Plurality of host materials and organic electroluminescent device comprising the same

A plurality of host materials comprising at least one first host compound and at least one second host compound, wherein the first host compound is represented by the following formula 1, and the second host compound is represented by the following formula 2, and wherein at least one of the first host compound and the second host compound comprises deuterium:

• in formula 1,
• X1 to X3, each independently, represent —N═ or —C(R)═, in which R represents hydrogen or deuterium;
• provided that at least two of X1 to X3 represent —N═;
• and
• Ar21 to Ar23, each independently, represent a (C6-C30)aryl unsubstituted or substituted with at least one of deuterium and a (C6-C30)aryl(s);
• provided that when Ar21 to Ar23, each independently, comprise fluorene, Ar21 to Ar23, each independently, are represented by the following formula 1-A, and at least one of Ar21 to Ar23 is represented by the following formula 1-A;
• in formula 1-A,
• L21 represents a single bond, or a (C6-C30)arylene unsubstituted or substituted with at least one of deuterium and a (C6-C30)aryl(s);
• R11 and R12, each independently, represent a (C1-C30)alkyl unsubstituted or substituted with at least one of deuterium and a (C6-C30)aryl(s), or a (C6-C30)aryl unsubstuted or substituted with at least one of deuterium and a (C6-C30)aryl(s);
• and
• R21 to R28, each independently, represent hydrogen, deuterium, or a (C6-C30)aryl unsubstituted or substituted with at least one of deuterium and a (C6-C30)aryl(s), or may be linked to an adjacent substituent(s) to form a ring(s);
• in formula 2,
• A1 and A2, each independently, represent a substituted or unsubstituted (C6-C30)aryl, a substituted or unsubstituted dibenzofuranyl, a substituted or unsubstituted dibenzothiophenyl, or a substituted or unsubstituted carbazolyl;
• any one of X15 to X18 and any one of X19 to X22 are linked to each other to form a single bond;
• and
• X11 to X14, X23 to X26, and X15 to X22 not forming a single bond, each independently, represent hydrogen, deuterium, a substituted or unsubstituted (C6-C30)aryl, or a substituted or unsubstituted (3- to 30-membered)heteroaryl;
• or may be linked to an adjacent substituent(s) to form a ring(s).