Influence Of Interfacial Concave-convex Structure On Performance Of Organic Light-emitting Diodes

Owing to the different mobility between electron and hole, quenching appeared easily in prime monolayer organic light-emitting diode, which affects directly the luminous efficiency and lifetime of the device. In recent years, many scholars have been committed to technique improvement and design for innovation structure. In this paper, we made a series of devices with concave-convex interiace,or wnicn the advantage is simple ana cneap. it is a kind of effective method for improving device efficiency.Firstly, the effect of interfacial concave-convex structure on electroplex of Zn(4-TfmBTZ)2/NPB interface was studied. We made several devices, of which the structures are ITO/NPB/Zn(4-TfinBTZ)2/BCP/Alq3/LiF/Al. It was found that interfacial concave-convex structure could increase relative emitting intensity of interfacial electroplex and reduce relative emitting intensity of excitons. The interfacial contact's area and NPB thickness are two contrary impact factors of interfacial electroplex formation, so we could increase luminous efficiency of interfacial electroplex by increasing the contact's area and reducing NPB thickness. With the voltage rises, relative emitting intensity of interfacial electroplex for interfacial concave-convex devices decrease, and relative emitting intensity of excitons increase. This law is consistent with traditional flat interface device.Secondly, we studied the effect of interfacial concave-convex structure on photoelectric performance of device. The device structure with concave-convex interface is ITO/NPB/Zn(BTZ)2/LiF/Al. The results are as fallows:(1) for devices with concave-convex structure at Zn(BTZ)2/liF/Al interface, proper concave thickness could increase the ability of electronic injection, (2) for devices with concave-convex structure at NPB/Zn(BTZ)2 interface, proper concave thickness could increase current efficiency because of expanding contact's area, (3) with the number of convex increasing, the maximum current efficiency increase. (4) With the convex thickness increasing, the maximum current efficiency reduces.Finally, under the condition of invariable flat thickness, we studied the effect of different concave thickness on photoelectric performance of devices with the structure of ITO/NPB/Alq3/LiF/Al. It was found that for traditional device with flat interface the photoelectric properties are better when the thickness of NPB and Alq3 are 50 and 70nm, respectively. Its maximum current efficiency is 2.05cd/A at 103.6mA/cm. For interfacial concave-convex device with NPB concave of 15nm thickness, the maximum current efficiency is 2.33cd/A at 104.2mA/cm2, its photoelectric property is better than that of the devices with flat interface.