Butterflies: inspiration for solar cells and sunlight water-splitting catalysts

Solar cells and photocatalysts to yield hydrogen are two significant strategies for taking advantage of clean and sustainable solar energy, and their light manipulation and harvesting ability will play a dominant role in their conversion efficiencies. Butterflies demonstrate their brilliant colors due to their wonderful skills of light manipulation, originating intrinsically from their elaborate architectures. We review the inspiration of butterflies for solar cells and sunlight water-splitting catalysts, focusing on the nipple arrays in butterfly compound eyes, as well as ridge and hole arrays, and the photonic crystal structures in butterfly wing scales. After giving a brief introduction to the typical architectures, we reveal the physical principles lying behind antireflection of compound eyes and black scales and iridescence of wing scales, respective prototypes are extracted and highlighted for the design and fabrication of solar cells and sunlight water-splitting catalysts. We conclude by reviewing the prospects for the integration of these prototypes and the appropriate materials for solar energy, which is the product of an intimate conversation between humanity and nature, as well as close cooperation between scientists from diverse fields.