The series of osmium(ii) complexes [Os(bpy)3−n(btz)n][PF6]2(bpy = 2,2′-bipyridyl, btz = 1,1′-dibenzyl-4,4′-bi-1,2,3-triazolyl,1n= 0,2n= 1,3n= 2,4n= 3), have been prepared, characterised and used as phosphors within light-emitting electrochemical cells.