High voltage Cu(In,Ga)S2 solar modules

Sulfurcell (SC) has been running a pilot production for thin-film solar modules using CuInS₂-chalcopyrite (CIS) as absorber material since 2004. Since then production technology has been constantly improved with module power values exceeding 64 W, corresponding to an aperture area efficiency level of about 9%. Small area (0.5 cm2) cells cut out of such CIS modules reach maximum efficiencies close to 11%. Strong efforts have been made to develop a new sequential Cu(In,Ga)S₂ (CIGS) process suitable for production of large-scale CIGS solar modules thereby enabling module efficiencies above 10%. CIGS-based solar cells are—quite similar to CIS-based modules—prepared from sputtered metals subsequently sulfurized using rapid thermal processing in sulfur vapor. Such Cu(In,Ga)S₂ solar cells reach material record efficiencies about 13%. The cells are characterized by high open-circuit voltages up to 890 mV. Based on the results of the “Helmholtz Zentrum Berlin” (HZB), Sulfurcell has successfully scaled this process to our typical module size of 125 cm × 65 cm and is currently piloting the process for mass production. This paper will give an overview of electrical and structural parameters of world's first large-scale CIGS modules. CIGS module and cell parameters will be compared with standard CIS module and cell parameters and measured CIGS efficiency temperature coefficients will be compared with typical temperature coefficients of modules based on established PV technologies.