Post-functionalization of poly(3-hexylthiophene) via anodic chlorination

Selective anodic chlorination of a poly(3-hexylthiophene) was successfully carried out by electrochemical polymer reaction. NMR and EDX analyses revealed the selective and sufficient substitution of chlorine atom at the 4-position of the repeating thiophene ring. GPC measurement of the polymer before and after electrolysis indicated that neither decomposition nor propagation of the polymer occurred even after passage of the excess charge. The optical and electrochemical properties of the obtained chlorinated polymer were investigated in detail.     

Spectroscopic and electrical evaluation of poly(3-hexylthiophene) nanotubules made using template wetting nanofabrication

The unique properties of conjugated polymer nanostructures as compared to thin films of the same materials have fueled the investigation of a number of different polymer nanofabrication techniques. Here we examine the optoelectronic properties of poly(3-hexylthiophene)P3HT nanotubules made using one of the simplest of these techniques, template wetting nanofabrication. Comparison is made with results from our previous study in which in poly(2-methoxy-5-(2?-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV) nanotubules prepared in this manner were shown to have dramatically different properties in comparison with thin films due to increased molecular order in the nanostructures. With semicrystalline P3HT, the differences are much more subtle, we believe due to the greater inherent order in this material. In P3HT nanotubules, a small bathochromic shift (～0.05 eV) in the onset of Uv–vis absorption was observed indicating increased long range order and a greater effective conjugation length in the polymer. Polarized FTIR spectroscopy indicated a small degree of preferential alignment of the inter-ring C–C bond with the axis of the nanotubules as the stretching vibration for this bond showed a dichroic ratio of 1.73. The degree of increased conjugation length and chain alignment in P3HT nanotubules indicated by both the UV–vis and polarized FTIR spectra were much smaller than that previously observed for MEH-PPV. No significant improvement in mobility as measured from the current voltage characteristics of simple single carrier devices based on the P3HT nanotubules was observed, in sharp contrast to previously studied MEH-PPV where more than an order of magnitude increase was seen. Unlike in amorphous MEH-PPV, the increase in molecular order suggested by spectral data was insufficient to significantly impact mobility of semicrystalline P3HT when using template wetting nanofabrication for either of the 100 or 200 nm nanotubules examined.     

Thienylmanganese halides for the preparation of regioregular poly(3-hexylthiophene)

For the first time, thienylmanganese halides have been used for the synthesis of regioregular head-to-tail poly(3-hexylthiophene). A variety of conditions were examined, and the polymerization was successfully completed in the presence of Ni(dppe)Cl₂ at ambient temperature affording the title polymer in high yields with excellent regioregularity.     

A comparative study on liquid-state photoelectrochemical cells based on poly(3-hexylthiophene) and a composite film of poly(3-hexylthiophene) and nanocrystalline titanium dioxide

A comparative study was done between liquid-state photoelectrochemical cells (PECs) consisting of photoactive electrodes of poly(3-hexylthiophene), P3HT, and a composite film of nanocrystalline titanium dioxide (nc-TiO₂) and P3HT. The nc-TiO₂/P3HT based device shows better performance with an open-circuit voltage of 0.51 V, a short-circuit current of 0.31 mA/cm², and a fill factor of 0.51 when illuminated with white light intensity of 100 mW/cm². The IPCE% obtained at 550 nm for P3HT based device was 0.18% while for that of the nc-TiO₂/P3HT based device was 4%. In P3HT based devices, P3HT showed its p-type behavior while in nc-TiO₂/P3HT based devices, P3HT acted as a sensitizer to nanocrystalline TiO₂.     

Improved device performance based on crosslinking of poly (3-hexylthiophene)

Diode devices (glass/ITO/polymer/Al) have been fabricated using poly (3-hexylthiophene) (P3HT) crosslinked with two different biaryl crosslinkers. Crosslinking was performed by exposing the thin films with different wt% of crosslinker to UV irradiation and progress of crosslinking was monitored by IR spectroscopy. An increase in hole mobility of two orders of magnitude has been observed after crosslinking.     

