Antireflective coatings with enhanced adhesion strength†
The importance of tuning refractive index in a multilayer antireflection coating (ARC) system can not be denied. In practical applications, regulation of refractive index is complex due to limited choice and availability of appropriate materials for the trilayer AR coating assembly. To overcome this issue, we used a single inorganic material, HfO2, for the construction of a trilayer AR light harvesting moth eye, resembling hierarchical nanostructure coatings, for exploring new generation photovoltaics and optoelectronic devices. In the trilayer AR HfO2 (TAR-H) assembly, using a glancing angle deposition technique (GLAD), the dense bottom layer was steadily changed into a spongy middle layer that further changed to a highly porous top layer micmiking a moth eye, reducing the refractive index of the coating from 1.87 to 1.30. The broadband omnidirectional properties of the TAR-H coating, with superior thermal stability and improved scratch resistance, in the visible wavelength range were experimentally demonstrated. The TAR-H coating on FTO and sapphire substrates achieved reflectance of up to <1% in the visible wavelength range.