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ABSTRACT A series of well‐defined poly(3‐hexylthiophene)s (P3HT) of different molecular weight (MW) and high regioregularity was investigated for charge transport properties in as‐cast and melt‐crystallized films. The semicrystalline structure of the P3HT was characterized by X‐ray scattering and Atomic force microscopy. Crystallization by cooling from the melt led to a substantial increase in crystallinity and a stronger alignment of the crystals in comparison to as‐cast films. The increase in crystallinity went along with an increase in hole mobility of up to an order of magnitude as measured by the space charge limited current method. Additionally, the hole mobility depended on the long period of P3HT lamellae and consequently on the MW. In compliance with the long period, the charge carrier mobility first increased with the MW before decreasing again at the onset of chain folding. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51 , 943–951

Trennung auf Zeit: In einem Farbstoff-sensibilisierten nanokristallinen TiO2-Film (siehe Schema) kann ein bemerkenswert langlebiger (4 s) ladungsgetrennter Zustand erzeugt werden. Als Schlüsselparameter für die Steuerung des Ladungstransfers an der Farbstoff/TiO2-Grenzfläche erwies sich der Abstand zwischen dem Kationenzentrum des Farbstoffs und der Elektrodenoberfläche. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2005/z500363_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Abstract The classical acceptor motifs diketopyrrolopyrrole (DPP) and thienopyrrolodione (TPD) are copolymerized to yield the acceptor–acceptor polymer “Poly(DPP‐TPD).” The fundamental design idea is to maximize the electron affinity (EA), thus increasing the ambient stability of the reduced state against oxygen and water while ensuring high ion compatibility through the incorporation of hydrophilic oligoethylene glycol N‐substituents. Additionally, a highly planarized polymer structure is anticipated, due to the extended noncovalent interactions (conformational locking) between the carbonyl oxygen and the thiophene protons. Cyclic voltammetry, spectroelectrochemistry, ultraviolet photoelectron spectroscopy, ultraviolet‐visible absorption spectroscopy, and organic field effect transistor (OFET) characterization demonstrate the suitability for n‐type organic electrochemical transistor (OECT) devices. High EA, ionization potential, and good electron mobility (µ e(OFET) ) are shown, in addition to the electrochemical reduction of polymer films in aqueous electrolyte. In n‐type OECTs, poly(DPP‐TPD) demonstrates a moderate threshold voltage of V th = 0.58 V and an outstanding µC * value of 7.62 F cm −1 V −1 s −1 . Cycling studies consisting of pulsed on‐ and off‐switching of the device at gate voltages between V g = 0.6–0.8 V in the saturation regime reveal high stability for more than 2700 cycles with rapid switching kinetics.

In the present work the adsorption of a new dye, [Ru(dcbpyH(2))(2)(bpy-TPA(2))](PF(6))(2), and the well-known (Bu(4)N)(2)[Ru(dcbpyH)(2)(NCS)(2)] complex on mesoporous anatase films were investigated to clarify the role of the carboxylate groups in the anchoring process of the dyes on the semiconductor surface. For this purpose UV-vis, Raman, resonance Raman, and ATR-FTIR spectroscopies have been used. The results of the Raman experiments at different excitation wavelengths demonstrate that photoinduced charge-transfer processes take place efficiently between the adsorbate and the substrate. Moreover, this is the first time that the Raman spectrum of a Ru-bpy dye (in this case, the dye N719) adsorbed on TiO(2) has been obtained without the resonance condition, only by means of SERS enhancement. The coordination of both complexes on the TiO(2) paste films is proposed to occur via bidentate or bridging linkage.

Donor antenna dyes provide an exciting route to improving the efficiency of dye sensitized solar cells owing to their high molar extinction coefficients and the effective spatial separation of charges in the charge-separated state, which decelerates the recombination of photogenerated charges. Vertically oriented TiO(2) nanotube arrays provide an optimal material architecture for photoelectrochemical devices because of their large internal surface area, lower recombination losses, and vectorial charge transport along the nanotube axis. In this study, the results obtained by sensitizing TiO(2) nanotube arrays with the donor antenna dye Ru-TPA-NCS are presented. Solar cells fabricated using an antenna dye-sensitized array of 14.4 microm long TiO(2) nanotubes on Ti foil subjected to AM 1.5 one sun illumination in the backside geometry exhibited an overall conversion efficiency of 6.1%. An efficiency of 4.1% was obtained in the frontside illumination geometry using a 1 microm long array of transparent TiO(2) nanotubes subjected to a TiCl(4) treatment and then sensitized with the Ru-TPA-NCS dye. Open circuit voltage decay measurements give insight into the recombination behavior in antenna-dye sensitized nanotube photoelectrodes, demonstrating outstanding properties likely due to a reduction in the influence of the surface traps and reduced electron transfer from TiO(2) to ions in solution.