Photoelectrochemical response of poly(3-hexylthiophene) and poly(2,3-diethylquinoxaline-5,8-diyl) in aqueous media

The photoelectrochemical properties of poly(3-hexylthiophene) (P3HT) and poly(2,3-diethylquinoxaline-5,8-diyl) (PDEQx) thin films on ITO (indium-tin oxide) electrodes were investigated in aqueous media. Photoirradiation of the P3HT-coated electrode resulted in cathodic photocurrents in the presence of methyl benzoylformate, whereas the PDEQx-coated electrode generated stable anodic photocurrents in the presence of 2-mercaptoethanol. The action spectra indicate that photoexcitations of the polymers cause photoelectrochemical reactions. The films of P3HT and PDEQx exhibit a typical photochemical response of p- and n-type semiconducting materials, respectively.     

Enhanced stability of poly(3-hexylthiophene) transistors with optimally cured poly(methyl methacrylate) dielectric layers

Poly(3-hexylthiophene)-based organic field-effect transistors (OFETs) have been fabricated on poly(methyl methacrylate) (PMMA) gate dielectric layers under different process conditions, resulting in very different device stability in ambient air. The dielectric layers were prepared by spin coating and subsequently curing at various temperatures (120, 150, and 180 °C) or by ultraviolet light (UV) exposure. With respect to the variations of the on/off current ratio and the threshold voltage, dramatically enhanced stability of the OFETs with the PMMA layer cured at 150 °C has been demonstrated when compared to those cured at different temperatures. The devices cured by UV exposure showed even more superior stability, with reliable performance in ambient air for more than 10 days. The differences in the film surface morphology were analyzed and possible mechanisms for the enhanced stability are discussed.     

Effect of wetting solvent on poly(3-hexylthiophene) (P3HT) nanotubles fabricated via template wetting

Template wetting is a simple, solution based nanofabrication method that has been shown effective for a wide range of polymers. Like other solution based polymer processing methods, it is reasonable to expect that the choice of solvent will have a significant impact on the chain orientation in the final solid structure. Here we examine the impact of wetting solvent on the properties of 100 nm diameter poly(3-hexylthiophene) (P3HT) nanotubules made via template wetting. The degree of alignment of the P3HT backbone with the nanotubule axis as observed through dichroism in the FTIR spectrum was observed to depend on the strength of polymer–solvent interaction forces, observed experimentally through thermogravimetric analysis experiments. This solvent effect was not observed in other properties as neither the UV–Vis absorbance nor the hole mobility was observed to depend significantly on the wetting solvent. It is believed that the rigid rod structure and large side chain limited the degree of increase in the effective conjugation length and preventing even the aligned chains from being more tightly packed as would be necessary for an increase in inter-chain π-bond interactions sufficient to impact these performance characteristics of the material.     

Picosecond time-resolved infrared absorption study on photoexcited dynamics of regioregular poly(3-hexylthiophene)

Picosecond time-resolved infrared absorption spectra of the photoexcited states of a spin-coated film of regioregular poly(3-hexylthiophene) (RR-P3HT) have been recorded at 77 K. The time-resolved photoinduced infrared absorptions due to electronic transitions at 2500 cm^?1 and vibrational transitions at 1575 cm^?1 have fast and slow decay components. By comparing the picosecond time-resolved infrared absorption spectrum of long-lived (slow decay component) transient species with the doping-induced infrared difference spectrum of RR-P3HT, the long-lived transient species are assigned to polarons. The short-lived transient species are assigned to singlet excitons and/or polaron pairs.     

Nanostructured layers of a new cross-linkable poly(3-hexylthiophene) in organic photovoltaic cells

We report on the synthesis of a new cross-linkable poly(3-hexylthiophene) copolymer, P3HT-Ox10, consisting on regioregular blocks of 3-hexylthiophene and 10% molar of an oxetane-functionalized thiophene comonomer. This copolymer was used in the fabrication of organic photovoltaics (OPVs) upon combination with 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C₆₁ (PCBM), either as blends or in bilayer structures. Bilayer devices with a nanostructured donor/acceptor interface were fabricated using a patterning process based on the phase separation in P3HT-Ox10:polystyrene blends. Columnar-grain films of cross-linked P3HT-Ox10 with diameters of ca. 140 nm were thereby obtained. These are the lowest dimensions achieved so far by this approach. Despite the modest power conversion efficiencies achieved, we believe that this easily implemented approach is very effective to prepare OPVs with well-defined morphologies.     

