CdSe nanoplatelets with controlled morphology and their polarized emission

Abstract

This study investigates the morphology dependence of linearly polarized emission from colloidal CdSe nanoplatelets (NPLs). The lateral aspect ratio in NPLs can be tuned by varying the amount of acetate hydrate salts during the synthesis. When the concentration of acetate hydrate salts introduced shortly before the lateral growth step changes, the resulting CdSe NPLs exhibit the lateral aspect ratio controllably ranging from 1.2 to 4.5. Measurement of fluorescence anisotropy from the solution samples reveals that elongated NPLs with higher lateral aspect ratio exhibit higher fluorescence anisotropy. In order to identify the origin of the linear polarization of emission, we design a model in which the shape anisotropy of NPLs and optical transition polarization are correlated based on the local field effect. Theoretical results are in good accordance with experimental data, which suggests that the shape-dependent linearly polarized emission originates mainly from the anisotropic local field effect.