Effect of Dot Size on Exciton Binding Energy and Electron-Hole Recombination Probability in CdSe Quantum Dots.

Abstract

Exciton binding energy and electron–hole recombination probability are presented as two important metrics for investigating effect of dot size on electron–hole interaction in CdSe quantum dots. Direct computation of electron–hole recombination probability is challenging because it requires an accurate mathematical description of the electron–hole wave function in the neighborhood of the electron–hole coalescence point. In this work, we address this challenge by solving the electron–hole Schrodinger equation using the electron–hole explicitly correlated Hartree–Fock (eh-XCHF) method. The calculations were performed for a series of CdSe clusters ranging from Cd20Se19 to Cd74608Se74837 that correspond to dot diameter range 1–20 nm. The calculated exciton binding energies and electron–hole recombination probabilities were found to decrease with increasing dot size. Both of these quantities were found to scale as Ddot–n with respect to the dot diameter D. One of the key insights from this study is that the electron–hole recombination probability decreases at a much faster rate than the exciton binding energy as a function of dot size. It was found that an increase in the dot size by a factor of 16.1, resulted in a decrease in the exciton binding energy and electron–hole recombination probability by a factor of 12.9 and 4.55 × 105, respectively.