The effects of nanopillar surface texturing on the photoluminescence of polymer films

Abstract

We report on the enhancement of photoluminescence (PL) from polymer thin films by nanotexturing their surfaces using nanoporous anodic alumina oxide templates. Chromophore-embedded polystyrene films with nanostructured surfaces are prepared by imprinting 200 nm diameter nanopillars with various heights, and their PL output and angular emission are observed. The PL output increases and the angular distributions broaden as the height of the nanopillars increases. For 5 μm tall nanopillars, the PL output is enhanced by a factor of 2.5 relative to the smooth surface. An effective refractive index model provides a qualitative description of the angular emission and PL output of nanotextured surface but underestimates the degree of PL enhancement. Comparison of the nanopillared films with surfaces randomly roughened using sandpaper shows that the details of the texturing have a significant impact on the PL output characteristics. These results show that imprinted nanopillars provide a simple and controlled way to increase the PL output of luminescent polymer films.