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Energy Conversion Efficiency (energy + conversion_efficiency)
Selected AbstractsNew Concepts and Applications in the Macromolecular Chemistry of FullerenesADVANCED MATERIALS, Issue 38 2010Francesco Giacalone Abstract A new classification on the different types of fullerene-containing polymers is presented according to their different properties and applications they exhibit in a variety of fields. Because of their interest and novelty, water-soluble and biodegradable C60 -polymers are discussed first, followed by polyfullerene-based membranes where unprecedented supramolecular structures are presented. Next are compounds that involve hybrid materials formed from fullerenes and other components such as silica, DNA, and carbon nanotubes (CNTs) where the most recent advances have been achieved. A most relevant topic is still that of C60 -based donor-acceptor (D,A) polymers. Since their application in photovoltaics D,A polymers are among the most realistic applications of fullerenes in the so-called molecular electronics. The most relevant aspects in these covalently connected fullerene/polymer hybrids as well as new concepts to improve energy conversion efficiencies are presented. The last topics disccused relate to supramolecular aspects that are in involved in C60 -polymer systems and in the self-assembly of C60 -macromolecular structures, which open a new scenario for organizing, by means of non-covalent interactions, new supramolecular structures at the nano- and micrometric scale, in which the combination of the hydrofobicity of fullerenes with the versatility of the noncovalent chemistry afford new and spectacular superstructures. [source] Series resistance characterization of industrial silicon solar cells with screen-printed contacts using hotmelt pastePROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2007A. Mette Abstract This work presents the results of a detailed series resistance characterization of silicon solar cells with screen-printed front contacts using hotmelt silver paste. Applying the hotmelt technology energy conversion efficiencies up to 18·0% on monocrystalline wafers with a size of 12·5,cm,×,12·5,cm have been achieved, an increase of 0·3% absolute compared to cells with conventional screen-printed contacts. This is mainly due to the reduction in the finger resistance to values as low as 14,,/m, which reduces the series resistance of the solar cell significantly. To retrieve the lumped series resistance as accurately as possible under the operating condition, different determination methods have been analyzed. Methods under consideration were fitting of the two-diode equation function to a dark IV-curve, integration of the area A under an IV-curve, comparison of a jsc,Voc with a one-sun IV-curve, comparison of the jsc and Voc points of a shaded curve with the one-sun IV-curve as well as comparison of a dark IV-curve with a one-sun IV-curve, and comparison of IV-curves measured at different light intensities. The performed investigations have shown that the latter four methods all resulted in reliable series resistance values. Copyright © 2007 John Wiley & Sons, Ltd. [source] SHORT COMMUNICATION: ACCELERATED PUBLICATION: Diode characteristics in state-of-the-art ZnO/CdS/Cu(In1,xGax)Se2 solar cells,PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2005Miguel A. Contreras Abstract We report a new state of the art in thin-film polycrystalline Cu(In,Ga)Se2 -based solar cells with the attainment of energy conversion efficiencies of 19·5%. An analysis of the performance of Cu(In,Ga)Se2 solar cells in terms of some absorber properties and other derived diode parameters is presented. The analysis reveals that the highest-performance cells can be associated with absorber bandgap values of ,1·14,eV, resulting in devices with the lowest values of diode saturation current density (,3×10,8,mA/cm2) and diode quality factors in the range 1·30,<,A,<,1·35. The data presented also support arguments of a reduced space charge region recombination as the reason for the improvement in the performance of such devices. In addition, a discussion is presented regarding the dependence of performance on energy bandgap, with an emphasis on wide-bandgap Cu(In,Ga)Se2 materials and views toward improving efficiency to >,1;20% in thin-film polycrystalline Cu(In,Ga)Se2 solar cells. Published in 2005 John Wiley & Sons, Ltd. [source] Highly Efficient Quantum-Dot-Sensitized Solar Cell Based on Co-Sensitization of CdS/CdSeADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Yuh-Lang Lee Abstract Cadmium sulfide (CdS) and cadmium selenide (CdSe) quantum dots (QDs) are sequentially assembled onto a nanocrystalline TiO2 film to prepare a CdS/CdSe co-sensitized