Polymer Poly 3-hexylthiophene Research Articles

Development of conductive molecularly imprinted polymers (cMIPs) for limonene to improve and interconnect QCM and chemiresistor sensing

This paper presents a straightforward method to develop a chemiresistor based sensor for the detection of the plant volatile R-(+)-limonene. By using blends of polystyrene-based molecularly imprinted polymers (MIPs) and the organic semiconductor poly3-hexylthiophene (P3HT), electrical conductivity is introduced into the highly selective MIPs, allowing their application as sensing layers in robust and economic chemiresistor devices. Polystyrene-based MIPs and conductive blends were assessed on quartz crystal microbalances (QCMs) and chemiresistors and compared to non-imprinted polymer (NIP) and pristine P3HT layers. Blending MIPs and conductive polymers led to a strong signal enhancement, both on the QCM as well as during resistive measurements, allowing for detecting R-(+)-limonene gas concentrations as low as 50 ppm. The presented results provide a simple and valuable way for potential MIP sensing improvements and the possibility for a method transfer to cheap and simple chemiresistors.

Polarization Dependence of Charge Conduction in Conjugated Polymer Films Investigated with Time-Resolved Terahertz Spectroscopy.

Room temperature Time-Domain Terahertz (TDS) and Time-Resolved Terahertz (TRTS) spectroscopic methods are employed to measure carrier mobility and charge generation efficiency in thin-film semiconductor polymers. Interrogation of the dependence on excitation and probe polarizations yields insight into the underlying material properties that guide charge transport. We apply THz polarization anisotropy probes to analyze charge conduction in preparations of the copolymer PCDTPT, consisting of alternating cyclopenta-dithiophene (donor) and thiadiazolo-pyridine (acceptor) units. Comparisons are made among films of different ordering and morphology, including aligned films prepared by blade coating, a near isotropic dropcast film, and isotropic liquid dispersion. They are further contrasted with their population dynamics ascertained through transient absorption and the traditional photoconductive polymer poly-3-hexylthiophene (P3HT). Polarization anisotropy is observed as preferential charge conduction along the backbone propagation direction of PCDTPT, with various factors disproportionately influencing directional mobility and charge pair yield. PCDTPT exhibits unexpectedly strong conductivity when isolated in toluene dispersion. Quantitative comparisons yield a better understanding of polaron/free-charge relaxation and transfer mechanisms and illustrate dynamics among photoexcited charge carriers and their motion and diffusion through different material morphologies.

Impact of Molecular Order on Polaron Formation in Conjugated Polymers

The nature of polaron formation has profound implications on the transport of charge carriers in conjugated polymers, but still remains poorly understood. Here, we develop in situ electrochemical resonant Raman spectroscopy, a powerful structural probe that allows direct observation of polaron formation. We report that polaron formation in ordered poly(3-hexyl)thiophene (P3HT) polymer domains (crystalline phase) results in less pronounced changes in molecular conformation, indicating smaller lattice relaxation, compared to polarons generated in disordered polymer domains (amorphous phase) for which we observe large molecular conformational changes. These conformational changes are directly related to the effective conjugation length of the polymer. Furthermore, we elucidate how blending the P3HT polymer with phenyl C-61 butyric acid methyl ester affects polaron formation in the polymer. We find that blending disturbs polymer crystallinity, reducing the density of polarons that can form upon charge injecti...

Review: Fullerene based acceptors for efficient bulk heterojunction organic solar cell applications

