Spectrally stable deep blue - emitting polyfluorenes containing dibenzothiophene-S,S-dioxide moiety

摘要

Efficient deep blue - emitting poly[9, 9 - bis(2 - ethylhexyl) fluorene] derivatives were synthesized via incorporating 2, 8 - diyl - dibenzothiophene - S, S - dioxide (FSO) moiety into poly- fluorene backbone. The photoluminescence (PL) spectra exhibit excellent thermal stability and PL quantum efficiencies distinctly improved upon thermal annealing at various temperatures. Spectrally stable light-emitting diodes were obtained based on resulting copolymers at various driving voltages and operation times. The best device performances were achieved based on copolymer PF-FSO10, which shows a maximum external quantum efficiency of 1.78%, and 2.27% upon thermal annealing in the air, and as high as 3.52% by inserting an additional electron injection layer poly(9,9-bis(6'-(bromilamino)hexyl)) fluorene (PFNBr) between the polymer- cathode interface. The stable electroluminescence spectra with CIE coordinates of (0.16, 0.08) and superior device performances indicates that the copolymers could be a promising candidate of deep blue emitters in full-color displays.