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A silicon carbonitride (SICN) ceramic microrobot, biocompatible and magnetically activable, is developed for the delivery of viable cells to defective tissue by sequential steps of microstructuring, magnetization, and cell loading. The ceramic carrier of porous cylindrical framework is fabricated by 3D laser lithography using a photocurable preceramic polymer, chemically modified polyvinylsilazane, and subsequent pyrolysis at 600 °C under an inert atmosphere. Magnetic nanoparticles (MNP) are integrated into the surface-modified ceramic carrier by thiol-ene click reaction. Finally, the microrobot is loaded with fibroblast cells, which can be guided by a rotating external magnetic field. The proposed ceramic microrobot is mechanically durable, adequately controllable with external magnetic field, and quite compatible with mammalian cells., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Naphthalene diimide (NDI) dimers, NDI-Ph-NDI with a phenyl linker and NDI-Xy-NDI with a xylene linker, are designed and synthesized. The influence of the xylene and phenyl linkers on optical properties, electrochemical properties, morphology, and device performance is systematically investigated. Non-fullerene organic solar cells (OSCs) with NDI-Ph-NDI show poor device efficiency due to aggregation of polymer chains and/or NDI dimers caused by the highly planar structure of NDI-Ph-NDI. Although NDI-Xy-NDI is a non-planar structure, uniform surface morphology and weak bimolecular recombination lead to high power conversion efficiencies of 3.11%, which is the highest value in non-fullerene OSCs with NDI small molecules., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Graphene oxide nanoribbons for efficient and stable polymer solar cells are discussed. With controllable bandgap, good solubility and film forming property, graphene oxide nanoribbons serve as a new class of excellent hole extraction materials for efficient and stable polymer solar cells outperforming their counterparts based on conventional hole extraction materials, including PEDOT:PSS., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

For the practical application of dye-sensitized solar cells (DSSCs), it is important to replace the conventional organic solvents based electrolyte with environmentally friendly and stable ones, due to the toxicity and leakage problems. Here we report a noble water-based thixotropic polymer gel electrolyte containing xanthan gum, which satisfies both the environmentally friendliness and stability against leakage and water intrusion. For application in DSSCs, it was possible to infiltrate the prepared electrolyte into the mesoporous TiO2 electrode at the fluidic state, resulting in sufficient penetration. As a result, this electrolyte exhibited similar conversion efficiency (4.78% at 100 mW cm(-2)) and an enhanced long-term stability compared to a water-based liquid electrolyte. The effects of water on the photovoltaic properties were examined elaborately from the cyclic voltammetry curves and impedance spectra. Despite the positive shift in the conduction band potential of the TiO2 electrode, the open-circuit voltage was enhanced by addition of water in the electrolyte due to the greater positive shift in the I(-)/I3(-) redox potential. However, due to the dye desorption and decreased diffusion coefficient caused by the water content, the short-circuit photocurrent density was reduced. These results will provide great insight into the development of efficient and stable water-based electrolytes.

We demonstrate high-performance polymer solar cells using the plasmonic effect of multipositional silica-coated silver nanoparticles. The location of the nanoparticles is critical for increasing light absorption and scattering via enhanced electric field distribution. The device incorporating nanoparticles between the hole transport layer and the active layer achieves a power conversion efficiency of 8.92% with an external quantum efficiency of 81.5%. These device efficiencies are the highest values reported to date for plasmonic polymer solar cells using metal nanoparticles.

