Process R&D for CIS-Based Thin-Film PV: Annual Technical Report, 24 April 2002--23 April 2003

During this subcontract period, predictability of Shell Solar Industries's CIS process was demonstrated by continuously executing the process while increasing throughput. Cumulative production for 2002 exceeded 1 MW - about twice the production rate for 2001. Average laminate efficiency for 2002 is 10.8% with a full width of only 12% of the average. Dramatic increases in line yield were achievedfrom improved production protocols and by addressing disparate special causes for process variation. Line yield increased from about 60% in 2000 to about 85% in 2002. NREL confirmed a champion 12.8 % aperture-area conversion efficiency for a large-area (3626 cm2) CIS production module. Field failure mechanisms for prototype modules were clearly demonstrated. Additional circuit-plate or packagingprocess variables, although not as clearly established, were also found to affect long-term stability for pre-production modules. Significant progress was made toward developing a 'glass/glass' package that eliminates the TPAT backsheet for decreased cost, simplification of the package, and decreased operating temperature. Very promising preliminary results were demonstrated for edge sealsdeveloped in collaboration with the new NREL-sponsored National Thin-Film PV Module Reliability Team. Long-term outdoor stability has been demonstrated at NREL where~30x30 cm and~30x120 cm modules with multiple prototype package designs have undergone testing for over 14 years. The demonstrated high line yield is the major accomplishment. No one major process improvement was responsible forthe yield improvements. Judicious application of manufacturing engineering disciplines such as SPC, analysis of variation, and design of experiments led to a clear definition of near-term yield issues. Dramatic improvements in yield were the result of improving production protocols and addressing disparate special causes for process variation. This major accomplishment supports attractive costprojections for CIS. Process R&D at successive levels of CIS production has led to the continued demonstration of the prerequisites for commitment to large-scale commercialization.