A light-emitting device, comprising: a first electrode comprising a reflection layer and a metal oxide layer on the reflection layer; a second electrode spaced apart from the first electrode; a light-emitting layer between the first electrode and the second electrode; a hole injection layer between the first electrode and the light-emitting layer; and a hole transport layer between the hole injection layer and the light-emitting layer, wherein: a) the metal oxide layer is between the reflection layer and the light-emitting layer, the metal oxide layer comprises molybdenum dioxide and an oxide of a group-V element, and a content of the group-V element to a total amount of the metal oxide layer ranges from 2 at% to 10 at%; or b) the metal oxide layer is between the reflection layer and the light-emitting layer and comprises a first metal oxide and a second metal oxide, the first metal oxide comprises molybdenum, the second metal oxide comprises at least one selected from the group consisting of vanadium, niobium (Nb), tantalum (Ta), titanium (Ti), tungsten, germanium (Ge), tin (Sn), selenium (Se), and zirconium (Zr); and a content of vanadium, niobium (Nb), tantalum (Ta), titanium (Ti), tungsten, germanium (Ge), tin (Sn), selenium (Se), or zirconium (Zr) to a total amount of the metal oxide layer ranges from 2 at% to 10 at%. a first electrode comprising a reflection layer and a metal oxide layer on the reflection layer; a second electrode spaced apart from the first electrode; a light-emitting layer between the first electrode and the second electrode; a hole injection layer between the first electrode and the light-emitting layer; and a hole transport layer between the hole injection layer and the light-emitting layer, wherein: a) the metal oxide layer is between the reflection layer and the light-emitting layer, the metal oxide layer comprises molybdenum dioxide and an oxide of a group-V element, and a content of the group-V element to a total amount of the metal oxide layer ranges from 2 at% to 10 at%; or b) the metal oxide layer is between the reflection layer and the light-emitting layer and comprises a first metal oxide and a second metal oxide, the first metal oxide comprises molybdenum, the second metal oxide comprises at least one selected from the group consisting of vanadium, niobium (Nb), tantalum (Ta), titanium (Ti), tungsten, germanium (Ge), tin (Sn), selenium (Se), and zirconium (Zr); and a content of vanadium, niobium (Nb), tantalum (Ta), titanium (Ti), tungsten, germanium (Ge), tin (Sn), selenium (Se), or zirconium (Zr) to a total amount of the metal oxide layer ranges from 2 at% to 10 at%. a) the metal oxide layer is between the reflection layer and the light-emitting layer, the metal oxide layer comprises molybdenum dioxide and an oxide of a group-V element, and a content of the group-V element to a total amount of the metal oxide layer ranges from 2 at% to 10 at%; or the metal oxide layer comprises molybdenum dioxide and an oxide of a group-V element, and a content of the group-V element to a total amount of the metal oxide layer ranges from 2 at% to 10 at%; or b) the metal oxide layer is between the reflection layer and the light-emitting layer and comprises a first metal oxide and a second metal oxide, the first metal oxide comprises molybdenum, the second metal oxide comprises at least one selected from the group consisting of vanadium, niobium (Nb), tantalum (Ta), titanium (Ti), tungsten, germanium (Ge), tin (Sn), selenium (Se), and zirconium (Zr); and a content of vanadium, niobium (Nb), tantalum (Ta), titanium (Ti), tungsten, germanium (Ge), tin (Sn), selenium (Se), or zirconium (Zr) to a total amount of the metal oxide layer ranges from 2 at% to 10 at%. the second metal oxide comprises at least one selected from the group consisting of vanadium, niobium (Nb), tantalum (Ta), titanium (Ti), tungsten, germanium (Ge), tin (Sn), selenium (Se), and zirconium (Zr); and a content of vanadium, niobium (Nb), tantalum (Ta), titanium (Ti), tungsten, germanium (Ge), tin (Sn), selenium (Se), or zirconium (Zr) to a total amount of the metal oxide layer ranges from 2 at% to 10 at%.