To boost the UC efficiency further, the emissive dopant DBP was introduced into the rubrene layer by means of the co-deposition technique. The peak top shifted from 565 nm in the undoped rubrene/ITIC-Cl film to 606 nm in the 0.5% DBP-doped bilayer film owing to the energy transfer from the rubrene to the DBP. The calculated IQE of the 0.5% DBP-doped bilayer film in the saturation region was 2.53%. This increase in the IQE by DBP doping was a result of the absolute PL quantum yield of the emitter layer increasing from 39.7% in the pristine rubrene film to 71.2% in the 0.5% DBP-doped film. In particular, the EQE of the UC in the rubrene + 0.5% DBP/ITIC-Cl film was very high, namely 2.30% at 152 mW/cm 2 , which was more than 100 times more efficient under a smaller excitation intensity than that of recently reported solid-state UC systems. This was because of the large absorbance of the NFA layer as well as the high IQE in the novel system.