Spiro[fluorene-7,9′-benzofluorene] host and dopant materials for blue light-emitting electroluminescence device

Abstract

New spiro-type 5-biphenyl-spiro[fluorene-7,9′-benzofluorene] (BH-1BP) and 5-diphenyl amine-spiro[fluorene-7,9′-benzofluorene] (BH-1DPA) were synthesized for use as blue organic light-emitting host and dopant materials, respectively. Their optical properties, including their UV absorption, photoluminescence and energy levels, were measured and blue OLEDs were made from them. The structure of the blue device is ITO/DNTPD/α-NPD/BH-1BP:5% dopant/Alq 3 or ET4/Al–LiF. Here, α-NPD is used as the hole transport layer, DNTPD as the hole injection layer, BH-1DPA or diphenyl-[4-(2-[1,1;4,1]terphenyl-4-yl-vinyl)-phenyl]-amine (BD-1) as the blue dopant materials, Alq 3 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 444–448 nm at 7 V. A high efficiency of 3.28 cd/A and the CIE coordinates (0.14, 0.11) at 7 V can be achieved from the devices composed of BH-1BP:5% BD-1/ET4.