Munich, Germany
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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.


Grimm A.,Helmholtz Center Berlin | Kieven D.,Helmholtz Center Berlin | Klenk R.,Helmholtz Center Berlin | Lauermann I.,Helmholtz Center Berlin | And 3 more authors.
Thin Solid Films | Year: 2011

In an effort to eliminate the CdS buffer layer and its costly preparation process we are considering sputtered buffer layers. In particular, we report in this contribution on the reactive sputtering of wide gap Zn(O,S) compound semiconductors and their application in solar cells with different types of chalcopyrite absorbers. While we were able to freely adjust the composition through the oxygen partial pressure, the structural and optical properties are superior when the composition is close to the ternary endpoints. Open circuit voltage and short circuit current density as a function of Sulphur content in the buffer show opposite trends. Working cells were achieved with low band gap as well as wide band gap absorbers, however, their performance is so far inferior to that of the standard stacks. © 2011 Elsevier B.V. All rights reserved.


Lechner R.,Avancis Gmbh | Jost S.,Avancis Gmbh | Palm J.,Avancis Gmbh | Gowtham M.,Saint - Gobain | And 5 more authors.
Thin Solid Films | Year: 2013

In this contribution we report on the development of a two-step process for the formation of Cu2ZnSn(S,Se)4 thin films for solar cells. The two-step formation process of the pentanary kesterite consists of (i) sputter deposition of the metals Cu, Zn and Sn followed by thermal evaporation of chalcogen and (ii) rapid thermal processing of the metal/chalcogen precursors in chalcogen containing ambient. After the absorber formation process, solar cells were processed by deposition of CdS buffer, window layer and metal grid. We evaluated different metal precursor compositions in the ternary Cu-Zn-Sn metal systems regarding their behavior as appropriate precursors for the crystallization of Cu2ZnSn(S,Se)4 absorbers. X-ray diffraction analyses show the presence of secondary chalcogenide phases in absorbers with Cu-poor composition. In combination with Raman spectroscopy, the efficient sulfoselenization could be demonstrated. A broad compositional region is found giving cell efficiencies above 6% via this process route and the potentials for further improvements are discussed. The best solar cell measured so far reached 6.6% efficiency on 1.34 cm2 cell size. © 2012 Elsevier B.V.


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.


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.


Heise G.,Munich University of Applied Sciences | Heiss A.,Avancis Gmbh | Hellwig C.,Munich University of Applied Sciences | Kuznicki T.,Munich University of Applied Sciences | And 3 more authors.
Progress in Photovoltaics: Research and Applications | Year: 2013

We report on the optimization of selective picosecond laser structuring for the monolithic serial interconnection of (Cu(In,Ga)(S,Se)2) CIS thin film solar cells. We introduce a quantitative value to compare the energy efficiency of the different investigated laser processes, the specific ablation energy, which indicates the required energy to remove a certain volume of the specific material. We have examined the structuring efficiencies for induced laser ablation processes for a modification of the beam profile (elliptical and flat-top beam shaping) and for the application of different laser wavelengths (1064 and 532 nm). Application of induced laser processes (often referred as "lift-off") decreases the specific ablation energy dramatically by nearly one order of magnitude. Modifications of the beam profile such as elliptical and flat-top beam shaping are nearly halving the energy per ablated volume relative to a circular beam. The application of a laser wavelength 532 nm decreases the specific ablation energy compared with 1064 nm significantly for processes involving the CIS layer. We finally demonstrate that with a picosecond laser power of only 2 W, the molybdenum back contact (P1, glass side) and the ZnO front contact (P3, ZnO on CIS) can be structured with a process speed of up to 4 m/s. About 2 μm thick CIS layer (P2) is structured by standard direct laser ablation at higher energy densities with 200 mm/s. Copyright © 2012 John Wiley & Sons, Ltd.


Heise G.,Munich University of Applied Sciences | Dickmann M.,Munich University of Applied Sciences | Domke M.,Munich University of Applied Sciences | Heiss A.,Avancis Gmbh | And 5 more authors.
Applied Physics A: Materials Science and Processing | Year: 2011

The selective laser structuring of zinc oxide thin films, which serve as the transparent negative electrodes of copper-indium-selenide (CIS) thin film solar cells, is of great common interest as it can replace the mechanical scribing of the so-called pattern 3 (P3) process step for the monolithic serial interconnection of these cells. We present an investigation of the single-pulse ablation behavior of zinc oxide thin films on glass substrates and on CIS layers and of trench scribing with 10-ps laser pulses at 1064 nm and at 532 nm. We show that the ablation behavior strongly depends on the properties of the underling substrate and that the energy required to ablate a specific volume using induced laser processes (often referred to as 'lift off') is considerably reduced compared to the direct ablation of zinc oxide. With laser powers below 2 W at a wavelength of 1064 nm process speeds of 6 m/s for the P3 process have been achieved. © 2011 Springer-Verlag.


Kieven D.,Helmholtz Center Berlin | Grimm A.,Helmholtz Center Berlin | Lauermann I.,Helmholtz Center Berlin | Lux-Steiner M.C.,Helmholtz Center Berlin | And 3 more authors.
Physica Status Solidi - Rapid Research Letters | Year: 2012

Valence band offsets ΔE VBM at ZnS x O 1-x/Cu(In,Ga)(Se,S) 2 (CIGSSe) heterojunctions have been studied by photoemission spectroscopy (XPS, UPS) as a function of composition x in sputtered ZnS x O 1-x films. In the composition range from ZnO to ZnS we found ΔE VBM between -(2.1 ± 0.3) eV and -(0.8 ± 0.4) eV, respectively. Considering the optical band gaps, the conduction band offsets ΔE CBM range from -(0.1 ± 0.3) eV to +(1.4 ± 0.4) eV. These results suggest that sputtered ZnS x O 1-x is suitable as substitution for the CdS buffer and ZnO window layers in standard chalcopyrite-based solar cells. Current-voltage characteristics of the solar cells have been investigated as a function of the composition x. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Trademark
Avancis Gmbh | Date: 2012-06-19

solar panels for electricity generation; solar modules for electricity generation; photovoltaic panels for electricity generation; photovoltaic modules for electricity generation.

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