An organic light-emitting device comprising: a first electrode , a second electrode facing the first electrode , and an organic layer disposed between the first electrode and the second electrode , wherein the organic layer comprises an emission layer , the emission layer comprises an electron transport host, a hole transport host, and a dopant, the dopant comprises an organometallic compound, and the organometallic compound does not comprise iridium, the organic light-emitting device satisfies a condition of LUMO(dopant) - LUMO(host-E) ≥ 0.15 eV and LUMO(host-E) - HOMO(host-H) > T1(dopant), and characterised in that the dopant satisfies a condition of T1(dopant) ≤ Egap(dopant) ≤ T1(dopant) + 0.5 electron volts, wherein LUMO(dopant) indicates a lowest unoccupied molecular orbital (LUMO) energy level (expressed in electron volts) of a dopant in the emission layer , LUMO(host-E) indicates a LUMO energy level (expressed in electron volts) of an electron transport host in the emission layer , HOMO(host-H) indicates a highest occupied molecular orbital (HOMO) energy level (expressed in electron volts) of a hole transport host in the emission layer , T1(dopant) indicates a triplet energy level (expressed in electron volts) of a dopant in the emission layer , LUMO(dopant), LUMO(host-E), and HOMO(host-H) each indicate a negative value measured by differential pulse voltammetry using ferrocene as a reference material, T1(dopant) is a value calculated from a peak wavelength of a phosphorescence spectrum of the dopant measured using a luminescence measuring device, Egap(dopant) is a difference between HOMO(dopant) and LUMO(dopant) of the dopant, and HOMO(dopant) indicates a HOMO energy level of the dopant, which is a negative value measured by differential pulse voltammetry using ferrocene as a reference material; wherein the organic light-emitting device is not the organic light-emitting device of "Device 2c" or "Device 3b" of EP 3 435 438 A2. a first electrode , a second electrode facing the first electrode , and an organic layer disposed between the first electrode and the second electrode , wherein the organic layer comprises an emission layer , the emission layer comprises an electron transport host, a hole transport host, and a dopant, the dopant comprises an organometallic compound, and the organometallic compound does not comprise iridium, the organic light-emitting device satisfies a condition of LUMO(dopant) - LUMO(host-E) ≥ 0.15 eV and LUMO(host-E) - HOMO(host-H) > T1(dopant), and characterised in that the dopant satisfies a condition of T1(dopant) ≤ Egap(dopant) ≤ T1(dopant) + 0.5 electron volts, wherein LUMO(dopant) indicates a lowest unoccupied molecular orbital (LUMO) energy level (expressed in electron volts) of a dopant in the emission layer , LUMO(host-E) indicates a LUMO energy level (expressed in electron volts) of an electron transport host in the emission layer , HOMO(host-H) indicates a highest occupied molecular orbital (HOMO) energy level (expressed in electron volts) of a hole transport host in the emission layer , T1(dopant) indicates a triplet energy level (expressed in electron volts) of a dopant in the emission layer , LUMO(dopant), LUMO(host-E), and HOMO(host-H) each indicate a negative value measured by differential pulse voltammetry using ferrocene as a reference material, T1(dopant) is a value calculated from a peak wavelength of a phosphorescence spectrum of the dopant measured using a luminescence measuring device, Egap(dopant) is a difference between HOMO(dopant) and LUMO(dopant) of the dopant, and HOMO(dopant) indicates a HOMO energy level of the dopant, which is a negative value measured by differential pulse voltammetry using ferrocene as a reference material; wherein the organic light-emitting device is not the organic light-emitting device of "Device 2c" or "Device 3b" of EP 3 435 438 A2. <EOS>