3-octyl Thiophene Research Articles

Structure difference of sorbitol derivatives influences the crystallization and performance of P3OT/PCBM organic photovoltaic solar cells

In this work, we compare the effects of sorbitol derivatives (1,3:2,4-dibenzylidene sorbitol (DBS), 1,3:2,4-di(p-methylbenzylidene) sorbitol (MDBS) and 1,3:2,4-di(3,4-dimethylbenzylidene) sorbitol (DMDBS)) on the performances of poly(3-octyl thiophene)/[6,6]-phenyl C61-butyric acid methyl ester (P3OT/PCBM) bulk heterojunction (BHJ) organic photovoltaic (OPV) devices and explore the mechanism. Differential scanning calorimetry (DSC) and atomic force microscopy (AFM) measurements indicate that DBS, MDBS and DMDBS are nucleating agents of P3OT. DMDBS has the strongest molecular polarizability and exhibits the best propensity for self-assembly in 1,2-dichlorobenzene (ODCB). The strong π-π stacking of aromatic benzylidene group and the high density of the fibrillary aggregates supply more nucleation surfaces for P3OT, leading DMDBS has the highest nucleation efficiency (NE). Sorbitol derivatives accelerate the crystallization rate (G) of P3OT with the order as GP3OT/DMDBS > GP3OT/MDBS > GP3OT/DBS > GP3OT. The acceleration of the crystallization increases the number of tie molecules, causing the improvement of the connectivity between ordered regions, resulting dramatically increasing the carrier transport of P3OT. GP3OT/DMDBS is highest, the connectivity between ordered regions is best in P3OT with DMDBS. UV–vis measurement indicates that the intra-chain order of P3OT reduces with the addition of sorbitol derivative, and the intra-chain order of P3OT with DMDBS is lowest. The P3OT/PCBM/sorbitol derivative BHJ OPV devices were fabricated and show that the short circuit current JSC P3OT/DMDBS > JSC P3OT/MDBS > JSC P3OT/DBS > JSC P3OT. It hints that the connectivity of tie molecules plays a significant role in defining semiconducting polymer transport characteristics, and is perhaps more important than molecular level interactions (inter- and intra-chain order) for efficient macroscopic charge carrier transport. Finally, it shows that adding sorbitol derivatives can improve the power conversion efficiency (PCE) of P3OT/PCBM BHJ OPV device, the best PCE as 1.77% is obtained in the P3OT/PCBM/DMDBS device.

Single-step electrospinning of multi walled carbon nanotubes – Poly(3-octylthiophene) hybrid nano-fibers

Single-step electrospinning of micro-fibers from native solutions of poly(3-octyl thiophene) (P3OT) presents a simplified processes as compared to previously reported host-guest or core–shell strategies for production of conjugated-polymers fibers. Furthermore, as P3OT is a good dispersing agent for Multi-Walled Carbon Nanotubes (MWNT) the process is extended to spinning of MWNT-P3OT dispersions in a single step offering a unique opportunity for incorporation of carbon nanotubes (CNT) into well-shaped functional fibers without the need for the usage of a non-active mediating agent. Rheological characterization of the dispersions and structural analysis of the resulting fibers indicate that well dispersed CNT improve the spinnability of the polymer and enhance the crystallinity of the resulting fibers.

Preparation and physical characterization of conjugated polymer-polycarbonate polymer blends

Poly(3-octyl thiophene) (P3OT)–polycarbonate (PC) polymer blends were prepared at different P3OT weight ratios to investigate the effect of P3OT content on the optical, electrical, mechanical, rheological, and thermal properties of P3OT–PC polymer blends. Optical results showed that addition of P3OT to neat PC enhanced the ultraviolet/visible absorption of the neat PC. The optical energy gap of blend system was decreased with increasing P3OT up to 10% P3OT and the blend system appeared to be immiscible when P3OT content was 20% P3OT. Electrical results showed that incorporation of P3OT into neat PC up to 20% P3OT elevated the electrical up to six orders of magnitude and enhanced the polar character of the neat PC. Also, electrical results showed that P3OT–PC blend system became percolated above 0.8% P3OT. Mechanical and rheological results indicated that incorporation of P3OT into neat PC up to 10% P3OT will enhance elastic modulus, complex viscosity, storage modulus ( G′), and loss modulus ( G′) of the blend system while these parameters were found to be decreased when P3OT content in the blend system was 20% P3OT. Generally, all obtained results indicated that P3OT–PC blends are partially miscible blends up to 10% P3OT while this blend system appeared to be immiscible blend at 20% P3OT.

