Universal polymeric hosts adopting cardo-type backbone prepared by palladium-free catalyst with precisely controlled triplet energy levels and their application for highly efficient solution-processed phosphorescent organic light-emitting devices

Abstract

A series of polymeric hosts with cardo-type backbone have been successfully developed with cheap palladium-free catalyst through controlling the special orientation of different monomers. By engineering the configuration of polymer backbones with different number and kind of the functional groups attached to the monomers, the triplet energy-levels (ETs) of these new polymeric hosts can be precisely controlled from 1.92 to 2.83 eV. Importantly, the functional groups on the monomers can afford improved and balanced charge carrier injection/transporting ability to these polymeric hosts. In addition, these polymeric hosts can show good thermal property with decomposition temperatures (Td) higher 410 °C and glass transition temperatures (Tg) higher than 170 °C. Benefitting from all these advanced properties, solution-processed phosphorescent organic light-emitting devices (PhOLEDs) based on these polymeric hosts can show impressive electroluminescence (EL) performances. The optimized blue device B2 possesses a maximum luminance efficiency (ηL) of 25.5 cd A−1, corresponding to a power efficiency (ηP) of 19.9 lm W−1 and an external quantum efficiency (ηext) of 11.3%. The maximum ηL, ηP and ηext for the optimized green device G2 are 66.9 cd A−1, 62.8 lm W−1 and 19.5%, respectively, while EL efficiencies of the optimized red device R2 can reach 11.0 cd A−1, 9.4 lm W−1 and 15.5%. All of the promising EL data achieved by these polymeric hosts show their great potential application in developing high performance polymer-based OLEDs.