Optical properties of anisotropic CdSe nanocrystals from first principles

CdSe nanocrystals are popular light-emitting materials for optoelectronic devices and bioimaging applications. In contrast to zero-dimensional (0D) quantum dots, 1D nanorods and 2D nanoplatelets can have narrower emission bandwidths and anisotropic photophysical properties.



We use density functional theory to investigate the relationship between optical transition energies of CdSe nanocrystals within different confinement regimens and with different aspect ratios. We consider both zinc blende- and wurtzite-phase CdSe nanowires with quasi-circular cross-sections as well as anisotropic cross-sections with aspect ratios between 1 and 5. We also evaluate 2D slabs with different thicknesses. We calculate the ground-state DOS as well as the optical spectra of these materials to understand the transition between 1D and 2D regimes.



We observe a monotonic blue-shift and increased peak splitting of the band edge transition with decreased nanowire diameter and slab thickness. We attribute the blue-shift to increased confinement in the material and the increased peak splitting to the anisotropy of the plane-polarized transitions. As the nanowire aspect ratio increases with constant thickness, the transition energies shift towards the plane-symmetric transitions of the 2D slab with equivalent thickness.