Triple junction amorphous silicon based flexible photovoltaic submodules on polyimide substrates

This dissertation provides the first detailed description of the fabrication of flexible, monolithically interconnected photovoltaic sub-modules based on triple-junction amorphous silicon (a-Si) cell technology.; There are several problems encountered when progressing from small area (0.25 cm2) solar cells to series interconnected modules that are three orders of magnitude larger in area. This work involved the development of techniques required to overcome some of those problems, and the application of these in order to successfully fabricate triple-junction a-Si based solar sub-modules 10cm x 30cm (4'' x 12'') in size.; The solar cells were fabricated on Kapton-VN and Upilex-S polyimide films. Polyimide films were chosen because polyimides have the highest thermal and dimensional stability of any polymer commercially available in film form. Chromium or molybdenum tie-coat layers were introduced between the polyimide and back-reflector films in order to improve film adhesion, which is otherwise unsatisfactory. An improved electrochemical shunt passivation process (light assisted shunt passivation) was developed and used to passivate shunts in the cells. Shunt passivation is especially important for larger area solar cells. A combination of laser (dry) and wet chemical processing was used for the series interconnection. A laser-weld based interconnection scheme was chosen, for its compatibility with the shunt passivation process. The cells were encapsulated with the terpolymer THV (St. Gobain) and Tefzel (Dupont), using a vacuum laminator that was specially built for this purpose.; To summarize, triple-junction-amorphous-silicon-based, series interconnected photovoltaic submodules of size 10 cm x 30 cm were fabricated on lightweight and flexible substrates. The modules have an aperture area of approximately 200 cm 2. An initial AM1.5 efficiency of 4.75% (5.34% in natural sunlight) was obtained for a module with an aperture area of 204 cm2. The specific power of this module is approximately 40 W/kg.