Hybrid host materials for highly efficient electrophosphorescence and thermally activated delayed fluorescence independent of the linkage mode

Abstract

Three non-conjugated hybrid host materials, tBu-OXD-o-L-TPA, tBu-OXD-m-L-TPA, and tBu-OXD-p-L-TPA, have been synthesized and characterized for their thermal, electrochemical, fluorescence, phosphorescence, and electroluminescence properties. Due to the non-conjugated spacer, the three hosts have a similar E_T value as high as 2.71 eV, which is sufficiently high for blue phosphorescent and thermally activated delayed fluorescent (TADF) emitters. Different from the hosts with a direct linkage between a donor and an acceptor showing significantly distinct properties depending on linkage modes, the three new hosts demonstrate similar photophysical, electrochemical, and organic light-emitting device performances. Both phosphorescent and TADF devices with high efficiencies have been realized using all the three hosts. These results reveal a new merit of employing a non-conjugated spacer, which enables the synthesized hosts to show properties independent of the linkage mode. This might facilitate choosing materials with an economical synthesis process while not influencing their properties and thus enhance the potential of universal host materials.