We unveil a concept for the design of cross-linkable semiconducting polymers that is based on a modular tercopolymerization which stands out by its low synthetic effort, easy accessibility, and its broad range of applications. 3-(6-Azidohexyl)thiophene was used as a comonomer in the synthesis of a variety of low-bandgap copolymers using different polymerization techniques such as Suzuki–Miyaura cross-coupling and Stille cross-coupling. We show that when only a small amount (5–10 mol %) of azide groups is introduced into the polymers, the impact on absorption and electrochemical properties (HOMO/LUMO values) is negligible. The small amount of azide functionality is however enough to obtain polymers that can easily be cross-linked by UV illumination. Thermal stability of the solid state packing and alignment is studied in neat polymer thin films as well as in blends with [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) as a relevant model blend system. Solvent resistivity of these polymer films is investigated by absorption and photoluminescence measurements. It is finally shown in organic field effect transistors that the introduction of 10% azide-functionalized monomer does not considerably influence hole transport mobility (0.20–0.45 cm2 V–1 s–1).

We compare the results from time-resolved fluorescence anisotropy experiments and molecular modelling on perylene bisimide acrylate dimers which allows us to connect the observed spectral signatures unambiguously with the non-stacked and two (parallel and anti-parallel) stacked conformations. For the parallel stacked conformation the experimental data can be reproduced quantitatively using a model that assumes structural relaxation in the electronically excited state of the stacked aggregate. For the non-stacked conformation we find quantitative agreement between experiment and modelling only if a fast hopping of the electronic excitation between the perylene bisimide subunits is taken into account.

Poly(ethylene glycol) (PEG)-based bottlebrush polymer electrolytes exhibit improved room-temperature ionic conductivity and reduced crystallinity compared to those of semicrystalline poly(ethylene oxide) (PEO). However, these graft copolymers suffer from low mechanical stability. Therefore, we synthesized a PEG-based bottlebrush polymer having a polynorbornene backbone using ring-opening metathesis polymerization, and it was mechanically reinforced using three strategies: (a) by blending with a polynorbornene (PNb) homopolymer, (b) filling with TiO2 nanoparticles, or (c) via block copolymerization with a PNb segment. All three systems were converted to solid polymer electrolytes by adding LiTFSI, and their thermal, mechanical, and detailed electrochemical properties in symmetrical Li/SPE/Li cells over a large number of cycles are given. All solid-state lithium metal battery (Li/SPE/LFP) cells were fabricated, and charge/discharge cycles as well as the cycling behavior were comparatively studied. It was found that block copolymerization resulted in the highest storage modulus above 0.1 Hz and overall ionic conductivity (in the whole range of 25 to 80 °C) compared to those of the other two strategies. Furthermore, the highest accessible discharge capacities (159 mA h g–1) and highest capacity retention of 88% after 50 cycles were also achieved with the block copolymer concept.

A series of poly(3-hexylthiophene)-block-poly(ethylene glycol) (P3HT-b-PEG) with constant P3HT block length block and variable PEG block lengths are presented. Alkyne-functionalized P3HT with high absolute molecular weight of 11.4 kg/mol is combined with azide-functionalized PEGs via copper-catalyzed alkyne–azide cycloaddition (CuAAC). The resulting P3HT-b-PEG block copolymers have PEG weight fractions between 15 and 64 wt %. In bulk materials the crystallinity in the conjugated block is similar to pure P3HT, while the crystallinity of PEG is influenced with decreasing PEG block length. On addition of MeOH as a nonsolvent for the P3HT block, these block copolymers are able to form stable micellar aggregates if the PEG fraction is >31 wt %. In AFM, DLS, and cryo-TEM, P3HT-b-PEG micelles are found to have a spherical or cylindrical shape with diameters of around 25 nm and lengths between 40 nm and some hundred nanometers. It is found that short PEG blocks lead to bigger block copolymer micelles. Thus, a correlation of composition on solution structure and its consequences on the crystallization of both blocks is given.

