  The self-assembly of nanocrystals enables new classes of materials whose
properties are controlled by the periodicities of the assembly, as well as by
the size, shape and composition of the nanocrystals. While self-assembly of
spherical nanoparticles has advanced significantly in the last decade, assembly
of rod-shaped nanocrystals has seen limited progress due to the requirement of
orientational order. Here, the parameters critically relevant to self-assembly
are systematically quantified using a combination of diffraction and
theoretical modeling; these highlight the importance of kinetics on
orientational order. Through drying-mediated self-assembly we achieve
unprecedented control over orientational order (up to 96% vertically oriented
rods on 1cm2 areas) on a wide range of substrates (ITO, PEDOT:PSS, Si3N4). This
opens new avenues for nanocrystal-based devices competitive with thin film
devices, as problems of granularity can be tackled through crystallographic
orientational control over macroscopic areas.
