Strategy for the Realization of Efficient Solution-Processable Phosphorescent Organic Light-Emitting Devices: Design and Synthesis of Bipolar Alkynylplatinum(II) Complexes.

A new class of highly luminescent bipolar alkynylplatinum(II) complexes has been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of solution-processable organic light-emitting devices (OLEDs). Through the incorporation of a delicate balance of electron-donating carbazole moieties and electron-accepting phenylbenzimidazole or oxadiazole moieties into the platinum(II) core, the platinum(II) complexes have been demonstrated to exhibit bipolar charge transport character with high photoluminescence quantum yields of up to 0.75 in thin films. The introduction of meta-linkages into the complexes further helps weaken the donor-acceptor interactions, facilitating better carrier-transporting abilities. More importantly, high-performance solution-processable green-emitting OLEDs with maximum current efficiencies of up to 57.4 cd A and external quantum efficiencies of up to 16.0% have been realized. This is among the best performances for solution-processable phosphorescent OLEDs reported based on platinum(II) complexes as well as bipolar metal complexes.