International Journal of Photoenergy http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Conformational States of the Spiropyran Molecule Thu, 02 Jul 2015 12:37:27 +0000 http://www.hindawi.com/journals/ijp/2015/161248/ The form of the potential surface of the ground state was investigated on the basis of indoline spiropyran. As a result of this work the rotamers of an open-ring form of the spiropyran molecule were discovered, and the existence of the most probable rotamers was justified. The 3D potential surface of the ground state of the spiropyran molecule was built. The route of the isomerization of the molecule was discovered and values of barriers for this reaction were found. The part of the isomerization route that is responsible for changing the hybridization of spiroatom from sp3 to sp2 was found. Olha Kovalenko, Petro Kondratenko, and Yuriy Lopatkin Copyright © 2015 Olha Kovalenko et al. All rights reserved. New Energy Materials and Device Application Mon, 29 Jun 2015 06:14:27 +0000 http://www.hindawi.com/journals/ijp/2015/657152/ Sheng-Po Chang, Jun Zhu, Shyh-Jer Huang, Hsin-Chieh Yu, Ting-Jen Hsueh, and Hsin-Ying Lee Copyright © 2015 Sheng-Po Chang et al. All rights reserved. Power Quality Experimental Analysis on Rural Home Grid-Connected PV Systems Wed, 24 Jun 2015 11:28:32 +0000 http://www.hindawi.com/journals/ijp/2015/791680/ Microgeneration is the small-scale generation of heat or electric power or both, by individuals or buildings to meet their own needs. Recently, microgeneration is being regarded as a means to decentralize the power production of renewable energies, reducing the impacts on the grid caused by unexpected energy demands. Given the increase in microgeneration facilities, determining the quantity of energy produced and the power quality assumes growing importance in low, medium, or high voltage facilities. This paper presents a power quality analysis of two different facilities with photovoltaic generation localized in a rural area of Portugal, describing the voltage and frequency behaviour, the harmonic contents, and the total harmonic distortion. Statistical data are presented regarding the number of voltage events and occurrence of dips and swells in both facilities as a percentage of rated voltage. We conclude that some PV systems can severely affect voltage quality, forcing the grid to work at and even above the maximum voltage standard limit. Rita Jorge Cerqueira Pinto, Sílvio José Pinto Simões Mariano, and Maria do Rosário Alves Calado Copyright © 2015 Rita Jorge Cerqueira Pinto et al. All rights reserved. Optimization of μc-Si1−xGex:H Single-Junction Solar Cells with Enhanced Spectral Response and Improved Film Quality Wed, 24 Jun 2015 07:14:42 +0000 http://www.hindawi.com/journals/ijp/2015/382814/ Effects of RF power on optical, electrical, and structural properties of μc-Si1−xGex:H films was reported. Raman and FTIR spectra from μc-Si1−xGex:H films reflected the variation in microstructure and bonding configuration. Unlike increasing the germane concentration for Ge incorporation, low RF power enhanced Ge incorporation efficiency in μc-Si1−xGex:H alloy. By decreasing RF power from 100 to 50 W at a fixed reactant gas ratio, the optical bandgap of μc-Si1−xGex:H was reduced owing to the increase in Ge content from 11.2 to 23.8 at.%, while Ge-related defects and amorphous phase were increased. Consequently, photo conductivity of 1.62 × 10−5 S/cm was obtained for the μc-Si1−xGex:H film deposited at 60 W. By applying 0.9 μm thick μc-Si1−xGex:H absorber with of 48% and [Ge] of 16.4 at.% in the single-junction cell, efficiency of 6.18% was obtained. The long-wavelength response of μc-Si1−xGex:H cell was significantly enhanced compared with the μc-Si:H cell. In the case of tandem cells, 0.24 μm a-Si:H/0.9 μm μc-Si1−xGex:H tandem cell exhibited a comparable spectral response as 0.24 μm a-Si:H/1.4 μm μc-Si:H tandem cell and achieved an efficiency of 9.44%. Yen-Tang Huang, Pei-Ling Chen, Po-Wei Chen, Hung-Jung Hsu, Cheng-Hang Hsu, and Chuang-Chuang Tsai Copyright © 2015 Yen-Tang Huang et al. All rights reserved. Modeling and Maximum Power Point Tracking Techniques of Photovoltaic Systems Thu, 18 Jun 2015 06:35:06 +0000 http://www.hindawi.com/journals/ijp/2015/362471/ Marcelo Cabral Cavalcanti, Francisco de Assis dos Santos Neves, Denizar Cruz Martins, Emilio José Bueno Peña, and Euzeli Cipriano dos Santos Júnior Copyright © 2015 Marcelo Cabral Cavalcanti et al. All rights reserved. Superior Photocurrent