Semiconducting Polymer Blends Research Articles

Role of Molecular Weight Distribution on Charge Transport in Semiconducting Polymers

Model semiconducting polymer blends of well-controlled molecular weight distributions are fabricated and demonstrated to be a simple method to control intermolecular disorder without affecting intramolecular order or degree of aggregation. Mobility measurements exhibit that even small amounts of low molecular weight material are detrimental to charge transport. Trends in charge carrier mobility can be reproduced by a simple analytical model which indicates that carriers have no preference for high or low molecular weight chains and that charge transport is limited by interchain hopping. These results quantify the role of long polymer tie-chains and demonstrate the need for controlled polydispersity for achieving high carrier mobilities.

Organic Polymers: Photostimulation of Whole‐Cell Conductance in Primary Rat Neocortical Astrocytes Mediated by Organic Semiconducting Thin Films (Adv. Healthcare Mater. 3/2014)

On page 392, Valentina Benfenati, Maria Rosa Antognazza, Michele Muccini, and colleagues show how the photostimulation of a semiconducting polymer blend modulates the ion channel conductance of astrocytes cultured on top of the device. The device can be used as a selective tool to study ion channel conductances in non-excitable cells.

Solvent Additive Control of Morphology and Crystallization in Semiconducting Polymer Blends

4-bromoanisole is used as a very versatile processing additive to control the phase separation and phase purity of organic photovoltaic devices. Polymer-polymer blends based on P3HT as donor and a wide range of acceptor materials (F8TBT, PCDTBT,…︁) are investigated. The additive promotes the aggregation of P3HT which improves the morphology for both initially mixed and demixed blends.

Resistive Switches: Spinodal Decomposition of Blends of Semiconducting and Ferroelectric Polymers (Adv. Funct. Mater. 10/2011)

The operation of resistive switches based on phase-separated blends of organic ferroelectrics and semiconductors depends significantly on the microstructure of such systems. On page 1887, Kamal Asadi and co-workers show that the preferred bicontinuouse microstructure is formed by spinodal-decomposition phase separation of the blend. The cover image shows the corresponding microstructure probed by atomic force microscopy: the smooth valley is the featureless amorphous semiconductor phase surrounded by a crystalline ferroelectric matrix.

Design of highly emissive polymer dot bioconjugates for in vivo tumor targeting.

Lighting up brain tumors: Highly fluorescent nanodots that consist of semiconducting polymer blends were attached to the peptide ligand chlorotoxin. The nanodot–chlorotoxin conjugates were specifically targeted to malignant brain tumors in a transgenic mouse model, thus proving their potential as in vivo probes for clinical cancer diagnostics (see picture).

Spinodal Decomposition of Blends of Semiconducting and Ferroelectric Polymers

AbstractThe operation of resistive switches based on phase‐separated blends of organic ferroelectrics and semiconductors depends significantly on the microstructure of such systems. A wide range of analysis techniques are used to characterize spin‐coated films of the ferroelectric random copolymer poly(vinylidene fluoride‐trifluoroethylene) [P(VDF‐TrFE)], and the semiconducting polymer, regio‐irregular poly(3‐hexylthiophene) (rir‐P3HT). The blend separates into amorphous rir‐P3HT domains embedded in a crystalline P(VDF‐TrFE) matrix. The rir‐P3HT domains are continuous throughout the film, from the substrate/blend interface to the blend/air interface. We also investigate the rir‐P3HT domain size and number as a function of composition and find – unexpectedly – a rather mono‐disperse domain size distribution for a given rir‐P3HT:P(VDF‐TrFE) ratio. The domain size increases with rir‐P3HT content, indicating that the solidification is not dominated by nucleation processes. Spinodal decomposition is therefore more likely to be responsible for the microstructure induced in the rir‐P3HT:P(VDF‐TrFE) blends. Since spinodal decomposition occurs spontaneously without the presence of a nucleation step, this can facilitate processing considerably, since the intricate control of nucleation processes (homogenous or heterogenous) is rendered unnecessary. Measurement of the lateral conductivity of the blends demonstrates that the rir‐P3HT domains are electrically not connected, supporting the microstructural evidence. A perpendicular current through the film is measured using both Au and Ag electrodes as a function of blend composition. A model was used to interpret the electrical transport. The injection for Ag diodes poled into the ON‐state preferentially occurs at the circumference of the rir‐P3HT domains. An accumulation width over which the injection occurs is estimated to be of the order of a few hundred nm.

