Approaches to flexible CIGS thin-film solar cells

Even though the "standard" CIGS module fabrication on glass substrates is not yet really established, several CIGS (Cu(In,Ga)Se-2) newcomers directly start with the development of flexible devices. The reasons to do so are manifold and so are the methods. We will briefly introduce a few approaches-especially from European laboratories-to fabricate flexible CIGS-based modules and discuss their respective features. Mainly, however, the approaches on metal and polymer substrates at ZSW are presented. Functioning monolithically integrated modules on titanium were fabricated up to a substrate area of 20 x 30 cm. Also, mini-modules on 10 x 10-cm(2) polyimide sheets could be realised. Important challenges were the electrical insulation of titanium or steel substrates. Suitable dielectric barriers are, for example, pinhole-free SiOx layers deposited by a special plasma-CVD method which can withstand both the GIGS process and the structuring procedures. Adequate patterning methods such as direct laser scribing and mask-free photolithography were successfully applied to interconnect more than 30 cells. (c) 2004 Elsevier B.V. All rights reserved.