Effect of Size and Shape on Electronic and Optical Properties of CdSe Quantum Dots

摘要

In this paper, we used the 8-band k$\cdot$p model with valence force fieldconsiderations to investigate the effect of size and shape on electronic andoptical properties of cadmium selenide quantum dots. Major factors related totheir properties including band mixing probabilities, spatial chargedistributions, transition matrix elements and Fermi factors were studied.Volumetrically larger CdSe dots were found to have smaller band-gaps but highertransition matrix elements and Fermi factors. The maximum optical gain for dotswas observed to have an initially positive and then negative correlation withtheir real-space size as a result of combined effects of various factors. Forthe shape effects, cubic dots were found to have smaller band-gaps, Fermifactors and transition matrix elements than spherical dots due to higher levelof asymmetry and different surface effects. Consequently, cubic dots have loweremission energy, smaller amplification. The occurrence of near E1-H1 transitionbroadens the gain spectrum of cubic dots. Cubic and spherical dots are bothproven to be promising candidates for optical devices under visible range. Wehave demonstrated that size and shape change could both effectively alter theproperties of quantum dots and therefore recommend consideration of both whenoptimizing the performance for any desired application.