Synthesis and Optoelectronic Properties of Starlike Polyfluorenes with a Silsesquioxane Core

Abstract

A novel starlike polyfluorene derivative, PFO-SQ, was synthesized by the Ni(0)-catalyzed reaction of octa(2-(4-bromophenyl)ethyl)octasilsesquioxane (OBPE-SQ) and polydioctylfluoroene (PFO). The incorporation of the silsesquioxane core into polyfluorene could significantly reduce the aggregation as well as enhance the thermal stability. The DSC study showed an elimination of the glass transition and crystallization as well as a significant reduction of the melting enthalpy in PFO-SQ. The UV−vis absorption spectra in a different solvent combination or solid-state film showed an intensity reduction of the aggregation peak for PFO-SQ in comparison with that of PFO. The stability of the photoluminescence spectra of PFO-SQ could be up to 150 °C, while that of PFO showed a significant green emission at 530 nm. A single-layer LED device using PFO-SQ showed a turn on voltage of 6.0 V, a brightness of 5430 cd/m2 (at a drive voltage of 8.8 V), and a current density of 0.844 A/cm2. The maximum luminescence intensity and quantum efficiency of PFO-SQ were almost twice as good as those of the PFO electroluminescent device. Hence, the incorporation of the inorganic silsesquioxane core into polyfluorenes could provide a new methodology for preparing organic light-emitting diodes with improved thermal and optoelectronic characteristics.

Polyfluorenes

“…Introducing polyhedral oligomeric silsesquinoxane (POSS) into PFs can significantly reduce the formation of aggregation or keto defect in the PFs [79,80]. As in the POSS-tethered PF P18 (Scheme 9.13), they have well-defined architectures [81].…”

Synthesis and characterization of poly(fluorinated acrylate)/silica hybrid nanocomposites

“…[1][2][3][4][5] Actually, the combination of inorganic and organic components at the nanosize level in a single material has made accessible an immense new area of materials science, because this combination can dramatically improve material properties in engineering plastics, enhanced rubber, coatings and adhesives.…”

Excimer and electromer suppression of tetraphenylsilane‐based blue‐light‐emitting polymers

“…[7][8][9][10][11][12] The incorporation of polyhedral oligomeric silsesquioxane onto the polymer backbone could also improve PF's thermal stability and EL performance. [13][14][15][16] Significantly enhanced EL characteristics have been attributed to reduced aggregation and excimer formation or lower keto defects. [13][14][15][16] Recently, a series of tetraphenylsilane-based hyperbranched blue-light-emitting alkylfluorene copolymers were developed by He and coworkers.…”

“…[13][14][15][16] Significantly enhanced EL characteristics have been attributed to reduced aggregation and excimer formation or lower keto defects. [13][14][15][16] Recently, a series of tetraphenylsilane-based hyperbranched blue-light-emitting alkylfluorene copolymers were developed by He and coworkers. [17][18][19] No excimer formation in longer wavelength like emissions at 500-600 nm was observed for such hyperbranched PFs.…”