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We demonstrated a highly efficient color conversion layers (CCLs) by using nanosphere arrays for white organic light-emitting diodes. The introduced periodical nanospheres not only help extract the confined light in devices, but also increase the effective light path to achieve more efficient color conversion. By applying the nanospheres patterned CCL on a PVK-based phosphorescent blue OLED, 137% color conversion ratio had been achieved, which was 2.68 times higher than flat CCL. The resulting luminous efficiency of white device with patterned CCL (20.97 cd/A, 1000 cd/m2) was twice higher than the efficiency of the flat device (10.26 cd/A, 1000 cd/m2).

In this paper, we discuss liquid lenses driven by various mechanisms. By properly designing the device structure and choosing the optimal materials, the liquid lenses offer great potential for practical uses. The driving mechanism dictates the application and performance of the liquid lenses. Here we categorize the driving mechanisms into mechanical and electrical ones. In general, mechanical driving with an elastic membrane and an external pump drives liquids in a cavity by controlling the hydraulic pressure. The mechanical driving method can be applied to most of the liquids, but the application of the electrical driving method would be limited by the conductivity or the permittivity of the liquids. Therefore, the properties of the different liquids, e.g., dielectric liquids, liquid crystal molecules, and conductive liquids, deeply affect the mechanism we may choose to realize a liquid lens. Among various electrical methods, dielectrophoresis (DEP), electrostatic forces, and electrowetting-on-d...

A composite film is coated on the FTO using a solution, containing a synthesized dispersant, poly(oxyethylene)-segmented imide (POEM), dihydrogen hexachloroplatinate (H2PtCl6), and multi-wall carbon nanotube (MWCNT); the thus coated FTO is used as the counter electrode (CE) for a dye-sensitized solar cell (DSSC). The annealing temperature of the composite film, in the range of 110–580 °C, is found to be crucial for optimizing its catalytic ability to obtain the best possible performance for the DSSC. About 47% loss in mass for the POEM/H2PtCl6/MWCNT composite is observed from 110 to 390 °C, due to not only the progressive formation of PtNPs from H2PtCl6 but the decomposition of POEM. Therefore, the efficiencies (η) of DSSCs applying these CEs are enhanced from 1.28 ± 0.08% (110 °C) to 8.47 ± 0.21% (390 °C). The mass of the composite loses dramatically under heating above 390 °C, due to the decomposition of MWCNTs. The η decreases to 7.77 ± 0.15% at 450 °C because the decrease in surface roughness of film. PtNPs grow in sizes from 450 to 580 °C, resulting in the further decrease in catalytic ability of film and the observed η from 7.77 ± 0.15% to 7.19 ± 0.21%.

A p-type NiO film was prepared by doctor-blading of Ni(OH) 2 paste onto FTO glass, followed by sintering at 450 °C for 30 min. The influence of nucleation condition of Ni(OH) 2 on the morphology of NiO films and consequently charge transporting behavior is investigated. A smooth and compact NiO film is obtained with smaller Ni(OH) 2 sol–gel particle size, which is confirmed by the surface topography examination. The hole transporting ability of NiO semiconductor is enhanced with such a compact film because of better interconnection between particles, as evidenced from electrochemical impedance analysis. The NiO film obtained is employed as the photocathode in p-type dye-sensitized solar cells (DSSCs) using arylamine-based dyes. The short-circuit photocurrent is two times improved to ca. 2.0 mA cm −2 compared to rough films.