Preparation and characterization of poly(3-octyl thiophene)/polyvinyl chloride polymer blends

Different weight ratios of poly(3-octyl thiophene) / polyvinyl chloride blends were prepared using the casting method by dissolving poly(3-octyl thiophene) and polyvinyl chloride polymers in chloroform and Tetrahydrofuran, respectively. Fourier transform infrared spectroscopy indicates the existence of carbonyl group in both polyvinyl chloride neat and poly(3-octyl thiophene)–polyvinyl chloride blends. Electrical measurements reveal that the impedance values are increased with the increasing of both weight fraction of poly(3-octyl thiophene) and temperature. Optical results reveal that the increase of poly(3-octyl thiophene) weight fraction in blends enhances the UV-visible absorption of polyvinyl chloride and reduces the optical energy gap of blends. Differential scanning calorimetric measurements and thermal gravimetric analysis show that the glass transition temperature value and thermal stability of blend increases with increasing of poly(3-octyl thiophene) weight ratio. The obtained results, generally, indicate that the increase of poly(3-octyl thiophene) weight fraction enhances the interaction between poly(3-octyl thiophene)–polyvinyl chloride chains and as a result will restrict the chain mobility of polymers.

1-Hexyl-3-methylimidazolium hexafluorophosphate as new component of polymeric membrane of lead ion-selective electrode

abstract The ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate is used as a new lipophilic ionic additive in the polymeric membrane of a solid contact type lead ion-selective electrode. The membrane is deposited on an internal glassy carbon electrode with poly(3-octyl)thiophene as an intermediate layer. The sensor exhibits good analytical parameters: low detection limit of 3.5 × 10−9 mol L−1, Nernstian response slope of 29.8 mV/decade, a wide concentration range of 1 × 10−8−1 × 10−1 mol L−1, short response time of 7 s, and relatively long lifetime of 100 days. The proposed sensor has a working pH range of 4.0–6.9 and excellent selectivity for Pb(II) ions over a wide variety of other metal ions. The efficiency of the proposed sensor was demonstrated by its application for direct determination of Pb2+ ions in real water samples.

Synthesis and photovoltaic property of poly(3-octylthiophene)/titanium dioxide/ferric oxide composite

Titanium dioxide and ferric oxide were prepared by the supercritical fluid drying (SCFD) method. A conducting polymer composite, poly(3-octylthiophene)/titanium dioxide/ferric oxide (POT/TiO 2/Fe 2O 3) was first synthesized by chemical method. Transmission electron microscope (TEM) and scanning electron microscope (SEM) depicted the morphology of the samples, defining that TiO 2 and Fe 2O 3 were successfully coated by poly(3-octylthiophene) molecules. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) showed the chemical interaction between poly(3-octylthiophene) and inorganic compounds in the composite. Cyclic voltammetry (CV) curves showed that the forbidden band gap of the POT/TiO 2/Fe 2O 3 composite is 0.691 eV, realizing the complementary advantages of n and p semiconductor. UV–vis spectra (UV) and fluorescence spectra (PL) showed that its optical performance is far superior to poly(3-octyl thiophene), titanium dioxide and ferric oxide separately. Solar cell was sensitized by POT/TiO 2/Fe 2O 3. A solar-to-electric energy conversion efficiency of 0.499% was attained with the system.

Long-term behavior and side chain crystallization of poly(3-alkyl thiophenes)

The influence of slow side chain crystallization and densification processes during physical aging below Tg on relaxation behavior, calorimetric properties and structure is studied for a series of regio-random poly(3-alkyl thiophenes) (P3ATs) containing C = 6–12 alkyl carbons per side chain. Shear measurements on these samples show typical features known from other nanophase-separated side chain polymers containing long alkyl groups. In particular, there is strong evidence for the existence of self-assembled alkyl nanodomains in non-crystalline samples with an independent dynamics at low temperatures indicated by an additional αPE process. Results for regio-random poly(3-dodecyl thiophene) show that the intensity of this process decreases on logarithmic time scales if methylene units crystallize within the alkyl nanodomains. This decrease is accompanied by an increase in the plateau modulus and a slowing down of the conventional α relaxation at higher temperatures. Similar but less pronounced changes are observed for poly(3-octyl thiophene) during physical aging slightly below Tg. This can be understood as precursor of side chain crystallization. The results show that densification processes driven by the crystallization tendency of the alkyl groups lead to significant changes in the properties. Interestingly, there are three different polymorphic states in which the methylene units can crystallize in poly(3-dodecyl thiophene) depending on the crystallization conditions. The influence of polymorphism on average interlayer distance dnps and overall structure is shown. A hypothetical picture describing the observed changes is proposed. The implications of the presented results for existing structural models for regio-regular P3ATs and the optimization of application relevant P3ATs containing thiophene rings and attached alkyl groups are discussed.