Bulk hetro-junction organic solar cells (BHJ-OSCs) which made by coating the blend of highly electron rich, poly-3-hexylthiophene (P3HT) as a donor and extremely electron deficient, soluble C60 derivative, [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as an acceptor between the high work function positive electrode, ITO and low work function metal negative electrode Al, showed exciting results than the bilayer counterpart in the last two decades, thus the scientific circle and solar cell manufacturing groups are focusing on this treasured field. Fullerene derivative based BHJ-OSCs showed astonishing efficiencies due the high donor-acceptor (D-A) interface, high open-circuit voltage (Voc), easy processing, and thermal stability. Hence, the design of the fullerene derivative plays a vital role in the efficiency of the OSCs. Numerous papers were published on the PC61/71BM and various functionally modified fullerene acceptors in the past several years with higher efficiency, higher LUMO level, and improved solubility. The symmetrical structure of PC61BM showed high aggregation properties, insufficient absorption in the visible region, but unsymmetrical PC71BM had a good optical absorption in the visible region, hence it was the most desirable choice for best performing solar cells. From the comparison, it was clear that the modification in the PC61/71BM core with aryl group, alkyl chain length, and end group modification didn’t show any significant difference in the PCE with the P3HT polymer donor in BHJ-OSCs device structure. Fullerenes multi-adducts performed better than the PC61/71BM due to the development in the Voc. In multi-functionalization, mainly bis-functionalization showed better performance than mono-adduct. C60 and C70 based hetro bis-adducts namely, C60(CH2)(Ind), and OQMF70 showed the highest PCE of 5.90%, and 6.61% respectively, which was comparable with the indene based bis-adducts. Commonly, tris-adduct fullerenes showed the lowest PCE due to the isomer effect and electron trapping, but OQBMF was a hetro tris-adduct of C60-methanofullerenes, which showed a excellent PCE of 6.43% due to improved Voc. Similarly, indene substituted C60 and C70 fullerenes based bis-adducts showed supreme PCE, of 6.5% (IC60BA) and ~6.7% (IC70BA) respectively, peak PCE was attributed to the high electron donating indene group, which enhanced the LUMO level due to the shrinkage in the π-system. The dihydronapthyl based fullerene bis-adduct derivatives such as, NC60BA, and NC70BA showed the best performance of 5.37%, and 5.95% respectively, than the mono-adduct. Even though abundant fulleropyrrolidines were reported, the performance of the fulleropyrrolidines based device was very deprived than the PC61/71BM based devices. Though the OSCs are comparatively efficient for commercial application due the insufficient efficiency and lower environmental stability factors controls the early arrival to the market. Therefore, it is essential to go through the recent fullerene derivatives based literatures, including mono-, bis-, tris- and multi-adducts of various methanofullerene derivative, indene based fullerene derivatives, dihydronaptyl substituted fullerenes, fulleropyrolidines, 1,2 and 1,4-adducts and fullerene derivatives for OSCs applications. In this regard, we discussed the present development in fullerene derivative and summarized the efficient fullerene derivatives for the BHJ-OSCs application and suggest a possible scenario for the future development in the fullerene cage.

Optical Dedoping Mechanism for P3HT:F4TCNQ Mixtures.

Doping-induced solubility control (DISC) is a recently introduced photolithographic technique for semiconducting polymers, which utilizes reversible changes in polymer solubility upon doping to allow the polymer to function as its own photoresist. Central to this process is a wavelength sensitive optical dedoping reaction, which is poorly understood but generates subdiffraction-limited topographic features and provides optical control of the polymer doping level. Here, we examine the mechanism of optical dedoping in the semiconducting polymer poly-3-hexylthiophene (P3HT) doped by 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), via a combination of ultrafast and steady-state spectroscopy, ab initio calculations, and multidimensional NMR. A simple photoinduced back electron transfer mechanism from reduced F4TCNQ to oxidized P3HT does not explain the observed photophysics. Instead, photoexcited F4TCNQ* reacts with THF solvent molecules to form a neutral, nondoping, and highly soluble F4TCNQ-THF complex. Hence, ionized F4TCNQ is removed from the P3HT indirectly by depletion of the neutral F4TCNQ. Because the reaction involves only the dopant and similar photoreactivity would expected for most other dopant molecules, we expect optical DISC patterning should be generalizable to a wide range of polymer:dopant systems.

Electrical characterization of fluorinated benzothiadiazole based conjugated copolymer – a promising material for high-performance solar cells

Measurements of electrical conductivity, electron work function, carrier mobility of holes and the diffusion length of excitons were performed on samples of conjugated polymers relevant to polymer solar cells. A state of the art fluorinated benzothiadiazole based conjugated copolymer (PBDTTHD − DTBTff) was studied and benchmarked against the reference polymer poly-3-hexylthiophene (P3HT). We employed, respectively, four electrode conductivity measurements, Kelvin probe work function measurements, carrier mobility using charge extraction by linearly increasing voltage (CELIV) measurements and diffusion length determinaton using surface photovoltage measurements.

