98 research outputs found
Understanding Oregonians' coastal values and priorities through participatory GIS mapping
No full textKaegan Scully-Engelmeyer, Dr. Elise Granek, Dr. Max Nielsen-Pincus, Portland State University, Department of Environmental Science & Management ; conducted for and in cooperation with Oregon Department of Fish and Wildlife, Oregon Marine Reserves Program with help from Oregon SeaGrant.Title from PDF cover (viewed on March 22, 2021).This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Includes bibliographical references (pages 25-27).Mode of access: Internet from the Oregon Government Publications Collection.Text in English
Hocheffiziente rückseitenkontaktierten Silizium-Solarzellen
No full textIn this thesis high-efficiency back-contact back-junction (BC-BJ) silicon solar cells for one-sun applications were studied. The focus was put on the development of a low-cost and industrially feasible manufacturing technology in order to utilize the full cost reduction potential of this elegant cell structure. At the same time the performance of the developed solar cells was investigated in details by experimental work, analytical modeling and numerical device simulations. The complex and costly photolithography masking steps were replaced by techniques which are of low cost and relevant for mass production, such as screen-printing of the masking layers and local laser ablation of the dielectric and silicon layers. The highest solar cell efficiency of 21.1 % (JSC = 38.6 mA/cm^2, VOC = 668 mV, FF = 82.0 %) was achieved on 160 um thick 1 Ohm cm n-type FZ Si with the designated area of 4 cm^2. A detailed study of the loss mechanisms limiting the efficiency of the developed back-contact back-junction silicon solar cell was performed. The reduction of the cell efficiency was determined to be 3.9 %abs. due to recombination processes, 2.0 %abs. due to optical losses, 0.3 %abs. due to series resistance effects and 0.7 %abs. due to electrical shading. The developed model of the loss mechanisms is a powerful tool for the further optimization study of the solar cell structure. Positive effects of the phosphorus doped n+ front surface field (FSF) on the performance of the BC-BJ solar cells were studied in details. These effects are: (i) Surface passivation and passivation stability: The optimal surface passivation was obtained with a deep diffused Gaussian phosphorus FSF doping profile with sheet resistance of 148 Ohm/sq. In contrast to solar cells without the FSF diffusion, the solar cells with the FSF diffusion profile did not show any performance degradation under exposure to UV illumination. (ii) Lateral current transport: The front diffused n+ layer can be seen as a parallel conductor to the lateral base resistance. This way the lateral base resistance losses can be reduced. (iii) Low-illumination performance: The front surface field improves the performance of the BC-BJ solar cells under low illumination intensity. Therefore the BC-BJ cells with FSF seem to be the best ones suited for achieving a high energy yield when also operating under low illumination intensity.Im Rahmen dieser Arbeit wurden hocheffiziente rückseitig kontaktierte und rückseitig sammelnde (BC-BJ) Silicium-Solarzellen für Anwendungen bei einer Beleuchtungsintensität von einer Sonne untersucht. Der Schwerpunkt lag hierbei auf der Entwicklung eines preiswerten und industriell umsetzbaren Herstellungsprozesses, um das Kosteneinsparungspotential dieser neuartigen Zellstruktur auszunutzen. Ebenfalls wurden die elektrische Eigenschaften der Zellen und die zugrunde liegenden physikalischen Effekte durch verschiedener Experimente sowie analytischen und numerischen Simulationen detailliert untersucht. Die komplexen und kostspieligen photolithographischen Maskierungsschritte sind dabei durch einfachere und preiswertere Techniken für die industrielle Massenproduktion, wie siebgedruckte Maskierungsschichten und lokale laserunterstützte Abtragung von dielektrischen Schichten und Silicium, ersetzt worden. Der beste Solarzellenwirkungsgrad von 21.1 % (Kurzschlussstromdichte 38.6 mA/cm^2, Leerlaufspannung 668 mV, Füllfaktor 82.0 %) wurden bei einer 160 um dicken, auf 1 Ohm cm n-typ FZ Silicium prozessierten Solarzelle mit eine Aperturfläche von 4 cm^2 erreicht. Eine ausführliche Betrachtung der Verlustmechanismen, welche die Effizienz der untersuchten rückseitig sammelnden und rückseitig kontaktierten Solarzellen limitieren, wurde durchgeführt. Die Verringerung der Zelleffizienz beträgt aufgrund von Rekombinationsprozessen 3.9 % absolut, 2.0 % absolut aufgrund von optischen Verlusten, 0.3 % absolut aufgrund von Serienwiderstandseffekten und 0.7 % absolut aufgrund elektrischer Abschattung. Das entwickelte Modell der Verlustmechanismen ist ein mächtiges Werkzeug, um die Struktur der Solarzellen weiter zu verbessern. Der positive Effekt eines Phosphor-dotierten n+ „front surface fields (FSF) auf die Leistungscharakteristik der BJ-BC Solarzellen ist weiterhin im Detail untersucht worden Diese Effekte beinhalten: (i) Oberflächenpassivierung und die Passivierungsstabilität: Die optimale Obereflächenpassivierung wurde mit einem tief eingetriebenen Gauss-förmigen Phosphor FSF Dotierprofil mit einem Schichtwiderstand von 148 Ohm/sq erreicht. Im Vergleich zu Solarzellen ohne einem zusätzlichen FSF Diffusionsprofil, zeigten Solarzellen mit einem FSF Diffusionsprofil keine Degradation der Solarzellenleistung unter UV-Beleuchtung. (ii) Laterale Stromtransport: Die hochdotierte n+-Schicht kann als paralleler Leiter zur lateralen Basisleitung betrachtet werden. Dadurch können der laterale Widerstand der Basis reduziert werden. (iii) Leistung unter Schwachlichtverhältnissen: Das hochdotierte FSF verbessert die Leistungscharakteristik der BC-BJ Solarzellen bei schwachen Beleuchtungsstärken. Daher sind diese hier untersuchten BC-JC Solarzellen mit zusätzlichem FSF hervorragend geeignet, um eine hohe Stromausbeute auch unter Schwachlichtbedingengen zu erreichen
High-efficiency silicon solar cells with boron local back surface fields formed by laser chemical processing
No full textS.1257-1259The successful implementation of industrially feasible local boron dopings as local back surface field (LBSF) for high-efficiency silicon solar cells processed with laser chemical processing (LCP) is demonstrated for the first time. The processed passivated-emitter rear locally diffused solar cells with LCP LBSFs show cell efficiencies of up to 20.9% with a cell efficiency benefit of up to 0.3-0.4%abs. in comparison to the reference passivated emitter and rear cells processed with a doping-free LCP opening. The results show the potential of LCP to create boron dopings in order to decrease the contact resistance and reduce the minority carrier recombination at the local metal contacts in order to improve the fill factor and the open-circuit voltage, respectively.32Nr.
