Omni-directional light capture in PERC solar cells enhanced by stamping hierarchical structured silicone encapsulation that mimics leaf epidermis.

Conventional crystalline silicon solar cell photovoltaic module technology requires much more development due to the challenges of efficiency loss and reliability problems such as browning damage. As an alternative to conventional ethylene-vinyl acetate (EVA)-glass encapsulation, silicone-based encapsulation is a promising innovation. Added to the many advantages of silicone based encapsulation for Si solar cells, here we present surface modification of silicone encapsulation with hierarchical structures inspired by leaf epidermis structures that improve light capture and hydrophobicity of the module surface using a simple, large-area silane and ozone treatment technique. The hierarchical structures comprise tens-of-micrometer-scale hills, valleys, and bump structures and sub-micrometer-scale wave patterns; the combination of these surface structures improved light transmission, light haze, and the wetting angle. These synergistic structures improve efficiency under vertical illumination compared to a bare cell, which is significant considering the efficiency loss in conventional EVA-glass encapsulation from those of bare cells. Furthermore, the enhancement increased the angle of incidence and improved the omni-directional performance so that electrical energy was generated more efficiently. We demonstrated that the modification of module surfaces by mimicking leaf epidermis structures yields considerable benefits, and further studies are expected to optimize this structure and identify the underlying principles for technological innovations based on silicone encapsulation.