An organometallic compound represented by Formula 1, wherein the organometallic compound has a horizontal orientation ratio of a transition dipole moment in a range of about 85 percent to about 100 percent: M(L1)n  Formula 1 wherein, in Formula 1, M is selected from a first-row transition metal of the Periodic Table of Elements, a second-row transition metal of the Periodic Table of Elements, and a third-row transition metal of the Periodic Table of Elements, n is 2 or 3, L1 is a bidentate organic ligand bound to M, wherein L1 does not comprise a fluoro group (—F), and wherein L1 groups in the number of n are identical to each other.