P3HT Solution Research Articles

Deep characterization of the electrical features of Ag/P3HT/SiNWs Schottky diodes by machine learning models based on experimental study

In the present paper, silicon nanowires (SiNWs) surface covered by organic semiconducting polymer (P3HT) were used as the base material for the formation of the Ag/P3HT/SiNWs Schottky diode. Based on Current-Voltage (I-V) experimental study, different machine learning models are used to predict the current output of the Ag/P3HT/SiNWs diode taking into account changes in the applied voltage and immersion time of SiNWs in P3HT polymer solution. We used mathematical, decision tree, and Artificial Neural Network (ANN) models. The ANN model is the best model describing the changes of I-V characteristics with different immersion durations. The ANN, which is a perception layer with 48 neurons in its hidden layer, was trained using real current readings collected at different immersion times in P3HT solution ranging from 30 min to 210 min and voltages from -10 V to +10 V. ANN model achieves a mean squared error of 4.24 10−7, a mean absolute error of 3.82 10−4, a root mean square error of 6.7 10−4, and an R-squared value of 0.999997, indicating its exceptional predictive accuracy. The input layer of the model includes 244 data points representing time and voltage values, while the output layer provides the corresponding values of 844 data points. Using only two hidden layers, this model accurately predicts the current output for the Ag/P3HT/SiNWs Schottky diode. Comparing it with other models, the ANN method offers very accurate and fast predictions.

Inkjet-printed thin-film transistors using surfactant-based transition-metal dichalcogenide nanocomposites suspended in polymeric semiconductors

Ink formulations containing a suspension of single-crystalline molybdenum disulfide (MoS2) nanosheets suspended in the polymeric semiconductor poly(3-hexylthiophene-2,5-diyl) (P3HT) were inkjet printed for the fabrication of thin-film transistors (TFT). The MoS2 nanosheets were treated with the surfactant trichloro(dodecyl)silane (DDTS) to functionalize the MoS2 surface and created a more stable suspension, reducing the agglomeration of MoS2 suspended in the P3HT solution. This ink formulation was inkjet printed onto the surface of thermal oxide coated, p+-Si wafers to form common-gate TFT device structures. The printed semiconductor formed the active region of a hybrid MoS2 suspension in P3HT of the TFTs. The field-effect mobility for the hybrid-ink TFTs was found to be three times (3×) higher compared to reference devices using pristine P3HT without the suspension. The functionalized MoS2 suspension was also found to form thinner nanosheet suspensions within the P3HT matrix that resulted in approximately 60% higher field-effect mobility compared to hybrid inks without the surfactant. The enhancement of the electrical properties of the TFTs was determined to be due to a structural change in the thin-film semiconductor. The observed current–voltage (I–V) changes were correlated to measurable structural alterations in the semiconductor thin film characterized by x-ray diffraction, atomic force microscopy, and UV–visible absorption spectroscopy.

Thermal Annealing Impact on Optical Properties of Spin-coated P3HT: CdS Thin Film

Polymers are flexible materials that can be easily processed and are formed into a thin film by several methods such as spin-coating, dip-coating, film-casting, and printing. The spin coating method has been extensively utilized in fabricating solution-prepared organic/inorganic electronic devices, this technique is positively efficient in generating thin film apart from being a flexible method to execute. In this study, poly(3-hexylthiophene) (P3HT) material is selected as polymer and cadmium sulphide (CdS) as nanoparticles to produce a hybrid nanocomposite thin film through the process spin-coating method. The P3HT and cadmium ion solution were used to fabricate a thin film onto a quartz glass substrate at a spin speed of 500 rpm for 10 seconds. This spin-coated thin film was heated at different temperatures such as 40°C, 80°C, 120°C, and 160°C for optical properties using a UV-Vis spectrophotometer. The UV-Vis absorption spectra of P3HT: CdS indicated absorption peaks in the UV region, which were ascribed to the band gap of the P3HT: CdS thin film. Our results showed that the optical properties of the P3HT: CdS be contingent on the annealing temperature. The film at room temperature yielded a band gap value of 1.98 eV, at 40°C it resulted in 1.99 eV. The band gap value was increased when annealed at 80°C with 2.02 eV. Annealing temperatures were then raised to 120°C and 160°C, leading to band gap values of 3.11 eV and 2.80 eV respectively.