Organic thin-film transistors with a photo-patternable semiconducting polymer blend

A blend of organic semiconductors and photocrosslinkable insulating polymers was photolithographically patterned to yield organic thin-film transistors (OTFTs). The semiconducting polymer of the blend, poly(3-hexylthiophene), was present as a nanofibrillar network and yielded excellent electronic properties. The insulating polymer matrix, poly(vinyl cinnamate), provided the photosensitivity required for photopatterning. The photopatterned TFT devices showed large on/off ratios (>105) and high mobilities (0.015 cm2 V−1s−1) comparable to those of devices patterned by conventional means using the same semiconducting materials. This simple method permitted the high-resolution cost-effective patterning of organic semiconductors and may play an important role in the mass-production of organic electronic devices.

Effects of Intercalation on the Hole Mobility of Amorphous Semiconducting Polymer Blends

Fullerenes have been shown to intercalate between the side chains of many crystalline and semicrystalline polymers and to affect the properties of polymer:fullerene bulk heterojunction solar cells. Here we present the first in-depth study of intercalation in an amorphous polymer. We study blends of the widely studied amorphous polymer poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-p-phenylene vinylene) (MDMO-PPV) with a variety of molecules using photoluminescence measurements, scanning electron microscopy, and space-charge limited current mobility measurements. The blends with elevated hole mobilities exhibit complete photoluminescence quenching and show no phase separation in a scanning electron microscope. We conclude that intercalation occurs in MDMO-PPV:fullerene blends and is responsible for the increase in the MDMO-PPV hole mobility by several orders of magnitude when it is blended with fullerenes, despite the dilution of the hole-conducting polymer with an electron acceptor.

Imaging of semiconducting polymer blend systems using environmental scanning electron microscopy and environmental scanning transmission electron microscopy

This study has investigated the potential of environmental electron microscopy techniques for studying the structure of polymer-based electronic devices. Polymer blend systems composed of F8BT and PFB were examined. Excellent contrast, both topographical and compositional, can be achieved using both conventional environmental scanning electron microscopy (ESEM) and a transmission detector giving an environmental scanning transmission electron microscope (ESTEM) configuration. Controllable charging effects present in the ESEM were observed, giving rise to a novel voltage contrast. This shows the potential of such contrast to provide excellent images of phase structure and charge distributions.

Nanoscale electrical characterization of semiconducting polymer blends by conductive atomic force microscopy (C-AFM)

For the first time local electrical characteristics of a blend of two semiconducting polymers were studied with conductive atomic force microscopy (C-AFM). The investigated mixture is potentially interesting as the active layer in plastic photovoltaic devices. Besides conventional topography analysis of morphology and phase separation, the internal structure of the active layer was investigated by observing the current distribution with nanoscale spatial resolution. Similar to force spectroscopy, current imaging spectroscopy was performed during scanning the sample surface. Different types of current–voltage ( I– V) characteristics were extracted from the array of spectroscopic data obtained from each point of the scans, and local heterogeneities of the electric characteristic were determined and discussed.

Time-Resolved Light Scattering Studies of Phase Separation in Thin Film Semiconducting Polymer Blends during Spin-Coating

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTTime-Resolved Light Scattering Studies of Phase Separation in Thin Film Semiconducting Polymer Blends during Spin-CoatingPaul C. Jukes, Sasha Y. Heriot, James S. Sharp, and Richard A. L. JonesView Author Information Department of Physics and Astronomy, University of Sheffield University, Sheffield S3 7RH, UK, and School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK Cite this: Macromolecules 2005, 38, 6, 2030–2032Publication Date (Web):February 24, 2005Publication History Received8 November 2004Revised31 January 2005Published online24 February 2005Published inissue 1 March 2005https://doi.org/10.1021/ma0477145Copyright © 2005 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1287Altmetric-Citations75LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (185 KB) Get e-AlertsSUBJECTS:Chemical structure,Optical properties,Phase separation,Scattering,Solvents Get e-Alerts

