Universal Display Corporation
ORGANIC ELECTROLUMINESCENT MATERIALS AND DEVICES

Abstract:

A compound comprising a first ligand L.sub.A of Formula I, ##STR00001## is disclosed. In Formula I, ring A is a 5- or 6-membered ring; K is selected from a direct bond and a linking group; two adjacent ones of X.sup.1 to X.sup.4 are CR and are fused to form a structure of Formula II, ##STR00002## each of X.sup.1 to X.sup.12 is CR or N; X is selected from a variety of linking groups; each R, R', R'', and R.sup.A is hydrogen or a substituent; L.sub.A is coordinated to a metal M through the dashed lines in Formula I; and wherein (1) when X is CR'R'', X.sup.5 is CR; and (2) when X is O, S, Se, or NR', at least one of the following is true: (a) the metal M is further coordinated to at least one substituted or unsubstituted acetylacetonate ligand; (b) at least one R comprises an electron withdrawing group; (c) at least two R.sup.A is not hydrogen or deuterium; or (d) at least one R is selected from a specific group of structures.