Provided is a light-emitting device including a first electrode, a second electrode facing the first electrode, an emission layer between the first electrode and the second electrode, and an electron transport region between the emission layer and the second electrode, wherein the electron transport region includes an electron injection layer including a first material and a second material, the first material and the second material each independently include an alkali metal, an alkaline earth metal, a transition metal, a post-transition metal, a lanthanide metal, or a combination thereof, the second material does not include Mg, the first material and the second material are different from each other, and a surface energy of the second material is greater than a surface energy of the first material.