The synthesis and electroluminescent properties of dithienylquinacridone-based copolymers for white light-emitting diodes

The dithienylquinacridone derivative that produces orange emission in fluorene, a representative blue light-emitting material, was added in a small quantity as a dopant to synthesize poly[fluorene-co-DTQuinacridone] (PFTQ) using the Suzuki coupling reaction. The copolymer was synthesized at various mole ratios and was soluble in organic solvents. The luminous efficiency of PFTQ3 was 0.50 cd/A, the power efficiency was 0.24 lm/W, and the maximum brightness was 1450 cd/m2. In addition, the device made from PFTQ3 emitted white light with the CIE coordinates of (0.31, 0.35). After thermal treatment, its luminous efficiency, power efficiency and maximum brightness were 0.71 cd/A, 0.34 lm/W, and 3905 cd/m2, respectively, corresponding to an improvement of about 1.4 times of the sample prior to thermal treatment.

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► We synthesized the dithienylquinacridone derivative as an orange dopant.
► The synthesized PFTQ polymer series showed good solubility and thermal stability.
► Charge trapping was more effective in DTquinacridone compared to quinacridone.
► Polymers of PFTQ3, PFoxdTQ3 and PFoxdCzTQ3 showed white color emission.