Optical, Structural and Morphological Properties of Ternary Thin Film Blend of P3HT:PCBM:ZnO Nanoparticles

Ternary blend film of conjugated polymer, fullerene and inorganic nanoparticles has intensively studied as active material for high power conversion efficiency (PCE) of hybrid organic-inorganic solar cells. The incorporation of two electron acceptor materials of organic fullerene and inorganic nanoparticles into hybrid with electron donor conjugated polymer is strongly believed can improve the PCE of solar cells by increasing exciton dissociation efficiency due to an increase of interface area between donor and acceptor materials where the positive and negative charges dissociated. We studied optical, structural and morphological properties of ternary thin film containing blend of conjugated polymer poly(3-hexylthiophene (P3HT):fullerene derivative PCBM:Zinc oxide nanoparticles (ZnO-NP) by measuring its optical absorption, crystal structure and film surface morphology. Zinc oxide nanoparticle was prepared by sol-gel method. It has optical absorption below 370 nm and average particle size 40 nm as shown by TEM picture. Ternary thin blend films of P3HT:PCBM:ZnO-NP were prepared by use of spin-coating method. The UV-Vis spectrum of thin film contains absorption peaks originated from contribution of P3HT at wavelengths 520 nm, 550 nm and 600 nm, from contribution of PCBM at 260 nm and 330 nm and from ZnO-NP at wavelengths below 370 nm which confirms that these three materials were well mixed in the films. Its XRD pattern also contains the peaks from each of these three-materials. In this report, we compare surface morphology of thin films of pure P3HT, pure ZnO-NP, blend of P3HT:PCBM, blend of P3HT:ZnO-NP and ternary blend of P3HT:PCBM:ZnO-NP.

Conjugated polymer P3HT-Au hybrid nanostructures for enhancing photocatalytic activity.

Metal-semiconductor nanostructures have been the subject of great interest, mainly due to their interesting optical properties and their potential applications in light harvesting, photocatalysis and photovoltaic devices. Here, we have designed raspberry type organic-inorganic hybrid nanostructures of the poly-3-hexylthiophene (P3HT)-Au nanoparticle (NP) composite by a simple solution based synthetic method. The electronic interaction of semiconducting P3HT polymer nanoparticles with Au nanoparticles exhibits a bathochromic shift of absorption bands and significant photoluminescence quenching of P3HT nanoparticles in this organic-inorganic hybrid system. The photocatalytic activity of this raspberry type hybrid nanostructure is demonstrated under the visible light irradiation and the degradation efficiency is found to be 90.6%. Such organic-inorganic hybrid nanostructures made of a semiconducting polymer and plasmonic nanoparticles could pave the way for designing new optical based materials for applications in photocatalytic and light harvesting systems.

Poly(3-hexylthiophene) (P3HT)/Graphene Nanocomposite Material Based Organic Field Effect Transistor with Enhanced Mobility

The major drawback of organic field effect transistors (OFETs) is its lower mobility, which restricts their applications for high performance devices. Recently, graphene exhibits excellent carrier mobility, therefore, is used as a novel electronic substance for the fundamental research and several potential applications. Pristine graphene is not applicable in field effect transistors (FETs) for satisfactory on/off current ratio as it has no forbidden energy gap. Here, we report the fabrication as well as characterizations of poly-3-hexylthiophene (P3HT)/graphene nanocomposite (with two distinct concentrations i.e., 0.05 and 0.1 mg/ml of graphene in P3HT solution) based FETs to over come the limitations. The current-voltage (I-V) characteristics of P3HT/graphene based FETs are measured and key performance parameters of device are compared against only polymer P3HT based FETs. The analysis demonstrates that, in P3HT/graphene transistors some crucial parameters such as drain saturation current and mobility enhanced drastically although the on/off ratio reduced significantly. Our study demonstrates that presence of graphene in organic semiconductor and a synergic effect due to uniform distribution in the nanospace is an ordinary route to achieve high mobility OFETs which impart an affordable way for raising the performance of organic transistors.

