Core-and-Surface-Functionalized Polyphenylene Dendrimers for Solution-Processed, Pure-Blue Light-Emitting Diodes Through Surface-to-Core Energy Transfer

Several pyrene-based polyphenylene dendrimers (PYPPDs) with different peripheral chromophores (PCs) are synthesized and characterized. Deep blue emissions solely from the core are observed for all of them in photoluminescence spectra due to good steric shielding of the core and highly efficient surface-to-core Förster resonant energy transfers (FRETs). Device performances are found in good correlation with the energy gaps between the work function of the electrodes and the frontier molecular orbital (FMO) levels of the PCs. Pure blue emission, luminance as high as 3700 cd m−2 with Commission Internationale de l'Éclairage 1931 (CIExy) = (0.16, 0.21), and a peak current efficiency of 0.52 cd A−1 at CIExy = (0.17, 0.20) are achieved. These dendrimers are among the best dendritic systems so far for fluorescent blue light-emitting materials.