Effect of thermal annealing on the corrosion protection of stainless steel by poly(3-octyl thiophene)

Poly(3-octyl thiophene) (P3OT) coatings have been chemically deposited by drop casting onto 304-type stainless steel. P3OT films were thermally annealed at 55, 80 and 100 °C in air during 30 h and their corrosion resistance was estimated by using polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy measurements, EIS. P3OT films decreased the corrosion rate of the substrate by at least one order of magnitude, although the best corrosion protection was given by annealing it at 100 °C whereas the worst corrosion protection was given by annealing the coating at 80 °C.

Corrosion protection of carbon steel by thin films of poly(3-alkyl thiophenes) in 0.5 M H 2SO 4

Poly(3-octyl thiophene) (P3OT) and poly(3-hexylthiophene) (P3HT) dissolved in toluene were deposited onto 1018 carbon steel and corroded in 0.5 M H 2SO 4. P3OT and P3HT films were chemically deposited by drop casting onto 1018-type carbon steel with two surface finishing, i.e. abraded with 600-emery paper and with alumina (Al 2O 3) particles of 1.0 μm in diameter (mirror finish). Their corrosion resistance was estimated by using potentiodynamic polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy, EIS, techniques. In all cases, polymeric films protected the substrate against corrosion, but the protection was improved if the surface was polished with Al 2O 3 particles of 1.0 μm in diameter. The polymer which gave the best protection was P3HT because the amount of defects was much lower than that for the P3OT films. The polymers did not act only as a barrier layer against aggressive environment, but they improved the passive film properties by decreasing the critical current necessary to passivate the substrate, increasing the pitting potential and broadening the passive interval.

State of partial oxidation of the regioregular sexi (3-octyl thiophene) oligomer in solid phase on electrode surface

An existence of a new, stable oligomer state of the solid film is reported, which is produced under electrochemical conditions. In this state, a formal charge exchanged in the redox process is about one-half of electron per oligomer molecule. The procedure, which allows controlling precisely the amount of oligomer on the electrode surface, is proposed that together with the coulometric evaluation of the electric charge provides the number of electrons involved in a redox process. This is demonstrated for a case of α-monochloro-substituted regioregular sexi (3-octylthiophene) oligomer (6OTCl). The electrochemical results are discussed together with UV–Vis–NIR spectroelectrochemical data obtained for both solution and solid phase that support the proposed interpretation.

Cocrystallization mechanism of poly(3-alkyl thiophenes) with different alkyl chain length

The crystallization rates of poly(3-alkyl thiophene) (P3AT) cocrystals having different alkyl chain length (e.g. hexyl and octyl) of the components are measured using differential scanning calorimetry (DSC) technique. Two pairs of cocrystals with varying compositions of the components viz. poly(3-octyl thiophene) (P3OT(R), regioregularity 89mol%) and poly(3-hexyl thiophene) [P3HT(R), regioregularity 92mol% and P3HT-2 regioregularity 82mol%] are used. In both the systems the isothermal temperature range (TR) in the same time scale of crystallization is found to decrease with increasing alkyl chain length in the blends. The crystallization rate at the same Tc decreases with increasing alkyl chain length P3AT concentration and the Avrami exponent values of cocrystals are same with those of the component values. The low Avrami exponent values (0.23–1.16) in all the samples suggest the presence of rigid amorphous portion which can not diffuse out quickly from the crystal growth front (soft impingement). Analysis of crystallization rate using Laurintzen–Hoffman (L–H) growth rate theory indicates that there is regime-I to regime-II transition in all the samples. The product of lateral (σ) and end surface energy (σe) values are found to decrease with increasing the concentration of longer alkyl chain P3AT in the blend. Analysis of σ values according to a theory of Hoffman et al. [Hoffman JD, Miller RL, Marand H, Rotiman DR. Macromolecules 1992;25:2221. [14]] indicates that there is chain extension of the components in the melt of the blends, however, the entropy of cocrystallization has different sign to the two systems. Cocrystallization in P3HT(R)/P3OT(R) system is an entropy driven process but that in P3HT(2)/P3OT(R) system is entropy forbidden process. A possible explanation of cocrystallization in the later system has been attributed from small interaction between the components.

