Primary and Secondary Reflective Color Realized by Full‐Solution‐Processed Multi‐Layer Structures

Abstract A full solution‐based method is reported to fabricate multilayer thin film stacks for structural color applications. This is in contrast to the conventional fabrication methods that require high vacuum processes such as physical vapor deposition and magnetron sputtering, which significantly limits their practical use due to the high cost and long processing time. Copper/silicon dioxide/copper (Cu/SiO₂/Cu) and copper/titanium dioxide/copper (Cu/TiO₂/Cu) are chosen as the model system due to their simple structure and wide color tunability. A systematic investigation is carried out for each layer to ensure good film quality as well as its compatibility with all previous layers. Especially, a particulate Cu layer having optical properties distinct from that of bulk is obtained through such solution deposition, where the refractive index of Cu can be continuously tuned with deposition time. Both primary and secondary colors are achieved with a continuous manipulation of both the dielectric thickness and top Cu morphology on different substrates (e.g., silicon, glass, plastics, etc.).