photoelectrode for QD-sensitized solar cell application. The results show that CdS and CdSe QDs have a complementary effect in the light harvest and the performance of a QDs co-sensitized solar cell is strongly dependent on the order of CdS and CdSe respected to the TiO2. In the cascade structure of TiO2/CdS/CdSe electrode, the re-organization of energy levels between CdS and CdSe forms a stepwise structure of band-edge levels which is advantageous to the electron injection and hole-recovery of CdS and CdSe QDs. An energy conversion efficiency of 4.22% is achieved using a TiO2/CdS/CdSe/ZnS electrode, under the illumination of one sun (AM1.5,100,mW cm,2). This efficiency is relatively higher than other QD-sensitized solar cells previously reported in the literature. [source] Dye-Sensitized Back-Contact Solar CellsADVANCED MATERIALS, Issue 38 2010Dongchuan Fu Dye-sensitized back-contact solar cells are fabricated on back plates comprising a patterned FTO glass substrate, a selectively deposited Pt coating, a protective ZrO2 coating covering the Pt layers and a screen printed TiO2 film. Such devices show a solar energy conversion efficiency of 3.64% under AM 1.5 sunlight and a peak incident photon to electron conversion efficiency of 54%. [source] Device Performance of APFO-3/PCBM Solar Cells with Controlled MorphologyADVANCED MATERIALS, Issue 43 2009Cecilia M. Björström Svanström Polymer/fullerene solar cells with three different device structures: A) diffuse bilayer, B) spontaneously formed multilayer, and C) vertically homogenous thin films, are fabricated. The photocurrent/voltage performance is compared and it is found that the self-stratified structure (B) yields the highest energy conversion efficiency. [source] Enhancing high water content biomass gasification with impregnated Ca in fuel dryingAICHE JOURNAL, Issue 10 2006Guangwen Xu Abstract In view of energy conversion efficiency, the gas production from high water content (>60 wt.%) biomass via gasification is necessarily conducted with fuel drying in advance. In regard to this kind of processes, the present study was devised to impregnate Ca onto fuel during fuel drying and thereby to increase fuel's gasification reactivity to raise the gas production efficiency with minimal additional cost. By employing wet coffee grounds as a model biomass fuel and slurry dewatering in kerosene as the adopted drying technology, the Ca impregnation was implemented through dosing Ca(OH)2 into a fuel-kerosene slurry and in turn treating the slurry in the same way as for the case without Ca addition. The resulting Ca (4.0 wt.% load in CaO base) exhibited high dispersion through the fuel matrix in both SEM-EDX image and XRD spectrum. Gasification of the fuel in a pilot dual fluidized gasification setup further demonstrated that the fuel possessed distinctively high reaction reactivity. This led it to show C and H conversions of 91% and 138%, respectively, at a reaction temperature of about 1083 K, whereas these conversions were only 70% and 92% for the fuel with a similar amount of physically mixed CaO. The catalytic effect of the impregnated Ca manifested also on hydrocarbon reforming and water gas shift, making the resulting product gas evidently rich in H2 and lean in CO and hydrocarbons. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Combined effects of conjugation pattern and alkoxy side chains on the photovoltaic properties of thiophene-containing PPE-PPVsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2007Daniel Ayuk Mbi Egbe Abstract This contribution presents the synthesis and properties of four thiophene-containing poly(- p -arylene-ethynylene)/poly(- p -arylene-vinylene)s, PIa-b and PIIa-b, whose repeating units (RU) consist either of 1:2 or 2:2 triple bond/double bond ratio, and which bear linear alkoxy side chains not longer than octyloxy and branched 2-ethylhexyloxy. PIa-b and PIIa-b exhibit similar absorption and emission behaviour in dilute solution (,a = 483,486 nm, ,e = 540 nm) as well as in solid state (,a = 500, 530 nm, ,e = 560 nm), whereby slightly higher fluorescence quantum yields (,f) were obtained for PI than for PII systems, as a result of higher number of thiophene units within the RU of PII. An enhancement of the ,f -value from 0% to 3% is obtained after replacing linear octadecyloxy in PIIc-e by bulky branched 2-ethylhexyloxy in PIIa-b. Nonoptimized solar cells of configuration ITO/PEDOT:PSS/polymer: PCBM (1:3 weight ratio)/LiF/Al show open circuit voltages as high as 900 mV for PIa-b and 800 mV for PIIa-b. Reducing the size of the side chain from R = 2- ethylhexyl in PIa to R = methyl in PIb leads to a significant increase of the short circuit current, ISC, from ca. 2.5 mA to ca. 3.7 mA and consequently to an