of Quantum Dot Sensitized Solar Cells Based on PbS : In/CdS Quantum Dots Wed, 17 Jun 2015 07:28:23 +0000 http://www.hindawi.com/journals/ijp/2015/657871/ PbS : In and CdS quantum dots (QDs) are sequentially assembled onto a nanocrystalline TiO2 film to prepare a PbS : In/CdS cosensitized photoelectrode for QD sensitized solar cells (QDSCs). The results show that PbS : In/CdS QDs have exhibited a significant effect in the light harvest and performance of the QDSC. In the cascade structure of the electrode, the reorganization of energy levels between PbS and TiO2 forms a stepwise structure of band-edge levels which is advantageous to the electron injection into TiO2. Energy conversion efficiency of 2.3% is achieved with the doped electrode, under the illumination of one sun (AM1.5, 100 mW cm2). Besides, a remarkable short circuit current density (up to 23 mA·cm−2) is achieved in the resulting PbS : In/CdS quantum dot sensitized solar cell, and the related mechanism is discussed. Zongbo Huang and Xiaoping Zou Copyright © 2015 Zongbo Huang and Xiaoping Zou. All rights reserved. Maximum Power Point Tracking Based on Sliding Mode Control Tue, 16 Jun 2015 14:26:34 +0000 http://www.hindawi.com/journals/ijp/2015/380684/ Solar panels, which have become a good choice, are used to generate and supply electricity in commercial and residential applications. This generated power starts with the solar cells, which have a complex relationship between solar irradiation, temperature, and output power. For this reason a tracking of the maximum power point is required. Traditionally, this has been made by considering just current and voltage conditions at the photovoltaic panel; however, temperature also influences the process. In this paper the voltage, current, and temperature in the PV system are considered to be a part of a sliding surface for the proposed maximum power point tracking; this means a sliding mode controller is applied. Obtained results gave a good dynamic response, as a difference from traditional schemes, which are only based on computational algorithms. A traditional algorithm based on MPPT was added in order to assure a low steady state error. Nimrod Vázquez, Yuz Azaf, Ilse Cervantes, Eslí Vázquez, and Claudia Hernández Copyright © 2015 Nimrod Vázquez et al. All rights reserved. MPPT Technique Based on Current and Temperature Measurements Tue, 16 Jun 2015 12:49:22 +0000 http://www.hindawi.com/journals/ijp/2015/242745/ This paper presents a new maximum power point tracking (MPPT) method based on the measurement of temperature and short-circuit current, in a simple and efficient approach. These measurements, which can precisely define the maximum power point (MPP), have not been used together in other existing techniques. The temperature is measured with a low cost sensor and the solar irradiance is estimated through the relationship of the measured short-circuit current and its reference. Fast tracking speed and stable steady-state operation are advantages of this technique, which presents higher performance when compared to other well-known techniques. Eduardo Moreira Vicente, Robson Luiz Moreno, and Enio Roberto Ribeiro Copyright © 2015 Eduardo Moreira Vicente et al. All rights reserved. A New Fractional-Order Based Intelligent Maximum Power Point Tracking Control Algorithm for Photovoltaic Power Systems Tue, 16 Jun 2015 12:48:30 +0000 http://www.hindawi.com/journals/ijp/2015/493452/ This paper proposes a new type of variable fractional-order incremental conductance algorithm (VFOINC), combined with extenics variable step size (EVSS) control into the maximum power point tracking (MPPT) design for photovoltaic power systems. At the beginning of maximum power tracking, the fractional-order number is selected as 1; the good transient tracking characteristic of traditional incremental conductance method is used. When the maximum power point is approached, the fractional-order number is selected as variable fractional order; the curve profile of in fractional order is used to approximate, so that the system has good tracking effect in transient and steady states. The experimental and simulation results show that, compared with traditional incremental conductance method (INC) and fractional-order incremental conductance method (FOINC), this method has better MPPT effect. Kuo-Nan Yu, Chih-Kang Liao, and Her-Terng Yau Copyright © 2015 Kuo-Nan Yu et al. All rights reserved. Biaxial Solar Tracking System Based on the MPPT Approach