Light-trapping and Superhydrophobic Plant Surfaces

Abstract

In a process spanning over 400 millions years of evolution, plants have developed multifunctional surfaces that are highly adapted to environmental conditions. Nature provides several millions varieties of plant species resulting in an extreme diversity of functionalized surfaces, which are often characterized by a hierarchically structured architecture. These sophisticated surface designs may protect leaves against contaminations or mechanical stress, play an important role in the plant´s hydrological balance, protect the metabolic system against harmful radiation or support the optical attractiveness of flowers. The architecture and chemistry of these surfaces determine their functionalities. Analysis of these optimized biological surfaces could be the key to optimizing technical surfaces. Over the last years these functionalized plant surfaces have often been used as models for the development of, e.g. self-cleaning (Lotus-Effect) or air retaining (Salvinia-Effect) biomimetic surfaces. Yet the technical potential of the optical properties of plant surfaces has only been examined marginally, especially for the optimization of light-trapping and water-repellent solar cells. Therefore this study analyses the optical and wetting properties of hierarchically structured leaf and flower surfaces as well as their technical replicas. As a result of this work a new, light-trapping and superhydrophobic surface architecture for the optimization of high efficiency solar cells is presented.