Preparation and characterization of graphene nanosheets/poly(3-hexylthiophene) thermoelectric composite materials

Graphene nanosheets/poly(3-hexylthiophene) (GNs/P3HT) composites were prepared by oxidative polymerization of 3-hexylthiophene in a GNs dispersed chloroform solution. The phase composition of the composite materials was analyzed by X-ray diffraction and Fourier transform infrared spectra. The thermoelectric properties of the cold pressed composite pellets with different GNs loadings were measured at room temperature. As the GNs loading increased from 0 to 30 wt.%, the electrical conductivity of the composites dramatically increased from ∼10⁻⁶ to ∼1.2 S/cm while the Seebeck coefficient slightly increased from 33.15 to 35.46 μV/K. The highest power factor (∼0.16 μW m⁻¹ K⁻²) was obtained in the 30 wt.% GNs/P3HT composite material.     

Unique structural features and electrical properties of electrospun conjugated polymer poly(3-hexylthiophene) (P3HT) fibers

This study examines and compares the internal structure conjugated polymeric fibers fabricated by electrospinning with cast films. Despite rigidity of polymer chain and the inability of its molecular chains to entangle to form viscoelastic jets, regioregular poly(hexyl-3-thiophene) (P3HT) exhibited the remarkable capability to be electrospun when the solution was subjected to gelation. In order to investigate the influence of additional mechanical stretching on the fibers, P3HT was electrospun with the aid of a rotating disc collector. Structure of electrospun fibers was probed via characterization techniques such as differential scanning calorimetry (DSC), Fourier transform infrared and photoluminescence (PL) spectroscopies. The findings indicated internal structural modifications developed within P3HT fibers, as a consequence of additional mechanical stretching induced by the rotating collector. Polarized FTIR and PL spectroscopies suggested that the molecular chains were aligned along the fiber axis. Electrical conductivity of iodine doped P3HT electrospun fibers was between 3 × 10³ S/m and 6 × 10³ S/m.     

High energy ion irradiation effect on light-emitting poly(3-methylthiophene) (P3MT) nanowires

Light-emitting poly(3-methylthiophene) (P3MT) nanowires with a diameter of ∼200 nm were fabricated using an electrochemical polymerization method based on an anodic alumina oxide (Al₂O₃) nanoporous template. The relatively high energy (3 MeV) Cl²⁺ ions were irradiated onto the P3MT nanowires with dosages from 1 × 10¹³ to 1 × 10¹⁵ ions/cm². To study the effect of high energy ion irradiation on P3MT nanowires, we measured UV/vis absorbance, Raman spectra, and laser confocal microscope photoluminescence (PL) on the nanometer scale. The relative atomic concentrations of carbon elements in the pristine and the 3 MeV Cl²⁺ ion-irradiated P3MT nanowires were investigated through XPS experiments. As the dosage of the 3 MeV Cl²⁺ ion irradiation increased, we observed that the P3MT nanowires changed to a partially carbonized form, and that the PL efficiency of the systems decreased.     

Computation method of magnetic fluid in strong magnetic field

When the magnetic fluid lays in the magnetic field, interaction effects exist between them. Thus, the precise computation is considered as one of the precise methods of analyzing magnetic fluid in the magnetic field.Comparing with it, the linear computation will bring more error. The more error exists between the decoupled computation and the linear computation, the more saturation magnetization does on the border. Besides, the value of magnetic flux density is bigger when using the decoupled computation than that of linear computation. What's more,the equal magnetic flux density linear on the border varies slightly in the strong magnetic field when using the two computations. In a weaker magnetic field, the difference is bigger.     