Integrating ICTs for Photovoltaic Applications Tue, 16 Jun 2015 12:36:50 +0000 http://www.hindawi.com/journals/ijp/2015/202986/ The smart grid and distributed generation based on renewable energy applications often involve the use of information and communication technology (ICT) coupled with advanced control and monitoring algorithms to improve the efficiency and reliability of the electrical grid and renewable generation systems. Photovoltaic (PV) systems have been recently applied with success in the fields of distributed generation due to their lower environmental impact where the electrical energy generation is related to the amount of solar irradiation and thus the angle of incident ray of the sun on the surface of the modules. This paper introduces an integration of ICTs in order to achieve the maximum power point tracking (MPPT) using a biaxial solar tracking system for PV power applications. To generate the references for the digital control of azimuth and elevation angles a Global Positioning System (GPS) by satellites is used which enables acquiring the geographic coordinates of the sun in real-time. As a total integration of the system a communication platform based on the 802.15.4 protocol for the wireless sensor networks (WSNs) is adopted for supervising and monitoring the PV plant. A 2.4 kW prototype system is implemented to validate the proposed control scheme performance. Raúl Gregor, Yoshihiko Takase, Jorge Rodas, Leonardo Carreras, Derlis Gregor, and Andrés López Copyright © 2015 Raúl Gregor et al. All rights reserved. Investigating the Effect of Piezoelectric Polarization on GaN-Based LEDs with Different Prestrain Layer by Temperature-Dependent Electroluminescence Tue, 16 Jun 2015 12:17:18 +0000 http://www.hindawi.com/journals/ijp/2015/135321/ The effect of piezoelectric polarization on GaN-based light emitting diodes (LEDs) with different kinds of prestrain layers between the multiple quantum wells (MQWs) and n-GaN layer is studied and demonstrated. Compared with the conventional LED, more than 10% enhancement in the output power of the LED with prestrain layer can be attributed to the reduction of polarization field within MQWs region. In this study, we reported a simple method to provide useful comparison of polarization fields within active region in GaN-based LEDs by using temperature-dependent electroluminescence (EL) measurement. The results pointed out that the polarization field of conventional LED was stronger than that of the others due to larger variation of the wavelength transition position (i.e., blue-shift change to red-shift) from 300 to 350 K, and thus the larger polarization field must be effectively screened by injecting more carriers into the MQWs region. C. K. Wang, Y. Z. Chiou, T. H. Chiang, and T. K. Lin Copyright © 2015 C. K. Wang et al. All rights reserved. Photovoltaic Array Reconfiguration Strategy for Maximization of Energy Production Tue, 16 Jun 2015 10:28:10 +0000 http://www.hindawi.com/journals/ijp/2015/592383/ This paper presents a dynamic reconfiguration method for electrical connections in a Series-Parallel connected photovoltaic array under partial shading conditions. It is desirable to extract the maximum energy from the array, but it does not occur in situations where the modules have different points of operation caused by shading. The proposed method is then characterized by the maintenance of the PV array dimensions, that is; no module is removed or added to the array. Furthermore, the control algorithm is based on the Rough Sets Theory, which allows the fast and efficient implementation of a control system, comprising rules that identify the system optimal configuration. Paula dos Santos Vicente, Tales Cleber Pimenta, and Enio Roberto Ribeiro Copyright © 2015 Paula dos Santos Vicente et al. All rights reserved. An Ultrafast Maximum Power Point Setting Scheme for Photovoltaic Arrays Using Model Parameter Identification Tue, 16 Jun 2015 09:25:09 +0000 http://www.hindawi.com/journals/ijp/2015/424628/ Maximum power point tracking (MPPT) for photovoltaic (PV) arrays is essential to optimize conversion efficiency under variable and nonuniform irradiance conditions. Unfortunately, conventional MPPT algorithms such as perturb and observe (P&O), incremental conductance, and current sweep method need to iterate command current or voltage and frequently operate power converters with associated losses. Under partial overcast conditions, tracking the real MPP in multipeak P-I or P-V curve