Effect of periodically modified n-type electron transport layers on the optoelectrical performance of organic light-emitting diodes

We have investigated the characteristics of Cs2CO3 doped 4, 7-Diphenyl-1, 10-phenanthroline (Bphen) film and the effects of its thickness on the optoelectrical performance of microcavity organic light-emitting diodes. By doping Cs2CO3 into Bphen, higher current density and lower turn-on voltage could be achieved with barely changing the external quantum efficiency. Three types of resonators were fabricated by varying the thickness of every a quarter of electron transport layers, i.e. 152.5 nm (0.25 λ), 305 nm (0.5 λ), and 610 nm (1.0 λ). The 0.25λ-based microcavity organic light-emitting diode was found to exhibit the lowest waveguided loss coefficient of 118.0 cm−1, while the relative emission intensity of edge mode to surface reached about 2118.8 times, indicating that this mode underwent a very low attenuation during its propagation.