A compound having the structure of Formula I, A-L-B-M-D, is disclosed. In the structure of Formula I:A is selected from L is a linker selected from a single bond, an aryl group, a heteroaryl group, and combinations thereof, and may be further substituted;L-B-M has the structure: M is selected from an aryl group, a heteroaryl group, and combinations thereof, and may be further substituted;D has the structure: X is O, S, Se, or CR′R″; X1-X8, Y1-Y12, Z1, Z3-Z8, and Z11-Z18 are each independently N or CR; each R, R′, and R″ are selected from a wide variety of substituents; where adjacent R substituents can form a fused ring; and R′ and R″ can form a ring. Formulations and devices, such as an OLEDs, that include the compound of Formula I are also described.