A highly crystalline and low bandgap donor polymer, EI-PFDTBT, is developed by inserting ethylene bridging units to ensure a coplanar configuration between the side chains and the main chain. Polymer solar cells based on the EI-PFDTBT and PC(71) BM blends spincoated at elevated temperatures exhibit a power conversion efficiency of 5.1%., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The surface plasmon effect on polymer solar cells and polymer light-emitting diodes is demonstrated by using metal nanoparticles prepared from block copolymer templates. Light absorption of the polymer thin layer is increased with the incorporation of metallic nanostructures, resulting in a significant surface plasmon effect in the optoelectronic devices., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A novel multifunctional conjugated polymer (RCP-1) composed of an electron-donating backbone (carbazole) and an electron-accepting side chain (cyanoacetic acid) connected through conjugated vinylene and terthiophene has been synthesized and tested as a photosensitizer in two major molecule-based solar cells, namely dye sensitized solar cells (DSSCs) and organic photovoltaic cells (OPVs). Promising initial results on overall power conversion efficiencies of 4.11% and 1.04% are obtained from the basic structure of DSSCs and OPVs based on RCP-1, respectively. The well-defined donor (D)-acceptor (A) structure of RCP-1 has made it possible, for the first time, to reach over 4% of power conversion efficiency in DSSCs with an organic polymer sensitizer and good operation stability., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Bifunctional catalysts based on noble metals have achieved practical‐level performances in round‐trip energy conversion systems. However, the required amount of noble metals should be substantially reduced via a new catalyst design that can pursue the synergy of the constituent materials' intrinsic properties and architectural maneuver over reactant/product transport. In this study, cross‐stacked Ir and Pt nanowires resolved the bottlenecks of two reactions essential for the hydrogen‐based energy system: i) hydrogen spillover phenomenon between Pt and Ir nanowires to expedite the hydrogen oxidation reaction and ii) spacing Ir nanowires sufficiently to enhance the mass transport of the oxygen evolution reaction. Simultaneously accommodating the different strategies within the single catalyst layer, a new horizon to design a bifunctional electrode is proposed with the high performance of polymer electrolyte membrane unitized regenerative fuel cells: 47% of round‐trip efficiency at 0.5 A cm−2 with total noble metal loading < 0.3 mg cm−2. [ABSTRACT FROM AUTHOR]

The photoactive layer of non‐fullerene organic solar cells (OSCs) generally consists of a low band‐gap acceptor and conjugated polymer with a deep highest occupied molecular orbital (HOMO) because the hole transfer from the acceptor to the donor as well as the electron transfer from the donor polymer to the acceptor is very important to achieve better performance. Therefore, energy level matching between the HOMO of the donor polymer and the work‐function (WF) of the hole transport layer is required. Since the intrinsic p‐type NiO has a lower WF value, the efficiency of NiO‐based PBDB‐T‐2F:Y6 OSCs is somewhat suppressed. In this work, the energy barrier between the NiO (5.1 eV) and HOMO of PBDB‐T‐2F (5.6 eV) by modifying the NiO surface using a 4‐(trifluoromethyl)benzoic acid (PTF‐BOA) dipole layer (NiO‐PTF‐BOA) is successfully eliminated. The carboxyl group of PTF‐BOA is bonded with Ni atoms on the NiO surface, while the CF3 group attracts electrons, thus resulting in a partial negative charge on the CF3 side. This PTF‐BOA dipole layer induces the vacuum level upshift thus enhancing the work function of NiO‐PTF‐BOA to 5.5 eV. The PBDB‐T‐2F:Y6 OSCs with NiO‐PTF‐BOA exhibit an efficiency of 16.36%, which is the highest reported efficiency for NiO‐based OSCs. [ABSTRACT FROM AUTHOR]

