Inverted Bottom-Emission Organic Light Emitting Diode Using Two n-Doped Layers for the Enhanced Performance

We fabricate an inverted bottom-emission organic light emitting diode (IBOLED) employing two n-doped layers, i.e., 5 nm lithium carbonate doped PTCDA (1:2 Li₂CO₃:PTCDA) with 5 nm Li₂CO₃ doped BCP (1:4 Li₂CO₃:BCP) on top, where PTCDA and BCP stand for 3, 4, 9, 10 perylenetetracarboxylic dianhydride and bathcuporine, respectively. Compared to the IBOED using a layer of 10 nm 1:4 Li₂CO₃:BCP, the one utilizing the two-layer combination of 5 nm 1:2 Li₂CO₃:PTCDA and 5 nm 1:4 Li₂CO₃:BCP shows decreasing operation voltage and thereby increasing power efficiency, mainly attributed to the higher electron conductivity of 1:2 Li₂CO₃:PTCDA than that of 1:4 Li₂CO₃:BCP. The mechanism of the electron transport through the interface of 1:2 Li₂CO₃:PTCDA and 1:4 Li₂CO₃:BCP is also discussed. We provide a simply and effective structure to enhance the current conduction for IBOLEDs.