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Nanocavities composed of lipids and block polymers have demonstrated great potential in biomedical applications such as sensors, nanoreactors, and delivery vectors. However, it remains a great challenge to produce nanocavities from fluorescent semiconducting polymers owing to their hydrophobic rigid polymer backbones. Here, we describe a facile, yet general strategy that combines photocrosslinking with nanophase separation to fabricate multicolor, water-dispersible semiconducting polymer nanocavities (PNCs). A photocrosslinkable semiconducting polymer is blended with a porogen such as degradable macromolecule to form compact polymer dots (Pdots). After crosslinking the polymer and removing the porogen, this approach yields semiconducting polymer nanospheres with open cavities that are tunable in diameter. Both small molecules and macromolecules can be loaded in the nanocavities, where molecular size can be differentiated by the efficiency of the energy transfer from host polymer to guest molecules. An anticancer drug doxorubicin (Dox) is loaded into the nanocavities and the intracellular release is monitored in real time by the fluorescence signal. Finally, the efficient delivery of small interfering RNA (siRNA) to silence gene expression without affecting cell viability is demonstrated. The combined features of bright fluorescence, tunable cavity, and efficient drug/siRNA delivery makes these nanostructures promising for biomedical imaging and drug delivery., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Complementary semiconducting polymer blends (c-SPBs) have been proposed and tested to achieve melt-processed high-performance organic field-effect transistors (OFETs). Prior to this study, melt processing requires temperatures as high as 180 °C. To implement this technique into low-cost and large-area thin-film manufacturing for flexible organic electronics, semiconducting materials meltable at temperatures tolerable by ubiquitous plastic substrates are still needed. We report here the design and melt processing of a c-SPB consisting of a matrix polymer (DPP-C5) and its fully conjugated analogue. By utilizing a siloxane-terminated alkyl chain and a branched alkyl chain as solubilizing groups, the matrix polymer DPP-C5 presents a melting temperature of 115 °C. The resulting c-SPB containing as low as 5% of the fully conjugated polymer could be melt-processed at 130 °C. The obtained OFET devices exhibit hole mobility approaching 1.0 cm 2 /(V s), threshold voltages below 5 V, and I ON /I OFF around 10 5 . This combination of efficient charge-carrier transport and considerably low processing temperatures bode well for melt processing of semiconducting polymer-based organic electronics.

Intra- and intermolecular ordering greatly impact the electronic and optoelectronic properties of semiconducting polymers. Despite much prior efforts regarding molecular packing, the interrelationship between ordering of alkyl sidechains and conjugated backbones has not been fully detailed. We report here the discovery of a highly ordered alkyl sidechain phase in six representative semiconducting polymers, determined from distinct spectroscopic and diffraction signatures. The sidechain ordering exhibits unusually large coherence lengths of at least 70 nm, induces torsional/twisting backbone disorder, and results in a vertically layered multilayer nanostructure with ordered sidechain layers alternating with disordered backbone layers. Calorimetry and in-situ variable temperature scattering measurements in a model system PBnDT-FTAZ clearly delineate this competition of ordering that prevents the simultaneous long-range order of both moieties. The long-range sidechain ordering can be exploited as a transient state to fabricate PBnDT-FTAZ films with an atypical edge-on texture and 2.5x improved OFET mobility. The observed influence of ordering between the moieties implies that improved molecular design could produce synergistic rather than destructive ordering effects. Given the large sidechain coherence lengths observed, such synergistic ordering should greatly improve the coherence length of backbone ordering and thereby improve electronic and optoelectronic properties such as charge transport and exciton diffusion lengths.

We demonstrate that homopolypeptides covalently tethered to anisotropically shaped silica particles induce crystalline ordering of representative semiconducting polymers. Films drop-cast from chloroform dispersions of poly(γ-stearyl-l-glutamate) (PSLG) composite particles and poly(3-hexythiophene) (P3HT) led to highly ordered crystalline structures of P3HT. Hydrophobic-hydrophobic interactions between the alkyl side chains of P3HT and PSLG were the main driving force for P3HT chain ordering into the crystalline assemblies. It was found that the orientation of rigid P3HT fibrils on the substrate adopted the directionality of the evaporating front. Regardless of the PSLG-coated particle dimensions used, the drop-cast films displayed patterns that were shaped by the coffee ring and Marangoni effects. PSLG-coated particles of high axial ratio (4.2) were more efficient in enhancing the electronic performance of P3HT than low axial ratio (2.6) homologues. Devices fabricated from the ordered assemblies displayed improved charge-carrier transport performance when compared to devices fabricated from P3HT alone. These results suggest that PSLG can favorably mediate the organization of semiconducting polymers.

