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Manova D.,Leibniz Institute fur Oberflachenmodifizierung E.V. | Bergmann A.,Leibniz Institute fur Oberflachenmodifizierung E.V. | Bergmann A.,Solarion AG | Mandl S.,Leibniz Institute fur Oberflachenmodifizierung E.V. | And 2 more authors.
Review of Scientific Instruments | Year: 2012

Here, the integration of a low energy, linearly variable ion beam current density, mechanically in situ adjustable broad beam ion source with a high-temperature x-ray diffraction (XRD) vacuum chamber is reported. This allows in situ XRD investigation of phase formation and evolution processes induced by low energy ion implantation. Special care has been taken to an independent adjustment of the ion beam for geometrical directing towards the substrate, a 15 mm small ion source exit aperture to avoid a secondary sputter process of the chamber walls, linearly variable ion current density by using a pulse length modulation (PLM) for the accelerating voltages without changing the ion beam density profile, nearly homogeneous ion beam distribution over the x-ray footprint, together with easily replaceable Kapton® windows for x-rays entry and exit. By combining a position sensitive x-ray detector with this PLM-modulated ion beam, a fast and efficient time resolved investigation of low energy implantation processes is obtained in a compact experimental setup. © 2012 American Institute of Physics.


Theelen M.,HIGH-TECH | Theelen M.,Technical University of Delft | Daume F.,Solarion AG | Daume F.,University of Leipzig
Solar Energy | Year: 2016

As Cu(In,Ga)Se2 (CIGS) photovoltaic (PV) technology matures to production on an industrial scale, its long-term stability becomes increasingly important: The electric yield and thus the revenue of a PV system depend on both the initial conversion efficiency as well as its development over time. Increasing this long-term stability by understanding and lowering the degradation of this PV technology is therefore a key strategy for CIGS market success. Furthermore, increasing the long-term stability of individual solar cells allows to lowering the demands and thus the cost of barrier materials within CIGS modules.Many authors have contributed to this subject over the years. In this review article, we have studied 143 publications related to the stability of CIGS solar cells and (mini-)modules. This review focuses on the behavior of unencapsulated CIGS solar cells and (mini-)modules when exposed to different accelerated lifetime tests, like elevated temperature and humidity. We describe the changes in electrical and physical performance due to these tests, as well as the chemical reactions that are causing these changes.Additionally, the state of knowledge on the influence of these tests on the individual layers of the CIGS solar cell has been summarized. Dedicated chapters review the stability of both, the transparent conducting ZnO:Al front contact and the molybdenum back contact, as well as on the CIGS and buffer layers. Stability issues related to the module design of CIGS PV, like the application of grid structures and monolithic interconnection, are discussed as well. © 2016 Elsevier Ltd.


Wang X.,Nanjing University of Science and Technology | Wang X.,Leibniz Institute of Surface Modification | Ehrhardt M.,Leibniz Institute of Surface Modification | Lorenz P.,Leibniz Institute of Surface Modification | And 4 more authors.
Review of Scientific Instruments | Year: 2013

Laser scribing of functional thin-film stacks attracts increasing attention especially for applications of flexible electronics or photovoltaics. Laser can perform selective removal of the thin-film stacks that is essential for the isolation and interconnection of the solar cells. The optimization of the laser scribing process concerning the functional properties of the device requires customized characterization techniques minimizing side effects. The proposed and demonstrated nested circular laser scribing technique allows the in-process measurement of the electrical characteristics, e.g., the shunt formation due to laser scribing of the thin-film stack, minimizing secondary effects originating from aging, contacting, changing of sample characteristics, or alterations of the measurement conditions. This technique enables the identification of reliable and quick information on the changes of the solar cell characteristics by laser scribing as this is demonstrated in this work. © 2013 AIP Publishing LLC.


