Self-Assembled Biomimetic Antireflection Coatings for High Efficiency Photovoltaics

Millions of years before we began to generate functional nanostructures, biological systems were using nanometer-scale architectures to produce unique functionalities. Some nocturnal moths use hexagonal arrays of subwavelength nipples as antireflection coatings (ARCs) to reduce reflection from their compound eyes. Similar periodic arrays of pillars have also been observed on the wings of cicada to render superhydrophobic surfaces for self-cleaning functionality. Inspired by these natural nanostructures, we have developed a simple and scalable templating technique for fabricating self-cleaning, broadband ARCs on a large variety of technologically important substrates (e.g., crystalline Si, GaAs, GaSb, glass, and polymer). The technique is based on a spin-coating platform that combines the simplicity and cost benefits of bottom-up colloidal self-assembly with the scalability and compatibility of standard top-down microfabrication. The resulting subwavelength-structured ARCs exhibit superior broadband antireflection properties than traditional multilayer dielectric ARCs and are promising for applications ranging from highly efficient solar cells and photodetectors to flat-panel displays.