Highly Efficient Fluorescent/Phosphorescent Hybrid White Organic Light Emitting Devices

White organic light emitting devices(WOLEDs) have important application prospect in the field of solid state lighting, how to improve the device performance and save the device fabrication cost is the key technology to the research. Fluorescent/phosphorescent hybrid white OLED(F/P-WOLED) is acknowledged as the ideal strategy to realize high-efficiency and long-lifetime. In this paper, a series of new fluorescent materials have been designed, synthesized and utilized in monochrome and fluorescent/phosphorescent hybrid white devices. Furthermore, the structure of F/P-WOLED has been optimized to achieve a series of surprising results.1. New fluorescent materials PhPC, NFBC, SQTPA and DQTPA have been synthesized and investigated. Both PhPC and NFBC showed high quantum yield and deep-blue emission with the central peak of 420 nm and 404 nm, whereas SQTPA and DQTPA owned blue emission with emission peak of 486 nm and 496 nm.2. Blue fluorescent OLED, orange phosphorescent OLED and F/P-WOLED have been fabricated by using above materials. Blue fluorescent OLED using PhPC as blue emitter showed maximum efficiency of 1.8 cd/A(3.6%) and the CIE coordinates of(0.15, 0.05). PhPC based F/P-WOLED achieved high efficiency of 35.1 cd/A(17.4%), which is comparable to the best reported results. Orange phosphorescent OLED using NFBC as the host material showed maximum efficiency of 32 cd/A(15.3%), it is noteworthy that the current efficiency-luminance curve presented very little efficiency roll-off and the efficiency maintained at 31.9 cd/A at the luminance of 1000 cd/m2.3. Ultra stable F/P-WOLED using single doped co-host structure has been designed and fabricated. The device solved some critical problems, such as the spectral instability of WOLEDs, the huge efficiency roll-off at high luminance. In this structure, TCTA and TmPyPB were mixed and used as the co-host, NAA was the fluorescent dopant, Ir(2-phq)3 and Ir(ppy)3 were respectively used as orange and green phosphorescent dopants. The EL spectral showed little change when the luminance rised from 1000 to 10000 cd/m2. Simultaneously, the efficiency roll-off of the device is very mild. The obtained maximum efficiency is 27.5 cd/A(12.3%), when the luminance of the device rised to 5000 and 10000 cd/m2, the efficiency could be kept at 26.5 cd/A(11.8%) and 25.0 cd/A(11.0%).4. Highly efficient F/P-WOLED based on an efficient hole-transporting blue emitter has been designed and fabricated. In the device, DPFA was choiced as blue fluorophor for it’s good hole-mobility and high fluorescent quantum efficiency. The white device showed maximum efficiency of 42.5 cd/A(38.2 lm/W, 15.5%), which is among the best of reported F/P-WOLEDs.The results of this paper enriched the species of fluorescent materials and provided more strategies to fabricate highly efficient F/P-WOLED, and also promoted the process of high performance F/P-WOLEDs.