White polymer light-emitting diode materials with efficient electron injection backbone containing polyfluorene, oxadiazole and quinoxaline derivatives

Copolymer including dithienylquinoxaline (TQ) (<0.1 mol%) as a dopant and oxadiazole derivative as a side chain has been synthesized on a Polyfluorene (PF) backbone based on the Suzuki coupling reaction. The UV–vis spectra of polymers showed similar behaviors in the solution and on the film. However, PL spectra were similar to that of PF in solution, but the peak around 524 nm increased as the amounts of TQ were increased in the casting film. With increase in TQ, effective Forster energy transfer (from PF and PFOxd15 to TQ) was observed. According to CV measurement, HOMO and LUMO levels declined as the amount of oxadiazole derivative increased. In case of PFOxd15TQ10, the luminous efficiency and power efficiency were 1.23 cd/A and 0.64 lm/W, respectively with a maximum brightness of 6940 cd/m2. CIE coordinates were close to pure white (0.33, 0.39).