Synthesis of thiol modified CdSe nanoparticles/P3HT blends for hybrid solar cell structures

Thioglycolic acid (TGA) capped cadmium selenide (CdSe) nanoparticles were synthesised in aqueous medium through wet chemical method using sodium selenite as the selenium source. The synthesised particles were transformed into organic medium using 1-dodecanethiol through efficient partial ligand exchange strategy. The UV–visible spectra recorded for the particles reveal the size distribution in water as well as in organic solvent. TEM analysis of the synthesised particles shows the size and the nature of distribution of the particles in solution. The phase transferred particles were blended with the polymer poly-3-hexyl thiophene (P3HT) in chloroform. UV–visible and photoluminescence spectra of the polymer with various volumes of the nanoparticles clearly indicate the effective coupling and the efficient charge transfer process in the blend. SEM analysis of the CdSe–P3HT blends confirms the effective distribution of the nanoparticles in the polymeric matrix. AFM studies reveal the morphology of the nanoparticles and the phase separation process in the blends.

SWNT nano-engineered networks strongly increase charge transport in P3HT.

We demonstrate the formation of arrays of 3D nanosized networks of interconnected single-wall carbon nanotubes (SWNTs) with well defined dimensions in a poly-3-hexylthiophene (P3HT) thin film. These novel nanotube nano-networks produce efficient ohmic charge transport, even at very low nanotube loadings and low voltages. An increase in conductivity between one and two orders of magnitude is observed compared to a random network. The formation of these nano-engineered networks is compatible with large area imprinting and roll to roll processes, which makes it highly desirable for opto-electronic and energy conversion applications using carbon nanotubes.

Plasmon-Enhanced Cell Efficiency in Hybrid Solar Cell Based on CdS Nanorod and Poly (3-Hexythiophene)

A bulk-heterjunction hybrid solar cell based on CdS nanorods as electron acceptor and conjugated polymers P3HT (Poly (3-Hexylthiophene)) as donor was fabricated through solution processing. Plasmon-active silver nanoparticle layers were introduced in the hybrid solar cell. Silver nanoparticle layers were fabricated using thermal evaporation deposition of 10 nm of silver thin layers on indium tin oxide (ITO) substrate followed by annealing. Under the surface plasmon excitation in Ag nanoparticles deposited on a semiconductor surface, increasing optical electrical field inside the photoactive layer led to an increased short circuit current density (Jsc) and improved fill factor (FF) of the cell. Consequently, under AM1.5G illumination (100 mW.cm-2), the plasmon-decorated cell based on CdS-nanorods/P3HT showed a four-times increase of the power conversion efficiency (PCE) compared with the undecorated one.

Improving CdSe Quantum Dot/Polymer Solar Cell Efficiency Through the Covalent Functionalization of Quantum Dots: Implications in the Device Recombination Kinetics

Novel quantum dot capping ligands based on fullerene derivatives were attached through click-chemistry to the surface of semiconductor CdSe nanocrystals (C70–CdSe). Steady-state and time-correlated luminescence studies in solution show efficient quenching of the quantum dot (QD) emission in C70–CdSe. When this material was blended with the polymer poly-3-hexyl thiophene (P3HT) to fabricate bulk-heterojunction solar cells, P3HT/C70–CdSe devices doubled the light-to-energy conversion efficiency when compared to P3HT/Py–CdSe reference devices prepared using pyridine as the capping agent. This is due to an increase in both photocurrent and fill factor showing the beneficial efficient effect of fullerene to improve light harvesting and charge transport in these devices. However, C70 also appears to increase recombination in these devices as evidenced by both transient absorption spectroscopy and transient photovoltage measurements. This work also discusses the effects on the CdSe functionalization with C70 over the device charge recombination kinetics that limit the efficiency in CdSe QDs/polymer solar cells.

Assembl y of Poly-3-Hexylthiophene Nano-Crystallites into Low Dimensional Structures Using Indandione Derivatives.

