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 including:
• an emission layer,
• a hole transport region between the first electrode and the emission layer, the hole transport region including at least one of a hole transport layer, a hole injection layer, and a buffer layer, and
• an electron transport region between the emission layer and the second electrode, the electron transport region including at least one of a hole blocking layer, an electron transport layer, and an electron injection layer,
• wherein the emission layer includes at least one host (H) and at least one phosphorescent dopant (D), an electron affinity (EA) and an ionization potential (IP) simultaneously satisfying the relationships represented by Equation (1) and Equation (2) below:
• EA(D)−EA(H)≧0.2 eV (1)
• IP(H)−IP(D)≧0.2 eV (2), and
• wherein the hole transport region and the electron transport region each include a layer that is adjacent to the emission layer and that includes a material having a triplet energy (T1) that is greater than that of the phosphorescent dopant,
• wherein the electron transport region includes the electron transport layer, and
• wherein the material having the triplet energy that is greater than that of the phosphorescent dopant of the electron transport region:
• is included in the electron transport layer, and
• includes a carbazole moiety or is Compound ET1, below,