Effect of dielectric constant on emission of CdSe quantum dots

The effect of dielectric constant on the exciton ground state energy of CdSe Quantum Dots (QD) is investigated on four different QD sizes (2.46, 2.60, 2.71, and 2.8 nm). We studied (1) the exciton energy when the dielectric constants of the quantum dot and the surrounding material are different and (2) the exciton energy when the dielectric constant of the dots is size-dependent. Four different materials for surrounding the QD were used (chloroform, toluene, heptane, and hexane). The CdSe QD have been characterized by high resolution scanning electronic microscope (HR-SEM), X-ray diffraction, (XRD) and transmission electron microcopy (TEM) with the aim to control the QD shape and the average size. The optical absorption and photoluminescence (PL) spectra were investigated in order to get exciton energies and to understand the effect of dielectric constant on PL emission. The results have shown that the leaking of the wave function and the difference of the dielectric constant between QD and the surrounding material are essential for rectifying Coulomb interaction energy and reproducing experimental data.