High-efficiency and reduced efficiency roll-off of top-emitting organic light-emitting diodes

Abstract:

Top-emitting organic light-emitting diodes (TEOLEDs) have attracted extensive attention for their high brightness and flat-panel display. However, the efficiency roll-off at high brightness is the issue that needs to be resolved for further practical applications using TEOLED devices. Herein, a serial of high-efficiency tandem TEOLED introducing a fullerene/zinc-phthalocyanine organic semiconductor heterojunction as a charge generation layer is demonstrated. With unique photovoltaic properties, 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 thickness of the charge generation layer, the pure green electroluminescent TEOLED device manufactured has a high brightness of 156 000 cd/cm2 and a maximum current efficiency of 86 cd/A. Importantly, relying on the energy between the photovoltaic and the microcavity effects, only 1.5% of the efficiency roll-off is obtained at 1 000—10 000 cd/cm2. Introducing fullerene/zinc-phthalocyanine as the charge-generating layer provides a promising alternative for developing high-efficiency tandem TEOLED devices.