Grayscale evaporation of organic thin-film microstructures

We demonstrate that the deposition of organic thin films whose thickness is spatially shaped with sub-100-µm lateral resolution can be achieved by evaporation through a reusable flux-controlling micrometric-hole sieve that is separated from the to-be-coated substrate. This approach offers a practical way to grayscale-pattern organic materials without exposing them to detrimental ambient air or chemical solutions. As such, it facilitates the fabrication of long-lasting organic microstructured devices such as the reported spatially-varying absorptive color filters based here on the organic semiconductor (4,4'-Bis[4-(di-p-tolylamino)-styryl]biphenyl (DPAVBi)). Additionally, the ability to readily make multiple thickness-coated samples offers a material-sparing yet convenient way to measure the properties of the evaporated material, a feature exploited hereafter to extract the optical dielectric constants of DPAVBi over the visible and near-infrared range. This work and its extensions to inorganic compounds and freeform shaping pave the way for a new generation of devices that should find applications in light-matter coupling studies, hyperspectral imaging, structural coloring, or optical systems exploiting freeform optics.