Influence of pulse duration on the doping quality in laser chemical processing (LCP)-a simulative approach
No full textS.643-648The laser chemical processing (LCP) technique for the local doping of crystalline silicon solar cells is investigated. Here, a liquid jet containing a dopant source acts as a waveguide for pulsed laser light, which results in the melting and subsequent doping of the silicon surface. Typical LCP pulse durations are in the 15 ns range, giving satisfactory results for specific parameter settings. While great potential is assumed to exist, optimization of the pulse duration has until now not been deeply investigated, because it is hard to change this parameter in laser systems. Therefore, this paper accesses the influence of the pulse duration by a simulative approach. The model includes optics, thermodynamics, and melt dynamics induced by the liquid jet and dopant diffusion into the silicon melt. It is solved by coupling our existing finite differences Matlab-code LCPSim with the commercial fluid flow solver Ansys Fluent. Simulations of axial symmetric single pulses were p erformed for pulse durations ranging from 15 ns to 500 ns. Detailed results are given, which show that for longer pulse durations lateral heat conduction significantly homogenizes the inhomogeneous dopant distribution caused by the speckled intensity profile within the liquid jet cross section. The melt expulsion by the liquid jet is low enough that a sufficiently doped layer remains after full resolidification for all pulse durations. Last, temperature gradients are evaluated to give an indication on the amount of laser damage induced by thermal stress.110Nr.
Influence of pulse duration on the doping quality in laser chemical processing (LCP) - A simulative approach
No full textThe laser chemical processing (LCP) technique for the local doping of crystalline silicon solar cells is investigated. Here, a liquid jet containing a dopant source acts as a waveguide for pulsed laser light, which results in the melting and subsequent d
Dynamics of small unilamellar vesicles
No full textThis article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in J. Chem. Phys. 148, 104901 (2018) and may be found at https://doi.org/10.1063/1.5009424.In this paper, we investigate the dynamics of small unilamellar vesicles with the aid of neutron spin-echo spectroscopy. The purpose of this investigation is twofold. On the one hand, we investigate the influence of solubilised cosurfactant on the dynamics of the vesicle’s surfactant bilayer. On the other hand, the small unilamellar vesicles used here have a size between larger vesicles, with dynamics being well described by the Zilman-Granek model and smaller microemulsion droplets which can be described by the Milner-Safran model. Therefore, we want to elucidate the question, which model is more suitable for the description of the membrane dynamics of small vesicles, where the finite curvature of the bilayer is felt by the contained amphiphilic molecules. This question is of substantial relevance for our understanding of membranes and how their dynamics is affected by curvature, a problem that is also of key importance in a number of biological questions. Our results indicate the even down to vesicle radii of 20 nm the Zilman-Granek model appears to be the more suitable one.BMBF, 05K13KT1, Probenumgebung und paralle Charakterisierung bei hochpräzisen Neutronen Spin-Echo (NSE) Messungen an komplexen Systemen der weichen Materi
Analysis of the current linearity at low illumination of high‐efficiency back‐junction back‐contact silicon solar cells
No full textSimulation supported description of the local doping formation using laser chemical processing (LCP)
No full textS.165-170We present an enhanced model to describe the physics of laser chemical processing (LCP), a liquid jet guided laser technique, for local doping processes applied to crystalline silicon solar cells. The main improvement of the numerical model is the consideration of the inhomogeneous laser light intensity profile within the liquid jet cross section. Measurements of the intensity profile show local superelevations of up to factor five compared to the average intensity. A measured intensity profile was implemented into the numerical model and yields good agreement between simulated and measured dopant distributions. Inhomogeneities of the spatial dopant distribution are observed and their impact on LCP line scans for producing doped lines is investigated with respect to solar cell manufacturing.104Nr.
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