Modeling of electronic states and angular absorption anisotropy in cadmium telluride nanocrystals with different geometric dimension ratios

Control over the electronic and optical properties of semiconductor nanocrystals is often considered primarily in terms of changes in their size. However, particle shape and the ratio of longitudinal to transverse dimensions may also influence their optical properties. In this work, numerical modeling of electronic states and optical density spectra was performed, and the angular anisotropy of absorption was investigated for cadmium telluride nanocrystals of different shapes by varying the ratio of their longitudinal to transverse dimensions. The calculations were carried out for spheroidal, cylindrical, and conical cadmium telluride nanocrystals with a fixed volume of 422 nm 3 . Electronic states and optical density spectra were calculated within the effective-mass approximation at a temperature of 300 K. The angular dependence of the optical density spectra was analyzed for incident angles of 0°, 30°, 45°, 60°, and 90°. It was shown that variation in the ratio of longitudinal to transverse dimensions changes the ground-state energy E 0 and the first excited-state energy E 1 . The highest values, E 0 = 1.7618 eV and E 1 = 1.9528 eV, were obtained for conical nanocrystals, which may be associated with stronger spatial confinement of the electronic state due to the nonuniform transverse cross-section of the cone and the presence of an apex. It was also found that changing the ratio of longitudinal to transverse dimensions at a fixed volume leads to a restructuring of the optical density spectra. A pronounced angular anisotropy of absorption was revealed for cadmium telluride nanocrystals. The maximum positive value of the angular anisotropy coefficient was 16.12 % for spheroidal nanocrystals, whereas the most negative value was −10.59 % for cylindrical nanocrystals. In contrast to the conventional approach based on changing the overall size of nanocrystals, the proposed approach enables tuning of their electronic and optical properties by varying the ratio of longitudinal to transverse dimensions at a fixed volume. These results may be useful for tailoring the energy levels, absorption spectra, and angular sensitivity of cadmium telluride nanocrystals for the development of optoelectronic and photonic devices based on this material.