Novel nanofabrication techniques of organic optical cavities

We implemented and developed a number of different mechanical patterning methods, including soft hot embossing, rapid prototyping, sub-µm fluidics, high-temperature and room-temperature nanoimprinting lithography, to fabricate planar periodic structures based on organic materials. Patterns were faithfully transferred to many different organic compounds, including polymers, low-molar-mass compounds, and blends, up to 100-nm scale resolution. Lithography does not reduce the emission yields of light-emitting organic compounds, thus opening the way to the one-step realization of organic-based confined optoelectronic devices. We carefully investigated the possible changes in the optical properties (absorbance, luminescence, and quantum yield) of light-emitting species, thus ruling out any possible degradation of the active materials after patterning. In particular, the observed increase in the external luminescence yield is ascribed to the reduced self-absorption within the dielectric slab of the organic film, as a consequence of the pattern-induced enhanced forward scattering.