Research On Simple-structured Organic Light-emitting Devices Based On A New Bipolar Host

Organic light-emtting devices(OLEDs)have attracted a great deal of attention from research institutes and enterprises because of its excellent characteristics and have been used in lighting and display fields as their continuous development.In order to make OLED products meet the needs of the market and accelerate its promotion and civilians,its price will inevitably need to be further reduced.Simplifying the device structure to reduce the complexity of device fabrication plays an important role in reducing the production cost and thus reducing the price of the product.Based on the new bipolar material EBBPC,this article explores its application in simple structure devices.First of all,we study a new synthesized material(EBBPC)and test its photophysical,electrochemical and carrier transport properties.The results show that EBBPC is a bipolar material with a balanced electron and hole mobility,high triplet energy level and high decomposition and glass transition temperatures.On the basis of above results,we fabricate multilayer devices with EBBPC as host,and the blue,green,yellow and red devices based on EBBPC host can realize maximum external quantum efficiency of 16.0,15.6,16.2 and 14.9%,respectively,which shows the effectiveness of the material used as host.At the same time,based on the better electron transport ability of the material,we wonder whether it can be used as an electron transport material(ETM),we fabricate a device with EBBPC as ETM and compared its performance with that of devices with common ETM(Bphen,Tm Py PB,Bm Py Ph B)as electron transport layer,the device with EBBPC as ETM exhibits comparable even better performance than other commonly used ETMs,demonstrating the effectiveness of the material as an ETM.Based on the characterristics of the material that it can be used as host and ETM,simple structure devices based on the material are considered.Then,the effects of different anode modification layers(AML)on the performance of bilayer devices are studied.The bilayer devices without AML,with Mo O3,HAT-CN or PEDOT: PSS as AML are prepared.The performances of the device with PEDOT: PSS are the best,as a result,PEDOT: PSS is chosen as AML for the subsequent devices.After that,bilayered monochromatic devices with the material as host and ETM are prepared based on the characteristics of the material.The device structures are ITO / PEDOT: PSS / EBBPC: Guest(X nm)/ EBBPC(Y nm)/Li F(0.5 nm)/ Ag: Mg(1:15 120 nm).The maximum current efficiency of 22.0,39.0,28.2,and 16.6 cd/A can be achieved for the bilayered blue,green,yellow and red devices,respectively.Finally,the structures of the devices are further simplified based on the bilayer devices.Single-layer monochromatic devices are fabricated and a single-layer white OLED is prepared by doping FIrpic and PO-01 in EBBPC.The device structure is ITO / PEDOT: PSS / EML(Z nm)/ Li F(0.5 nm)/ Ag: Mg(1: 15,mass ratio,120 nm).The maximum current efficiency of 13.1,52.3,26.6 and 7.9 cd/A can be achieved for single-layer blue,green,yellow and red devices,respectively,and the maximum current efficiency of single-layer white device is 10.1 cd / A.