Inverted and large flexible organic light-emitting diodes with low operating voltage

Green phosphorescent inverted organic light-emitting diodes (IOLEDs) with 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN)/aluminium/n-doped 4,7-diphenyl-1,10-phenanthroline (Bphen) used as an electron injection layer (EIL) were demonstrated. The IOLED shows the lowest driving voltage of 4.5 V at 10000 cd m−2 to date. The electron injection effects of different interlayers were further investigated by ultraviolet photoelectron spectroscopy (UPS) and evaluating the electron injection efficiency. For application in large-sized OLEDs, a 120 × 120 mm2 flexible IOLED was successfully fabricated based on this inverted structure.