Numerical comparison of quantum-confined Stark effect on emission spectra between InP- and CdSe-based colloidal quantum dots

We numerically compare the quantum-confined Stark effect (QCSE) on emission spectra between InP/ZnSe/ZnS and CdSe/ZnSe/ZnS colloidal quantum dots (QDs). Because the bandgap energy of InP is greater than that of CdSe, the total layer thickness of an InP/ZnSe/ZnS QD is determined to be less than that of a CdSe/ZnSe/ZnS QD for both QDs to have the same emission peak wavelength of 563 nm. After strain-modified band-edge energies for electron and heavy hole are calculated, a three-dimensional Schrodinger equation is numerically solved based on the finite element method. The changes in ground-state energy levels, wave-function overlap integrals, and exciton binding energies of the thick CdSe-based QD are much greater than those of the thin InP-based QD when the external electric field intensity increases from 0 to 100 kV/cm. In calculated emission spectra, the CdSe-based QD shows the integrated emission intensity reduction of 6% and ground-state emission peak shift of 0.91 nm. In contrast, the integrated emission intensity decreases by 0.02% and its ground-state emission peak shifts by 0.06 nm for the InP-based QD. Because the degree of the QCSE is proportional to the size of QDs, the emission spectrum of thin InP-based QDs is less sensitive to the QCSE than that of thick CdSe-based QDs when they have the similar peak emission wavelength.