Low-voltage inverted organic light-emitting diodes with double-layer election injection layer based on silicon dioxide

We demonstrated low operating voltage and highly efficient inverted bottom-emission organic light-emitting diodes using SiO2/n-doped 4,7-diphenyl-1,10-phenanthroline (Bphen) as an electron injection layer (EIL) at the interface between the indium tin oxide (ITO) cathode and the organic electron transport layer. The current and power efficiencies exceed 79.2cd A(-1) and 67.8lm W-1 at 3.6V. The ultraviolet photoelectron spectroscopy measurement showed that the insertion of the SiO2 layer reduced the electron injection barrier between ITO and Li doped Bphen. Based on the energy levels and the current-voltage characteristics of electron-dominated devices, we demonstrate that the interface between ITO and the n-doped electron transporting layer (ETL) is important for efficient electron injection into ETL.