Stille polymerization was employed to synthesize a low-band-gap (LBG) conjugated main-chain polymer PBTH consisting of bithiazole, dithieno[3,2-b:2′,3′-d]pyrroles (DTP), and pendent melamine derivatives. Novel supramolecular polymer networks PBTH/C and PBTH/F were developed by mixing proper molar amounts of polymer PBTH (containing melamine pendants) to be hydrogen-bonded (H-bonded) with complementary uracil-based conjugated cross-linkers C and F (i.e., containing two symmetrical uracil moieties connected with carbazole and fluorene units through triple bonds). The formation of multiple H-bonds between polymer PBTH and cross-linkers C or F was confirmed by FT-IR measurements. In contrast to polymer PBTH , the supramolecular design with multiple H-bonds can enhance the photovoltaic properties of polymer solar cell (PSC) devices containing H-bonded polymer networks PBTH/C and PBTH/F by tuning their light harvesting capabilities, HOMO energy levels, and crystallinities. Initially, the power conversion efficiency (PCE) values of PSC devices containing supramolecular polymer networks PBTH/C and PBTH/F as electron donors and [6,6]-phenyl-C 71 -butyric acid methyl ester (PC 70 BM) as an electron acceptor (polymer:PC 70 BM = 1:1 w/w) are found to be 0.97 and 0.68%, respectively, in contrast to 0.52% for polymer PBTH . The highest PCE value of 1.56% with a short-circuit current densities ( J sc ) value of 7.16 mA/cm 2 , a open circuit voltages ( V oc ) value of 0.60 V, and a fill factor (FF) of 0.36 was further optimized in the PSC device containing a supramolecular polymer network PBTH/C as polymer:PC 70 BM = 1:2 w/w. These results indicate that supramolecular design is an effective route towards better photovoltaic properties of V oc , J sc , and PCE values in polymer solar cells.

In this article, we have systematically studied the effect of molecular weight on poly[(4,4′-bis(2-ethylhexyl)dithieno[3,2-b:2′,3′-d]silole)-2,6-diyl- alt -(5,5′-thienyl-4,4′-dihexyl-2,2′bithiazole)-2,6-diyl], a novel cathodically coloring electrochromic polymer. The polymer with higher molecular weight can stack much better due to the stronger π – π ⁎ interaction and was found to exhibit better charge transfer property and lower internal resistance. These results have shown to enhance the coloration efficiency of the polymer remarkably. For the molecular weight of 33.6 kg/mol, the coloration efficiency is 423 cm 2 /C, much higher compared with the low molecular weight polymer (6.3 kg/mol, 226 cm 2 /C).

In this study, we partially grafted geminal silanol groups in the protecting organic shells on the surfaces of gold nanoparticles (AuNPs) and then assembled the alkyl-AuNP-Si(OH)4 particles onto the surfaces of silicon (Si) wafers. The density of assembled AuNPs on the Si surface was adjusted by varying the geminal silanol group content on the AuNP surface; at its optimal content, it approached the high assembly density (0.0254 particles/nm2) of an AuNP assembled monolayer. Using reactive-ion etching (RIE) with the templates as masks, we transferred the patterned AuNP assemblies to form large-area, size-tunable, Si nanopillar arrays, the assembly density of which was controlled by the dimensions of the AuNPs. Using this colloidal lithography (CL) process, we could generate Si nanopillars having sub-10-nm diameters and high aspect ratios. The water contact angles of the high-aspect-ratio Si nanopillars approached 150°. We used another fabrication process, involving electron beam lithography and oxygen plasma treatment, to generate hydrophilic 200-nm-resolution line patterns on a Si surface to assemble the AuNPs into 200-nm-resolution dense lines for use as an etching mask. Subsequent CL provided a patterned Si nanopillar array having a feature size of 200 nm on the Si surface. Using this approach, it was possible to pattern sub-10-nm Si nanopillar arrays having densities as high as 0.0232 nm−2.

Two random (Zn(II)-based P1-P2) and two alternating (Ru(II)-based P3-P4) metallo-copolymers containing bis-terpyridyl ligands with various central donor (i.e., fluorene or carbazole) and acceptor (i.e., benzothiadiazole) moieties were synthesized. The effects of electron donor-acceptor interactions with metal (Zn(II) and Ru(II)) ions on their thermal, optical, and electrochemical properties were investigated. Because of the strong ICT transitions between donor and acceptor ligands in both Zn(II)- and Ru(II)-based metallo-coplymers and MLCT transitions in Ru(II)-based metallo-coplymers, the absorption spectra covered a broad range of 260-750 nm with the band gaps of 1.57-1.77 eV. In addition, the introduction of Ru(II)-based metallo-coplymer P4 mixed with PC(60)BM as an active layer of the BHJ solar cell device exhibited the highest PCE value up to 0.90%.

