Design, Synthesis And Properties Of High Efficiency, Long Life Phosphorescent OLED Monolithic And Object Materials

Since the first demonstration in late 80 s, Organic light emitting diodes(OLEDs) have has advanced rapidly in the last thirty years to its current stage. OLEDs have been the topic of intense interest to both scientific and industrial community. OLED devices nowadays have achieved high levels of performance including high efficiencies, color purities and device lifetimes. However, stability of high energy OLED materials is still one of the problems that need to be addressed to achieve a long device lifetime of blue devices. This dissertation follows the mainstream of the emitting layer(EL) in phosphorescent organic light emitting diodes(PHOLED) research, designing and synthesizing different functional organic materials, trying to fabricate some PHOLED devices with high efficacy and long life-time. The materials studied include high triplet energy hosts, stable blue and efficient green phosphorescent emitters.First part is about host materials. Chapter 2 focuses on the spiro structure spiro[acridine-9,9’-fluorene](SAF), which had been proven to be a stable unit with improved carrier transportability. The most direct and convenient derivatization position of fluorene is the C2 position, which is a para position. This para substitution of most functional groups will affect both the single and triplet states in a conjugated system. The C4 position as an ortho linkage has been developed to prepare blue host materials, but the device efficiencies are not very high. We use the SAF as the spiro-backbone and diphenylamine or carbazole to form the C-N meta-linking, and the resulting new host materials SAFDPA and SAFCz show good device performance in blue and white PHOLEDs. The best efficiencies of 19.4%/21.5% of blue/white devices are achieved by SAFCz.The second part is about guest materials, it will be demonstrated in chapter 3 and chapter 4. As we all known, blue PhOLEDs still show inferior quantum efficiencies, color coordinates of emission, and significantly poor lifetimes, which need to be greatly improved for use in practical applications. So, we want do some meaningful works to solve the difficult problem. In chapter 3, we synthesized a new stable blue dopant material, named(DMIP)3Ir. The T50(time to 50% of the initial luminance L0 = 1000cd/m2)) are 446 and 737 h for blue and white PHOLED, respectively. In chapter 4, we synthesized an efficient green dopant, the maximum emission of device is 550 nm with a high full width at half maximum(83 nm) of emission spectra, external quantum efficiency achieved 22.3%. Furthermore, the device performances are optimized at low doping concentration of 3%. This work provides a probability to fabricate PHOLEDs with low phosphors concentrations while keeping optimum device performances, which may greatly reduce the cost of OLED lightings.