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Stuwe D.,Fraunhofer Institute for Solar Energy Systems | Hartmann P.,Fraunhofer Institute for Solar Energy Systems | Keding R.,Fraunhofer Institute for Solar Energy Systems | Clement F.,Fraunhofer Institute for Solar Energy Systems | And 6 more authors.
International Conference on Digital Printing Technologies | Year: 2013

Back contact solar cell concepts feature both metal contact polarities on the rear side of the wafer. PVD (Physical Vapor Deposition) is one option for high quality metal layers. To create a working device the metal contacts must be separated. This work reports on the evaluation of an economic process route using an etching ink that is inkjet-printed onto metal layers. Drop on demand inkjet technology is very well suited for the deposition of such etchants onto the thin wafers as it allows for the well-defined deposition of complex structures needed e.g. for the rear side of back-contact solar cells. It is investigated how the amount of ink and thus reactive species influences the width of the etched structures and if they are electrically isolated. The width of the etched structures has been reduced down to 65 pm on 1000 nm thick Al-layers by adjusting the amount of ink printed on the metal layers. The separation was demonstrated by measuring the electrical resistance between the separated metal areas. The presented process provides a structuring solution for the cost effective contact separation for back contact solar cells. The feasibility has been shown by printing a meander structure which is the typical contact separation layout for a BC-BJ (Back-Bontact Back-Junction) solar cell. ©2013; Society for Imaging Science and Technology. Source

Keding R.,Fraunhofer Institute for Solar Energy Systems | Keding R.,Albert Ludwigs University of Freiburg | Stuwe D.,Fraunhofer Institute for Solar Energy Systems | Kamp M.,Fraunhofer Institute for Solar Energy Systems | And 6 more authors.
IEEE Journal of Photovoltaics | Year: 2013

In this paper, first generation back-contact back-junction (BC-BJ) silicon solar cells with cell efficiencies well above n = 20% were fabricated. The process sequence is industrially feasible, requires only one high-temperature step (co-diffusion), and relies only on industrially available pattering technologies. The silicon-doping is performed from pre-patterned solid diffusion sources, which allow for the precise adjustment of phosphorus-and boron-doping levels. Based on the investigated process technologies, BC-BJ solar cells with gap and without gap between adjacent n+-and p+-doped areas were processed. On the one hand, a strong reduction of the process effort is possible by omitting the gap regions. On the other hand, parasitic tunneling currents through the narrow space charge region may occur. Hence, deep doped areas were realized to avoid tunneling currents in gap-free BC-BJ cells. This paper finishes with a detailed characterization of the manufactured cells including important cell measurements like I-V, SunsVOC, quantum efficiency, and an analysis of the cell specific fill factor losses. © 2011-2012 IEEE. Source

Tsakraklides V.,Total New Energies | Brevnova E.,Total New Energies | Stephanopoulos G.,Novogy Inc. | Stephanopoulos G.,Massachusetts Institute of Technology | Shaw A.J.,Novogy Inc.
PLoS ONE | Year: 2015

Gene targeting is a challenge in organisms where non-homologous end-joining is the predominant form of recombination. We show that cell division cycle synchronization can be applied to significantly increase the rate of homologous recombination during transformation. Using hydroxyurea-mediated cell cycle arrest, we obtained improved gene targeting rates in Yarrowia lipolytica, Arxula adeninivorans, Saccharomyces cerevisiae, Kluyveromyces lactis and Pichia pastoris demonstrating the broad applicability of the method. Hydroxyurea treatment enriches for S-phase cells that are active in homologous recombination and enables previously unattainable genomic modifications. © 2015 Tsakraklides et al. Source

Brooks A.E.,University of Arizona | Cormode D.,University of Arizona | Cronin A.D.,University of Arizona | Kam-Lum E.,Total New Energies
2015 IEEE 42nd Photovoltaic Specialist Conference, PVSC 2015 | Year: 2015

Power loss due to partial shade was compared for two types of commercial photovoltaic modules. We also tested both types of modules with bypass diodes removed to simulate diode failure. Modules with uniformly low reverse bias voltage (VBR) cells (of -4V) lost significantly less power compared to modules with high VBR cells (of -15V) when subjected to partial shade. Differences in power loss were even larger when bypass diodes were removed. Associated with higher power loss, we observed several types of degradation on modules with high-VBR cells. A model to simulate power loss in an array due to partial shading that uses VBR as the main parameter was found to be in good agreement with measured power losses in the field. © 2015 IEEE. Source

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