Investigation of P3HT:WO3 hybrid electrochromic thin films prepared by solution blending doping

Although poly(3-hexylthiophene) (P3HT) is a promising p-type conjugating polymer to optimize optical and electrical properties, it is known to be chemically unstable. To overcome this unstability, WO3 incorporated P3HT hybrid thin films has been synthesized by very simple solution blending doping method. Different amounts of WO3 were added into the P3HT solution and the incorporation of WO3 particles was confirmed by scanning electron microscopy, atomic force microscopy, and photoluminescence spectroscopy. The electrochemical reactions in 1 M lithium perchlorate (LiClO4)/propylene carbonate (PC) were studied by cyclic voltammetry and by electrochemical impedance spectroscopy. With the increase amount of WO3 in P3HT, the electrochromic efficiency increases first and then decreases. The optimum concentration was found as 30 wt% of WO3. The efficient interaction and well distribution between WO3 and P3HT improves the capacitive properties and electrochromic performance resulting a 110% increase in coloration efficiency (from 220 cm2/C to 464 cm2/C). Moreover, WO3 doped hybrid films shows long-term cyclability than undoped P3HT films. Structural and electrochemical investigations suggest that the optimum amount of WO3 doping is an alternative way to obtain high performance and environmentally stable electrochromic devices.

Dynamics of Poly(3-hexylthiophene) Monolayers at Solution/Graphite Interfaces.

We have studied the dynamics of poly(3-hexylthiophene) (P3HT) monolayers at the interfaces between highly oriented pyrolytic graphite (HOPG) and P3HT solutions in 1,2,4-trichlorobenzene, using scanning tunneling microscopy (STM). Real-time STM observation at room temperature reveals that P3HT molecules adsorbed on graphite are substantially mobile even in densely packed conditions, causing significant fluctuations of the self-organized monolayer of P3HT. We find that in the monolayers, the orientational order is limited to a short range comparable to the polymer chain length. We show that our observations can be understood based on a 2D semiflexible lattice polymer model by performing kinetic Monte Carlo simulations.

Nanostructure-assisted solvent vapor annealing of conjugated polymer thin films for enhanced performance in volatile organic compound sensing

Controlling both the charge transport properties and morphologies of conjugated polymer (CP) films is critical for the practical use of CP-based organic field-effect transistor (OFET) sensors in diverse applications. Herein, we report a facile processing strategy for improving the sensing performance of OFET-based volatile organic compound (VOC) sensors, which significantly enhances charge transport and increases the surface-to-volume ratio of conjugated polymer thin films using solvent vapor annealing (SVA) in the presence of pre-formed nanostructures (PNs) on the films. In this study, two different PN-embedded poly(3-hexylthiophene) (P3HT) films, viz. PN1-P3HT and PN2-P3HT, were obtained from a sonication-treated P3HT solution with nanocrystals (NCs) and nanorods (NRs) and UV-light-irradiated P3HT solution with NCs and nanowires (NWs), respectively. The effect of SVA on the morphologies and charge transport of the PN-embedded P3HT films was systematically studied by atomic force microscopy, polarized optical microscopy, X-ray diffraction analysis, and charge-carrier mobility measurements. Gas sensing measurements were performed by exposing the sensors to VOCs in a concentration range of 1–100 ppm. After SVA, longer, one-dimensional P3HT nanostructures were formed in the PN-embedded films, while some small nanostructures appeared in the pristine P3HT films. Consequently, the PN2-P3HT OFETs exhibited a significant enhancement (2-fold) in charge transport and an increase (1.7-fold) in the surface-to-volume ratio after the SVA. Furthermore, the OFET sensors exhibited excellent responsivities (20–70%) and rapid response/recovery times (110–160 s) in the detection of VOCs.

An insight into the mechanism of charge transfer of organic (P3HT): inorganic (CZTS) composites for hybrid photovoltaics

ABSTRACT In the present work, Cu2ZnSnS4 (CZTS) nanoparticles were prepared with different S-sources using a hot injection colloidal route. The morphological and structural properties have been analyzed. The dendrimers like nanocrystals were observed using thiourea while, spherical and triangular-shaped nano-particles were observed using elemental-S, and 1-Dodecanthiol (1-DDT) respectively. The charge transfer studies have been carried out and analyzed using Stern-Volmer curves for all three CZTS NPs with P3HT solution. CZTS NPs with thiourea as S-source were found to have the best charge-transfer capabilities. These nanoparticles were then mixed with a polymer and aromatic fullerene and were used as the active layer material for the hybrid photovoltaic solar cell. The increment of 34% power conversion efficiency (PCE) was observed with a small amount (6%) of CZTS nanoparticles. Surface morphology observed using atomic force microscopy of an active layer shows an increase in PCE with the decrease in the roughness of the film.