model becomes highly challenging, with associated increase in search time and converter operation, leading to unnecessary power being lost in the MPP tracking process. In this paper, the noted drawbacks in MPPT-controlled converters are addressed. In order to separate the search algorithms from converter operation, a model parameter identification approach is presented to estimate insolation conditions of each PV panel and build a real-time overall P-I curve of PV arrays. Subsequently a simple but effective global MPPT algorithm is proposed to track the MPP in the overall P-I curve obtained from the identified PV array model, ensuring that the converter works at the MPP. The novel MPPT is ultrafast, resulting in conserved power in the tracking process. Finally, simulations in different scenarios are executed to validate the novel scheme’s effectiveness and advantages. Zhaohui Cen Copyright © 2015 Zhaohui Cen. All rights reserved. A Reinforcement Learning-Based Maximum Power Point Tracking Method for Photovoltaic Array Tue, 16 Jun 2015 09:23:40 +0000 http://www.hindawi.com/journals/ijp/2015/496401/ A reinforcement learning-based maximum power point tracking (RLMPPT) method is proposed for photovoltaic (PV) array. By utilizing the developed system model of PV array and configuring the environment for the reinforcement learning, the proposed RLMPPT method is able to observe the environment state of the PV array in the learning process and to autonomously adjust the perturbation to the operating voltage of the PV array in obtaining the best MPP. Simulations of the proposed RLMPPT for a PV array are conducted. Experimental results demonstrate that, in comparison to an existing MPPT method, the RLMPPT not only achieves better efficiency factor for both simulated weather data and real weather data but also adapts to the environment much fast with very short learning time. Roy Chaoming Hsu, Cheng-Ting Liu, Wen-Yen Chen, Hung-I Hsieh, and Hao-Li Wang Copyright © 2015 Roy Chaoming Hsu et al. All rights reserved. Hydrothermal Growth of Quasi-Monocrystal ZnO Thin Films and Their Application in Ultraviolet Photodetectors Tue, 16 Jun 2015 07:16:48 +0000 http://www.hindawi.com/journals/ijp/2015/261372/ Quasi-monocrystal ZnO film grown using the hydrothermal growth method is used for the fabrication of Cu2O/ZnO heterojunction (HJ) ultraviolet photodetectors (UV-PDs). The HJ was formed via the sputtering deposition of p-type Cu2O onto hydrothermally grown ZnO film (HTG-ZnO-film). The effect of annealing temperature in the nitrogen ambient on the photoluminescence spectra of the synthesized ZnO film was studied. The optoelectronic properties of Cu2O/ZnO film with various Cu2O thicknesses (250–750 nm) under UV light (365 nm; intensity: 3 mW/cm2) were determined. The UV sensitivity of the HTG-ZnO-film-based UV-PDs and the sputtered ZnO-film-based UV-PDs were 55.6-fold () and 8.8-fold (), respectively. The significant gain in sensitivity ( = 630%) of the proposed ZnO-film-based device compared to that for the device based on sputtered film can be attributed to the improved photoelectric properties of quasi-monocrystal ZnO film. Yung-Chun Tu, Shui-Jinn Wang, Tseng-Hsing Lin, Chien-Hsiung Hung, Tsung-Che Tsai, Ru-Wen Wu, Kai-Ming Uang, and Tron-Min Chen Copyright © 2015 Yung-Chun Tu et al. All rights reserved. Scalability of Phase Change Materials in Nanostructure Template Tue, 16 Jun 2015 07:15:32 +0000 http://www.hindawi.com/journals/ijp/2015/253296/ The scalability of In2Se3, one of the phase change materials, is investigated. By depositing the material onto a nanopatterned substrate, individual In2Se3 nanoclusters are confined in the nanosize pits with well-defined shape and dimension permitting the systematic study of the ultimate scaling limit of its use as a phase change memory element. In2Se3 of progressively smaller volume is heated inside a transmission electron microscope operating in diffraction mode. The volume at which the amorphous-crystalline transition can no longer be observed is taken as the ultimate scaling limit, which is approximately 5 nm3 for In2Se3. The physics for the existence of scaling limit is discussed. Using phase change memory elements in memory hierarchy is believed to reduce its energy consumption because they consume zero leakage power in memory cells. Therefore, the phase change memory applications are of great importance in terms of energy saving. Wei Zhang, Biyun L. Jackson, Ke Sun, Jae Young Lee, Shyh-Jer Huang, Hsin-Chieh