A quantum dot, and a composite and a display device including the quantum dot. The quantum dot comprises a semiconductor nanocrystal core comprising indium and phosphorous, a semiconductor nanocrystal shell disposed on the semiconductor nanocrystal core, the first semiconductor nanocrystal shell comprising zinc, selenium, and sulfur, wherein the quantum dot does not comprise cadmium wherein the quantum dot has a maximum photoluminescence peak in a green light wavelength region, and wherein in an ultraviolet-visible (UV-Vis) absorption spectrum of the quantum dot, a ratio A450/Afirst, of an absorption value at 450 nm to an absorption value at a first excitation peak is greater than or equal to about 0.7, and a valley depth (VD) defined by the following equation is greater than or equal to about 0.4: (Absfirst−Absvalley)/Absfirst=VD wherein, Absfirst is an absorption value at the first absorption peak wavelength and Absvalley is an absorption value at a lowest point of the valley adjacent to the first absorption peak.