Conductive polymer poly-3-hexylthiophene (P3HT) needles were self-assembled using a second component (indandione derivatives) as a linking agent to enhance their long range alignment. The morphologies of the hybrid organic/organic materials were characterized by transmission electron microscopy (TEM). Both linear and branched structures could be produced, with the degree of branching depending upon the linker used. Incorporation of indandione derivatives broadened the UV absorbance band of P3HT without significant change to its photoluminescence. This hybrid material could open a promising avenue in photovoltaic applications due to its interesting morphologies and optical properties.

Ultrafast spectroscopic investigation of a fullerene poly(3-hexylthiophene) dyad

We present the femtosecond spectroscopic investigation of a covalently linked dyad, PCB-P3HT, formed by a segment of the conjugated polymer P3HT (regioregular poly(3-hexylthiophene)) that is end capped with the fullerene derivative PCB ([6,6]-phenyl-C-61-butyric acid ester), adapted from PCBM. The fluorescence of the P3HT segment in tetrahydrofuran (THF) solution is reduced by 64% in the dyad compared to a control compound without attached fullerene (P3HT-OH). Fluorescence upconversion measurements reveal that the partial fluorescence quenching of PCB-P3HT in THF is multiphasic and occurs on an average time scale of 100 ps, in parallel to excited-state relaxation processes. Judging from ultrafast transient absorption experiments, the origin of the quenching is excitation energy transfer from the P3HT donor to the PCB acceptor. Due to the much higher solubility of P3HT compared to PCB in THF, the PCB-P3HT dyad molecules self-assemble into micelles. When pure C-60 is added to the solution, it is incorporated into the fullerene-rich center of the micelles. This dramatically increases the solubility of C-60 but does not lead to significant additional quenching of the P3HT fluorescence by the C-60 contained in the micelles. In PCB-P3HT thin films drop-cast from THF, the micelle structure is conserved. In contrast to solution, quantitative and ultrafast (<150 fs) charge separation occurs in the solid-state films and leads to the formation of long-lived mobile charge carriers with characteristic transient absorption signatures similar to those that have been observed in P3HT: PCBM bulk heterojunction blends. While p-stacking interactions between neighboring P3HT chains are weak in the micelles, they are strong in thin films drop-cast from ortho-dichlorobenzene. Here, PCB-P3HT self-assembles into a network of long fibers, clearly seen in atomic force microscopy images. Ultrafast charge separation occurs also for the fibrous morphology, but the transient absorption experiments show fast loss of part of the charge carriers due to intensity-induced recombination and annihilation processes and monomolecular interfacial trap-mediated or geminate recombination. The yield of the long-lived charge carriers in the highly organized fibers is however comparable to that obtained with annealed P3HT: PCBM blends. PCB-P3HT can therefore be considered as an active material in organic photovoltaic devices.

Self-Assembly and Its Impact on Interfacial Charge Transfer in Carbon Nanotube/P3HT Solar Cells

Charge transfer at the interface of conjugated polymer and nanoscale inorganic acceptors is pivotal in determining the efficiency of excitonic solar cells. Despite intense efforts, carbon nanotube/polymer solar cells have resulted in disappointing efficiencies (<2%) due in large part to poor charge transfer at the interface. While the interfacial energy level alignment is clearly important, the self-assembly and the interface structure also play a major role in facilitating this charge transfer. To understand and control this effect to our advantage, we study the interface of commonly used conductive polymer poly-3-hexylthiophene (P3HT) and single-walled carbon nanotubes (SWNTs) with a combination of molecular dynamics simulations, absorption spectra experiments, and an analysis of charge transfer effects. Classical molecular dynamics simulations show that the P3HT wraps around the SWNTs in a number of different conformations, including helices, bundles, and more elongated conformations that maximize planar π-π stacking, in agreement with recent experimental observations. Snapshots from the MD simulations reveal that the carbon nanotubes play an important templating role of increasing the π-conjugation in the system, an effect deriving from the π-π stacking interaction at the interface and the 1-dimensional (1D) nature of the SWNTs, and independent of the SWNT chirality. We show how this increase in the system conjugation could largely improve the charge transfer in P3HT-SWNT type II heterojunctions and support our results with absorption spectra measurements of mixtures of carbon nanotubes and P3HT. These findings open possibilities for improved preparation of polymeric solar cells based on carbon nanotubes and on 1D nanomaterials in general.

