Red electroluminescent polyfluorenes containing highly efficient 2,1,3-benzoselenadiazole- and 2,1,3-naphthothiadiazole-based red dopants in the side chain

By attaching small amounts of highly efficient D-A-D'-type 2,1,3-benzoselenadiazole and 2,1,3-naphthothiadiazole derivatives to the side chain of a polyfluorene host, we developed two series of red polymers, PFR-xBS and PFR-xNT. By tuning the doping concentration, complete energy transfer from the PF host to the red dopant occurs. The EL spectra of these red polymers show predominantly a red emission, attributed to the dopants. Single-layer devices (ITO/PEDOT:PSS/polymer/Ca/Al) of red polymers realized pure red light with a peak at 620 nm, a luminous efficiency of 2.91 cd A(-1) and CIE coordinates of (0.62, 0.36) for PFR-10BS, and a saturated red light with a peak at 632 nm, a luminous efficiency of 3.04 cd A(-1) and CIE coordinates of (0.63, 0.35) for PFR-10NT, respectively. To the best of our knowledge, the device performance of PFR-10NT is among the best single-layer saturated red PLEDs based on fluorescent polymers.