High-efficiency blue fluorescence organic light-emitting diodes with DPVBi inserted in the doping emmision layer

Abstract

We have fabricated high-efficiency blue fluorescence organic light-emitting diodes(OLEDs) with DPVBi inserted in the doping emmision layer(EML). The OLEDs with a configuration of ITO/2T-NATA/NPB/DPVBi:DSA-ph(inserted with DPVBi thin layer)/Alq3/LiF/Al are fabricated, using 2T-NATA as hole injection layer, NPB as hole transport layer, DPVBi:DSA-ph as emission layer and Alq3 as electron transport layer, respectively. The DPVBi thin layer inserted in EML leads to an increase in device efficiency as a results of an improvement of the balanced carrier injection, which results in an efficient radiative recombination in the emission zone. In addition, DPVBi ability of hole blocking can also be another reason for the improvement on the luminous gain. Hence, high radiative recombination is expected to take place in DPVBi:DSA-ph emission layer. This high efficient recombination results in high brightness and enhanced efficiency in our OLEDs. By optimizing the location and the number of layers of DPVBi thin layer, a maximum current efficiency of 6.77 cd/A is achieved at a current density 6.84 mA/cm2, which is nearly 67.6% more than that of non-inserted device. At a luminance of 1000 cd/m2, the current efficiency of the optimizing device is 6.49 cd/A at 6.7 V with a CIE (0.179, 0.317).