A light emitting device comprising an anode, a cathode, a light emissive layer located between the anode and the cathode, said light emissive layer comprising a compound for emitting light, said compound comprising a metal complex and X, said metal complex containing a metal (M) and a phosphorous atom that is coordinated directly to M, and an aryl or heteroaryl group Ars that is directly bonded to the phosphorous atom, where Ars is substituted with X, and characterized in the X comprises an aryl or heteroaryl group.