Sodium triphosphate as an efficient electron injection layer in organic light-emitting diodes

A multilayer organic light-emitting diode (OLED) with favorable performance was fabricated via using sodium triphosphate (Na3PO4) material as an efficient electron injection layer. Luminance and efficiency of the devices are notably improved due to a thin Na3PO4 layer inserted between electron transport layer (ETL) and aluminum cathode. The optimal thickness of electron injection layer is confirmed to be 1 nm, and the electroluminescent efficiency of OLED reaches 3.5 cd/A. The role of Na3PO4 was investigated on the enhanced performance of OLED through X-ray photoelectron spectroscopy (XPS). The effect of different positions of Na3PO4 layer inside Alq3 layer on the performance of OLED was systematically studied. By comparing with the devices based on ETL/Na3PO4/Al, ETL/LiF/Al and ETL/NaCl/Al, the electroluminescent efficiency of Na3PO4-based device is the highest. Na3PO4 as electron injection material has a promising potential application in OLED.