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Munich, Germany

Karg F.,Avancis Gmbh
Energy Procedia | Year: 2012

Record efficiency of up to 15.5 % on 30 × 30 cm 2 and 13.9 % on 1 m 2 sized fully integrated thin film solar modules have been achieved at AVANCIS using rapid thermal annealing of stacked elemental layers of Cu(Ga), In and Se. The relatively small performance offset between tightly tuned prototype modules from the pilot line and average modules from mass manufacturing demonstrate that scale up of CIGS technology was successful. The key prerequisites in terms of basic semiconductor material properties and coating uniformities leading to high device performance will be described. Namely large area mapping of semiconductor properties via XRF, photoluminescence decay time, Raman spectroscopy and IR thermography have proven instrumental to transfer champion efficiencies from the lab into continuous mass manufacturing. Nevertheless there are further options for improvements of basic device performance. In particular bandgap gradings using indium / gallium grading towards the back of the device and sulphur / selenium grading towards the front of the device show promise for higher open circuit voltages. A second area for improvements concerns the film properties of the front electrode, which is sputter deposited Al-doped ZnO in our case. Via changes in the plasma deposition conditions the trade-off between transmission and conductivity could be optimised and as a consequence the fill factor and short circuit current of the devices improved. © 2011 Published by Elsevier Ltd.

Grimm A.,Helmholtz Center Berlin | Just J.,Helmholtz Center Berlin | Kieven D.,Helmholtz Center Berlin | Lauermann I.,Helmholtz Center Berlin | And 4 more authors.
Physica Status Solidi - Rapid Research Letters | Year: 2010

In an effort to eliminate the standard CdS buffer layer from chalcopyrite-based thin film solar cells we have investigated sputtered Zn(O,S) films. They were prepared by partially reactive sputtering from a ZnS target in an argon/oxygen mixture. Single phase, polycrystalline films were achieved for substrate temperatures of at least 100 °C. Test devices prepared in a completely dry process showed superior blue response and active area conversion efficiencies up to 13.7%. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Erfurth F.,University of Wurzburg | Grimm A.,Helmholtz Center Berlin | Palm J.,Avancis Gmbh | Niesen T.P.,Avancis Gmbh | And 3 more authors.
Applied Physics Letters | Year: 2011

The electronic and chemical properties of the (Zn1-x, Mg x) O/CuIn (S,Se)2 interface, prepared by sputtering of thin (Zn,Mg)O layers, were investigated with direct and inverse photoelectron spectroscopy on in situ prepared samples. With the combination of both techniques we have determined the band alignment at this interface as a function of Mg-content in the range 0 ≤ x ≤ 0.30. We find that the band alignment at the interface can be tailored between a "cliff" (downward step) in the conduction band for pure ZnO and a "spike" (upward step) for high Mg-contents. A direct influence of the band alignment modifications on the solar cell parameters is found. © 2011 American Institute of Physics.

Pepelyshev A.,RWTH Aachen | Steland A.,RWTH Aachen | Avellan-Hampe A.,Avancis Gmbh
Progress in Photovoltaics: Research and Applications | Year: 2014

The quality control of photovoltaic modules in terms of the output power to satisfy the technical specification is of great importance for producers as well as consumers and also represents a major issue of certification procedures. Previous work focused on one-sided specification limits to reject underperforming samples (lots) of photovoltaic modules or solar cells. In the present paper, we generalize the classic acceptance sampling methodology and derive sampling plans on the basis of two-sided specification limits. Those sampling plans can be constructed for arbitrary output power distributions by making use of flash data tables. For the out-of-spec setting, the sampling plans are solutions of rather involved nonlinear equations. Explicit formulas, which resemble known sampling plans, can only be obtained under symmetry assumptions. Further, the solution depends on the ratio of overperforming modules to underperforming modules. We investigate by numerical studies to which extent the required sample size depends on that ratio and the shape of the underlying output power distribution. The application to real examples indicates that in practice, the new approach often results in substantially smaller control samples than classic approaches. Copyright © 2012 John Wiley & Sons, Ltd.

Keller J.,University of Oldenburg | Schlesiger R.,University of Munster | Riedel I.,University of Oldenburg | Parisi J.,University of Oldenburg | And 3 more authors.
Solar Energy Materials and Solar Cells | Year: 2013

In this study grain boundaries (GBs) and grain interiors in a sulfurized Cu(In,Ga)(S,Se)2 (CIGSSe) photovoltaic thin film have been investigated by atom probe tomography. Grain boundaries could be clearly localized by the strong agglomeration of sodium, which was additionally observed in tube-shaped clusters. These GBs were proven to contain no oxygen or alkali metals which confirms the blocking function of the used diffusion barrier sputtered on the soda lime glass substrate. Further, the concentrations of the CIGSSe matrix atoms across the GBs were studied. Here, copper deficiency and enrichment appear to be correlated with the distance from the back contact (BC). Agglomeration of sulfur in all grain boundaries near to the BC indicates interface diffusion of sulfur. Moreover, our measurements reveal the existence of a thin layer upon the back contact in which the sulfur, copper and gallium contents are significantly increased. The corresponding band-gap widening may establish the function of minority carrier repulsion from the back contact. © 2013 Elsevier B.V.

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