An organic light-emitting device (10, 100, 200) comprising: a first electrode (11, 110, 210), a second electrode (19, 190, 290) facing the first electrode (11, 110, 210), and an organic layer disposed between the first electrode (11, 110, 210) and the second electrode (19, 190, 290), 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 (10, 100, 200) 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 (11, 110, 210), a second electrode (19, 190, 290) facing the first electrode (11, 110, 210), and an organic layer disposed between the first electrode (11, 110, 210) and the second electrode (19, 190, 290), 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 (10, 100, 200) 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.