In this study we developed efficient polymer solar cells (PSCs) and polymer light emitting diodes (PLEDs) incorporating multilayer structures prepared through solution processing. To prevent dissolution of the bottom layer by the subsequent layer, we used a polydimethylsiloxane stamp to transfer the film onto the target surface. The active layer of the PSCs consisted of a poly(3-hexylthiophene) (P3HT)-rich layer and a [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)-rich layer; the active layer of the PLEDs consisted of a blue-polyfluorene as the light emitting layer (LEL) and poly(9,9-di-n-octylfluorene-alt-(1,4-phenylene-((4-sec-butylphenyl)imino-1,4-phenylene))) (TFB) as the electron blocking layer (EBL). We found that the efficiency of devices was readily manipulated by changing the constitution of each stacking layer. After optimizing the fabrication conditions for each functional layer, we obtained PSCs reaching a power conversion efficiency of 3.52%. The efficiency of PLEDs incorporating an EBL was 27% greater (reaching 4.7 cdA−1) than that prepared without an EBL layer.

New star poly(N-isopropylacrylamide)-b-polyhedral oligomeric silsesquioxane (PNIPAm-b-POSS) copolymers were synthesized from octa-azido functionalized POSS (N3-POSS) and alkyne-PNIPAm, which was prepared using an alkyne-functionalized atom transfer radical polymerization (ATRP) initiator (propargyl 2-bromo-2-methylpropionamide), via click chemistry. These star PNIPAm-b-POSS copolymers undergo a sharp coil-globule transition in water at above 32°C changing from a hydrophilic state below this temperature to a hydrophobic state above it, which is similar to linear PNIPAm homopolymers. More interestingly, we found that these star polymers exhibited strong blue photoluminescence in water above a lower critical solution temperature (LCST). This photoluminescence was likely due to the constrained geometric freedom and relatively rigid structure caused by intramolecular hydrogen bonding within the star PNIPAm polymers, which exhibit an intrinsic fluorescent behavior.

A new polyhedral oligomeric silsesquioxane ionomer (HCl-doped POSS-C11-Py) has been investigated. This new ionomer is able to self-assemble through macromers by quadruple hydrogen bonding interactions into a physically crosslinked polymer-like material that can be easily fabricated into films with micro-phase separation. This HCl-doped POSS-C11-Py membrane exhibits higher proton conductivity than a typical Nafion® membrane at high temperature, which is extremely rare for a non-sulfonic acid system. This newly developed material may provide an alternative route toward design and fabrication of a new type of proton exchange membranes.

a b s t r a c t Conducting polymer materials, i.e., polythiophene (PT), polypyrrole (PPy), and poly(3,4- ethylenedioxythiophene) (PEDOT) were used to prepare counter electrodes (CEs) for quantum-dot-sensitized solar cells (QDSSCs). The QDSSC with PEDOT-CE exhibited the highest solar-to-electricity conversion efficiency (� ) of 1.35%, which is remarkably higher than those of the cells with PT-CE (0.09%) and PPy-CE (0.41%) and very slightly higher than that of the cell with sputtered- gold-CE (1.33%). Electrochemical impedance spectra (EIS) show that this highest conversion efficiency of the PEDOT-based cell is due to higher electrocatalytic activity and reduced charge transfer resistance at the interface of the CE and the electrolyte, compared to those in the case of the cells with other conducting polymers and bare Au. Furthermore, the influences of morphology of the PEDOT film and the charge passed for its electropolymerization on the performance of its QDSSC were also studied. The higher porosity and surface roughness of the PEDOT matrix, with reference to those of other polymers are understood to be the reason for PEDOT to possess higher electrocatalytic activity at its interface with electrolyte.

A conjugated main-chain copolymer (PBT) consisting of bithiazole, dithieno[3,2-b:2′,3′-d]pyrroles (DTP), and pendent melamine units was synthesized by Stille polymerization, which can be hydrogen-bonded (H-bonded) with proper molar amounts of bi-functional π-conjugated crosslinker F (i.e., two uracil motifs covalently attached to a fluorene core through triple bonds symmetrically) to develop a novel supramolecular polymer network (PBT/F). The effects of multiple H-bonds on light harvesting capabilities, HOMO levels, and photovoltaic properties of polymer PBT and H-bonded polymer network PBT/F are investigated. The formation of supramolecular polymer network (PBT/F) between PBT and F was confirmed by FTIR and XRD measurements. Because of the stronger light absorption, lower HOMO level, and higher crystallinity of H-bonded polymer network PBT/F, the solar cell device containing PBT/F showed better photovoltaic properties than that containing polymer PBT. The preliminary results show that the solar cell device containing 1:1 weight ratio of PBT/F and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) offers the best power conversion efficiency (PCE) value of 0.86% with a short-circuit current density (Jsc) of 4.97 mA/cm2, an open circuit voltage (Voc) of 0.55 V, and a fill factor (FF) of 31.5%. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

