Highly Integrated Mid-Infrared Laser Source for Processing Organic Solar Cells

Published on December 17, 2010 at 9:12 PM

Imec will actively participate in a new European project called IMPROV (‘Innovative mid-infrared high-power source for resonant ablation of organic based photovoltaic devices’) that aims at the investigation, development and realization of a fibre integrated short-pulse mid-infrared laser source. The industrial application driver is the development of a laser source for the fabrication of organic solar cells. The new source will offer advantages over existing systems in terms of parameter specifications, flexibility, reliability and usability.

The new fibre laser source will bring a solution for the fabrication of organic flexible devices, in particular for the patterning of organic solar cells. Conventional processing techniques can either not cope with selectivity issues or are too complex and costly to be compatible with an industrial environment. The proposed solution will provide a reliable, compact and maintenance free pulsed mid-IR source that allows resonant infrared laser ablation (RIA) of the polymer, a technique that is selective in respect of processing a diversity of polymers. The laser system can therefore be more largely applied to other polymer and organic materials processing needs as well as in other ICT or medicine applications.

The laser will combine a short pulse thulium all-fibre laser operating around 2µm with a subsequent wavelength conversion stage. It will operate in the wavelength region from 2.5µm to 11µm with a pulse energy of up to 30µJ, a pulse duration between tens to hundreds of picoseconds and a repetition rate between 0.1 to 1MHz.

For a compact and integrated solution, the best configuration is combining a master oscillator power amplifier (MOPA) all-fibre laser with a quasi-phase matched GaAs crystal for wavelength conversion. For the MOPA pump source different integration aspects will be addressed in order to fully benefit of a waveguide device. These include the development of fibre-coupled saturable absorbers, large mode area (LMA) photonic crystal fibres (PCF) with functionalities regarding wavelength tuning capability, mode-filtering and high power operation, pump/signal combiners based on LMA-PCFs and novel concepts for fibre amplifiers with integrated core-pumping schemes. The wavelength conversion unit will be realized with integrated wavelength tunability and structural design.

Within the project, imec will lead the work package on ‘resonant infrared ablation for structuring organic PV’ and will be responsible for the preparation of the process evaluation set-up and for ablation tests using the developed laser source. Imec is well equipped for this task as it has strong experiences in developing solar cells and plastic electronics, assembly of various substrates, e.g. thin film technology on flexible and stretchable substrates bringing together expertise from electronics, mechanics, physics and chemistry. Therefore, imec is in the position of analyzing the ablation results with respect to the laser parameters. These important results will be applied as feedback for adjusting the final laser parameters. Imec’s work in IMPROV will be performed at imec’s Centre for Microsystems Technology (CMST) at Ghent University.

The consortium, coordinated by Dr. Dieter Wandt, Laser Zentrum Hannover, represents the whole value chain including exploitation and this will significantly improve the competitiveness of related European industry and strengthen Europe’s scientific and technology base.

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