An OLED device comprises an anode, a cathode and therebetween a light emitting layer containing a compound represented by Formula I below: ##STR00001## wherein: each A is independently selected from N and P; each E is independently selected from N, P, and As; each Z is a radical independently selected from ##STR00002## each R is an independently selected substituent; and each R' is independently selected from H and a substituent; provided that two substituent groups can join to form a ring.