Texture of the Viola Flower for Light Harvesting in Photovoltaics

Nature's evolution provides a multitude of answers to scientific and key technological challenges such as the light harvesting. In this work, we investigate the optical properties of the unique texture of viola petals for the purpose of improved light harvesting in photovoltaics. We find that crystalline silicon solar cells encapsulated with a transparent coating show a 6% improvement in power conversion efficiency if the viola petal texture is replicated onto the front surface. This gain is based on a broadband enhancement in current generation that originates from the exceptional optical properties of the viola surface texture, combining micro- and nanotexture. The microcones of this hierarchical texture demonstrate strong and broadband light incoupling effects as well as retro-reflection capabilities, and the nanowrinkles further decrease the reflection losses. Using rigorous optical simulation, we analyze and explain the working principle ruling the light harvesting properties of this dual-scale texture.