Characterization of N, N′-bis-2-(1-hydoxy-4-methylpentyl)-3, 4, 9, 10-perylene bis (dicarboximide) sensitized nanocrystalline TiO2 solar cells with polythiophene hole conductors

We have fabricated solid-state, dye-sensitized nanocrystalline TiO2 solar cells (DSSC) based on perylene derivative dye, N,N′-bis-2-(1-hydoxy-4-methylpentyl)-3,4,9,10-perylene bis (dicarboximide) (HMPER) with two different polythiophenes as hole conductors; i.e. poly (3-octyl thiophene) (P3OT) and poly (3-hexyl thiophene) (P3HT), respectively. HMPER adsorbs strongly to the surface of nanocrystalline TiO2 and inject electrons into TiO2 conduction band upon absorption of light. Polythiophene derivatives are well-known materials as hole conductors in solid-state dye-sensitized solar cells. We obtained quite similar results with P3OT and P3HT yielding a short-circuit current density of around 80 μA/cm2 and open-circuit voltage of around 0.7 V at 80 mW/cm2 AM 1.5 light intensity. The results are compared with Ru-535 TBA-sensitized nc-TiO2 cells prepared by using the same polythiophene derivatives.

Hybrid TiO2:polymer photovoltaic cells made from a titanium oxide precursor

Hybrid TiO 2 :polymer photovoltaic cells were made from mixtures of titanium(IV) isopropoxide and poly[2-methoxy-5-(3′,7′-dimethyloctyl)- p -phenylene vinylene] (MDMO-PPV) or poly(3-octyl thiophene) (P3OT) via hydrolysis in air. Cells were made with varying titanium(IV) isopropoxide:polymer ratios. Current–voltage measurements (at 0.7–0.8 sun equivalent) of a TiO 2 :P3OT (10 vol.% TiO 2 ) photovoltaic cell show a short-circuit current of 0.7 mA/cm 2 , an open-circuit voltage of 450 mV and a fill factor of 0.41, resulting in a calculated AM1.5 (100 mW/cm 2 ) power conversion efficiency of 0.17%. Devices based on MDMO-PPV and TiO 2 (20 vol.% TiO 2 ) show an open-circuit voltage of 600 mV and a short-circuit current of 0.6 mA/cm 2 (at 0.7 sun equivalent), resulting in a calculated AM1.5 power conversion efficiency of 0.22%.

Hybrid TiO 2:polymer photovoltaic cells made from a titanium oxide precursor

Hybrid TiO 2:polymer photovoltaic cells were made from mixtures of titanium(IV) isopropoxide and poly[2-methoxy-5-(3′,7′-dimethyloctyl)- p-phenylene vinylene] (MDMO-PPV) or poly(3-octyl thiophene) (P3OT) via hydrolysis in air. Cells were made with varying titanium(IV) isopropoxide:polymer ratios. Current–voltage measurements (at 0.7–0.8 sun equivalent) of a TiO 2:P3OT (10 vol.% TiO 2) photovoltaic cell show a short-circuit current of 0.7 mA/cm 2, an open-circuit voltage of 450 mV and a fill factor of 0.41, resulting in a calculated AM1.5 (100 mW/cm 2) power conversion efficiency of 0.17%. Devices based on MDMO-PPV and TiO 2 (20 vol.% TiO 2) show an open-circuit voltage of 600 mV and a short-circuit current of 0.6 mA/cm 2 (at 0.7 sun equivalent), resulting in a calculated AM1.5 power conversion efficiency of 0.22%.

