A device including a substrate and a crystalline organic semiconductor film formed on the substrate from an organic semiconductor film, the crystalline organic semiconductor film including a plurality of features, each feature comprising a peak, and exhibiting a periodicity of at least 100 nm, the plurality of features form spontaneously with crystallization of the organic semi-conductor film;
- the device further including a second organic or nonorganic layer placed underneath the crystalline organic semiconductor film and configured to engineer crystallinity.