.38 and 0.54 and correlated color temperature of 4200 K. The warm white OLED exhibits the yield of 10.3 cd/A and the luminous power efficiency of 5.4 lm/W at a luminance of 1000 cd/m2. A desirable Lambertian-like far-field pattern is detected from the white OLEDs with the yellow phosphor containing PDMS film. This method is simple, reproducible, and cost-effective, proving to be a highly feasible approach to realize white OLED. Cheng-Chang Chen, Huang-Yu Lin, Cheng-Hung Li, Jin-Han Wu, Zong-Yi Tu, Li-Ling Lee, Ming-Shan Jeng, Chien-Chung Lin, Jwo-Huei Jou, and Hao-Chung Kuo Copyright © 2014 Cheng-Chang Chen et al. All rights reserved. Low-Cost ZnO:YAG-Based Metal-Insulator-Semiconductor White Light-Emitting Diodes with Various Insulators Tue, 15 Jul 2014 14:25:39 +0000 ZnO:YAG-based metal-insulator-semiconductor (MIS) diodes with various insulators were synthesized on an indium tin oxide (ITO) glass by ultrasonic spray pyrolysis. SiO2 and MnZnO (MZO) were separately used as insulators. X-ray diffraction revealed the crystalline structure of the ZnO:YAG film. The photoluminescence (PL) properties of the ZnO:YAG film were studied and the color of photoluminescence was found to be almost white. The electrical properties of the diodes with different insulators and thicknesses were compared. The diode with the SiO2 insulator had a lower threshold voltage, smaller leakage current, and a higher series resistance than that with the MZO insulator layer. Lung-Chien Chen, Chih-Hung Hsu, Xiuyu Zhang, and Jia-Ren Wu Copyright © 2014 Lung-Chien Chen et al. All rights reserved. Effect of Electrodeposition Potential on Composition of CuIn1−xGaxSe2 Absorber Layer for Solar Cell by One-Step Electrodeposition Mon, 14 Jul 2014 10:00:22 +0000 CIGS polycrystalline thin films were successfully fabricated by one-step cathodic electrodeposition on Mo-coated glass. In this study, we applied a galvanometry mode with three-electrode potentiostatic systems to produce a constant concentration electroplating solution, which were composed of CuCl2, InCl3, GaCl3, and SeO2. Then these as-electrodeposited films were annealed in argon atmosphere and characterized by X-ray diffraction. The results revealed that annealing treatment significantly improved the crystallinity of electrodeposited films and formed CIGS chalcopyrite structure, but at low applied deposition voltage (−950 mV versus SCE) there appeared second phase. The cross-section morphology revealed that applied voltage at −1350 mV versus SCE has uniform deposition, and higher applied voltage made grain more unobvious. The deposition rate and current density are proportional to deposition potential, and hydrogen was generated apparently when applying potential beyond −1750 mV versus SCE. It was found that the CIGS compound did not match exact stoichiometry of . This result suggests the possibility of controlling the property of thin films by varying the applied potential during electrodeposition. Rui-Wei You, Kar-Kit Lew, and Yen-Pei Fu Copyright © 2014 Rui-Wei You et al. All rights reserved. Device Modeling of the Performance of Cu(In,Ga)Se2 Solar Cells with V-Shaped Bandgap Profiles Mon, 14 Jul 2014 08:17:25 +0000 The effect of Cu(In,Ga)Se2 (CIGS) with V-shaped bandgap on device performance is investigated in detail. A series of Ga/(In+Ga) ratio are set to study the influence of V-shaped bandgap profile on the electricity of CIGS thin film solar cells. The modeling of device current density-voltage (J-V) curve and bandgap grading profile corresponded well to measurement results. Detailed characteristic and modeling results show that an increased gradient of bandgap from valley to the buffer layer CdS will result in a barrier and lead to an enhanced recombination in the valley. This phenomenon can be modified by the back electric field resulting from a gradient bandgap from valley (bandgap minimum) to the Mo back contact. These results indicate CIGS-based solar cells can achieve higher performance by optimizing the V-shaped bandgap profile. Shou-Yi Kuo, Ming-Yang Hsieh, Dan-Hua Hsieh, Hao-Chung Kuo, Chyong-Hua Chen, and Fang-I Lai Copyright © 2014 Shou-Yi Kuo et al. All rights reserved. Fabrication of Antireflection Nanodiamond Particle Film by the Spin Coating Deposition Technique Mon, 14 Jul 2014 00:00:00 +0000 Diamond-based antireflective (AR) coatings were