A 113 fs fiber laser operating at 156 μm using a cascadable film-type saturable absorber with P3HT-incorporated single-wall carbon nanotubes coated on polyamide

We successfully fabricated a cascadable film-type single-wall carbon nanotube (SWNT) saturable absorber coated on aromatic polyamide film, in which the saturable absorption effect can be controlled with the number of films. A conductive polymer P3HT (poly-3-hexylthiophene) was adopted to obtain a uniform SWNT solution. We applied saturable absorber films to a passively mode-locked fiber laser and successfully generated a 113 fs, 42 MHz pulse by inserting two film layers between fiber connectors in the cavity.

Absence of Photoinduced Charge Transfer in Blends of PbSe Quantum Dots and Conjugated Polymers

We use photoluminescence (PL) quenching and photoinduced absorption (PIA) spectroscopy to study charge transfer in bulk heterojunction blends of PbSe quantum dots with the semiconducting polymers poly-3-hexylthiophene (P3HT) and poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-para-phenylene vinylene] (MDMO-PPV). PIA spectra from the PbSe blends are compared to spectra from similar blends of the polymers with phenyl-C(61)-butyric acid methyl ester (PCBM) and blends with CdSe quantum dots. We find that the MDMO-PPV PL is quenched, and the PL lifetime is shortened upon addition of PbSe quantum dots, while the PL of the P3HT is unaffected upon blending. However, for PbSe blends with both polymers, the PIA spectra show very little polaronic signal, suggesting that few, if any, long-lived charges are being produced by photoinduced charge transfer.

Bulk-heterojunction Based on Blending of Red and Blue Luminescent Silicon Nanocrystals and P3HT Polymer

AbstractBlending of red and blue photoluminescent silicon nanocrystals (Si-ncs) with poly(3-hexylthiophene (P3HT) conjugated polymer is demonstrated. The room temperature luminescent and ambient conditions stable Si-ncs prepared by electrochemical etching and laser ablation in water are used for the blend fabrication. Furthermore photo-electric properties in parallel configuration on platinum interdugitated contact are shown. Both types of Si-ncs results the bulk-heterojunction formation and photoconductivity is observed when the blends are irradiated AM1.5. The increase in photoconductivity is rather the same and ratio between photo- and dark-conductivity is about 1.7. The nanocrystal oxidation during laser ablation fabrication process in water hinders the transport properties of the blend.

Hybrid Polymer/Zinc Oxide Photovoltaic Devices with Vertically Oriented ZnO Nanorods and an Amphiphilic Molecular Interface Layer

We report on the effect of nanoparticle morphology and interfacial modification on the performance of hybrid polymer/zinc oxide photovoltaic devices. We compare structures consisting of poly-3-hexylthiophene (P3HT) polymer in contact with three different types of ZnO layer: a flat ZnO backing layer alone; vertically aligned ZnO nanorods on a ZnO backing layer; and ZnO nanoparticles on a ZnO backing layer. We use scanning electron microscopy, steady state and transient absorption spectroscopies, and photovoltaic device measurements to study the morphology, charge separation, recombination behavior and device performance of the three types of structures. We find that charge recombination in the structures containing vertically aligned ZnO nanorods is remarkably slow, with a half-life of several milliseconds, over 2 orders of magnitude slower than that for randomly oriented ZnO nanoparticles. A photovoltaic device based on the nanorod structure that has been treated with an amphiphilic dye before deposition of the P3HT polymer yields a power conversion efficiency over four times greater than that for a similar device based on the nanoparticle structure. The best ZnO nanorod:P3HT device yields a short circuit current density of 2 mAcm(-2) under AM1.5 illumination (100 mW cm(-2)) and a peak external quantum efficiency over 14%, resulting in a power conversion efficiency of 0.20%.