To successfully develop a regioregular polymer, poly[4,8‐bis(5‐(2‐hexyldecyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene][5,5′‐bis(7‐(4‐(2‐butyloctyl)thiophen‐2‐yl)‐6‐fluorobenzo[c][1,2,5]thiadiazol‐4‐yl)‐2,2′‐bithiophene] (PDBD‐FBT), a symmetric monomer synthesized in high yield by tin homo‐coupling reactions. PDBD‐FBT is suitable as a donor material in organic photovoltaics (OPVs) because it shows high crystallinity and strong face‐on packing properties. These properties were amplified by thermal annealing (TA). This causes a power conversion efficiency (PCE) enhancement in PDBD‐FBT‐based OPVs. Using PDBD‐FBT as a polymer donor and 2,2′‐((2Z,2′Z)‐((12,13‐bis(2‐heptylundecyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2″,3″:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2‐g]thieno[2′,3′:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (Y6‐HU) as an electron acceptor, a PCE of 7.91% was achieved without any additive and TA at optimized active layer film thickness of approximately 100 nm. After TA, a PCE of 12.53% was achieved with a 58% increase compared with the reference devices. Owing to the strong crystallinities, trap‐assisted recombination occurs by excessively formed grain boundaries; however, efficient exciton dissociation sufficiently covers these drawbacks. Even in the approximately 340 nm‐thick film condition, this tendency is more pronounced (73% PCE enhancement is observed from 6.17% to 10.69% of PCE in the without and with TA devices, respectively). Our study demonstrates that it is possible to manufacture thickness‐insensitive OPVs based on regioregular polymers with strong crystallinity and face‐on characteristics, thereby providing a solution to the thickness variation of large‐area organic solar cell modules. [ABSTRACT FROM AUTHOR]

Improved performance of polymer-based solar cells based on poly[2,6-(4,4-bis-(2-ethylhexyl)-4H- cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-benzo-thiadiazole)] PCPDTBT has been obtained by using 1,8-octanedithiol (ODT) as a processing additive in the polymer solution used to spin cast the bulk heterojunction films. Although ultrafast spectroscopy studies indicate that the carrier losses are reduced in the films processed with ODT [similar to the reduced carrier losses after thermal annealing of bulk heterojunction (BHJ) materials made from P3HT:PCBM], the magnitude of the reduction is not sufficient to explain the observed factor of 2 increase in the power conversion efficiency. From the analysis of carrier transport in field effect transistors, we find increased electron mobility in the PCPDTBT:PC70BM composites when fabricated with ODT, which is indicative of enhanced connectivity of PC70BM networks. The improved electron mobility appears to be the primary origin of the improved power conversion efficiency in BHJ films. [ABSTRACT FROM AUTHOR]

The ability to capture, store, and use CO2 is important for remediating greenhouse‐gas emissions and combatting global warming. Herein, Au nanoparticles (Au‐NPs) are synthesized for effective electrochemical CO2 reduction and syngas production, using polyethylenimine (PEI) as a ligand molecule. The PEI‐assisted synthesis provides uniformly sized 3‐nm Au NPs, whereas larger irregularly shaped NPs are formed in the absence of PEI in the synthesis solution. The Au‐NPs synthesized with PEI (PEI−Au/C, average PEI Mw=2000) exhibit improved CO2 reduction activities compared to Au‐NPs formed in the absence of PEI (bare Au NPs/C). PEI−Au/C displays a 34 % higher activity toward CO2 reduction than bare Au NPs/C; for example, PEI−Au/C exhibits a CO partial current density (jCO) of 28.6 mA cm−2 at −1.13 VRHE, while the value for bare Au NPs/C is 21.7 mA cm−2; the enhanced jCO is mainly due to the larger surface area of PEI−Au/C. Furthermore, the PEI−Au/C electrode exhibits stable performance over 64 h, with an hourly current degradation rate of 0.25 %. The developed PEI−Au/C is employed in a CO2‐reduction device coupled with an IrO2 water‐oxidation catalyst and a proton‐conducting perfluorinated membrane to form a PEI−Au/C|Nafion|IrO2 membrane‐electrode assembly. The device using PEI−Au/C as the CO2‐reduction catalyst exhibits a jCO of 4.47 mA/cm2 at 2.0 Vcell. Importantly, the resulted PEI−Au/C is appropriate for efficient syngas production with a CO ratio of around 30–50 %. [ABSTRACT FROM AUTHOR]

Ternary structures are demonstrated as a promising approach to increase the efficiency and light harvesting of solar cells. A high power conversion efficiency of 10.2% is achieved for ternary organic solar cells with two efficient polymer donors. The improved performance is attributed to the synergistic effects of enhanced light absorption and charge transport, efficient energy transfer, improved charge generation and morphology. [ABSTRACT FROM AUTHOR]

