Conclusions and Outlook

Abstract

In conclusion, this thesis outlines the invention of a series of novel, bipolar partially conjugated polyarylether hosts containing triphenylphosphine oxide/carbazole as electron-/hole-transport units. The high E _Ts of these hosts (up to 2.96 eV) have broken through the limitations of traditional conjugated polymer hosts. The significance of this breakthrough is that the long-standing bottleneck problem of triplet energy back transfer from dopants to hosts in blue PhPLEDs is overcome, and thus high efficiency of 23.3 cd/A can be achieved for these devices. As a consequence of this achievement, the design of high-efficiency blue electrophosphorescent polymers and all-phosphorescent white ones, which was unachievable before, becomes available in this work, with state-of-the-art efficiencies of 19.4 and 18.4 cd/A achieved for blue and white PhPs, respectively. In addition, the author also describes a spiro-linked hyperbranched architecture for PhPs to inhibit undesired triplet energy back transfer without high triplet energy hosts, which provides us a new insight into the nature of the triplet energy transfer process.