Stable Blue Emission from a Polyfluorene/Layered‐Compound Guest/Host Nanocomposite

Abstract

In this study a blue‐light‐emitting conjugated polymer, poly(9,9‐dioctylfluorene), is confined to the interlayer space of inorganic, layered metal dichalcogenide materials, metallic MoS2, and semiconducting SnS2. The nanocomposites are prepared through Li intercalation into the inorganic compound, exfoliation, and restacking in the presence of the polymer. X‐ray diffraction and optical absorption measurements indicate that a single conjugated polymer monolayer, with an overall extended planar morphology conformation, is isolated between the inorganic sheets, so that polymer aggregation or π–π interchain interactions are significantly reduced. Photoluminescence (PL) measurements show that the appearance of the undesirable green emission observed in pristine polymer films is suppressed by incorporating the polymer into the inorganic matrix. The blue emission of the intercalated polymer is stable for extended periods of time, over two years, under ambient conditions. Furthermore, the green emission is absent in the PL spectra of nanocomposite films heated at 100 °C for 7 h in air with direct excitation of the keto defect. Finally, no green emission was observed in the electroluminescence spectrum of light‐emitting devices fabricated with a polymer‐intercalated SnS2 nanocomposite film. These results support the proposed hypothesis that fluorenone defects alone are insufficient to generate the green emission and that interchain interactions are also required.

Luminescence properties of poly(9,9-dioctylfluorene)/polyvinylcarbazole blends: Role of composition on the emission colour stability and electroluminescence efficiency

“…Other approaches involve PFO chain isolation. In particular, blending of PFO with a photo-and electrically inert polymer (polystyrene) or with an electron-transporting polymer [13] or the PFO intercalation into nanocomposites [14,15], were shown to improve the blue emission stability.…”

Growth of Large-Area and Highly Crystalline MoS2 Thin Layers on Insulating Substrates

“…3,4 Meanwhile, when the dimension of MoS 2 is reduced from a bulk form to a 2-d monolayer sheet, its optical properties change due to the transformation of the band gap from indirect to direct one. [5][6][7][8][9][10][11] Significant efforts have been devoted to prepare MoS 2 thin layers, including scotch tape assisted micromechanical exfoliation, [3][4][5]12 intercalation assisted exfoliation, [13][14][15][16][17][18][19][20] solution exfoliation, 15,16,[21][22][23] physical vapor deposition, 25,26 hydrothermal synthesis, 27 electrochemical synthesis, 28 sulfurization of molybdenum oxides 29,30 and thermolysis of the precursor containing Mo and S atoms. 23 However, MoS 2 tends to form zero-dimensional closed structures (fullerene-like nanoparticles) or one-dimensional nanotube structures during the synthesis.…”

Self-assembled lamellar MoS 2 , SnS 2 and SiO 2 semiconducting polymer nanocomposites

“…The devices based on semiconducting guest/metallic host nanocomposites, polymer-incorporated MoS 2 , show ohmic character with no diode performance and no light output. In contrast, diode performance and electroluminescence are obtained from devices based on polymer-incorporated SnS 2 nanocomposites, with light turn-on at approximately 6 V and luminance of 1 cd m K2 at approximately 9 V. SnS 2 is a semiconductor and maintains its semiconductivity upon polymer incorporation (Aharon et al 2006a). Therefore, the semiconducting polymer-incorporated SnS 2 lamellar nanocomposite is effectively a continuous sequence of molecular semiconductorsemiconductor junctions.…”

“…However, typical peaks in the absorption spectra of incorporated PFO and MEHPPV polymers could not be accurately assigned because: (i) the inhomogeneous scattering of light by the surfactant/silica matrix (approx. 15%), (ii) the strong absorption of the metallic MoS 2 , and (iii) the direct and indirect band gap absorptions of SnS 2 at 2.88 eV (430 nm) and 2.1 eV (590 nm), respectively (Aharon et al 2006a). Nevertheless, the observed similarities between the spectrum of the pristine semiconducting polymer films and those of the incorporated polymer chains indicate that the incorporated polymers retain their p-conjugated structure in the insulating silica, semiconducting SnS 2 and metallic MoS 2 matrices (Kim et al 2006).…”

“…We recently reported the intercalation of the semiconducting polymer poly(9,9 0 -dioctylfluorene), PFO, into the galleries of layered MoS 2 and SnS 2 by exfoliating the Li-intercalated MS 2 host in methanol rather than in water (Aharon et al 2006a). Since methanol and xylene, a common solvent for semiconducting polymers, are relatively miscible, it was possible to introduce a xylene-conjugated polymer solution into the methanol MS 2 single-layer suspension, without phase separation.…”