Improving electron injection and microcavity effect for constructing highly efficient inverted top-emitting organic light-emitting diode

We demonstrated a highly efficient inverted top-emitting organic light-emitting diode (ITOLED) by using Ag/Al bilayer reflective cathode and CsOx electron-injection layer. With tris(8-hydroquinoline) aluminum as electron-transport and emitting layer, the maximum luminous efficiency and power efficiency of ITOLED with CsOx electron-injection layer reached 8.3 cd/A and 4.3 lm/W, respectively, which have been enhanced by ∼40% and ∼80%, respectively, in comparison with the counterpart using LiF as electron-injection layer (5.9 cd/A and 2.3 lm/W). The improved performance is resulted from the enhanced electron-injection ability of CsOx. The superior electron-injection ability of CsOx was further verified by ‘Electron-only’ device using current density versus voltage characteristics and impedance spectroscopy measurements. Our results indicated that CsOx electron-injection layer combined with Ag/Al bilayer reflective cathode provides a convenient approach for constructing highly efficient ITOLED.

► Highly efficient inverted top-emitting OLED is demonstrated.
► CsOx enhances electron injection and improves device performance.
► Impedance spectroscopy is used to characterize electron injection property.