A host material is disclosed. The host material, as a compound which is represented by the following formula 1, has a chemical structure in which nitrogen and silicon atoms are chemically and directly bonded to each other. Wherein the “a” is one selected from a material group which includes N, S, O, SO2 and NSiG1G2G3, and the “G1, G2 and G3” each become one of a hydrogen, and aromatic, heterocyclic and aliphatic groups which are or not substituted, respectively.