Yu, Sheng-Po Chang, Shoou-Jinn Chang, and Ya-Hong Xie Copyright © 2015 Wei Zhang et al. All rights reserved. An Accurate Thermoviscoelastic Rheological Model for Ethylene Vinyl Acetate Based on Fractional Calculus Mon, 15 Jun 2015 12:40:25 +0000 http://www.hindawi.com/journals/ijp/2015/252740/ The thermoviscoelastic rheological properties of ethylene vinyl acetate (EVA) used to embed solar cells have to be accurately described to assess the deformation and the stress state of photovoltaic (PV) modules and their durability. In the present work, considering the stress as dependent on a noninteger derivative of the strain, a two-parameter model is proposed to approximate the power-law relation between the relaxation modulus and time for a given temperature level. Experimental validation with EVA uniaxial relaxation data at different constant temperatures proves the great advantage of the proposed approach over classical rheological models based on exponential solutions. Marco Paggi and Alberto Sapora Copyright © 2015 Marco Paggi and Alberto Sapora. All rights reserved. Improving Crystalline Silicon Solar Cell Efficiency Using Graded-Refractive-Index SiON/ZnO Nanostructures Mon, 15 Jun 2015 12:08:16 +0000 http://www.hindawi.com/journals/ijp/2015/275697/ The fabrication of silicon oxynitride (SiON)/ZnO nanotube (NT) arrays and their application in improving the energy conversion efficiency (η) of crystalline Si-based solar cells (SCs) are reported. The SiON/ZnO NT arrays have a graded-refractive-index that varies from 3.5 (Si) to (Si3N4 and ZnO) to (SiON) to 1 (air). Experimental results show that the use of 0.4 μm long ZnO NT arrays coated with a 150 nm thick SiON film increases by 39.2% under AM 1.5 G (100 mW/cm2) illumination as compared to that of regular SCs with a Si3N4/micropyramid surface. This enhancement can be attributed to SiON/ZnO NT arrays effectively releasing surface reflection and minimizing Fresnel loss. Yung-Chun Tu, Shui-Jinn Wang, Chien-Hung Wu, Kow-Ming Chang, Tseng-Hsing Lin, Chien-Hsiung Hung, and Jhen-Siang Wu Copyright © 2015 Yung-Chun Tu et al. All rights reserved. Optical Properties of Indium Doeped ZnO Nanowires Mon, 15 Jun 2015 12:06:06 +0000 http://www.hindawi.com/journals/ijp/2015/760376/ We report the synthesis of the ZnO nanowires (NWs) with different indium concentrations by using the thermal evaporation method. The gold nanoparticles were used as the catalyst and were dispersed on the silicon wafer to facilitate the growth of the ZnO NWs. High resolution transmission electron microscopy confirms that the ZnO NWs growth relied on vapor-liquid-solid mechanism and energy dispersion spectrum detects the atomic percentages of indium in ZnO NWs. Scanning electron microscopy shows that the diameters of pure ZnO NWs range from 20 to 30 nm and the diameters of ZnO:In were increased to 50–80 nm with increasing indium doping level. X-ray diffraction results point out that the crystal quality of the ZnO NWs was worse with doping higher indium concentration. Photoluminescence (PL) study of the ZnO NWs exhibited main photoemission at 380 nm due to the recombination of excitons in near-band-edge (NBE). In addition, PL results also indicate the slightly blue shift and PL intensity decreasing of NBE emission from the ZnO NWs with higher indium concentrations could be attributed to more donor-induced trap center generations. Tsung-Shine Ko, Sin-Liang Ou, Kuo-Sheng Kao, Tz-Min Yang, and Der-Yuh Lin Copyright © 2015 Tsung-Shine Ko et al. All rights reserved. Optoelectric Properties of GaInP p-i-n Solar Cells with Different i-Layer Thicknesses Mon, 15 Jun 2015 11:58:24 +0000 http://www.hindawi.com/journals/ijp/2015/703045/ The optoelectric properties of GaInP p-i-n solar cells with different intrinsic layer (i-layer) thicknesses from 0.25 to 1 μm were studied. Both emission intensity and full width at half maximum features of the photoluminescence spectrum indicate that the optimum i-layer thickness would be between 0.5 and 0.75 μm. The integrated current results of photocurrent experiment also point out that the samples with 0.5 to 0.75 μm i-layer thicknesses have optimum value around 156 nA. Electroreflectance measurements reveal that the built-in electric field strength of the sample gradually deviates from the theoretical value larger when i-layer thickness of the sample is thicker than 0.75 μm. I-V measurements also confirm crystal quality for whole samples by obtaining the information about short currents of