Vertical aligned nanorod assembly by electrophoretic deposition from organic solvents

The perpendicular alignment of II-VI nanorods in hybrid nanorod/polymer and all-nanorod solar cells is sought to reduce charge recombination by providing directional charge pathways to the electrodes. Here we describe the organization of II-VI nanorods into perpendicular assemblies over centimeter squared areas by a novel electrophoretic deposition approach. Monolayer assemblies are obtained by completely immersing parallel electrodes in a dilute solution of pyrolysis synthesized nanorods. The negatively charged nanorods deposit on the positive ITO electrode in ordered arrays which completely coat the electrode surface. The nanorods are hexagonally close packed with an interparticle separation of 2 nm occupied by interdigitated phosphonic acid surfactants. The nanorods are characterized by TEM, HRTEM, and HRSEM. This approach allows deposition of CdSe, CdS and CdTe nanorods in very large areas optimal for perpendicularly aligned nanorod solar cell application.