a19 may be an integer of 0 to 12,
a18 may be an integer of 0 to 8,
a17 may be an integer of 0 to 7,
a16 may be an integer of 0 to 6,
a15 may be an integer of 0 to 5,
a14 may be an integer of 0 to 4,
* may be a binding site to Ir in Formula 1, and,
*″ may be a binding site to an adjacent atom in Formula 1.
In one or more embodiments, in Formula 1, the group represented by
may be a group represented by one of Formulae 4-1 to 4-126.