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

Abstract

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 $20000\mathrm{cd}∕{\mathrm{m}}^2$ . The maximum luminous efficiency is $3.55\mathrm{cd}∕\mathrm{A}$ at $4228\mathrm{cd}∕{\mathrm{m}}^2$ while the maximum power efficiency is $1.6\mathrm{lm}∕\mathrm{W}$ at $\mathrm{310}\mathrm{cd}∕{\mathrm{m}}^2$ . 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.