Dynamically omniphobic and highly transparent polyurethane coating towards efficient self-cleaning on photovoltaic modules

Abstract

Photovoltaic (PV) modules have become a powerful contributor to global CO₂ emissions mitigation, but have suffered a significant loss in power generation efficiency caused by the deposition of surface contamination. Conventional self-cleaning coatings typically require laborious fabrication processes, elaborate texturing, and fluorinated materials, which are difficult to integrate with transparency, environmental compatibility, and adaptability. Herein, we show a highly transparent, fluorine-free, and dynamically omniphobic liquid-like polyurethane coating (LLPuC) prepared by well cross-linking between polydimethylsiloxane (PDMS)-grafted hydroxyacrylate (P_xHA_y) copolymer and polyisocyanate at elevated or room temperature. The LLPuC could be applied to various substrates by spraying or blading methods and has demonstrated good transparency (91.79 % at 550 nm) of the coated glass. The liquid-like flexible chains of PDMS were enriched on the LLPuC and moved spontaneously, resulting in a smooth surface with dynamic omniphobicity (WSA = 11.5 ± 0.6°, OSA ≤ 15°), anti-smudge, and self-cleaning capability, as evidenced by the LLPuC coated PV module achieving a 92.83 % efficiency recovery ratio after the self-cleaning process. Moreover, the obtained coating also exhibited good adhesion strength, flexibility, anti-abrasion, and stability. Thus, the approaches and findings in this work have opened up a new avenue for self-cleaning coatings of PV modules and various outdoor transparent devices.