Self-Cleaned Photonic-Enhanced Solar Cells with Nanostructured Parylene-C

Abstract

Photonic front-coatings with self-cleaning properties are presented as means to enhance the efficiency and outdoor performance of thin-film solar cells, via optical enhancement while simultaneously minimizing soiling-related losses. This is achieved by structuring parylene-C transparent encapsulants using a low-cost and highly-scalable colloidal-lithography methodology. As a result, superhydrophobic surfaces with broadband light-trapping properties are developed. The optimized parylene coatings show remarkably high water contact angles of up to 165.6° and extremely low adhesion, allowing effective surface self-cleaning. The controlled nano/micro-structuring of the surface features also generates strong anti-reflection and light scattering effects, corroborated by numeric electromagnetic modeling, which lead to pronounced photocurrent enhancement along the UV–vis–IR range. The impact of these photonic-structured encapsulants is demonstrated on nanocrystalline silicon solar cells, that show short-circuit current density gains of up to 23.6%, relative to planar reference cells. Furthermore, the improvement of the devices' angular response enables an enhancement of up to 35.2% in the average daily power generation.