fabricated using a spin coating of diamond suspension at room temperature as nucleation enhancement procedure and microwave plasma enhanced chemical vapour deposition. Various working pressures were used to investigate their effect on the optical characterization of the as-deposited diamond films. Scanning electron microscopy (SEM) and atomic forced microscopy (AFM) were employed to analyze the surface properties of the diamond films. Raman spectra and transmission electron microscopy (TEM) also were used for analysis of the microstructure of the films. The results showed that working pressure had a significant effect on thickness, surface roughness, and wettability of the as-deposited diamond films. Deposited under 35 Torr or working pressure, the film possessed a low surface roughness of 13.8 nm and fine diamond grain sizes of 35 nm. Reflectance measurements of the films also were carried out using UV-Vis spectrometer and revealed a low reflectance value of the diamond films. The achievement demonstrated feasibility of the proposed spin-coating procedure for large scale production and thus opens up a prospect application of diamond film as an AR coating in industrial optoelectronic device. Chii-Ruey Lin, Hong-Ming Chang, Minh-Khoa BenDao, Hsiu Hsien Chiang, and Wei-En Chen Copyright © 2014 Chii-Ruey Lin et al. All rights reserved. Development of High-Performance UV Detector Using Nanocrystalline Diamond Thin Film Sun, 13 Jul 2014 13:59:11 +0000 Nanocrystalline diamond (NCD) films are promising materials for wide-spread applications due to their outstanding characteristics of chemical, physical, and highly smooth surface. Our present work aimed at the fabrication of high performance diamond-based UV detector. NCD films were prepared by microwave plasma enhanced chemical vapor deposition process, and then Au interdigital electrodes were deposited onto the surface of the as-grown NCD film by sputtering technique. Annealing procedures were conducted at various temperatures to obtain Ohmic contact of NCD/Au structure. The surface morphology, microstructure, and wettablity of the NCD films were analyzed by scanning electron microscopy, atomic forced microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and water contact angle measurement, respectively. The electrical property and photoconductivity of the fabricated devices were tested for UV detection application. It was found that the NCD films possessed high sp3 fraction of 68.6%, low surface roughness of 9.6 nm, and good hydrophobicity, as deposited under working pressure of 40 Torr. Also, the NCD/Au structure annealed at 500°C exhibited a good Ohmic contact characteristic, high detection efficiency, and fast response to UV irradiation in air ambient. The proposed study indeed demonstrates prospective applications of NCD films in UV detector, photocatalyst, solar cell, and so on. C. R. Lin, D. H. Wei, M. K. BenDao, W. E. Chen, and T. Y. Liu Copyright © 2014 C. R. Lin et al. All rights reserved. Novel Terthiophene-Substituted Fullerene Derivatives as Easily Accessible Acceptor Molecules for Bulk-Heterojunction Polymer Solar Cells Thu, 10 Jul 2014 10:39:26 +0000 Five fulleropyrrolidines and methanofullerenes, bearing one or two terthiophene moieties, have been prepared in a convenient way and well characterized. These novel fullerene derivatives are characterized by good solubility and by better harvesting of the solar radiation with respect to traditional PCBM. In addition, they have a relatively high LUMO level and a low band gap that can be easily tuned by an adequate design of the link between the fullerene and the terthiophene. Preliminary results show that they are potential acceptors for the creation of efficient bulk-heterojunction solar cells based on donor polymers containing thiophene units. Filippo Nisic, Alessia Colombo, Claudia Dragonetti, Alessandra Cominetti, Andrea Pellegrino, Nicola Perin, Riccardo Po, and Alessandra Tacca Copyright © 2014 Filippo Nisic et al. All rights reserved. Using Pre-TMIn Treatment to Improve the Optical Properties of Green Light Emitting Diodes Thu, 10 Jul 2014 10:06:45 +0000 We investigated the effects of pre-TMIn treatment on the optical properties of green light emitting diodes (LEDs). Although pre-TMIn treatment did not affect the epitaxial structure of quantum wells, it significantly