Provided are compounds comprising a Si or Ge atom to which three monocyclic or fused polycyclic ring systems comprised of one or more 5-membered or 6-membered rings as well as one selected from the group consisting of B, BR, Al, Ga, N, P, As, Sb, Bi, P═X′, As═X′, Sb═X′, and Bi═X′ are attached. Also provided are formulations comprising these compounds. Further provided are organic light emitting diodes (OLEDs) and related consumer products that utilize these compounds.