Graphene/nanoporous-silica heterostructure based hydrophobic antireflective coating. (September 2016) - De, Sucheta
Graphical abstract: Highlights: For the first time, we have demonstrated that graphene can be used to enhance the hydrophobicity of nanoporous silica based single layer ARC. Such cost-effective single layer ARC shows the broadband and wide-angle nature without complexity having good adhesive property. The inherent anticorrosive property of such ARC film provides long term reliability and repeatability against harsh environmental condition. This could have wide range of applications, such as, in solar panel glass, smart windows, automobiles etc. This cost effective and facile technological development can have a potential for future industrial adoption. Abstract: Highly transparent with hydrophobic noncorrosive antireflective (AR) coating of Graphene/Nanoporous-silica heterostructure is designed for advance solar devices. On a standard glass matrix, a thin layer of silica coating is prepared by acid-catalyzed sol–gel method and porosity is introduced with the controlled addition of polyethylene glycol (PEG) with different molecular weights to optimize wide angle and broadband transmittance. The test results of atomic force microscope and field emission scanning electron microscope show that the PEG significantly affects the porosity and surface morphology of the coating layer. The presence of groove-like porous structure within the film matrix effectively reduces the refractive index (1.46–1.41) of the silica coating and thereby enhancing the percent (%) transmission. This nanoporous silica thin film with PEG4000 shows the highest transmittance of 98.19% with an average pore size 1–3 nm. The hydrophobicity is imparted by adopting a novel approach by depositing large area homogeneous graphene layer on top of the silica film. This heterostructure film demonstrates 6-fold enhancement of hydrophobicity due to graphene layers and is compromised with a loss of 1–2% transmittance. The hardness analysis of the graphene coated AR film by 100 times abrasion test shows the strong van der Waals interactions between the porous silica film and graphene layers. The prolong acid test for long term durability proves great sustainability of such hydrophobic coating against harsh weather conditions without altering its intrinsic properties of wide angle and broadband transmittance.