photovoltaic performances. A series of experiments reflect that thicker i-layer structure would induce more defects generation lowering crystal quality. Tsung-Shine Ko, Der-Yuh Lin, You-Chi He, Chen-Chia Kao, Bo-Yuan Hu, Ray-Hua Horng, Fan-Lei Wu, Chih-Hung Wu, and Yu-Li Tsai Copyright © 2015 Tsung-Shine Ko et al. All rights reserved. Plasmon-Enhanced Photoluminescence of an Amorphous Silicon Quantum Dot Light-Emitting Device by Localized Surface Plasmon Polaritons in Ag/SiOx:a-Si QDs/Ag Sandwich Nanostructures Mon, 15 Jun 2015 11:52:25 +0000 http://www.hindawi.com/journals/ijp/2015/140617/ We investigated experimentally the plasmon-enhanced photoluminescence of the amorphous silicon quantum dots (a-Si QDs) light-emitting devices (LEDs) with the :a-Si QDs/Ag sandwich nanostructures, through the coupling between the a-Si QDs and localized surface plasmons polaritons (LSPPs) mode, by tuning a one-dimensional (1D) Ag grating on the top. The coupling of surface plasmons at the top and bottom :a-Si QDs interfaces resulted in the localized surface plasmon polaritons (LSPPs) confined underneath the Ag lines, which exhibit the Fabry-Pérot resonance. From the Raman spectrum, it proves the existence of a-Si QDs embedded in Si-rich film (:a-Si QDs) at a low annealing temperature (300°C) to prevent the possible diffusion of Ag atoms from Ag film. The photoluminescence (PL) spectra of a-Si QDs can be precisely tuned by a 1D Ag grating with different pitches and Ag line widths were investigated. An optimized Ag grating structure, with 500 nm pitch and 125 nm Ag line width, was found to achieve up to 4.8-fold PL enhancement at 526 nm and 2.46-fold PL integrated intensity compared to the a-Si QDs LEDs without Ag grating structure, due to the strong a-Si QDs-LSPPs coupling. Tsung-Han Tsai, Ming-Yi Lin, Wing-Kit Choi, and Hoang Yan Lin Copyright © 2015 Tsung-Han Tsai et al. All rights reserved. Effects of Sheet Resistance on mc-Si Selective Emitter Solar Cells Using Laser Opening and One-Step Diffusion Sun, 14 Jun 2015 12:20:47 +0000 http://www.hindawi.com/journals/ijp/2015/208270/ In order to simplify process procedure and improve conversion efficiency (η), we present new steps of laser opening and one-step POCl3 diffusion to fabricate selective emitter (SE) solar cells, in which heavily doped regions (HDR) and lightly doped regions (LDR) were formed simultaneously. For HDR, we divided six cells into two groups for POCl3 diffusion with sheet resistance () of 40 Ω/sq (for group A) and 50 Ω/sq (for group B). The dry oxidation duration at a temperature of 850°C was 18, 25, and 35 min for the 3 different cells in each group. This created six SE samples with different pairings for the HDR and LDR. The optimal cell (sample SE2) with values of 40/81 Ω/Sq in HDR/LDR showed the best η of 16.20%, open circuit voltage () of 612.52 mV, and fill factor (FF) of 75.83%. The improvement ratios are 1.57% for η and 14.32% for external quantum efficiency (EQE) as compared with those of the two-step diffusion process of our previous study. Moreover, the one-step laser opening process and omitting the step of removing the damage caused by laser ablation especially reduce chemistry pollution, thus showing ecofriendly process for use in industrial-scale production. Sheng-Shih Wang, Jyh-Jier Ho, Jia-Jhe Liou, Jia-Show Ho, Song-Yeu Tsai, Hsien-Seng Hung, Chi-Hsiao Yeh, and Kang L. Wang Copyright © 2015 Sheng-Shih Wang et al. All rights reserved. Quantification of Unimolecular Photoreaction Kinetics: Determination of Quantum Yields and Development of Actinometers—The Photodegradation Case of Cardiovascular Drug Nisoldipine Sun, 14 Jun 2015 07:09:48 +0000 http://www.hindawi.com/journals/ijp/2015/454895/ The lack of integrated rate-laws for photoreactions has led to carry out the treatment of drugs photodegradation kinetic data using the classical zeroth-, first-, and second-order kinetics that were originally developed for thermal reactions. The recent developments of Φ-order kinetic models has opened new perspectives in the treatment of photoreaction kinetics of systems involving a photolabile molecule (A) transforming into a photochemically and thermally stable product (B), that is, the AB(1Φ) photoreaction systems. Within this framework, the kinetics of cardiovascular and photosensitive drug nisoldipine (NIS) has been rationalised. Continuous and monochromatic irradiation of NIS in ethanol obeyed Φ-order kinetics with a sigmoid-shaped quantum yield variation with irradiation