An ionic terfluorene derivative for saturated deep-blue solid state light-emitting electrochemical cells

In this study, we obtained saturated deep-blue electroluminescence (EL) from solid state light-emitting electrochemical cells (LECs) incorporating the ionic terfluorene derivative 1, which we synthesized through covalent tethering of methylimidazolium moieties as pendent groups of terfluorene. Compound 1 exhibited the deep-blue emission, extremely high quantum yield, and reversible redox behavior that are characteristic of terfluorene derivatives. LEC devices incorporating terfluorene 1 exhibited deep-blue EL with CIE coordinates of (0.159, 0.115) and (0.151, 0.122) in the absence and presence, respectively, of the ionic liquid (IL) BMIM center dot PF6. The peak external quantum efficiency and peak power efficiency of 1 in the presence of the IL reached 1.14% and 1.24 lmW(-1), respectively. These CIE coordinates are the most saturated blue emissions ever reported for LECs.