A quantum dot includes copper (Cu), a Group III element, and a Group VI element, wherein the quantum dot further includes a halogen component that is an iodide ion, a bromide ion, a chloride ion, a fluoride ion, or a combination thereof. A molar ratio of the halogen component to the copper (Cu) and a molar ratio of the halogen component to the Group III element is each independently in a range of about 0.01 to about 0.5, and a full width at half maximum (FWHM) of a photoluminescence spectrum of the quantum dot is equal to or less than about 80 nm.