Considering that a high compatibility at hybrid organic/inorganic interfaces can be achieved using polar and hydrophilic functionalities, this approach is used to improve inverted polymer solar cell performance by introducing nonionic phosphonate side chains (at 0%, 5%, 15%, and 30% substitution levels) into a series of isoindigo-based polymers (PIIGDT-P n). This approach led to ≈20% improvement in power conversion efficiency compared to a nonmodified control polymer, via an increased short-circuit current ( JSC). This enhancement is believed to stem from reduced nongerminate recombination and improved charge carried extraction when the level of phosphonate substitution is optimized. These results are substantiated by a combination of detailed electrical measurements including space-charged limited current modeling, light intensity-dependent photocurrent ( Jph) analysis, and morphological studies (grazing-incidence wide-angle X-ray scattering and atomic force microscopy). This is the first practical report demonstrating the use of nonionic polar side chains to control charge carrier dynamics in an existing photovoltaic polymer structure. It is envisioned that this simple strategy may be applied to other material systems and yield new materials with the potential for even higher performance. [ABSTRACT FROM AUTHOR]

Polymer films with halohydrocarbon solvents as additive solvents were fabricated to investigate the solvent effect on dielectric performance. Bromobenzene, chlorobenzene (CB), chloroform, and fluorobenzene (FB) were used as halohydrocarbon solvents. The cyanoethyl pullulan (CRS) polymer film with CB had a dielectric constant of 21.5 with a dielectric loss of 0.017 at 100 Hz, which exhibited a 37% increase in dielectric constant compared to the neat CRS polymer film. Increment of the dielectric constant is attributed to the high polarizability of carbon–chlorine bonds originated from CB absorbed in CRS. For the case of the CRS polymer film with FB, the dielectric constant did not increase due to the low polarizability of carbon–fluorine bonds. In order to verify the dielectric performance of the CRS polymer film with CB (CRS/CB), AC-driven inorganic powder electroluminescent (EL) device was fabricated using the green emission ZnS:Cu,Cl phosphor particles. An EL device with CRS/CB polymer film as a dielectric layer exhibited a 37% and 55% increase in luminance and efficiency, respectively compared to that with neat CRS polymer. This increase in EL performance was attributed to the increase of charge carrier density at the interface between the emitting and dielectric layers, resulting in the increased possibility of the charge carrier tunneling into phosphor particles. [ABSTRACT FROM AUTHOR]

Organic optoelectronic devices including organic light-emitting diodes (OLEDs) and polymer solar cells (PSCs) have many advantages, including low-cost, mechanical flexibility, and amenability to large-area fabrication based on printing techniques, and have therefore attracted attention as next-generation flexible optoelectronic devices. Although almost 100% internal quantum efficiency of OLEDs has been achieved by using phosphorescent emitters and optimizing device structures, the external quantum efficiency (EQE) of OLEDs is still limited due to poor light extraction. Also, although intensive efforts to develop new conjugated polymers and device architectures have improved power conversion efficiency (PCE) up to 8%-9%, device efficiency must be improved to >10% for commercialization of PSCs. The surface plasmon resonance (SPR) effect of metal nanoparticles (NPs) can be an effective way to improve the extraction of light produced by decay of excitons in the emission layer and by absorption of incident light energy within the active layer. Silver (Ag) NPs are promising plasmonic materials due to a strong SPR peak and light-scattering effect. In this review, different SPR properties of Ag NPs are introduced as a function of size, shape, and surrounding matrix, and review recent progress on application of the SPR effect of AgNPs to OLEDs and PSCs. [ABSTRACT FROM AUTHOR]

