CIGS thin-film solar module processing

09.02.2017

Laser scribing is a key enabling technology for the industrial roll-to-roll production of CIGS thin-film solar modules. Researchers at the Applied Fiber Technology laboratory, part of the BFH-ALPS institute have been working on the topic for more than 6 years in national and international projects and have contributed substantially to the industrial adoption of laser scribing.

Thin-film solar cells based on Cu(In,Ga)Se2 absorber technology are very attractive due to their high theoretical conversion efficiency and their suitability for streamlined mass production. Selective removal of thin-film layers – the so-called scribing – is necessary for monolithic interconnection of individual cells into modules. Traditional needle scribing is not applicable for flexible substrates used on roll-to-roll production machines. Laser scribing does not have this limitation and is therefore the method of choice for industrial producers. Unfortunately, CIGS is very difficult to process as it is subject to electrical degradation when heated during the laser process. Ultrashort pulsed lasers are known to limit the heat deposited in the processed material to a minimum. However, even with the use of femtosecond laser pulses, heat accumulation limited the achieved scribing speeds to typically 100 200 mm/s – still ten times too slow for industrial production.

As a major partner in the large European FP7 project APPOLO , BFH ALPS joined forces with academic partners from all over Europe to overcome these limitations. By developing alternative scribing process schemes (as in the featured article) and using sophisticated optical beam shaping and scanning strategies, scribing throughput was increased to an industrially exploitable level of 1-50 m/s. Since APPOLO puts a strong focus on assessment of developed technologies, all optimized laser scribing processes were also validated in functional mini modules produced on production equipment at industrial partners’ facilities.

Full paper | nature.com/scientificreports 13.01.2017
Project Appolo | appolo-fp7.eu
Institute for Applied Laser, Photonics and Surface Technologies | alps.bfh.ch