Superhydrophobic nanoshell array for application in solar cell

Abstract

In this work, a superhydrophobic property was demonstrated on a cylindrical poly-crystalline silicon nanoshell array fabricated by spacer lithography. Nanoshell array showed superhydrophobic property even without chemical coating on the surface with low surface energy material. The proposed structure showed superior water-repellency compared to a conventional pillar structure with an identical structural dimension. This superhydrophobic property is attributed to an air pillar that exists in the nanoshell. Through the calculation of capillary pressure, the stability of the air pillar was confirmed. Furthermore, a droplet impinging test was conducted on the fabricated cylindrical nano-shell array to verify the stability of Cassie state under a dynamic condition. Furthermore, Gibbs free energy difference of two wetting states was calculated to show that the stability of Cassie state can be enhanced by increasing the height of nanoshell array. As a result, various heights of nanoshell array were fabricated and wetting behavior on each of the structure was studied. Inspired from the structural advantage of nanoshell array, transparent and superhydrophobic PDMS microshell array was fabricated. Self cleaning effect of PDMS microshell array was demonstrated on the solar cell module when dust particle was imposed on the surface. As a result, PDMS microshell array showed superior dust removal effect, hence showing better solar cell efficiency recovery over flat PDMS. Cylindrical shell-like superhydrophobic surface is a promising candidate for self cleaning application in solar cell.