We designed and synthesized a single polymer with TADF characteristics by grafting the TADF emitter, 10-(4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl)-10H-phenoxazine, onto the side chain of the polymer backbone of polycarbazole. Employing these copolymers as emitting layers, an efficient bluish-green polymer LED with a maximum external quantum efficiency of 4.3% was achieved, corresponding to a high exciton utilization efficiency (EUE) of 63.7%.