Synthesis And Application Of Phosphorescence Host Materials Based On 9,10-dihydroacridine

Up to now, the red and green phosphorescent organic light-emitting diodes(PHOLEDs) have been able to meet the requirements of industrialization. However,high efficiency and long lifetime blue PHOLEDs are still not satisfactory, which restricted the application of OLEDs in the full-color display and white lighting fields.The reasons why high performance blue PHOLEDs are hard to obtain are exhibited as following:(1) high efficiency and long lifetime blue phosphors are still quite limited now, and conventional blue phosphors are lack of long-term stability, which results in blue PHOLEDs having short lifetimes in practical application and the emission spectra changing with the driving voltage.(2) In order to complement the blue phosphors, the host materials usually need to have large energy gaps, which will increases the difficulties of molecule design and synthesis. In addition, these kinds of host materials often have deeper highest occupied molecular orbital(HOMO) energy levels as well as shallower lowest unoccupied molecular orbital(LUMO) energy levels,which will increases the injection barriers of electrons and holes. Meanwhile the device needs much higher driving voltage, which will further limit the application of blue PHOLEDs. Therefore, it is of great theoretical value and practical significance to improve the performance of blue PHOLEDs. In recent years, high external quantum efficiency blue PHOLEDs have been achieved based on new device structures,phosphor emitters or host materials. In this regard, most of the host materials in PHOLEDs rely on the aromatic amine derivatives, such as diphenylamine and carbazole.Both diphenylamine and carbazole blocks are widely studied but another aromatic amine derivative, named 9,10-dihydroacridine, is less reported. From the view of reactive positions, 9,10-dihydroacridine has a lot of common properties withdiphenylamine and carbazole, for instance, all of them can be further modified on the N atom and the benzene ring. In consideration of 9,10-dihydroacridine additional position of the sp3 bridgehead carbon atom, it could provide more options for the further modification. Predictably, 9,10-dihydroacridine block in the building novel and high efficient host materials has a broad developing prospect. Consequently, in this work, we mainly base on 9,10-dihydroacridine block to do some research as follows to provide more possibilities for the future application.1. Based on the 10-position N atom of 9,10-dihydroacridine, we designed and synthesized two novel host materials FPhAc and TPhAc, and their various properties were fully characterized. The experiment results showed that good thermal stability,suitable HOMO/LUMO level and high triplet energy made FPhAc and TPhAc achieve relatively high device performance.2. Based on the C-9 sp3 bridged carbon atom of 9,10-dihydroacridine, we synthesized a new type spiro-system. In order to study the influence of traditional9,9’-spirobifluorene(SF) spiro-system and SAF spiro-system, two new host materials3 SFCz Ph and 3SAFCzPh were designed and synthesized. The experiment results showed that SAF not only influenced the charge transport ability, but also spiroconjugation, HOMO/LUMO distributions and other relative photophysical properties. As a result, high efficiency blue device was achieved by using 3SAFCzPh as host.3. Based on the C-3 position of 9,10-dihydroacridine backbone, we prepared a new compound DPhAc Py as host material. Based on good thermal stability, suitable HOMO/LUMO level and high triplet energy the blue and red devices showed relatively high performance.