Photovoltaic Properties of a Conjugated Polymer Blend of MDMO−PPV and PCNEPV

Photovoltaic properties of solution-processed semiconducting polymer blends have been studied. It is demonstrated that photoinduced charge transfer occurs in binary mixtures of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO−PPV) and poly[oxa-1,4-phenylene-(1-cyano-1,2-vinylene)−(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene)-1,2-(2-cyanovinylene)-1,4-phenylene] (PCNEPV). Further, it is shown that the photovoltaic performance is improved by a thermal treatment which alters the morphology of the photoactive layer. The temperature necessary to achieve the enhanced performance is related to transition temperatures of the pure polymers. Device optimization yields solar cells with a power conversion efficiency of 0.75% under standard test conditions (AM 1.5, 1000 W/m2).

White Electrophosphorescence from Semiconducting Polymer Blends

White emission from polymer light‐emitting diodes (PLEDs) is demonstrated using semiconducting polymers blended with organometallic emitters and spin‐cast from solution. Because a single semiconducting polymer was used as the common host for red, green, and blue emission, the color coordinates, color temperatures, and color rendering indices of the white emission are insensitive to the brightness, applied voltage, and applied current density. The PLEDs have luminous efficiency of 4.3 cd A–1 and luminance of 223 cd m–2 at current density of 5.2 mA cm–2 (V = 14 V); at 17 V, L = 1.2 × 104 cd m–2.

Templating organic semiconductors via self-assembly of polymer colloids.

A route for producing semiconducting polymer blends is demonstrated in which a doped pi-conjugated polymer is forced into a three-dimensionally continuous minor phase by the self-assembly of colloidal particles and block copolymers. The resulting cellular morphology can be viewed as a high-internal phase polymeric emulsion. Compared with traditional blending procedures, this process reduces the percolation threshold for electrical conductivity by a factor of 10, increases the conductivity by several orders of magnitude, and simultaneously improves thermal stability. Following this route, new applications can be envisaged for semiconducting polymer blends that require only minimal concentrations of doped pi-conjugated polymer.

Excitation energy migration in highly emissive semiconducting polymer blends probed by photoluminescence detected magnetic resonance

The excitation energy migration (EEM) in methyl-substituted ladder-type poly( para-phenylene) (m-LPPP) doped with small amounts of the red emitter poly(perylene-co-diethynylbenzene) (PPDB) was studied by photoluminescence (PL) detected magnetic resonance (PLDMR). It is suggested that the EEM process proceeds via two steps: (1) migration within the host and (2) transfer from the host to the guest. The contributions of the emissions from m-LPPP and PPDB to the PL-enhancing polaron PLDMR at g=2, which are due to a reduction in the density of polarons acting as singlet exciton (SE) quenching centers, evolve differently with temperature. This provides clear evidence for SE migration in m-LPPP. The triplet exciton (TE) PLDMR at g=4 shows a distinct peak for each polymer, with the intensity of the PPDB feature being proportional to its concentration. However, the spectral dependence recorded at the peak of each resonance is the same. This rules out the triplet–triplet-annihilation-mechanism in these blends for simple energetic reasons. Instead we propose that the resonance at g=4 is due to a SE-quenching mechanism similar to that for the polaron resonance at g=2. At the field-for-resonance the number of TE’s decreases, and hence the PL increases.

Enhanced electroluminescence from semiconducting polymer blends

We demonstrate the enhancement of electroluminescence (EL) from blends of poly(3-hexylthiophene) (P3HT) in poly(2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylene vinylene) (MEH-PPV). The external EL quantum efficiency η of Ca/P3HT:MEH-PPV/ITO diodes initially increases with P3HT content and goes through a maximum at η = 1.7% photons/electron with only 1 wt.% P3HT; greater than in Ca/MEH-PPV/ITO by a factor of two to three and greater than in Ca/P3HT/ITO by more than three orders of magnitude. At 4 V forward bias, these devices emit signal-red light with brightness of about 220 cd/m 2.