Copper hexadecafluorophthalocyanine and copper phthalocyanine as a pure organic connecting unit in blue tandem organic light-emitting devices

A nondoped organic system of copper hexadecafluorophthalocyanine (F16CuPc)∕copper phthalocyanine (CuPc) has been investigated as a connecting unit for deep-blue electrofluorescent tandem organic light-emitting devices (OLEDs) based on 2-methyl-9,10-di(2-naphthyl) anthracene emission. Such devices exhibited a doubling in current efficiency from 0.63to1.47cd∕A at J=100mA∕cm2 as compared to the single-unit device. The pure organic connecting unit showed superior optical transparency (∼100%), resulting in minimal microcavity effect in the devices. Interface dipole and band bending on both sides of the F16CuPc∕CuPc interface suggested the formation of an intrinsic p-n junction, which is a prerequisite of an effective connecting unit leading to a dramatic performance improvement in the tandem OLEDs.