The coupling of surface plasmons and excitons in organic materials can improve the performance of organic optoelectronic devices. Here, we prepare carbon-dot-supported silver nanoparticles (CD-Ag nanoparticles) using the carbon dots both as a reducing agent and a template to fabricate solution-processable polymer light-emitting diodes and polymer solar cells. The surface plasmon resonance effect of CD-Ag nanoparticles allows significant radiative emission and additional light absorption, leading to remarkably enhanced current efficiency of 27.16 cd A−1 and a luminous efficiency of 18.54 lm W−1 in polymer light-emitting diodes as well as a power conversion efficiency of 8.31% and an internal quantum efficiency of 99% in polymer solar cells compared with control devices (current efficiency = 11.65 cd A−1 and luminous efficiency = 6.33 lm W−1 in polymer light-emitting diodes; power conversion efficiency = 7.53% and internal quantum efficiency = 91% in polymer solar cells). These results demonstrate that CD-Ag nanoparticles constitute a versatile and effective route for achieving high-performance polymer optoelectronic devices. [ABSTRACT FROM AUTHOR]

Abstract: An alternating current driven electroluminescence (EL) device consisting of a phosphor dispersed in a polymer matrix device was fabricated as a tandem structure. This structure can be formed by duplicating the emitting and conducting layers. The EL device with the tandem structure, particularly the device with the triple emitting layer, was six times brighter than (1460cd/m2 at an alternating voltage application of 50V) the structure with a single emitting layer. This tandem structure plays important roles by increasing the chance of electron–hole tunneling into the phosphor with leading to an increase in brightness by combining the light emitted from several emitting layers in a device. In addition, the adoption of a spin-coating method for the deposition of an emitting layer can allow the production of a dielectric part on the lower-lying emitting phosphor powder particles. The implementation of a dielectric part and emitting part by one spin-coating procedure simplifies the overall fabrication process, particularly for the tandem structure. The significant increase in brightness with each additional emitting layer as well as a facile fabrication process would help to make the EL device a competitive candidate in future displays and lightings. [Copyright &y& Elsevier]

Abstract: New electroluminescent polymer with tetrakis-alkoxy group, poly[2,3,5,6-tetrakis(2-ethylhexyloxy)-1,4-phenylenevinylene] (TEH-PPV), has been synthesized by the Gilch polymerization. In solid film state, the TEH-PPV exhibits absorption spectra with maximum peaks at 451nm, and PL spectrum at 505–545nm. As compared to MEH-PPV, TEH-PPV with tetrakis-ethylhexyloxy groups in phenylene unit can get shorter conjugation length, and had more blue shifted absorption and emission peaks due to steric hindrance, in spite of increasing the number of alkoxy substituents which may increase the effective conjugation length caused by the electron-donating effect. The polymer LEDs (ITO/PEDOT/polymer/Al) of TEH-PPV showed emission with maximum peaks at around 505–590nm. Tetrakis-ethylhexyloxy groups induced very typical vibronically structured band in solid film state, since the conjugated backbone is twisted by steric hindrance. And they can enhance the internal efficiency of the conjugated polymer as emissive layer in PLED because of the restraint of inter-chain interaction by the avoidance of close packing to give decent device performance. [Copyright &y& Elsevier]

The characteristics of a hybrid polymer light-emitting diode (HPLED) with an active layer of poly [2-methoxy,5-(2-ethylhexoxy)-1,4-phenylenevinylene] blended with Au-capped TiO2 nanocomposites are reported. Both the increased current in the active layer and low turn-on voltage were attributed to incorporation of Au-capped TiO2 in the electroluminescent polymer. The maximal brightness of 11 630 cd/m2 was observed in HPLED with a 1:1 ratio of Au-capped TiO2. The enhanced performance was attributed to the roughness assisted charge transport induced by the Au-capped TiO2 nanocomposites in the active polymer. [ABSTRACT FROM AUTHOR]

Organic Photovoltaics: Study of Burn-In Loss in Green Solvent-Processed Ternary Blended Organic Photovoltaics Derived from UV-Crosslinkable Semiconducting Polymers and Nonfullerene Acceptors (Adv. In article number 1901829, Jin Young Kim, Taiho Park and co-workers report that cross-linkable semiconducting polymers and nonfullerene acceptors can lead to thermal stability in a green-solvent processed organic photovoltaic. The burn-in loss due to thermal aging and light soaking is dramatically suppressed due to the frozen morphology from the cross-linkable polymers and high miscibility from the nonfullerene acceptors. [Extracted from the article]

