Omnidirectional Current Enhancement From Laminated Moth-Eye Textured Polymer Packaging for Large-Area, Flexible III-V Solar Modules

Epitaxial lift-off (ELO) processes have allowed for cheaper development of mechanically flexible, ultra-thin, and high-efficiency III-V solar cells. ELO solar cells are natural candidates for applications where solar cells must conform to curved surfaces and provide high efficiency and high specific power generation (W/kg). Such examples include power generation for unmanned aerial vehicles, electric vehicles, and portable electrical power. However, when considering these mobile solar applications, large variations in angle of incidence (AOI) that inevitably occur can greatly decrease overall system efficiency due to significant Fresnel reflections. In this article, we demonstrate the integration of moth-eye antireflection nanostructures on the polymer packaging layer of ELO solar cell arrays using a low-cost, colloidal self-assembly process. The moth-eye structures mitigate Fresnel reflections and increase photocurrent generation over all measured angles of incidence relative to ELO solar cell arrays with traditional untextured polymer packaging. The nanostructures survive a commercial lamination procedure, an important criterion that must be met to ensure the feasibility of integration into commercial processing. Outdoor solar characterization measurements are performed and, under direct optical illumination, moth-eye textured solar cell arrays show a maximum I _sc enhancement of ~58% at 79° AOI relative to traditional untextured polymer packaged solar cell arrays, and when exposed to both direct and diffuse optical illumination a maximum I _sc enhancement of ~23% at 79° AOI is observed.