Thin-Film Amorphous Silicon Alloy Research Partnership: Final Technical Progress Report, 2 February 1995-28 February 1998

This report describes the status and accomplishments of work performed by United Solar Systems Corp. under this subcontract. Investigations were carried out on Ag/ZnO, Ag/TiO2/ZnO and Ag/MgF2/ZnO back reflectors to assess their suitability for use in cell structures. Arrays of high-efficiency component cells were made over 1-ft2 areas. Single-junction top cells were made with an averagestabilized power density of 5.4 mW/cm2 measured under global AM1.5 illumination. Single-junction middle cells were optimized to give average stabilized power density of 3.6 mW/cm2 under global AM1.5 illumination with a cut-on filter with ..lamda..> 530 nm. Arrays of high-efficiency triple-junction cells of 0.25-cm2 active area were fabricated over 1-ft2 area with average stabilized efficiency of12% as measured under AM1.5 illumination. A triple-junction module of a 416-cm2 aperture area was fabricated with an initial efficiency of 11.7% and stabilized efficiency of 10.24%. A 922-cm2 aperture-area module exhibited an initial efficiency of 11.5%. The novel laser-drilling approach was used successfully to fabricate modules of 1-ft2 area with shadow loss of approximately 1%. Using thislaser- drilling approach, an initial total-area efficiency of 11.5% was achieved in a triple-cell structure of 12.6 cm2 area. An initial total-area efficiency of 10.6% was achieved in a module of 300-cm2 area. Reliability studies based on NREL's Interim Qualification Testing were carried out to confirm the suitability of the module encapsulation materials and processes.