Improved Energy Transfer through the Formation of the β Phase for Polyfluorenes Containing Phosphorescent Iridium(III) Complexes

Abstract

The formation of a β phase and its influence on the energy transfer efficiency were investigated for a series of polyfluorenes containing different contents of phosphorescent iridium(III) complex under various conditions. The effects of iridium(III) complex content, solution concentration, solvent/nonsolvent ratio, as well as temperature on the β-phase formation in the copolymers were studied through UV–vis absorption, photoluminescence, and excitation spectra. First, it was easier to form a β phase for the copolymers with a low content of iridium(III) complex than those with a high content of iridium(III) complex. Second, an aggregation-induced β-phase formation for the copolymers was significantly displayed in the highly concentrated THF solution or THF/H2O mixtures. In addition, temperature was another factor for β-phase formation. And the β phase could be easily formed at low temperatures for copolymer films. On the basis of the above experimental results, the improved energy transfer from polyfluoren...