Effects of solvation shell relaxation on chain association mechanisms in poly(3-hexylthiophene) solutions.

Using poly(3-hexylthiophene) (P3HT) as a model conjugated polymer and atomistic molecular dynamics simulations with carefully verified force fields, we performed in-depth investigations of solvation shell properties of P3HT chains (15 repeating units per chain) in two representative groups of non-polar (or aprotic) organic solvents (better solvents: ortho-dichlorobenzene, bromobenzene, and chlorobenzene; poorer solvents: chloroform, para-xylene, and toluene). We demonstrated that solvation shell relaxation properties in P3HT solutions dictate the formation of regular π-π associations and, hence, crystallinity through the initial chain association and subsequent chain sliding. In contrast, the mean features of polymer-solvent interactions, including solvation free energy and radial distribution function, present little or no difference for all solvent media investigated. Better-solvent media were revealed to bear relatively large values of the first solvation shell relaxation time (τ1 ≫ 100 ps) as well as larger ratios of relaxation times for the first two solvation shells (τ1/τ2 > 2), and vice versa for poorer-solvent media (τ1 ≪ 100 ps and τ1/τ2 < 2). The linear hexyl side-chain unit was noted to substantially enlarge both quantities while notably reducing the solvation free energy as well. As discussed herein, these findings shed new light on the mechanistic features by which solvent quality impacts the degree of π-π association crucial for modern applications with crystalline conjugated polymers.

Dynamics of the sub-ambient gelation and shearing of solutions of P3HT and P3HT blends towards active layer formation in bulk heterojunction organic solar cells.

Organic solar cells (OSCs) containing an active layer consisting of a nanostructured blend of a conjugated polymer like poly(3-hexylthiophene) (P3HT) and an electron acceptor have the potential of competing against silicon-based photovoltaic panels. However, this potential is largely unfulfilled first due to interrelated production and stability issues of organic solar cells and second due to the unscalable nature of the generally employed spin coating process used for the fabrication of organic solar cells. Furthermore, alternatives to spin coating, especially relying on continuous polymer processing methods like extrusion and coating, cannot be readily applied due to the typically low shear viscosity and elasticity of polymer solutions making up the active layer. Recently, He et al. have reported that the gelation of P3HT with [6,6]-phenyl-C61-butyric acid methyl ester (PC60BM) under sub-ambient conditions can provide a new route to the processing of the active layers of bulk heterojunction solar cells. Furthermore, increases in power conversion efficiencies (PCEs) of the P3HT/PC60BM active layer were determined to be possible under certain shearing and thermal histories of the P3HT/PC60BM gels. Here oscillatory and steady torsional flows were used to investigate the gel formation dynamics of P3HT with a recently proposed non-fullerene acceptor o-IDTBR under sub-ambient conditions and compared with the gelation behavior of P3HT/PC60BM blends. The rheological material functions as well as the gel strengths defined on the basis of linear viscoelastic material functions, characterized via small-amplitude oscillatory shearing, were observed to be functions of the P3HT and o-IDTBR concentrations, the solvent used and the shearing conditions. Overall, the P3HT gels which formed upon quenching to sub-zero temperatures were found to be stable during small-amplitude oscillatory shear (linear viscoelastic range) but broke down even at the relatively low shear rates associated with steady torsional flows, suggesting that the shearing conditions used during the processing of gels of P3HT and blends of P3HT with small molecule acceptors can alter the gel structure, possibly leading to changes in the resulting active layer performance.

The nonlinear optical properties of P3HT under picosecond laser irradiation

The nonlinear optical properties of P3HT in orthodichlorobenzene were investigated by Z-scan technique using second harmonic generation (532 nm) of mode-locked Nd:YAG laser in the picosecond domain. The experimental results show the magnitude of their nonlinear refraction indices was up to the order of 10−11 esu. The reverse saturable absorption of P3HT solution was observed and their nonlinear absorption coefficients reach up to 3.4 cm/GW. The strong optical nonlinearity of P3HT may find its new application in the photoclectric field.