This work deals with the investigation of burn‐in loss in ternary blended organic photovoltaics (OPVs) prepared from a UV‐crosslinkable semiconducting polymer (P2FBTT‐Br) and a nonfullerene acceptor (IEICO‐4F) via a green solvent process. The synthesized P2FBTT‐Br can be crosslinked by UV irradiation for 150 s and dissolved in 2‐methylanisole due to its asymmetric structure. In OPV performance and burn‐in loss tests performed at 75 °C or AM 1.5G Sun illumination for 90 h, UV‐crosslinked devices with PC71BM show 9.2% power conversion efficiency (PCE) and better stability against burn‐in loss than pristine devices. The frozen morphology resulting from the crosslinking prevents lateral crystallization and aggregation related to morphological degradation. When IEICO‐4F is introduced in place of a fullerene‐based acceptor, the burn‐in loss due to thermal aging and light soaking is dramatically suppressed because of the frozen morphology and high miscibility of the nonfullerene acceptor (18.7% → 90.8% after 90 h at 75 °C and 37.9% → 77.5% after 90 h at AM 1.5G). The resulting crosslinked device shows 9.4% PCE (9.8% in chlorobenzene), which is the highest value reported to date for crosslinked active materials, in the first green processing approach. [ABSTRACT FROM AUTHOR]

The physical and chemical degradations of a state‐of‐the‐art proton exchange membrane (PEM) composed of a perfluorinated sulfonic acid (PFSA) ionomer and polytetrafluoroethylene (PTFE) reinforcement are induced through the repeated expansion/shrinkage of the ionomer and free radical attacks. Such degradations essentially originate from the loose structure of the materials and the low interactive binding force among the PEM constituents. In this study, the need for simplified design principles of adhesives led to the use of mussel‐inspired polydopamine (PD) as an interfacial modifier for the fabrication of highly durable PEM. Indeed, a self‐polymerized dopamine layer acts as an interfacial glue, and enables efficient impregnation of a hydrophilic PFSA ionomer into porous hydrophobic PTFE with high packing density, resulting in strong adhesion between the PTFE and the PFSA polymers in the membrane. In addition, the redox property of the PD end groups spontaneously reduces the partial Ce salts in the ionomer solution and anchors them to the PD@PTFE substrate as defective cerium oxide (CeOx) nanoparticles, reducing the dissolution and subsequent migration under cell operations. Finally, a CePD@PTFE membrane shows outstanding durability in fuel cells under an accelerated humidity cycling test with a reduction in the degree of physical and chemical failures. Mussel‐inspired polydopamine and Ce salts are introduced to porous polytetrafluoroethylene (PTFE) substrates for highly durable composite membranes. The multifunctional features of polydopamine, i.e., (i) interfacial glues between perfluorinated sulfonic acid and PTFE layers; and (ii) immobilization of Ce based radical scavengers give rise to outstanding cell performance with long‐term operation of proton exchange membrane fuel cells under humidity cycles. [ABSTRACT FROM AUTHOR]

In article number 1600637, Alan J. Heeger, Han Young Woo, Jin Young Kim, and co‐workers demonstrate high performance ternary blend polymer solar cells including two donor polymers which share the same polymeric backbone. Real charge carrier behavior of ternary blends is firstly clarified via transient absorption spectroscopy as parallel bulk‐heterojunction. [ABSTRACT FROM AUTHOR]

