| Top-emitting organic light-emitting diodes (TEOLED) have attracted extensive attention for the high-brightness and flat-panel display. However, the efficiency roll-off at high-brightness is the issue that need to be resolved for further practical applications using TEOLED devices. Herein, a serials of high-efficiency tandem TEOLED introducing a fullerene/zinc-phthalocyanine organic semiconductor heterojunction as charge generation layer are demonstrated. With unique photovoltaic property, the charge generation layer can absorb part of the photons emitted by the emission layer (Ir(ppy)3) and generate electrons and holes. By optimizing the charge generation layer thickness, the as-fabricated TEOLED device shows a high luminance of 156000 cd/cm2 and pure green electroluminescence with a maximum current efficiency of 86 cd/A. Importantly, relying on the energy between the photovoltaic effect and the microcavity effect, only 1.5% of the efficiency roll-off is obtained at 1000-10000 cd/cm2. We believe the introduction of fullerene/zinc-phthalocyanine as charge generating layer here provide a very promising alternative way for developing high-efficiency tandem TEOLED devices. |
