Blue organic light-emitting diode with improved color purity using 5-naphthyl-spiro[fluorene-7,9′-benzofluorene]

Novel spiro-type blue host material, 5-naphthyl-spiro[fluorene-7,9′-benzofluorene] (BH-1SN) and dopant material, 5-diphenyl amine-spiro[fluorene-7,9′-benzofluorene] (BH-1DPA) were successfully synthesized, and a blue OLED was made from them. The structure of the blue device is ITO/DNTPD/α-NPD/BH-1SN:5% dopant/Alq3 or ET4/Al-LiF. Here, α-NPD is used as the hole transport layer, DNTPD as the hole injection layer, BH-1DPA or BD-1 as the blue dopant materials, Alq3 or ET4 as the transporting layer and Al as the cathode. The blue devices doped with 5% BH-1DPA and BD-1 show blue EL emissions at 444 and 448 nm at 7 V, respectively, and a high efficiency of 3.4 cd/A at 5 V for the device was obtained from BH-1SN:5% BD-1/ET4. The CIE coordinates of the blue emission are 0.15, 0.08 at an applied voltage of 7 V for the device obtained from BH-1SN/5% BH-1DPA/Alq3.