Organic light-emitting device

An organic light-emitting device comprising:

• a first electrode;
• a second electrode facing the first electrode;
• and
• an organic layer between the first electrode and the second electrode, the organic layer comprising an emission layer,
• wherein the organic layer comprises a first compound, a second compound, a third compound, and a fourth compound, and
• the first compound to the fourth compound satisfy Equations 1 to 8:
• E1,LUMO≥E2,LUMO+0.15 electron volts(eV) Equation 1
• E1,HOMO≥E2,HOMO+0.15 eV Equation 2
• E1,T1≥E4,T1 Equation 3
• E2,T1≥E4,T1 Equation 4
• E3,T1≥E4,T1 Equation 5
• E3,LUMO≥E2,LUMO+0.1 eV Equation 6
• −5.6 eV≥E3,HOMO Equation 7
• Egap1≥Egap3, Equation 8
• wherein, in Equations 1 to 8,
• E1,LUMO indicates a lowest unoccupied molecular orbital (LUMO) energy level of the first compound,
• E2,LUMO indicates a LUMO energy level of the second compound,
• E3,LUMO indicates a LUMO energy level of the third compound,
• E1,HOMO indicates a highest occupied molecular orbital (HOMO) energy level of the first compound,
• E2,HOMO indicates a HOMO energy level of the second compound,
• E3,HOMO indicates a HOMO energy level of the third compound,
• E1,T1 indicates a lowest excited triplet energy level of the first compound,
• E2,T1 indicates a lowest excited triplet energy level of the second compound,
• E3,T1 indicates a lowest excited triplet energy level of the third compound,
• E4,T1 indicates a lowest excited triplet energy level of the fourth compound,
• Egap1 indicates a gap between the LUMO energy level of the first compound and the HOMO energy level of the first compound, and
• Egap3 indicates a gap between the LUMO energy level of the third compound and the HOMO energy level of the third compound.