High-efficiency white-light emission from a single copolymer: Fluorescent blue, green, and red chromophores on a conjugated polymer backbone

High-efficiency white-light emission is obtained from a single copolymer with three emissive units, poly(9,9-dioctylfluorene) (PFO), benzothiadiazole (BT), and 4,7-bis(2-thienyl)-2,1,3-benzothia-diazole (DBT), in a conjugated polymer backbone. The electroluminescent device fabricated from the PFO-R010-G018 copolymer exhibited the best performance, with an external quantum efficiency of 3.84%, luminance efficiency of 6.20 cd A-1, and Commission Internationale de L'Éclairage (CIE) coordinates of (0.35,0.34) after annealing for 10 mm at a temperature of 150°C. The color coordinates of the resulting white-light emission remained extremely stable over a wide range of driving voltages. Incomplete energy transfer from the blue polyfluorene backbone to the green and red units, and restricted energy transfer from the green to red chromophores due to sufficient isolation of these units along the conjugated backbones, led to three distinguishable primary emissions.