Injection and transport of high current density over 1000 A/cm2 in organic light emitting diodes under pulse excitation

Abstract

We succeeded in injecting and transporting a maximum high current density of J = 1163 A/cm2 in organic light-emitting diodes using short-pulse excitation combined with a highly thermally conductive silicon substrate (thermal conductivity: 148Wm-1 K-1) and a small cathode configuration (cathode radius r = 50 μm). A maximum current density almost 20 times higher than that associated with direct current (DC) operation was observed by driving an OLED with a short pulse voltage. With short-pulse excitation, the decrease in external quantum efficiency (ηext) obeyed a typical singlet-singlet exciton annihilation model well, indicating that the generation of Joule heat in OLEDs can be suppressed under pulse operation. © 2005 The Japan Society of Applied Physics.