wavelength (0.0041–0.35 within 235–390 nm spectral region). Both NIS initial concentration-induced self-photostabilisation effect and the photostabilisation by absorption competitors were quantified (up 70%) and related to a reduction of the photokinetic factor. Finally, the Φ-order kinetics also served to demonstrate the actinometric potential of NIS for the 320–400 nm dynamic range. Mounir Maafi and Wassila Maafi Copyright © 2015 Mounir Maafi and Wassila Maafi. All rights reserved. Laser Enhanced Hydrogen Passivation of Silicon Wafers Thu, 11 Jun 2015 07:49:57 +0000 http://www.hindawi.com/journals/ijp/2015/193892/ The application of lasers to enable advanced hydrogenation processes with charge state control is explored. Localised hydrogenation is realised through the use of lasers to achieve localised illumination and heating of the silicon material and hence spatially control the hydrogenation process. Improvements in minority carrier lifetime are confirmed in the laser hydrogenated regions using photoluminescence (PL) imaging. However with inappropriate laser settings a localised reduction in minority carrier lifetime can result. It is observed that high illumination intensities and rapid cooling are beneficial for achieving improvements in minority carrier lifetimes through laser hydrogenation. The laser hydrogenation process is then applied to finished screen-printed solar cells fabricated on seeded-cast quasi monocrystalline silicon wafers. The passivation of dislocation clusters is observed with clear improvements in quantum efficiency, open circuit voltage, and short circuit current density, leading to an improvement in efficiency of 0.6% absolute. Lihui Song, Alison Wenham, Sisi Wang, Phillip Hamer, Mohammad Shakil Ahmmed, Brett Hallam, Ly Mai, Malcolm Abbott, Evatt R. Hawkes, CheeMun Chong, and Stuart Wenham Copyright © 2015 Lihui Song et al. All rights reserved. Thin-Film Photovoltaics 2014 Wed, 10 Jun 2015 09:25:55 +0000 http://www.hindawi.com/journals/ijp/2015/936458/ Gaetano Di Marco, Giuseppe Calogero, Aldo Di Carlo, Salvatore Lombardo, Leonardo Palmisano, and Olindo Isabella Copyright © 2015 Gaetano Di Marco et al. All rights reserved. Enhancement of Spectral Response in -:H Thin-Film Solar Cells with a-Si:H/c-Si:H P-Type Window Layers Mon, 08 Jun 2015 12:21:55 +0000 http://www.hindawi.com/journals/ijp/2015/841614/ The hydrogenated amorphous silicon (a-Si:H)/hydrogenated microcrystalline silicon (c-Si:H) double p-type window layer has been developed and applied for improving microcrystalline silicon-germanium p-i-n single-junction thin-film solar cells deposited on textured SnO2:F-coated glass substrates. The substrates of SnO2:F, SnO2:F/c-Si:H(p), and SnO2:F/a-Si:H(p) were exposed to H2 plasma to investigate the property change. Our results showed that capping a thin layer of a-Si:H(p) on SnO2:F can minimize the Sn reduction during the deposition process which had H2-containing plasma. Optical measurement has also revealed that a-Si:H(p) capped SnO2:F glass had a higher optical transmittance. When the 20 nm c-Si:H(p) layer was replaced by a 3 nm a-Si:H(p)/17 nm c-Si:H(p) double window layer in the cell, the conversion efficiency () and the short-circuit current density () were increased by 16.6% and 16.4%, respectively. Compared to the standard cell with the 20 nm c-Si:H(p) window layer, an improved conversion efficiency of 6.19% can be obtained for the cell having a-Si:H(p)/c-Si:H(p) window layer, with  = 490 mV,  = 19.50 mA/cm2, and FF = 64.83%. Yen-Tang Huang, Cheng-Hang Hsu, and Chuang-Chuang Tsai Copyright © 2015 Yen-Tang Huang et al. All rights reserved. Graded Carrier Concentration Absorber Profile for High Efficiency CIGS Solar Cells Mon, 08 Jun 2015 11:42:14 +0000 http://www.hindawi.com/journals/ijp/2015/410549/ We demonstrate an innovative CIGS-based solar cells model with a graded doping concentration absorber profile, capable of achieving high efficiency values. In detail, we start with an in-depth discussion concerning the parametrical study of conventional CIGS solar cells structures. We have used the wxAMPS software in order to numerically simulate cell electrical behaviour. By means of simulations, we have studied the variation of relevant physical and chemical parameters—characteristic of such devices—with changing energy gap and doping density of the absorber layer. Our results show that, in uniform CIGS cell, the efficiency, the open circuit voltage, and short circuit current heavily depend on CIGS