Study On Enhancing Performance Of Tandem Organic Light-Emitting Devices Utilizing Carrier Generation Layer

Tandem organic light-emitting diode (OLED) is fabricated by several individual electroluminescent units via carrier generation layer (CGL) with an entire device driven by a single power source. Tandem OLEDs have shown a large potential application in the solid lighting and flat panel display due to its high luminance, lower current density, high current efficiency and long-life, et al, which are the most effective structures for high performance OLEDs. However, the problem of the low power efficiency caused by the high operational voltage in tandem OLEDs still remains. And under the application of an electric field, Tandem white OLEDs (WOLEDs) can not get a stable white light emission that the intensities of generated electrons and holes will be lopsided with the increase of the voltage in a lot of CGL.Our works are mainly on performance enhancement including the efficiency, color stability of Tandem OLEDs utilizing highly efficiency CGL.Firstly, by employing a novel magnesium chloride (MgCl2) ultra-thin layer as a hole blocking layer, which is inserted into hole transport layer to adjust the balance of holes and electrons in emission layer. The same hole blocking MgCl2layer is also effective in another device using N-BD AVBi as a blue emitter.Secondly, by introduction C6o/NPB:Mo03as CGL for Tandem blue OLEDs, a stack consisting of0.5nm of LiF and1nm of Ca which is located from C6o to adjacent electron transporting layer is used as an electron injection layer. The current efficiency and the maximal power efficiency of tandem device with LiF/Ca/C6o/NPB:Mo03/Mo03-based CGL have been approximately enhanced by250%and126%, respectively.Thirdly, the organic bulk heterojunction C60doped. Rubrene as high quality CGL with a high transparency and superior carrier generating capability for Tandem OLEDs is developed. There is a stable white light emission including468and500nm peaks from blue emitting layer and620nm peak from red emitting layer in Tandem WOLEDs. A high efficiency of about17.4cd/A and CIE coordinates of (0.40,0.35) at100cd/m2and (0.36,0.34) at1000cd/m2have been demonstrated by employing the developed CGL, respectively.In the end, there are conclusions on Tandem OLEDs which is realized by introduction highly efficiency CGLs, and the plan of the further work are put forward.