Electroluminescence of blends of hole-transporting polymer and hole-blocking polymer

In this paper, the electroluminescence (EL) of the blends of a hole-transporting polymer and a hole-blocking polymer, i.e. poly (N-vinyl-carbazole) (PVK) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), in different weight ratios (k=MPVK:MBCP) is reported. Being different from the photoluminescence (PL) of PVK film and BCP film, the EL spectrum of device ITO/Blend/Alq3(15 nm)/Al (peaks at around 520 nm) where blend in weight ratios of k=1:1, k=2:1 and k=3:1, respectively, is different from that of blends in weight ratios of k=1:2 and k=1:3. By sandwiching another hole-blocking (BCP) layer, it peaks at around 500 nm for ITO/Blend/BCP(20 nm)/Alq3(12 nm)/Al under high electric field for blends in all the above weight ratios and it is suggested that this emission peaking at around 500 nm is from BCP in the blends layer.