Doping poly(p-phenylene vinylene) with phosphomolybdate through layer-by-layer fabrication for optoelectronic applications

Abstract

Electric field-modulated amplified spontaneous emission in waveguides based on poly [2-methoxy-5-( 2 ′ethylhexyloxy)-1, 4-phenylene vinylene] Appl.Poly͑p-phenylene vinylene͒ mulilayers have been prepared from its cationic precursor via the layer-by-layer deposition. The photoluminescence ͑PL͒ and film thickness of the multilayers have been examined via fluorimetry and atomic force microscopy. The PL of the multilayers has been observed that is consistent with the literature results. When phosphomolybdate PMo 12 is incorporated into the multilayer structure, PL quenching is detected that is proportional to the amount of PMo 12 used. The quenching is interpreted as exciton diffusion through the polymer multilayers, followed by exciton dissociation at the polymer/PMo 12 interface. We show that the modeling used for calculating the PL intensities derived from inorganic semiconductors is also applicable to conjugated polymers. According to the model, an exciton diffusion length is found to be 11.5± 0.4 nm.

Electrochemical Analysis of Conducting Polymer Thin Films

“…We recently prepared thin films of poly( p -phenylene vinylene) via the LbL method [ 31 ]. Thermal polymerization converts pre -PPV chains to highly intractable PPV, thus making the resulting films insoluble.…”

“…Thus, we first determine the number of (PPV│PSS) or (PPV│PAA) bilayers required to provide full coverage on an electrode surface by using atomic force microscopy (AFM). Figure 6 shows the three-dimensional AFM images (5 μm × 5 μm) for one, two and three bilayers of (PPV│PSS) on gold slides prepared by our previously published procedures [ 31 ]. We clearly observe incomplete, partial and complete coverage of the film for one, two and three bilayers, respectively.…”

“…However, when compared to the R f and R ct values of the non-conducting polymer films reported [ 18 ], sample III was about 35 times more conductive. One explanation to this is that PSS can induce p -type doping of PPV chains inducing higher hole transfer rate and eventually more conductivity than PAA [ 31 ]. For a similar film with PAA (sample V ), these values are about 8 times less conductive than sample III .…”

“…The entire cycle was repeated for three consecutive times to yield cyst-coated gold substrate with three bilayers of (PSS) and ( pre -PPV) that can be written as ( pre -PPV│PSS) 3 . After deposition, the prepared films were heated under vacuum at three different conditions: (i) 110 °C for 2 h [ 32 ], (ii) 180 °C for 4 h [ 33 ], and (iii) 210 °C for 12 h [ 29 – 31 ], where the heating conditions were chosen following the literature methods. The (PPV│PSS) 3 samples prepared according to conditions (i), (ii) and (iii) are termed I , II and III respectively while sample IV is a non-heated ( pre -PPV│PSS) 3 film used as a control.…”

“…A water soluble, commercially available PPV precursor ( pre -PPV) has been employed to prepare PPV thin films via the LbL method [ 29 , 30 ]. We have prepared PPV-containing thin films via the LbL method recently [ 31 ]. Thermal polymerization converts pre -PPV chains to highly intractable PPV, thus making the resulting films insoluble.…”