Crack formation is a frequent result of residual stress release from colloidal films made by the evaporation of colloidal droplets containing nanoparticles. Crack prevention is a significant task in industrial applications such as painting and inkjet printing with colloidal nanoparticles. Here, we illustrate how colloidal drops evaporate and how crack generation is dependent on the particle size and initial volume fraction, through direct visualization of the individual colloids with confocal laser microscopy. To prevent crack formation, we suggest use of a versatile method to control the colloid-polymer interactions by mixing a nonadsorbing polymer with the colloidal suspension, which is known to drive gelation of the particles with short-range attraction. Gelation-driven crack prevention is a feasible and simple method to obtain crack-free, uniform coatings through drying-mediated assembly of colloidal nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: The effect of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) as a buffer layer was investigated in polymer solar cells (PSCs). Four different types of PEDOT:PSS were used: PH, PH500 and their DMSO (dimethylsulfoxide)-doped counterparts. The efficiency of PSCs was independent of the electric conductivity of the buffer layer as a bulk property while it was significantly related to interfacial properties between the buffer layer and a bulk-heterojunction (BHJ) layer. The interfacial properties included charge transfer resistance (R CT ), hole mobility (μ h ) and contact angle (θ) of the solution of BHJ on the buffer layer. Lower R CT , higher μ h and smaller θ led to the higher fill factor (up to 72%), enabling highly efficient PSCs with efficiency (η)=4.25%. [Copyright &y& Elsevier]

We report optical spectroscopic measurements of plasma-polymerized thin films coated on aluminum (Al) substrates over a spectral range from 0.01 to 6 eV. While the reflectance spectra, R(ω), remain almost unchanged in the infrared range as compared with the bare Al, R(ω) starts to decrease significantly in the higher energy above 2.5 eV. This decrease in R(ω) arises from electronic absorptions characteristic of the polymer films. Moreover, the details of R(ω) in the energy above 3 eV depend on the fabrication conditions of the polymer films. Our results, therefore, demonstrate that this optical measurement can be an excellent method to characterize the quality of polymer films deposited by the plasma polymerization process. [Copyright &y& Elsevier]

Reduced graphene oxide (rGO) platelets are used to encapsulate barium titanate (BaTiO 3 , BTO) powder particles by functionalizing rGO and BTO, which is mixed with a polymer to become a dielectric composite. The polymer composite film exhibits improved dielectric characteristics--a dielectric constant of 219 (75% higher than that of the pure BTO film) mainly due to numerous micro-capacitors, composed of BTO as a dielectric medium and rGO as electrodes, in the polymer. The increase of the dielectric loss, a typical unwanted phenomenon by inclusion of conducting nanomaterials, is successfully suppressed below 7% (from 0.045 to 0.048). This is achieved by virtually removing free rGO platelets within the polymer matrix during the encapsulation process, impeding percolative connection between free rGO platelets. Only graphene encapsulation would facilitate both BTO-based micro-capacitors and the deprivation of free rGO, which would simultaneously yield to a high dielectric constant and a low dielectric loss. Thus, encapsulation, one way of elaborate mixing methods, is essential for high-performance dielectrics, which can be applied to other composite materials with ease. Image 1 • High dielectric constant and low dielectric loss obtained by rGO-encapsulated BTO. • Interfacial polarization of BTO-based micro-capacitors for high dielectric constants. • Removal of free rGO during encapsulation is a key for the low dielectric loss. • Dielectric constant of 219 and loss of 0.045 is obtained at 1 kHz. [ABSTRACT FROM AUTHOR]

Highlights: [•] We introduced fullerene-based self-assembled monolayer into the interface between titanium oxide and active layer. [•] We examine the changes in interfacial properties by fullerene-based self-assembled monolayer. [•] Fullerene-based self-assembled monolayer reduced surface roughness and improved wetting property with active layer. [•] Interfacial modification with fullerene-based self-assembled monolayer enhanced the performance of inverted polymer solar cells. [ABSTRACT FROM AUTHOR]

Abstract: We report substantial improvements in efficiency and thermal stability of the poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) (P3HT:PCBM) bulk heterojunction (BHJ) system by adding a diblock copolymer P3HT-b-P(St89BAz11)-C60 (P3HT=poly (3-hexylthiophene), St=styrene, BAz=benzyl azide) as a compatibilizer. Small amounts of the diblock copolymer alter the interfacial morphology between the P3HT and PCBM components, resulting in a noticeable difference in phase segregation of the BHJ films, as evident in atomic force microscopy images. The best performance is observed in the P3HT:PCBM cell with 10% P3HT-b-P(St89BAz11)-C60, which exhibits substantially improved power conversion efficiency and thermal stability compared to the P3HT:PCBM control device. [Copyright &y& Elsevier]