Gecys P.,Lithuanian Academy of Sciences | Raciukaitis G.,Lithuanian Academy of Sciences | Wehrmann A.,Leibniz Institute of Surface Modification | Zimmer K.,Leibniz Institute of Surface Modification | And 2 more authors.
Journal of Laser Micro Nanoengineering | Year: 2012

Continuous growth of the thin-film solar technology market stimulates the development of versatile technologies for large-scale patterning of thin-film materials on rigid and flexible substrates, and laser technologies are a promising method to accomplish the scribing processes. In this study we compare picosecond and femtosecond pulse laser scribing for thin-film solar cells. For this we selected a Nd:YVO 4 mode locked picosecond laser with the pulse duration of 10 ps and a Ti: sapphire laser with the pulse duration of 300 fs. We concentrated on so-called P3 step of laser scribing to expose the molybdenum back-contact. The visual quality of the scribes was controlled with optical and scanning electron microscopes. The conversion efficiency tests, LIT (lock-in thermography) and LBIC (laser-beam induced current) measurements were performed on the laser-scribed complete working solar cells of prefabrication stage. The damage-free exposure of molybdenum layer was possible in complex thin-film structure with both pulse durations. LIT and LBIC measurements did not show evidence of internal shunt formation near the scribed zone using lasers with both pulse durations. The efficiency tests confirmed an insignificantly higher solar cell performance after femtosecond laser scribing, although at both pulse durations marginal reduction in solar cell efficiency was observed.


Puttnins S.,Solarion AG | Puttnins S.,University of Leipzig | Levcenco S.,Helmholtz Center Berlin | Schwarzburg K.,Helmholtz Center Berlin | And 7 more authors.
Solar Energy Materials and Solar Cells | Year: 2013

Sodium is known to play an important role for the performance optimization of Cu(In Ga)Se2 (CIGSe) thin film solar cells i.e. it is found to significantly increase the open-circuit voltage (VOC). For this work CIGSe absorbers were produced in a low temperature deposition process on polyimide substrates with varying sodium content. In agreement with previous studies we find an increase of VOC and overall solar cell performance with increasing sodium content and a decrease of the overall performance for very high sodium content. At the same time time-resolved photoluminescence measurements indicate that the minority carrier lifetime decreases from 50 ns to about 5 ns for increasing sodium content in the absorber. This correlation was found to be valid for three different types of low-temperature CIGSe deposition processes. The results can be explained by an increase in deep defect density with increasing Na content proportional to the increased net charge carrier density as measured by capacitance-voltage profiling. For very high sodium content this leads to an actual decrease in the overall performance of the solar cells. © 2013 Elsevier B.V.


Gecys P.,Lithuanian Academy of Sciences | Raciukaitis G.,Lithuanian Academy of Sciences | Miltenisa E.,Lithuanian Academy of Sciences | Braun A.,Solarion AG | Ragnow S.,Solarion AG
Physics Procedia | Year: 2011

The thin-film CIGS technologies for photovoltaics are attractive due to their potential low cost and optimal performance. Efficiency of cells with a large area might be maintained if small segments are interconnected in series in order to reduce photocurrent in thin films and resistance losses, and laser scribing process is crucial for performance of the device. We present our results on scribing of CIGS thin-film solar cells with single and multiple parallel laser beams with the picosecond pulse duration. Solar-cell performance tests were performed before and after laser scribing together with Raman spectroscopy analysis. The quality of processing was evaluated with optical and scanning electron microscopes. © 2011 Published by Elsevier Ltd.


Wehrmann A.,Leibniz Institute of Surface Modification | Ehrhardt M.,Leibniz Institute of Surface Modification | Ruthe D.,Leibniz Institute of Surface Modification | Zimmer K.,Leibniz Institute of Surface Modification | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Low-damage laser scribing of thin films to perform series interconnection (external and integrated) of thin-film CIGS solar cells for module fabrication is still a challenge. In consequence, the influence of laser scribing parameters on the electrical characteristics of thin-film CIGS solar cells must be studied in addition to standard analytical techniques for imaging and spectroscopy. Hence, CIGS solar cells were scribed with ultrashort Ti:Sapphire laser pulses with a wavelength of 775 nm and a pulse length of 150 fs. The I-V curves with the open circuit voltage, parallel, and series resistance were measured directly after the laser-scribing process and were compared with initial cell parameters. Apart from studying the influence of laser fluence etc. also various laser-scribing geometries were examined. The most significant effect of the laser-scribing procedure can be found for the parallel resistance. Laser ablation and laser-induced material modifications during scribing results in (i) alterations of the material properties of the films, e.g. the CIGS, and (ii) material modifications outside of the laser scribe, where the interfaces, e.g. p-n junction, primarily are effected; both effects are leading to the sudden decrease in parallel resistance. Morphology, topography, geometry and material modifications of the laser-scribed areas were analyzed by scanning electron microscopy (SEM) in combination with energy-dispersive X-ray spectroscopy (EDX) and focused ion beam (FIB) cross sectioning. The results of the laser-scribing induced alterations are discussed in relation to the applied scribing parameters. A model is introduced to improve the understanding of the physical reasons of the measured solar cell degradation while scribing. © 2011 SPIE.