improved the quality of the surface morphology relative to that of the untreated sample. Indium cluster can be seen by high-resolution transmission electron microscopy (HR-TEM), which is the explanation for the red-shift of photoluminescence (PL). Time-resolved photoluminescence measurements indicated that the sample prepared with pre-TMIn treatment had a shorter radiative decay time. As a result, the light output power of the treated green LED was higher than that of the conventional untreated one. Thus, pre-TMIn treatment appears to be a simple and efficient means of improving the performance of green LEDs. Bing Xu, Hai Tao Dai, Shu Guo Wang, Fu-Chuan Chu, Chou-Hsiung Huang, Sheng-Fu Yu, Jun Liang Zhao, Xiao Wei Sun, and Ray-Ming Lin Copyright © 2014 Bing Xu et al. All rights reserved. The Structure and Stability of Molybdenum Ditelluride Thin Films Thu, 10 Jul 2014 08:42:24 +0000 Molybdenum-tellurium alloy thin films were fabricated by electron beam evaporation and the films were annealed in different conditions in N2 ambient. The hexagonal molybdenum ditelluride thin films with well crystallization annealed at 470°C or higher were obtained by solid state reactions. Thermal stability measurements indicate the formation of MoTe2 took place at about 350°C, and a subtle weight-loss was in the range between 30°C and 500°C. The evolution of the chemistry for Mo-Te thin films was performed to investigate the growth of the MoTe2 thin films free of any secondary phase. And the effect of other postdeposition treatments on the film characteristics was also investigated. Zhouling Wang, Wenwu Wang, Ya Yang, Wei Li, Lianghuan Feng, Jingquan Zhang, Lili Wu, and Guanggen Zeng Copyright © 2014 Zhouling Wang et al. All rights reserved. Love Wave Ultraviolet Photodetector Fabricated on a TiO2/ST-Cut Quartz Structure Thu, 10 Jul 2014 07:01:26 +0000 A TiO2 thin film deposited on a 90° rotated 42°45′ ST-cut quartz substrate was applied to fabricate a Love wave ultraviolet photodetector. TiO2 thin films were grown by radio frequency magnetron sputtering. The crystalline structure and surface morphology of TiO2 thin films were examined using X-ray diffraction, scanning electron microscope, and atomic force microscope. The effect of TiO2 thin film thickness on the phase velocity, electromechanical coupling coefficient, temperature coefficient of frequency, and sensitivity of ultraviolet of devices was investigated. TiO2 thin film increases the electromechanical coupling coefficient but decreases the temperature coefficient of frequency for Love wave propagation on the 90° rotated 42°45′ ST-cut quartz. For Love wave ultraviolet photodetector application, the maximum insertion loss shift and phase shift are 2.81 dB and 3.55 degree at the 1.35-μm-thick TiO2 film. Walter Water, Yi-Shun Lin, and Chi-Wei Wen Copyright © 2014 Walter Water et al. All rights reserved. Luminescent Solar Concentrators Fabricated by Dispersing Rare Earth Particles in PMMA Waveguide Wed, 09 Jul 2014 12:48:09 +0000 Luminescent solar concentrators (LSCs) were fabricated by dispersing CaAlSiN3 : Eu2+ particles in a PMMA waveguide. A series of LSCs (dimension 5.0 cm × 5.0 cm × 0.5 cm) with different CaAlSiN3 : Eu2+ particle concentration were obtained and their performance was evaluated. The maximum optical concentration ratio is 1.23 with a power conversion efficiency of 1.44% for the LSC containing 0.5 wt% CaAlSiN3 : Eu2+ particles concentration. This strategy of dispersing rare earth particles in PMMA waveguide represents an alternative approach to producing highly durable LSCs. Cheng Liu, Ruijiang Deng, Yanlin Gong, Cheng Zou, Yong Liu, Xiang Zhou, and Baojun Li Copyright © 2014 Cheng Liu et al. All rights reserved. Improvement of Dye Solar Cell Efficiency by Photoanode Posttreatment Wed, 09 Jul 2014 12:21:49 +0000 The basic concept for efficiency improvement in dye-sensitized solar cells (DSSC) is limiting the electron-hole recombination. One way to approach the problem is to improve the photogenerated charge carriers lifetime and consequently reduce their recombination probability. We are reporting on a facile posttreatment of the mesoporous photoanode by using a colloidal solution of TiO2 nanoparticles. We have investigated the outcome of the different sintering temperature of the posttreated photoanodes on their morphology as well