Abstract: We report the synthesis, characterization, and electrochemical properties of bis-PCBM dyad containing 4-nitro-α-cyanostilbene units for potential usage in efficient organic solar cells. The bis-PCBM dyad is fully characterized by NMR, UV–vis absorption, and electrochemical cyclic voltammetry. It is found that the presence of 4-nitro-α-cyanostilbenes affects the cyclic voltammetry and absorption spectrum very little. Whereas the 56 π-electron system in the bis-functionalized fullerene cage significantly influences on the electrochemical and photophysical properties, resulting in up-shifted LUMO and wider absorption compared to PCBM. Although the efficiencies of both conventional and the inverted cells based on P3HT/bis-PCBM dyad as the preliminary results are low in comparison with the optimized high-performance PSCs, it is believed that the efficiency would be improved through successful device optimization of P3HT/bis-PCBM dyad cells. [Copyright &y& Elsevier]

Two donor– (D−) acceptor (A) type polymersbasedon a soluble chromophore of phenothiazine (PT) unit that is a tricyclicnitrogen–sulfur heterocycle, have been synthesized by introducingan electron-deficient benzothiadiazole (BT) building block copolymerizedwith either PT or phenothiazine-S,S-dioxide (PT-SS) unit as an oxidized form of PT.The resulting polymers, PPTDTBTand PPTDTBT-SSare fully characterized by UV–visabsorption, electrochemical cyclic voltammetry, X-ray diffraction(XRD), and DFT theoretical calculations. We find that the maximumabsorption of PPTDTBTis not only markedly red-shiftedwith respect to that of PPTDTBT-SSbut also its band gap as well as molecular energy levelsare readily tuned by the insertion of S,S-dioxides into the polymer. The main interest is focused on the electronicapplications of the two polymers in organic field-effect transistors(OFETs) as well as conventional and inverted polymeric solar cells(PSCs). PPTDTBTis a typical p-type polymer semiconductorfor OFETs and conventional PSCs based on this polymer and PC71BM show a power conversion efficiency (PCE) of 1.69%. In case of PPTDTBT-SS, the devices characteristicsresult in: (i) 1 order of magnitude higher hole mobility (μ= 6.9 × 10–4cm2V–1s–1) than that obtained with PPTDTBTand (ii) improved performance of the inverted PSCs (1.22%), comparedto its conventional devices. Such positive features can be accountedfor in terms of closer packing molecular characteristics owing eitherto the effects of dipolar intermolecular interactions orientated fromthe sulfonyl groups or the relatively high coplanarity of PPTDTBT-SSbackbone. [ABSTRACT FROM AUTHOR]

In this study, low bandgap polymers containing a monofluoroquinoxaline (FQx) or a difluoroquinoxaline (DFQx) as the electron-deficient unit and 2-thiophenylbenzo[1,2- b :4,5- b' ]dithiophene as the electron-rich unit were synthesized by Stille polymerization. The polymers exhibit satisfactory thermal stability and a broad absorption band from 300 to 650 nm. The HOMO/LUMO energy levels of PB-FQx and PB-DFQx were − 5.62/− 3.64 and − 5.70/− 3.63 eV, respectively. We found that for a high number of fluorine atoms in the conjugated backbone, the HOMO energy levels were deeper, which led to increased V OC. The PB-DFQx:ITIC-based PSC exhibited the best power conversion efficiency of 6.31%, with its V OC of 0.99 V, J SC of 10.61 mA/cm2, FF of 60%. • Synthesis of low bandgap polymers with a difluoroquinoxaline unit. • The HOMO energy levels of the fluorinated polymers were lower. • Polymers with deeper HOMO energy levels are conductive for achieving a higher V OC. • Efficient polymer solar cells were fabricated by blending the synthesized copolymers with ITIC, and the PCE increased up to 6.31%. [ABSTRACT FROM AUTHOR]