Abstract
The dependence on the roll-off property of carrier accumulation at the heterojunction interface between the emission layer (EML) and carrier transport layers was investigated in organic light-emitting diodes (OLEDs). The roll-off property was mitigated in an OLED having an indium tin oxide (ITO, 145 nm, anode)/40 wt%-molybdenum(VI) trioxide (MoO3)-doped 9,10-diphenyl-anthracene (DPA, 30 nm)/DPA (10 nm)/5 wt%-5,6,11,12-tetraphenyl-naphthacene (rubrene)-doped DPA (40 nm)/DPA (20 nm)/14 wt%-cesium (Cs)-doped DPA (20 nm)/aluminum (Al, 100 nm, cathode) structure, although a conventional OLED having an ITO (145 nm, anode)/N,N´-Di-[(1-naphthyl)-N,N´-diphenyl]-1,1´-biphenyl)-4,4´- diamine (α-NPD, 20 nm)/5 wt%-rubrene-doped DPA (42 nm)/tris(8-hydroxyquinoline) aluminum (Alq3, 20 nm)/lithium fluoride (LiF, 0.5 nm)/Al (100 nm, cathode) structure exhibited a typical roll-off property. This difference can be attributed to a decrease in the electron accumulation at the interface between the EML and electron transport layer (ETL), following a reduction in the distinct heterojunction structures at the interface in the OLED.