Electrical Signature of Ultrasound-Induced Anisotropic Self-Assembly of Poly(3-Hexylthiophene) (P3HT) during Channel Formation

We probed ultrasound irradiation-induced structural ordering of poly(3-hexylthiophene) (P3HT) chains during solidification of a sonicated P3HT solution by monitoring the temporal evolution of the electrical and spectroscopic signals. We observed a peak source-drain current in the test devices during the electrical channel formation, followed by a significant decrease, which has not been observed in the pristine P3HT solution as the solvent evaporates. Through P3HT concentration-dependent gated-sheet conductance and in-situ Raman spectroscopy measurements during channel formation, we found that the competition between aggregation of the disentangled P3HT chains in solution by sonication and the concentration-dependent chain interactions with solvent evaporation led to a distinct electrical signature in the channel formation of the sonicated P3HT film compared to that of the pristine P3HT. The finding provides insights into new opportunities through optimization between the thermodynamic and kinetic considerations in designing pre-deposition treatments for enhanced charge transport.

Charge Photogeneration in Composites of Fluorinated Carbon Nanotubes and Semiconducting Polymer P3HT

Spectroscopic and photovoltaic properties of composites of purified and subsequently fluorinated single‐walled carbon nanotubes (F‐SWCNTs) with conjugated polymer poly(3‐hexylthiophene) (P3HT) are tested. Adding cyclohexanone into o‐dichlorobenzene solution of P3HT and F‐SWCNTs significantly affects the composite morphology and promotes P3HT/F‐SWCNT nanofilament formation, as evidenced from atomic force microscopy (AFM) images of spin‐coated composite films. Also, nanofilament formation enhances quenching of P3HT photoluminescence by F‐SWCNTs. The performance of P3HT‐based organic photovoltaics (OPV) devices with separated semiconducting SWCNTs and F‐SWCNTs as the acceptor component of the active layer is comparable. Light‐induced electron paramagnetic resonance (EPR) signal intensity in P3HT/F‐SWCNT composite films and frozen solutions grows with increase in F‐SWCNT content, which is a signature of photoinduced electron transfer. Dramatic change in SWCNT electronic structure upon fluorination is also evidenced by UV–vis– near infra red optical absorption spectra, from which the bandgap of about 1.0 eV is derived for F‐SWCNTs. Overall, the experimental results confirm that fluorination efficiently converts metallic SWCNTs into semiconducting ones, and F‐SWCNTs can be used for as an electron acceptor component in OPV devices, in combination with polymer donors. Presently, the performance of P3HT/F‐SWCNT devices is limited by F‐SWCNT aggregation into bundles, which decreases P3HT/F‐SWCNT interface area.

Photovoltaic Characterization of Hybrid Bulk Heterojunction Solar Cell Incorporated Gold Nanoparticles Embedded in Active Layer

We attempt to study the effect of gold nanoparticles embedded into the active polymer of regioreguler poly (3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) on the charge kinetic to enhance the performance of bulk-heterojunction solar cell. It has been known that the generation of localized surface plasmon resonance (LSPR) would both increase the photon absorption and improve the efficiency of charge separation. Synthesis of gold nanoparticles stabilized by oleylamine (AuOA) was carried out by reduction method and resulted in the spherical shape of nanoparticles with a diameter size of ~12 nm. The absorbance spectra show the typical of surface plasmon peak of AuOA in solution at ~527 nm. Fabrication of inverted bulk-heterojunction solar cell device was done in the configuration of ITO/ZnO/P3HT:PCBM:AuOA/PEDOT:PSS/Ag. Incorporation of AuOA in polymer solution is clearly detected from the enhanced absorbance peak resulted from UV-Vis measurement and the mix solution of P3HT:PCBM:AuOA is quite stable in the concentration of AuOA less than 10 wt%. In our experiment, fabricated solar cell reveals the enhancement in current density at short circuit condition (Jsc) from 44.57 mA/cm2 to 56.14 mA/cm2 with the addition of 3.9 wt% AuOA in polymer solution along with the enhancement of power conversion efficiency (PCE) from 4.07% to 6.23% as characterized by J-V measurement. In our case, the voltage at open circuit condition (Voc) of the device does not show significant improvement.

Preparation of Nanocomposite-based High Performance Organic Field Effect Transistor via Solution Floating Method and Mechanical Property Evaluation.

