Design of esthetic color for thin-film silicon semi-transparent photovoltaic modules

Color design for large-area hydrogenated amorphous silicon (a-Si:H) semi-transparent glass-to-glass (GTG) photovoltaic (PV) modules has been studied for the application to building integrated PV (BIPV) modules. Three-dimensional color space of CIE (Commission Internationale de l'éclairage) L*a*b* (CIELAB) is adopted for a systematic color analysis. Three kinds of design configurations are invented by combining the transparency of back contacts and laser patterning techniques. In addition, the realization of emotionally stable and esthetic color is challenged using color back encapsulating materials. Transparent back contact (TBC)-type modules with green color are fabricated via the most simplified processes without sacrificing any active area. Bright and esthetic hybrid-type modules are also fabricated using additional laser-scribed patterns and blue encapsulating film. It is found that opaque back contact (OBC)-type module design is the best way to achieve target color together with the highest conversion efficiency. Because color of the back encapsulating materials does not deteriorate the conversion efficiency, the developed design concepts are promising options for large-area semi-transparent BIPV modules.