An electroluminescent device having an anode and a cathode, one of which is transparent, and one or more organic layers between said anode and said cathode, at least one of said organic layers comprising an organic electroluminescent material, wherein at least one of said organic layers comprises a polymeric material having repeat units of Formula (1): wherein: Y1 represents, independently if in different repeat units, N, P, S, As and/or Se, preferably N; Ar1 and Ar2 are aromatic groups and Ar3 is present only if Y1 is N, P, or As in which case it too is an aromatic group; wherein Ar1 and Ar2 are the same or different and represent, independently if in different repeat units, a multivalent (preferably bivalent) aromatic group (preferably mononuclear but optionally polynuclear) optionally substituted by at least one optionally substituted C1-40carbyl-derived groups and/or at least one other optional substituent; and Ar3 represents, independently if in different repeat units, a mono or multivalent (preferably bivalent) aromatic group (preferably mononuclear but optionally polynuclear) optionally substituted by at least one optionally substituted C1-40carbyl-derived group and/or at least one other optional substituent, and wherein the average number, m, of said repeat units in the polymer is at least (35).