enhancement of the energy conversion efficiency, ,AM1.5, from ca. 1.2% to ca. 1.7%. This is due to an extended donor-acceptor interfacial area, as evidenced by AFM topology pictures showing smaller nanoscale clusters size in PIb than in PIa active layer. The same change led to minimal effect in PII systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1619,1631, 2007 [source] Nanowire,quantum-dot,polymer solar cellPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2008A. Nadarajah Abstract We report first results on a new solar cell structure which incorporates n-type ZnO nanowires, an undoped CdSe layer, obtained from quantum dot precursors, and a p-type polymer layer as the main components. In the fabrication process the quantum dot layer is converted to a conformal ,30 nm thick polycrystalline film. The fabrication of the cell occurs in lab air at temperatures below 100 °C. Several intermittent annealing steps raise the energy conversion efficiency to approximately 1%. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Application of polymer gel electrolyte with graphite powder in quasi-solid-state dye-sensitized solar cellsPOLYMER COMPOSITES, Issue 11 2009Qinghua Li A polymer gel electrolyte with ionic conductivity of 5.11 mS cm,1 was prepared by using poly (acrylonitrile- co -styrene) as polymer matrix, acetonitrile and tetrahydrofuran as binary organic mixture solvent, NaI + I2 as electrolyte, graphite powder and 1-methylimidazole as additives. The components ratio of the polymer gel electrolyte was optimized, and the influence of the components and temperature on the ionic conductivity of the polymer gel electrolyte and photoelectronic properties of dye sensitized solar cell were investigated. On the basis of the polymer gel electrolyte with the optimized conditions, a quasi-solid-state dye-sensitized solar cell was fabricated and its light- to-electricity energy conversion efficiency of 3.25% was achieved under irradiation of 100 mW cm,2. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] High efficiency all-GaAs solar cellPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2010Abderrahmane Belghachi Abstract The reduction of surface recombination in GaAs solar cells is known to be a major concern for photovoltaic cells designers. A common technique used to reduce this effect is to cover the GaAs surface with a wide band gap window layer, therefore the creation of a heterojunction. To avoid a heterojunction with its inconveniences; interface surface states, poor photon absorption in addition to the technological exigencies, one can use an all-GaAs solar cell. In this type of structure, a thin highly doped layer is created at the surface known as a front surface field (FSF). The main role of an FSF layer is to reduce the effect of front surface recombination and the enhancement of light-generated free carriers' collection. This is achieved by the drastic reduction of the effective recombination at the emitter upper boundary. In this work, a simple analytical model is used to simulate the influence of the FSF layer on GaAs solar cell parameters; photocurrent, open circuit voltage and energy conversion efficiency. The effects of the FSF layer doping density and its thickness on the cell performance are discussed by using computed results. Copyright © 2010 John Wiley & Sons, Ltd. [source] Photoelectron Generation by Photosystem,II Core Complexes Tethered to Gold SurfacesCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 4 2010Michele Vittadello, Prof. Abstract By using a nondestructive, ultrasensitive, fluorescence kinetic technique, we measure in,situ the photochemical energy conversion efficiency and electron transfer kinetics on the acceptor side of histidine-tagged photosystem,II core complexes tethered to gold surfaces. Atomic force microscopy images coupled with Rutherford backscattering spectroscopy measurements further allow us to assess the quality, number of layers, and surface density of the reaction center films. Based on these measurements, we calculate that the theoretical photoelectronic current density available for an ideal monolayer of core complexes is 43,,A,cm,2 at a photon flux density of 2000,,mol,quanta,m,2,s,1 between 365 and 750,nm. While this current density is approximately two orders of magnitude lower than the best organic photovoltaic cells (for an equivalent area), it provides an indication for future improvement strategies. The efficiency could be improved by increasing the optical cross section, by tuning the electron transfer physics between the core complexes and the metal surface, and by developing a multilayer structure, thereby making biomimetic photoelectron devices for hydrogen generation and chemical sensing more viable. [source] | |||||||||||||