ELECTRICAL ISOLATION BARRIERS FOR MONOLITHICALLY INTEGRATEDCU(IN,GA)SE2 SOLAR MODULES ON FLEXIBLE METAL FOILS

摘要

Commonly Cu(In,Ga)Se2 (CIGS) based thin-film solar cells are deposited on glass substrates attemperatures around 550°C. Highly efficient CIGS modules fabricated on thin and flexible non-glass substrateswould on the other hand open new application areas. Most promising alternative materials with regard to cost,flexibility and conversion efficiency are metallic foils. Due to their good conductivity, isolation barriers with perfectelectrical isolation properties on large areas are needed in order to attain monolithically integrated flexible CIGSmodules. This issue has been addressed in this paper.SiOx films as electrical isolation barriers were deposited by means of a low pressure microwave plasma-enhancedchemical vapour deposition (MWPECVD) technique using hexamethyldisiloxane as precursor. This method allowsthe deposition of dense films with good surface coverage at very high growth rates. With the help of an analysisbased on electrolysis measurements it was possible to identify the origins of pinhole formations in these films.Consequently, it became feasible to remove all pinholes and to achieve perfect electrical isolation even on largeareas. Moreover, these SiOx films proved to be stable under the highly demanding deposition conditions of the CIGScoevaporation procedure. Together with appropriate patterning techniques (photolithography for P1 and P3, directlaser scribing for P2) it has been possible to produce monolithically integrated CIGS modules on flexible metal foilswhich revealed conversion efficiencies of up to 6.8% (AM 1.5, 100 mW/cm2).