Organic light emitting device

An organic light emitting device, comprising:

• an anode;
• a hole transport region on the anode;
• an emission layer on the hole transport region;
• an electron transport region on the emission layer;
• and
• a cathode on the electron transport region,
• wherein the hole transport region includes:
• a first hole transport layer including a first hole transport material represented by the following Formula 1 or a second hole transport material represented by the following Formula 2;
• and
• a second hole transport layer on the first hole transport layer, the second hole transport layer including a third hole transport material represented by the following Formula 3 or a fourth hole transport material represented by the following Formula 4:
• wherein, in Formulae 1, 2, 3 and 4,
• Ar1, Ar2, Ar3, Ar4, Ar5, Ar6, Ar7, and Ar8 are each independently a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 30 ring carbon atoms, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted silyl group, a halogen atom, a deuterium atom, or a hydrogen atom,
• X is a direct linkage or CR14R15,
• R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14 and R15 are each independently a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 30 ring carbon atoms, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted silyl group, a halogen atom, a deuterium atom, or a hydrogen atom,
• L1 and L2 are each independently a direct linkage, a substituted or unsubstituted alkyl group having 6 to 30 carbon atoms, a substituted or unsubstituted arylene group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroarylene group having 5 to 30 ring carbon atoms,
• a, b, and c are each independently an integer of 0 to 4,
• d is an integer of 0 to 3, and
• e is an integer of 0 to 5,
• in the case where e is an integer of 2 to 5, adjacent ones of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14 and R15 are separate or are bound form a ring.