band gap. Our numerical analysis highlights that the band gap value of 1.40 eV is optimal, but both the presence of Molybdenum back contact and the high carrier recombination near the junction noticeably reduce the crucial electrical parameters. For the above-mentioned reasons, we have demonstrated that the efficiency obtained by conventional CIGS cells is lower if compared to the values reached by our proposed graded carrier concentration profile structures (up to 21%). Antonino Parisi, Riccardo Pernice, Vincenzo Rocca, Luciano Curcio, Salvatore Stivala, Alfonso C. Cino, Giovanni Cipriani, Vincenzo Di Dio, Giuseppe Ricco Galluzzo, Rosario Miceli, and Alessandro C. Busacca Copyright © 2015 Antonino Parisi et al. All rights reserved. Surface Photovoltage Spectroscopy and AFM Analysis of CIGSe Thin Film Solar Cells Mon, 08 Jun 2015 11:42:01 +0000 http://www.hindawi.com/journals/ijp/2015/829530/ The band gap, grain size, and topography of a Cu(In,Ga)Se2 (CIGSe) thin film solar cell are analyzed using surface photovoltage spectroscopy (SPV) and atomic force microscopy (AFM) techniques. From the steep increase in SPV signal the band gap of the CIGSe absorber, In2S3 and ZnO layers are extracted and found to be 1.1, 1.3 and 2.6 eV, respectively. Already below the band gap of ZnO layer, a slight SPV response at 1.40 eV photon energies is observed indicating the presence of deep donor states. The root mean square (rms) of the surface roughness is found to be 37.8 nm from AFM surface topography maps. The grain sizes are almost uniform and smaller than 1 μm. Nima E. Gorji, Ugo Reggiani, and Leonardo Sandrolini Copyright © 2015 Nima E. Gorji et al. All rights reserved. Optical Characterization of Different Thin Film Module Technologies Mon, 08 Jun 2015 10:21:04 +0000 http://www.hindawi.com/journals/ijp/2015/159458/ For a complete quality control of different thin film module technologies (a-Si, CdTe, and CIS) a combination of fast and nondestructive methods was investigated. Camera-based measurements, such as electroluminescence (EL), photoluminescence (PL), and infrared (IR) technologies, offer excellent possibilities for determining production failures or defects in solar modules which cannot be detected by means of standard power measurements. These types of optical measurement provide high resolution images with a two-dimensional distribution of the characteristic features of PV modules. This paper focuses on quality control and characterization using EL, PL, and IR imaging with conventional cameras and an alternative excitation source for the PL-setup. R. Ebner, B. Kubicek, G. Újvári, S. Novalin, M. Rennhofer, and M. Halwachs Copyright © 2015 R. Ebner et al. All rights reserved. Light Scattering and Current Enhancement for Microcrystalline Silicon Thin-Film Solar Cells on Aluminium-Induced Texture Glass Superstrates with Double Texture Mon, 08 Jun 2015 10:10:39 +0000 http://www.hindawi.com/journals/ijp/2015/358276/ Microcrystalline silicon (μc-Si:H) thin-film solar cells are processed on glass superstrates having both micro- and nanoscale surface textures. The microscale texture is realised at the glass surface, using the aluminium-induced texturing (AIT) method, which is an industrially feasible process enabling a wide range of surface feature sizes (i.e., 700 nm–3 μm) of the textured glass. The nanoscale texture is made by conventional acid etching of the sputter-deposited transparent conductive oxide (TCO). The influence of the resulting “double texture” on the optical scattering is investigated by means of atomic force microscopy (AFM) (studying the surface topology), haze measurements (studying scattering into air), and short-circuit current enhancement measurements (studying scattering into silicon). A predicted enhanced optical scattering efficiency is experimentally proven by a short-circuit current enhancement of up to 1.6 mA/cm2 (7.7% relative increase) compared to solar cells fabricated on a standard superstrate, that is, planar glass covered with nanotextured TCO. Enhancing the autocorrelation length (or feature size) of the AIT superstrates might have the large potential to improve the μc-Si:H thin-film solar cell efficiency, by reducing the shunting probability of the device while maintaining a high optical scattering performance. Yunfeng Yin, Nasim Sahraei, Selvaraj Venkataraj, Sonya Calnan, Sven Ring, Bernd Stannowski, Rutger Schlatmann, Armin G. Aberle, and Rolf Stangl Copyright © 2015 Yunfeng Yin et al. All rights reserved.