Different solvents effect on the performance of the solar cells based on poly(3-hexylthiophene):methanofullerenes

This paper reports the effect on the performance of the solar cells based on poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C₆₁-butyric acid methyl ester (PCBM) with different casting solvents. These blend films are characterized by UV–vis absorption spectra, photoluminescence spectra, charge-transport dark J–V curve, X-ray diffraction pattern curve, and AFM images. The results indicate that high boiling point solvent leads to an enhanced self-organization of P3HT in the active layer, which causes an increased charge transport. Increased incident light absorption and higher carrier mobility in the active layer contribute to the enhancement in the device performance, the power conversion efficiency of 3.69% and fill factor up to 65.3% are achieved with 1,2,4-trichlorobenzene as casting solvent without further heat treatment under Air Mass 1.5, 100 mW/cm².     

Electrical,optical and hole transport mechanism in thin films of poly(3-octylthiophene-co-3-hexylthiophene): Synthesis and characterization

The present study demonstrates the designing of copolymer poly(3-octylthiophene-co-3-hexylthiophene) (P3OT-HT) and study of the hole transport mechanism in it. Detailed structural, optical and thermal studies of P3OT-HT discuss its synthesis aspects. Current density–voltage characteristics have been studied at different temperatures (290–110 K) to understand the mechanism of hole transport in P3OT-HT. It has been established that current density in P3OT-HT thin films is governed by space charge limited conduction with traps distributed exponentially in energy and space. Hole mobility is both temperature and electric field dependent arising due to substituent functional groups attached the polymer backbone.     

Fabrication of poly-3-hexylthiophene/polyethylene oxide nanofibers using electrospinning

P3HT–PEO blend nanofibers were produced by electrospinning from chloroform solutions. A morphological study was carried out as a function of the processing parameters as well as the ratio between the two polymers. The fibers containing at least 60 wt.% of P3HT presented striated surfaces that could be explained by the alignment of the polymer domains along the fiber axis. The structural arrangement of the polymers was found to vary according to the polymers relative contents. The maximum electrical conductivity found for unaligned mats was 0.16 S/cm and increased to 0.3 S/cm when the nanofibers were aligned along a preferential direction.     

Structural effect of fullerene derivative on polaron relaxation and charge transfer in poly(3-hexylthiophene)/fullerene composite

The structural effect of a side chain in a fullerene derivative on electron relaxation and polaronic charge transfer in a poly(3-hexylthiophene)/fullerene composite was studied by 3 cm waveband electron paramagnetic resonance. All the systems with different fullerene derivatives demonstrate a sum spectrum of small localized and mobile polarons whose contributions depend on the structure of the fullerene derivative. Both the spin–lattice and spin–spin relaxation times were determined separately in a wide (77–320 K) temperature region using the steady-state saturation method. It was shown that spin relaxation, susceptibility and dynamics are governed by the dipole–dipole interaction of the polarons as well as by the structure of the side chains in the fullerene derivative. The treatment of the polymer matrix by the fullerene changes its dimensionality and accelerates polaron diffusion along polymer chains.     

Effects of annealing of poly(3-hexylthiophene) film on the performance of double-layered EL devices of ITO/polymer/Alq3/Mg–Ag

Double layer devices with a structure of ITO/pHT/Alq3/Mg–Ag (ITO = indium tin oxide, pHT = regio-regular or random poly(3-hexylthiophene), Alq3 = tris(8-hydroxyquinoline)aluminium) were fabricated. The device with a random pHT film emitted a green-yellow light in all voltage region, while that having a regio-regular pHT film exhibited a color change from green to red by applying the bias voltage higher than 15 V. Annealing the pHT films prepared on ITO at 200 °C for 1 h in nitrogen, prior to vapor-deposition of the Alq3 layer, improved the device performance with lowering the onset bias voltage by 2–3 V. The EL colors and spectra were also affected by annealing. X-ray reflectivity measurements before and after annealing the pHT film on ITO indicated increased density of the pHT layer and structural changes in the pHT/ITO interface by annealing, which seems to be responsible for the improved EL device performance.