Photogenerated charge carrier transport in p-polymer n-polymer bilayer structures

We investigate polymer bilayer structures that can be utilized effectively for efficient photovoltaic properties. The transport characteristics of photogenerated free charge carriers across the interface of a bilayer consisting of p-type polymer poly(3-octyl thiophene) (P3OT) or poly(2-methoxy, 5-(2-ethylhexoxy)-1, 4-phenylene vinylene) (MEHPPV) and n-type polymer poly(benzamidazobenzo phenanthroline) (BBL) are studied using photocurrent spectral response, intensity modulated photocurrent spectra, current-voltage, and thermally stimulated current measurements. The parameters governing the device efficiency are controlled by the interfacial defect characteristics and electric field redistribution in the device. A clear evidence of these defect states at the polymer–polymer interface is revealed using the time and frequency domain photocurrent measurements. We compare the figure of merits of the P3OT/BBL and MEHPPV/BBL structures and correlate these properties to the interfacial processes.

Photovoltaic properties of polymer p–n junctions made with P3OT/BBL bilayers

The photovoltaic and interfacial properties of heteorojunction polymer device consisting of p-type poly(3-octyl thiophene) and n-type poly(benzimidazobenzophenanthroline) are investigated. The photocurrent efficiency is enhanced at least by a factor of 100 in these bilayers compared to their respective single layer structures. The interfacial properties are studied using current–voltage characteristics, transient photocurrent measurement and modulated photocurrent spectroscopy. The open circuit photovoltage corresponds to the estimated fermi level difference of the polymers. The dispersive transport and interfacial charging in these bilayers are studied using transient and modulated photocurrent measurements.

Charge transport at low electric fields inπ-conjugated polymers

In low-mobility materials the charge carrier mobility is usually measured using time-of-flight (TOF) methods. However, the use of TOF methods calls for a necessary condition to be fulfilled: viz., that the dielectric relaxation time must be bigger than the charge carrier transit time, ${\ensuremath{\tau}}_{\ensuremath{\sigma}}\ensuremath{\gg}{t}_{\mathrm{tr}},$ through the interelectrode distance d. If this condition is not fulfilled, then the equilibrium charge carrier concentration ${p}_{0}$ is sufficient to redistribute the electric field inside the sample during a time interval shorter than the small-charge drift time. Consequently, in the low-field region, the apparent charge carrier mobility estimated by the TOF method increases when the electric field decreases, while in reality the mobility does not increase. We show how to estimate the real mobility values, using extraction current transients [G. Ju\ifmmode \check{s}\else \v{s}\fi{}ka et al., Phys. Rev. Lett. 84, 4946 (2000)] for which the fulfillment of the ${\ensuremath{\tau}}_{\ensuremath{\sigma}}>{t}_{\mathrm{tr}}$ condition is unnecessary. We demonstrate this effect in regioregular poly(3-octyl thiophene) using both the TOF and carrier extraction by a linearly increasing voltage methods and show that the true mobility does not increase as a function of decreasing field.

Relaxation process at conductive poly(thiophene) and its poly(alkyl) derivatives : kinetics of electrochemical doping

The kinetics of relaxation i.e. the kinetics of the doping process, have been investigated in poly(thiophene) and its alkyl substituted derivatives poly(3-methyl thiophene) and poly(3-octyl thiophene), by cyclic voltammetry. The polymer films, electrochemically deposited onto platinum and titanium electrodes, relax at various rates, depending on their structure and orientation in relation to the metal surface. The relaxation process is faster in polymers with longer alkyl chains.

Polarized doping-induced infrared absorption in highly oriented conjugated polymers

We present polarized, doping-induced absorption spectra obtained from conjugated polymers oriented by gel-processing in ultrahigh molecular weight polyethylene. Upon doping with iodine vapor, both poly(2-methoxy, 5-(2 ′ -ethyl)-hexyloxy) paraphenylene vinylene), MEH-PPV, and poly (3-octyl thiophene), P3OT, show absorption features in the mid-infrared (the infrared-active vibrational (IRAV) modes and the low energy electronic absorption) that are strongly polarized parallel to the chain axis. All observed features have predominantly parallel polarization. We suggest that carrier-induced and electrode-induced losses in electrically pumped waveguide structures could be greatly reduced by using highly oriented films, with molecular axes orthogonal to the electric field polarization of the waveguide mode.

K-Selective Solid-Contact Electrodes Based on Electron-Conducting Polymers

K-Selective solid-contact electrodes with potential-stabilizing transient layers based on two different electron-conducting polymers, poly(3-octyl)thiophene, polyaniline, and also on their mixture are developed. These electrodes are characterized by the operation limits, selectivity, and stability of the potentiometric response as well as by their electrochemical impedance.