Photoemission electron microscopy in combination with polarized laser light is presented as a tool permitting direct imaging of polymer-chain orientation and local degree of order in semicrystalline samples of semiconducting polymers, a promising class of materials for future electronics. The key advantages of this imaging tool are its nondestructive and fast measurements, straightforward data analysis, the low complexity of sample preparation, and the possibility of performing measurements on a broad variety of technologically relevant substrates. The high spatial resolution of the microscope provides insights into the nanoscale morphology, which is relevant for the material's performance in electronic devices., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

π-Conjugated polymers are an important class of materials for organic electronics. In the past decade, numerous polymers with donor-acceptor molecular structures have been developed and used as the active materials for organic devices, such as organic field-effect transistors (OFETs) and organic photovoltaics (OPVs). The choice of the building unit is the primary step for designing the polymers. Benzochalcogenadiazoles (BXzs) are one of the most familiar acceptor building units studied in this area. As their doubly fused system, naphthobischalcogenadiazoles (NXzs), i.e., naphthobisthiadiazole (NTz), naphthobisoxadiazole (NOz), and naphthobisselenadiazole (NSz) are emerging building units that provide interesting electronic properties and highly self-assembling nature for π-conjugated polymers. With these fruitful features, π-conjugated polymers based on these building units demonstrate great performances in OFETs and OPVs. In particular, in OPVs, NTz-based polymers have exhibited more than 10% efficiency, which is among the highest values reported so far. In this Progress Report, the synthesis, properties, and structures of NXzs and their polymers is summarized. The device performance is also highlighted and the structure-property relationships of the polymers are discussed., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Ions and electrons in blends of polymer-electrolyte can work in ensemble to operate light-emitting electrochemical cells (LECs), in which the unique features of in situ formed p-n homojunctions offer efficient charge injection and transport. However, electrochemical features give rise to significant stability and speed issues due to limited electrochemical stability and low ion mobility, resulting in low brightness and a slow response of LECs. Here, these issues are overcome by the separate control of ionic and electronic charges, using a simple driving pulse superimposed on a small base voltage; ions with slow response are rearranged by a constant base voltage, while a high-voltage pulse, superimposed upon the base, injects electrons/holes which have fast response, with minimal effect on the ions. This scheme successfully injects an extremely high current density of > 2 kA cm -2 with a balanced electron/hole ratio, at a high-speed response time of ≈ 50 ns; both properties demonstrate advantages of LECs in making polymers brighter. An in situ electron spin resonance measurement on the LECs further revealed that this impressive performance is due to the highly doped polymers, whose spin density reached 7 × 10 19 spins cm -3 , and an ordered polymer structure in the active layer blend., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Heteroblock copolymers consisting of poly(3-hexylthiophene) and fullerene-attached poly(3-alkylselenophene) (T-b-Se-PCBP) were synthesized for organic photovoltaic applications by quasi-living catalyst transfer polycondensation and subsequent conversion reactions. Characterization of the polymers confirmed the formation of well-defined diblock structures with high loading of the fullerene at the side chain (∼40 wt %). Heteroblock copolymer cast as a thin film showed a clear microphase-separated nanostructure approximately 30 nm in repeating unit after thermal annealing, which is identical to the microphase-separated nanostructure of diblock copolymer consisting of poly(3-hexylthiophene) and fullerene-attached poly(3-alkylthiophene) (T-b-T-PCBP). These heteroblock copolymers provide an ideal platform for investigating the effects of nanostructures and interfacial energetics on the performance of organic photovoltaic devices.

