Process optimization and investigation of exciton movement in high efficiency exciplex-based green organic light-emitting diodes

Abstract

In this paper, we optimized exciplex-based organic light-emitting diodes (OLEDs) using single-carrier devices to improve carrier balance and identify the location of the carrier recombination region, which can enhance OLED performance. Exciplex-based OLEDs with a Indium Tin Oxide structure / 4,4′,4′'-Tris[(3-methylphenyl)phenylamino]triphenylamine (m-MTDATA) (x nm) / m-MTDATA: Bathophenanthroline (Bphen) (40 nm, 1:1) / Bphen (30 nm) / LiF (1 nm) / Al (80 nm) were fabricated with various thicknesses of the hole transport layers. We controlled the m-MTDATA:Bphen emission layer evaporation rate at 0.8 Å/s, which was the best choice for indoor application in our previous study. The maximum OLED current efficiency of 71.5 cd/A at a luminous intensity of 443 cd/m2 and emission wavelength of 552 nm was obtained, which is suitable for indoor power-saving OLED applications. Furthermore, this study used a lower-energy red-doping layer to observe how excitons move in exciplex-based OLEDs when the external electric field increases.