as on the conversion efficiency of the DSSC. The DSSCs composed of posttreated photoanodes at 450°C showed an increase in and consequently an increase in efficiency of 10%. Investigations were made to determine the electron recombination via the electrolyte by the OCVD technique. We found that the posttreatment has the effect of reducing the surface trap states and thus increases the electron lifetime, which is responsible for the increase of the overall cell efficiency. Tanja Ivanovska, Zoran Saponjic, Marija Radoicic, Luca Ortolani, Vittorio Morandi, and Giampiero Ruani Copyright © 2014 Tanja Ivanovska et al. All rights reserved. Semitransparent Polymer Solar Cells Based on Liquid Crystal Reflectors Wed, 09 Jul 2014 10:29:08 +0000 The effects of liquid crystal (LC) reflectors on semitransparent polymer solar cells (PSCs) were investigated in this paper. By improving the cathode, we manufactured semitransparent PSCs based on the conventional PSCs. We then incorporated the LC reflector into the semitransparent PSCs, which increased the power conversion efficiency (PCE) from 2.11% to 2.71%. Subsequently adjusting the concentration and spinning speed of the active layer material changed its thickness. The maximum light absorption for the active layer was obtained using the optimum thickness, and the PCE eventually reached 3.01%. These results provide a reference for selecting LC reflectors that are suitable for different active layer materials to improve the PCE of semitransparent PSCs. Shaopeng Yang, Tiening Wang, Xiaohui Zhao, Luo Gu, Qiman Yang, Guang Li, Xiaowei Li, and Guangsheng Fu Copyright © 2014 Shaopeng Yang et al. All rights reserved. Inverted Metamorphic III–V Triple-Junction Solar Cell with a 1 eV CuInSe2 Bottom Subcell Wed, 09 Jul 2014 09:00:54 +0000 A new triple-junction solar cell (3J) design exploiting the highly absorptive I–III–VI chalcopyrite CuInSe2 material is proposed as an alternative to III–V semiconductor 3J solar cells. The proposed structure consists of GaInP (1.9 eV)/Ga(In)As (1.4 eV)/CuInSe2 (1 eV) which can be grown on a GaAs substrate in an inverted manner using epitaxial lift-off techniques. To lattice-match epitaxial CuInSe2 to Ga(In)As, a compositionally graded buffer region composed of GaxIn1−xP is used. The modeling and simulation of the device include the effects of threading dislocations on minority carrier lifetimes in the metamorphic buffer and bottom subcell active region. Studies focus on device performance under standard testing conditions and concentrated illumination. The results are compared to a reference lattice mismatched 3J composed of GaInP (1.9 eV)/Ga(In)As (1.4 eV)/GaInAs (1 eV) and to a lattice matched 3J composed of GaInP (1.9 eV)/Ga(In)As (1.4 eV)/Ge (0.67 eV). The advantage of CuInSe2 is its higher absorption coefficient, which requires only 1 μm of active material compared to 4 μm of GaInAs in the bottom subcell of the reference lattice mismatched cell. The proposed design reaches an efficiency of 32.6% under 1 sun illumination at 300 K with 105 cm−2 threading dislocations and 39.6% at 750 suns. A. W. Walker, F. Bouchard, A. H. Trojnar, and K. Hinzer Copyright © 2014 A. W. Walker et al. All rights reserved. Photocatalytic Degradation of Anthracene in Closed System Reactor Tue, 08 Jul 2014 06:37:25 +0000 Polycyclic aromatic hydrocarbons (PAHs) represent a large class of persistent organic pollutants in an environment of special concern because they have carcinogenic and mutagenic activity. In this paper, we focus on and discuss the effect of different parameters, for instance, initial concentration of Anthracene, temperature, and light intensity, on the degradation rate. These parameters were adjusted at pH 6.8 in the presence of the semiconductor materials (TiO2) as photocatalysts over UV light. The main product of Anthracene photodegradation is 9,10-Anthraquinone which isidentified and compared with the standard compound by GC-MS. Our results indicate that the optimum conditions for the best rate of degradation are 25 ppm concentration of Anthracene, regulating the reaction vessel at 308.15 K and 2.5 mW/cm2 of light intensity at 175 mg/100 mL of titanium dioxide (P25). Faiq F. Karam, Falah H. Hussein, Sadiq J. Baqir, Ahmed F. Halbus, Ralf Dillert, and Detelf Bahnemann Copyright © 2014 Faiq F. Karam et al. All rights reserved.