Self-assembly of semiconductor nanorods

The image represents the self-assembly of semiconductor nanorods (NR) on a substrate. Semiconductor cylinder-shaped nanoparticles of 6 nm in diameter and about 10 nm in height are typically prepared and solvated in organic solvents. Upon the evaporation of solvent, NRs are often found lying horizontally on the substrate. However, under certain conditions they could be found in a vertical orientation with respect to the substrate. Self-assembly of vertically oriented NRs is conceived to be a great support material for the future hybrid solar cells. Independent experiments have shown that these NRs have intrinsic electric dipole moments. Our computational studies on the self-assembled NRs help to clarify specific conditions under which NRs could be found vertically oriented on substrates upon solvent evaporation. The image represents the stable hexagonal formations of NRs with antiferroelectric orientation of their dipoles, so every other dipole is flipped upside down. The shown simple hexagonal superlattice represents the most energetically stable formation of vertically assembled NRs with permanent dipoles and agrees with the experimental observation.