Tailor-made synthesis and structure-property relationship of several swallow-tail N-substituted perylene bisimide (PBI) dyes are presented. PBI derivatives were synthesized by two distinct synthetic approaches, the details being evaluated herein. All the PBIs carry either alkyl swallow-tail or oligoethylenglycolether (OEG) swallow-tail moieties as N-substituents, and many of them are unsymmetrically substituted. We avoided substitution at bay positions of the perylene core to maintain the planarity and strong pi-pi interactions, which favor intermolecular order and charge carrier transport. The thermotropic behavior, which is strongly influenced by the nature of the substituents was investigated using differential scanning calorimetry (DSC), polarization optical microscopy (POM), and X-ray diffraction measurements (XRD). The introduction of OEG swallow-tail units facilitates thermotropic liquid crystalline behavior in most cases and the unsymmetrical substitution allowed the tuning of the mesophase-width. The mesophases exhibit characteristic columnar hexagonal (Col(h)) packing arising from pi-pi interactions between cofacially orientated perylene molecules. Thus, the inherent tendency of PBI molecules for crystallization could be effectively suppressed by incorporating flexible OEG swallow-tail units only at imide positions. This molecular design was crucial to obtain liquid crystallinity and intracolumnar long-range order. The substituents did not influence the electronic energy levels such as HOMO and LUMO.

Though several techniques have been reported on the alignment of conventional block copolymers, the macroscopic vertical orientation of semiconductor block copolymer microdomains in thin films has still not been accomplished. Here, we report the control on the alignment of nanostructures in a semiconductor amphiphilic block copolymer comprising an amorphous triphenyldiamine hole conductor block and a hydrophilic poly(styrene sulfonate) segment. Three different compositions with a hole conductor content of 57, 72, and 79 wt % were synthesized using a combination of controlled reversible addition/fragmentation transfer polymerization and "click" chemistry. All polymers feature a narrow molecular weight distribution. Cryo-TEM reveals the formation of micelles in DMF solutions of the amphiphilic copolymer having nanoscopic dimensions. The micelle size correlates well with the X-ray analysis of dried bulk samples. Atomic force microscopy (AFM) confirms the micellar structure in the as-cast films. Thermal annealing causes an aggregation of micelles but did not lead to morphologies known for conventional block copolymers. However, annealing in saturated DMF vapor induces a morphology transition and a vertical orientation of the microdomains which was determined by grazing incidence small-angle X-ray scattering and AFM. The morphology varies from lamella to cylinders with increasing content of the hole-conductor block. The orientation arises from the controlled evaporation of the solvent, a mechanism that is similar to that observed for conventional block copolymers. Our approach demonstrates the macroscopic vertical alignment of nanodomains in semiconductor block copolymers which is a key requirement for applications in hybrid devices.

Abstract PEDOT:PSS [poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate] is a widely used insoluble conducting polymer, which is therefore processed from dispersions. In this work, PEDOT homopolymers (PEDOT‐C 6 C 8 1 and 2) highly soluble in common solvents like toluene, tetrahydrofuran, and chloroform are synthesized with a high control of molecular weight and low dispersity using Kumada catalyst transfer polymerization of a newly synthesized EDOT monomer carrying a branched alkyl substituent. Pristine PEDOT‐C 6 C 8 allows the use in accumulation mode transistors with a high charge carrier mobility of 5 × 10 − 4 cm 2 V −1 s −1 . Moreover, these polymers can be doped in a controlled fashion, reaching conductivities of 10 −3 S cm −1 at 10 mol% of a dopant, Spiro‐MeOTAD(TFSI) 2 . The doped state is remarkably stable, retaining 80% of the initial value after annealing under nitrogen at 100 °C and being exposed to ambient atmosphere for up to 12 h. During doping, the hole injection barrier decreases and reaches an impressively low value of 130 meV at only 2.5 mol% dopant loading without loss in carrier mobility; as monitored using ultraviolet photoelectron‐ and impedance spectroscopy. This new design concept leading to highly soluble polymers with well‐controlled molecular weights provides solution‐processable PEDOT dopable in a well‐controlled fashion.