High-efficiency tandem organic light-emitting diodes

Abstract

Tandem organic light-emitting diodes (OLEDs), with multiple electroluminescent (EL) units connected electrically in series, have been fabricated. Using an optically transparent doped organic “p-n” junction as the connecting unit between adjacent EL units, excellent light out-coupling and carrier-injection properties have been realized. The luminous efficiency is found to scale almost linearly with the number of EL units in the stack, giving values as high as 32 or 136 cd/A for a three-unit tandem OLED using a fluorescent or a phosphorescent emitter, respectively.