Wehrmann A.,Leibniz Institute of Surface Modification | Puttnins S.,Solarion AG | Hartmann L.,Solarion AG | Ehrhardt M.,Leibniz Institute of Surface Modification | And 2 more authors.
Optics and Laser Technology | Year: 2012

Laser patterning of thin-film solar cells is essential to perform external serial and integrated monolithic interconnections for module application and has recently received increasing attention. Current investigations show, however, that the efficiency of thin-film Cu(In,Ga)Se 2 (CIGS) modules is reduced due to laser scribing also with ultrashort laser pulses. Hence, to investigate the reasons of the laser-induced material modifications, thin-film CIGS solar cells were laser-scribed with femto- and picosecond laser pulses using different scribing procedures and laser processing parameters. Besides standard electrical current voltage (IV) measurements, additional electrical and optical analysis were performed such as laser beam-induced current (LBIC), dark lock-in thermography (DLIT), and electroluminescence (EL) measurements to characterize and localize electrical losses due to material removal/ modifications at the scribes that effecting the electrical solar cell properties. Both localized as well as distributed shunts were found at laser scribe edges whereas the laser spot intensity distribution affecting the shunt formation. Already laser irradiation below the ablation threshold of the TCO film causes material modification inside the thin film solar cell stack resulting in shunt formation as a result of materials melting near the TCO/CIGS interface that probably induces the damage of the pn-junction. © 2012 Elsevier Ltd. All rights reserved.


Zachmann H.,Solarion AG | Puttnins S.,Solarion AG | Daume F.,Solarion AG | Rahm A.,Solarion AG | Otte K.,Solarion AG
Thin Solid Films | Year: 2011

Thin films of Cu(In,Ga)Se2 (CIGS) absorber layers for thin film solar cells have been manufactured on polyimide foil in a low temperature, ion beam assisted co-evaporation process. In the present work a set of CIGS thin films was produced with varying selenium ion energy. Solar cell devices have been manufactured from the films and characterized via admittance spectroscopy and capacitance-voltage profiling to determine the influence of the selenium ion energy on the electric parameters of the solar cells. It is shown that the impact of energetic selenium ions in the CIGS deposition process leads to a change in the activation energy and defect density and also in the spatial distribution of electrically active defects. For the interpretation of the results two defect models are taken into account. © 2011 Elsevier B.V.


Grant
Agency: European Commission | Branch: FP7 | Program: CP | Phase: ENERGY.2012.2.1.2 | Award Amount: 3.20M | Year: 2013

The overall objective of the ETFE-MFM Proposal is the development, evaluation and demonstration of a flexible multifunctional ETFE module for architectural faade lighting. The aim of this proposal is to provide a PV module with embedded additional functionalities designed to be used in ETFE textile architecture for BIPV applications. ETFE-MFM concept is based on the integration of different technologies creating a self-contained building element formed by: ETFE architecture, photovoltaic (PV) technology, illumination devices and flexible integrated circuits (IC). This new concept of multifunctional PV module will be able to work as a stand-alone or grid connected system. The solar energy supplied to the lighting devices will open new architectural faade lighting possibilities due to saving cost in the high energetic demand requested by this type of devices. The basic idea behind the development of ETFE-MFM is to enhance the use of building integrated photovoltaic (BIPV) elements in construction industry, as well as to provide new architectural faade lighting possibilities. The ETFE-MFM basic principles represent relevant innovative elements which are based on the combination of: - A novel attractive textile architecture based on ETFE as building material. The physical characteristics of ETFE allow construction cost savings by reducing greatly the weight of the structure whilst providing the same or even higher level of stability. - PV device, which acts as an electrical generator and shading during daylight, and supply the energy requested by the faade lighting devices at night, reducing the overall energy costs of the building. - Illumination devices, based on LED-RGB and OLED technologies, embedded on the module. - Flexible IC, which acts as individual module control of the PV device, providing the maximum power point (MPP) of the cells, as well as the control of the LED devices through wireless technology.

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