We demonstrate that using nanocomposite thin films consisting of semiconducting polymer, poly(3-hexylthiophene) (P3HT), and electrochemically exfoliated graphene (EEG) for the active channel layer of organic field-effect transistors (OFETs) improves both device performances and mechanical properties. The nanocomposite film was developed by directly blending P3HT solution with a dispersion of EEG at various weight proportions and simply transferring to an Si/SiO2 substrate by the solution floating method. The OFET based on P3HT/EEG nanocomposite film showed approximately twice higher field-effect mobility of 0.0391 cm2·V−1·s−1 and one order of magnitude greater on/off ratio of ~104 compared with the OFET based on pristine P3HT. We also measured the mechanical properties of P3HT/EEG nanocomposite film via film-on-elastomer methods, which confirms that the P3HT/EEG nanocomposite film exhibited approximately 2.4 times higher modulus (3.29 GPa) than that of the P3HT film (1.38 GPa), while maintaining the good bending flexibility and durability over 10.0% of bending strain and bending cycles (1000 cycles). It was proved that the polymer hybridization technique, which involves adding EEG to a conjugated polymer, is a powerful route for enhancing both device performances and mechanical properties while maintaining the flexible characteristics of OFET devices.

Doped Poly(3-hexylthiophene) Coatings onto Chitosan: A Novel Approach for Developing a Bio-Based Flexible Electronic.

Conductive and flexible bio-based materials consisting of chitosan films coated with conductive poly(3-hexylthiophene) (P3HT) were prepared. Thermal, optical, mechanical, morphological, wettability, and conductive properties were analyzed. In a very simple and effective method of chitosan film modification, a controlled volume of a P3HT solution was deposited onto a previously formed chitosan film, assisted by the spin coating method. Later, P3HT-coated chitosan films were doped by simple contact with an aqueous solution of HAuCl4. The use of HAuCl4 becomes attractive because the reports on the doping process in this type of material using this reagent are still scarce and recent to date. In addition, since this acid is a well-known metal nanoparticle precursor, its use opens new future perspectives for these materials into new applications. The effect of P3HT concentration and doping times on film properties was studied. Attenuated total reflectance spectroscopy and UV-Vis spectroscopy allowed us to demonstrate that the presence of the P3HT coating and its doping induce significant changes in the vibrational modes and optoelectronic properties of samples. Additionally, the images obtained by scanning electron microscopy showed a well-distributed and homogeneous coating on the surface of chitosan films. Measured conductivity values of doped film samples fall in the range from 821.3 to 2017.4 S/m, representing, to the best of our knowledge, the highest values reported in the literature for chitosan/chitin-based materials. Indeed, these values are around or even higher than those obtained for some materials purely consisting of conductive polymers.

Nanostructural Manipulation of Poly(3-hexylthiophene) Aggregates for Organic Electrolyte-Gated Transistors.

In this study, we combine solubility-driven formation of poly(3-hexylthiophene) (P3HT) nanoaggregates and ion-gel-based organic electrolyte-gated transistors (OEGTs), to develop high-performance low-voltage switching devices. By in-situ solution blending of a good solvent (chloroform) and a poor solvent (acetone), we obtain dispersions of P3HT nanoaggregates. The aggregation and molecular ordering of P3HT are analyzed by UV-Vis absorption spectroscopy, atomic force microscopy imaging, and X-ray diffraction. The resulting P3HT aggregates are used as an active component of high-capacitance ion-gel dielectric based on P(VDF-HFP)/[EMIM][TFSI]. Wellconnected conductive channels in thin films of P3HT aggregates allow the effective modulation of current in ion gel-gated transistors with an on-state current above 10-3 A at an operational voltage less than -1 V. In searching for the optimal ratio of solvents, the highest mobility of 1.36 cm² V-1 s-1 in the tested OEGTs was observed when 5 vol% of acetone was incorporated into the stock solution of P3HT. This observation suggests that the nanostructural manipulation of polythiophene-based semiconductor is an effective method to produce efficient pathways for charge transport in OEGTs.

Solvent Effects on Morphology and Electrical Properties of Poly(3-hexylthiophene) Electrospun Nanofibers.

Herein, poly(3-hexylthiophene-2,5-diyl) (P3HT) nanofiber-based organic field-effect transistors were successfully prepared by coaxial electrospinning technique with P3HT as the core polymer and poly(methyl methacrylate) (PMMA) as the shell polymer, followed by extraction of PMMA. Three different solvents for the core polymer, including chloroform, chlorobenzene and 1,2,4-trichlorobenzene, were employed to manipulate the morphologies and electrical properties of P3HT electrospun nanofibers. Through the analyses from dynamic light scattering of P3HT solutions, polarized photoluminescence and X-ray diffraction pattern of P3HT electrospun nanofibers, it is revealed that the P3HT electrospun nanofiber prepared from the chloroform system displays a low crystallinity but highly oriented crystalline grains due to the dominant population of isolated-chain species in solution that greatly facilitates P3HT chain stretching during electrospinning. The resulting high charge-carrier mobility of 3.57 × 10−1 cm2·V−1·s−1 and decent mechanical deformation up to a strain of 80% make the P3HT electrospun nanofiber a promising means for fabricating stretchable optoelectronic devices.

