Organic light-emitting device and apparatus including the same

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 and a hole transport region between the first electrode and the emission layer,
• wherein the hole transport region comprises a first hole transport stack, a second hole transport stack between the first hole transport stack and the emission layer, and an electron blocking layer between the second hole transport stack and the emission layer,
• the first hole transport stack comprises a first hole injection layer and a first hole transport layer,
• the second hole transport stack comprises a second hole injection layer and a second hole transport layer,
• the first hole injection layer is between the first electrode and the first hole transport layer,
• the second hole injection layer is between the first hole transport layer and the second hole transport layer,
• the first hole injection layer comprises a first compound,
• the first hole transport layer comprises a second compound,
• the second hole injection layer comprises a third compound,
• the second hole transport layer comprises a fourth compound,
• the electron blocking layer comprises a fifth compound,
• the first compound, the second compound, the third compound, the fourth compound, and the fifth compound all are different from one another, and
• the organic light-emitting device satisfies Equations 1 to 4:
• HOMO(HTM1)≥HOMO(HTM2) Equation 1
• HOMO(HTM3)≥HOMO(HTM4) Equation 2
• HOMO(HTM1)−HOMO(HTM2)≤0.5 eV Equation 3
• HOMO(HTM3)−HOMO(HTM4)≤0.5 eV, Equation 4
• wherein in Equations 1 to 4, the HOMO(HTM1) is a lower energy level from among the HOMO energy level (eV) of the first compound and the HOMO energy level (eV) of the second compound,
• the HOMO(HTM2) is a higher energy level from among the HOMO energy level (eV) of the third compound and the HOMO energy level (eV) of the fourth compound,
• the HOMO(HTM3) is a lower energy level from among the HOMO energy level (eV) of the third compound and the HOMO energy level (eV) of the fourth compound,
• the HOMO(HTM4) is the HOMO energy level (eV) of the fifth compound.