Endothermic Förster energy transfer from DPVBi to BCzVBi in high efficient blue organic light-emitting diodes

Abstract

In this study, we demonstrated high-efficiency blue organic light-emitting diodes (OLEDs) employing BCzVBi as a blue fluorescent dye doped into blue host material, DPVBi with various concentration. The optimized blue OLED device having high-efficiency was constructed with structure of NPB (500 Å)/DPVBi:BCzVBi-6% (150 Å)/Alq3 (300 Å)/Liq (20 Å)/Al (1000 Å). The maximum luminescence of blue OLED was 13200 cd/m2 at 13.8 V and current density and maximum efficiency were 26.4 mA/cm2 at 1000 cd/m2 and 4.24 cd/A at 3.9 V, respectively. Luminous efficiency shows two times higher than comparing with non-doped BCzVBi blue OLED whereas CIEx,y coordinate was similar with bare DPVBi blue OLED such as (0.16, 0.19). Electroluminescence of BCzVBi-6% doped blue OLED has two major peaks at 445 nm and 470 nm whereas pure DPVBi's blue peak appears at 456 nm and it is happened through endothermic Förster energy transfer by molecule's vibration between LUMO of DPVBi as host material and LUMO of BCzVBi as dopant in device.