Melt-processing of complementary semiconducting polymer blends provides an average charge carrier mobility of 0.4 cm 2 V -1 s -1 and current on/off ratios higher than 10 5 , a record performance for melt-processed organic field-effect transistors., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Carbon nanotubes have a variety of remarkable electronic and mechanical properties that, in principle, lend them to promising optoelectronic applications. However, the field has been plagued by heterogeneity in the distributions of synthesized tubes and uncontrolled bundling, both of which have prevented nanotubes from reaching their full potential. Here, a variety of recently demonstrated solution-processing avenues is presented, which may combat these challenges through manipulation of nanoscale structures. Recent advances in polymer-wrapping of single-walled carbon nanotubes (SWNTs) are shown, along with how the resulting nanostructures can selectively disperse tubes while also exploiting the favorable properties of the polymer, such as light-harvesting ability. New methods to controllably form nanoengineered SWNT networks with controlled nanotube placement are discussed. These nanoengineered networks decrease bundling, lower the percolation threshold, and enable a strong enhancement in charge conductivity compared to random networks, making them potentially attractive for optoelectronic applications. Finally, SWNT applications, to date, in organic and perovskite photovoltaics are reviewed, and insights as to how the aforementioned recent advancements can lead to improved device performance provided., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Charge carrier transport is one of the most important functions of semiconducting polymers when they are used in organic electronic devices. Due to the transport path limited in two directions, i.e., along the π-conjugated backbone and intermolecular π–π stacking, the backbones are required to be oriented in the desired motifs with respect to the substrate, such as “edge-on” and “face-on” in order to maximize the device performances. In this Feature Article, we focus on how the orientation of semiconducting polymer backbones are influenced by the chemical structure, e.g., backbone structure, molecular weight, and side chains, and processing conditions. Implications of the backbone orientation for the performance of organic devices such as transistors and solar cells are also discussed. [ABSTRACT FROM AUTHOR]

A novel electron-deficient building unit, dithienylthienothiophenebisimide, and its polymers (PTBIs) are reported. Organic photovoltaic (OPV) cells based on PTBIs as p-type material exhibit 8.0% efficiencies with open-circuit voltages higher than 1 V. Interestingly, PTBIs also function as n-type material in OPVs depending on the molecular structure. These polymers also exhibit p-channel, n-channel, and ambipolar behaviors in field-effect transistors., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Slab optical waveguide absorption spectra reveal that surface segregated monolayers of a vertically oriented poly(3-buthylthiophene) derivative have large optical anisotropy, and that confinement of the polymer chains in the isolated monolayer causes strong H-aggregation., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Ultrafast photoinduced carrier dynamics in prototypical low band gap polymer:fullerene photovoltaic blend films PTB7:PC70BM and P3HT:PC70BM is investigated using ultrafast terahertz (THz) spectroscopy. The subpicosecond and few-picosecond decays of THz-probed photoconductivities for both compounds are observed, attributed to the rapid formation of polaron pairs by exciton-exciton annihilation and subsequent polaron pair annihilation, respectively. The transient THz photoconductivity spectra of PTB7:PC70BM are well described by the Drude-Smith (DS) model, directly yielding the important charge transport parameters such as charge carrier density, momentum scattering time, and effective localization. By comparison with P3HT:PC70BM, we find that in PTB7:PC70BM the mobile charge carrier photoconductivity is significantly enhanced by a factor of 1.8 and prevails for longer times after charge formation, due to both improved mobile charge carrier yield and lower charge localization. In PTB7:PC70BM, a strong dependency of electron momentum scattering time on electron density was found, well parametrized by the empirical Caughey-Thomas model. The difference in ultrafast photoconductivities of both P3HT:PC70BM and PTB7:PC70BM is found to correlate very well with the performance of photovoltaic devices based on those materials.

The backbone orientation in the thiophene-thiazolothiazole (TzTz) copolymer system can be altered by tuning of the alky side chain composition. We highlight that the orientation significantly impact their solar cell efficiency in particular when using thicker active layers., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A thiazolothiazole-thiophene copolymer is examined as the active material in bulk heterojunction (BHJ) solar cells. By optimizing the molecular weight, the polymer-based cells exhibit power conversion efficiencies as high as 5.7%. The increase in molecular weight improves the orientational order, and blending with phenyl-C61-butyric acid methyl ester (PC61BM) changes the orientational motif from edge-on to face-on, which accounts for the trend in photovoltaic performances. These results might give new insight into the structure-property relationships in BHJ solar cells., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)