Efficient single-layer twistacene-doped polymer white light-emitting diodes

Bright, efficient, and stable white polymer light-emitting diodes based on blue polyfluorene doped by a twistacene, 6, 8, 15, 17-tetraphenyl-1.18, 4.5, 9.10, 13.14-tetrabenzoheptacene (3) (TBH), are demonstrated. In twistacene the terminal pyrene moieties serve two functions: (i) to stabilize the inherently unstable heptacene and (ii) to enable the oligoacene to be a strongly fluorescent molecule. As a result, efficient and very bright white polymer light-emitting diodes are obtained. The maximum luminance of the devices exceeds 20 000 cd/m(2). The maximum luminous efficiency is 3.55 cd/A at 4228 cd/m(2) while the maximum power efficiency is 1.6 lm/W at 310 cd/m(2). The device obtains a stable white balance by a combination of energy transfer from the blue polyfluorene to TBH by 1% TBH doping plus the host emission. The device emission color is not a function of bias current, which is ideal for various applications, from lighting to the backlight for liquid crystal displays. (C) 2004 American Institute of Physics.