Highly Efficient Pure-White-Light-Emitting Diodes from a Single Polymer: Polyfluorene with Naphthalimide Moieties

• Published in: Advanced functional materials Vol. 16; no. 1; pp. 101 - 106
• Main Authors: Tu, G. L., Mei, C. Y., Zhou, Q. G., Cheng, Y. X., Geng, Y. H., Wang, L. X., Ma, D. G., Jing, X. B., Wang, F. S.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 05.01.2006; WILEY‐VCH Verlag
• Subjects: Light-emitting diodes; Light‐emitting diodes, organic; organic; Polyfluorenes; White-light emitters
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200500028

Light‐emitting diodes exhibiting efficient pure‐white‐light electroluminescence have been successfully developed by using a single polymer: polyfluorene derivatives with 1,8‐naphthalimide chromophores chemically doped onto the polyfluorene backbones. By adjusting the emission wavelength of the 1,8‐naphthalimide components and optimizing the relative content of 1,8‐naphthalimide derivatives in the resulting polymers, white‐light electroluminescence from a single polymer, as opposed to a polymer blend, has been obtained in a device with a configuration of indium tin oxide/poly(3,4‐ethylenedioxythiophene)(50 nm)/polymer(80 nm)/Ca(10 nm)/Al(100 nm). The device exhibits Commission Internationale de l'Eclairage coordinates of (0.32,0.36), a maximum brightness of 11 900 cd m–2, a current efficiency of 3.8 cd A–1, a power efficiency of 2.0 lm W–1, an external quantum efficiency of 1.50 %, and quite stable color coordinates at different driving voltages, even at high luminances of over 5000 cd m–2. A highly efficient pure‐white‐light‐emitting polymer diode, exhibiting Commission Internationale de l'Eclairage (CIE) coordinates of (0.32,0.36), a current efficiency of 3.8 cd A–1, a power efficiency of 2.0 lm W–1, and an external quantum efficiency of 1.50 %, has been developed. The diode is based on a single polymer, polyfluorene, containing 1,8‐naphthalimide derivatives with different emission wavelengths (see Figure).