We present measurements of the degree of absorption anisotropy in PbSe nanorods as a function of aspect ratio. Our pump-probe spectroscopic technique exploits the polarization memory effect to measure anisotropic absorption in randomly oriented ensembles of nanorods. We find that the absorption anisotropy increases upon elongation from aspect ratio 1 to 4, and reaches a relatively constant value for longer rods. Our observations can be described classically by considering the effect of dielectric contrast on the local fields on an ellipsoidal nanostructure. Based on this model, we predict absorption anisotropy >0.9, Fig. 1, and an absorption cross-section >10x what would be observed in nanocrystals of the same volume for a film of aligned nanorods. Our results imply that the dielectric constant of the surrounding medium can be used to influence the optoelectronic properties of nanorods, including phonon modes, multiple exciton generation, and Auger recombination. Fig. 1 (left) Absorption anisotropy predicted for an isolated PbSe nanorod in air as a function of aspect ratio by on considering local field factors. (right) Schematic showing the axial and radial absorption cross-sections of a nanorod that give rise to anisotropic absorption.

Absorption anisotropy in PbSe nanorods

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.