Understanding the anti-reflective glasswing butterfly for enhanced solar concentrator optics

Solar cell absorption efficiencies have in the past been improved by the biomimicry of moth eye nano-patterns. There are however still many optical nanostructures within nature yet to be investigated for solar energy applications. The ‘Glasswing’ Greta Oto butterfly in particular boasts a minimal glare effect of its wings, which is investigated here for benefits to emerging photovoltaic and concentrator photovoltaic designs. Photovoltaic technologies such as thin film and low concentrator systems (stationary optics used to focus light to smaller areas of photovoltaic material) incorporate refractive optical components (including firstly the protective cover glass) and hence require antireflective coatings that optimize transmission. Understanding what aspects of the Glasswing butterflies nanostructured wings allow for their exceptionally low reflectivity opens up a significant resource of energy from new and existing photovoltaic technologies. We have characterized the optical properties of the Glasswing butterfly nanostructures utilizing Scanning Electron Microscope images, Spectrophotometry and measurements of the External Quantum Efficiency Signal of the wings coupled with photovoltaic material.