Studies On Red Organic Light Emitting Devices Based On Europium Complex And Yellow Organic Light Emitting Devices Based On Iridium Complex

Organic light-emitting diodes (OLEDs) have been attracting more and more attention as an important flat panel display technology for the merits of light weight, low cost, broad visual angle, fast response speed, active emitting, high brightness, high efficiency, capability for rich color emitting, etc. In addition, white OLEDs are also regarded as a potential candidate in solid-lighting field. The research works in this field gained rapid development especially after 1987 when C. W. Tang for the first time reported the high brightness OLED at low operating voltage. In recent ten years or so, OLED has become a project on the cutting-edge of scientific research that relates to many intercrossed branches of science and advanced technology. Great strides have been made towards the development and improvement of small molecular OLEDs for display applications. Intense research in both academia and industry over the past 4-5 years has yielded OLEDs with remarkable full color, device efficiencies and operational stability. In this thesis, the author adopted a new type of europium complex and designed devices with good color purity and high efficiency. Besides, the author also did some research on yellow organic light-emitting devices based on a high efficiency phosphorescent material (F-BT)2Ir(acac) as yellow dopant.We doped a new type of europium complex into bipolar transporting material (CBP), and inserted a Bphen layer between the EML and the ETL to comfine the holes into the EML, weakening the light emission from Alq3. The structure of devices we designed is ITO/m-MTDATA(30nm)/NPB(20nm) /CBP: Eu complex (2%, 30nm) /Bphen(X nm) /Alq3(30-Xnm)/LiF(0.8nm)/Al, with the thicknesses for Bphen being 0, 5, 10, 15nm, respectively. The color purity of device is improved with the thickness of Bphen increasing. When the thickness reached 10 or 15nm, the Commission International De L'Eclairage (CIE) coordinates for the devices can reach (0.64, 0.33), which is proved to be very pure red light. The device with 10nm Bphen had maximum luminance of 465.2cd/m2 under 16V forward bias, and maximum current efficiency of 3.0cd/A under 6V forward bias. Furthermore, we fabricated devices with structure of ITO/m-MTDATA(30nm)/NPB(20nm)/CBP: Eu complex(2%, 20nm) /Bphen: Eu complex(2%,Xnm)/ Bphen(20-Xnm)/Alq3 (20nm)/ LiF/Al, in order to use the part of excitons which would have diffused into Bphen and been lost due to non-radiative process. We find out that higher efficiency can be achieved by increasing X, and the device with 10nm Bphen: Eu complex layer had the highest efficiency. This device had maximum luminance of 488cd/m2 under 16V and maximum current efficiency of 4.0cd/A under 5V.Besides, we also made some research on yellow light-emitting devices. In our experiment, we adopted a high efficiency phosphorescent material (F-BT)2Ir(acac), doped into a bipolar transporting material CBP. In order to harvest high efficiency, we fabricated devices with the structure of ITO/NPB(40nm)/Ir(ppz)3(Xnm)/CBP:(F-BT)2Ir(acac)(8%,30nm) /Bphen (30nm)/LiF/Al. Due to the exciton-blocking function of Ir(ppz)3, excitons were confined effectively into the EML. The device with 10nm had the highest efficiency of 52.3cd/A at 6V and the maximum luminance of 28577cd/m2 at 14V.