Fabrication and properties of P3HT: PCBM/Cu2SnSe3 (CTSe) nanocrystals based inverted hybrid solar cells

Thin film solar cells with ITO/ZnO/P3HT:PCM:CTSe NCs/Ag structure were fabricated employing a fast and cost-effective procedure using blended solution of P3HT:PCBM:CTSe NCs deposited by spin casting, followed by thermal annealing steps. The CTSe NCs are prepared via solvothermal method. An inverted architecture of device with structure ITO/ZnO/P3HT: PCBM:CTSe NCs/Ag have been fabricated with different concentration of CTSe NCs in poly(3-hexyle thiophene) (P3HT): [6,6]phenyl-C61-butyric-acid-methyl-ester (PCBM) matrix. The effect of CTSe NCs on the performance of hybrid solar cell with optimized blend ratio of P3HT:PCBM and CTSe NCs has been investigated for optimum power conversion. The charge carrier extraction and recombination at the interface of donor-acceptor material were studied using Electrochemical impedance spectroscopy (EIS) under dark condition. EIS study has demonstrated that the charge transfer rate was higher for the device having optimized wt% of CTSe NCs (10 wt%) in P3HT:PCBM active layer. A significant improvement in the device performances was observed on incorporation of CTSe NCs. The device exhibited open circuit voltage (Voc) of 0.475 V, short circuit current density (Jsc) of 6.95 mA/cm2, fill factor (FF) of 0.41 and power conversion efficiency (PCE) of 1.35%.

Controlled Self-Assembly of Conjugated Polymers via a Solvent Vapor Pre-Treatment for Use in Organic Field-Effect Transistors.

A facile solution-processing strategy toward well-ordered one-dimensional nanostructures of conjugated polymers via a non-solvent vapor treatment was demonstrated, which resulted in enhancements to the charge transport characteristics of the polymers. The amount of crystalline poly(3-hexylthiophene) (P3HT) nanofibers was precisely controlled by simply varying the exposure time of solutions of P3HT solutions to non-solvent vapor. The effects of non-solvent vapor exposure on the molecular ordering and morphologies of the resultant P3HT films were systematically investigated using ultraviolet-visible (UV-vis) spectroscopy, polarized optical microscopy (POM), grazing incidence X-ray diffraction (GIXRD), and atomic force microscopy (AFM). The non-solvent vapor facilitates the π–π stacking in P3HT to minimize unfavorable interactions between the poor solvent molecules and P3HT chains. P3HT films deposited from the non-solvent vapor-treated P3HT solutions exhibited an approximately 5.6-fold improvement in charge carrier mobility as compared to that of pristine P3HT films (7.8 × 10−2 cm2 V−1 s−1 vs. 1.4 × 10−2 cm2 V−1 s−1). The robust and facile strategy presented herein would be applicable in various opto-electronics applications requiring precise control of the molecular assembly, such as organic photovoltaic cells, field-effect transistors, light-emitting diodes, and sensors.

Aggregate dispersions to enhance the intrachain order in surfactant-stabilized aqueous colloids of poly(3-hexylthiophene)

Aqueous colloids of conjugated polymers (CP), such as poly(3-hexylthiophene) (P3HT), are an attractive alternative for processing CP-based materials because (1) the microstructure of the conjugated polymers can be optimized during the formation of the colloid and (2) this method can significantly reduce the amount of hazardous organic solvents used during manufacturing. This investigation addresses the optimization of the polymer structure by studying the intrachain order of P3HT aggregates pre-assembled in mixtures of chloroform (CF) with dichloromethane (DCM) and subsequently dispersed in aqueous solutions of the surfactant sodium dodecyl sulfate (SDS) using a mini-emulsion method. Compared to an amorphous solution of P3HT, the observed intrachain order of P3HT in the colloids is much higher when using aggregate dispersions pre-assembled in the CF:DCM mixtures. Similar results are observed for aggregate dispersions of a benchmark organic photovoltaic system composed of P3HT and the fullerene derivative phenyl-C61-butyric acid methyl ester (PCBM), but in this case the intrachain order of P3HT in the P3HT:PCBM colloids is anomalously higher than the pure P3HT colloids. Atomic force microscopy (AFM) imaging reveals changes in the dominant structural motifs and morphology of the colloidal P3HT films, but not in a way that correlates with films processed from the aggregate dispersions.