A light-emitting device includes a first electrode, a second electrode facing the first electrode, an interlayer arranged between the first electrode and the second electrode and including an emission layer, and a capping layer, wherein the emission layer includes a first emitter, the first emitter is configured to emit first light having a first emission spectrum, the capping layer is arranged in a path on which the first light is configured to travel, an emission peak wavelength of the first light is in a range of about 610 nm to about 720 nm, the first emitter includes iridium, the capping layer includes an amine-containing compound, a value of ratio of reflective index to full width at half maximum of the first light configured to be extracted to the outside through the capping layer is 2.0 or more, and the RRF value is calculated by Equation 1.