We have investigated the effect of polymer molecular weight (MW) on the morphology and efficiency of bulk heterojunction (BHJ) solar cells comprised of poly[(4,4′-bis(2-ethylhexyl)dithieno[3,2-b:2′,3′-d]silole)-2,6-diyl- alt -(5,5′-thienyl-4,4′-dihexyl-2,2′-bithiazole)-2,6-diyl] (Si-PCPDTTBT) and [6,6]-phenyl C 61 butyric acid methyl ester (PCBM). Striking morphological changes are observed in BHJ films upon the change of the polymer MW. Atomic force microscopy and transmission electron microscopy studies suggest that high MW polymer generated high degree of phase separation, leading to formation of an interpenetrating network for carrier transport. The X-ray diffraction investigation indicated that increased π–π stacking in Si-PCPDTTBT with increasing polymer MWs results in an increase in hole mobility of Si-PCPDTTBT and electron mobility of PCBM as well as the red shift absorption spectrum in BHJ films. The solar cells based on PCBM with high-MW Si-PCPDTTBT deliver power conversion efficiencies of 3.33%.

The opening of an electrical band gap in graphene is crucial for its application for logic circuits. Recent studies have shown that an energy gap in Bernal-stacked bilayer graphene can be generated by applying an electric displacement field. Molecular doping has also been proposed to open the electrical gap of bilayer graphene by breaking either in-plane symmetry or inversion symmetry; however, no direct observation of an electrical gap has been reported. Here we discover that the organic molecule triazine is able to form a uniform thin coating on the top surface of a bilayer graphene, which efficiently blocks the accessible doping sites and prevents ambient p-doping on the top layer. The charge distribution asymmetry between the top and bottom layers can then be enhanced simply by increasing the p-doping from oxygen/moisture to the bottom layer. The on/off current ratio for a bottom-gated bilayer transistor operated in ambient condition is improved by at least 1 order of magnitude. The estimated electrical band gap is up to ∼111 meV at room temperature. The observed electrical band gap dependence on the hole-carrier density increase agrees well with the recent density-functional theory calculations. This research provides a simple method to obtain a graphene bilayer transistor with a moderate on/off current ratio, which can be stably operated in air without the need to use an additional top gate.

a b s t r a c t In this study, we have prepared a series of poly(3,4-ethylenedioxythiophene) (PEDOT) with various molecular weight by using an inhibitor, imidazole (Im). The X-ray diffraction (XRD) results show that the PEDOT with larger molecular weight enhances the polymer chain ordering and stacking which leads to higher conductivity. With increasing the amount of Im, the conductivity of PEDOT can be increased from 4.01 S cm −1 (Im = 0.0 M) to 153.6 S cm −1 (Im = 1.8 M). Comparisons of the cyclic voltam- metry (CV), it enables correlation between the conductivity and specific capacitance, which is important for understanding the electrochemical capacitive behavior of conjugated polymer for pseudo-capacitor application. The PEDOT prepared with 1.8 M Im shows a specific capacitance of 124 F g−1, which is 2.2 times larger than the one without Im (57 F g −1 ).

Five conjugated LBG polymers P1–P5 consisting of a DTP unit as an electron donor and various bithiazole units as electron acceptors are designed and synthesized for photovoltaic applications. The effects of the electron-deficient bithiazole derivatives on the thermal, optical, electrochemical, and photovoltaic properties are investigated. The molecular structures are confirmed and characterized. The resulting polymers have high thermal stabilities and broad absorption bands with low optical bandgaps. The hole and electron mobilities are calculated. PSC devices are fabricated utilizing the polymers as electron donors and PCBM as an electron acceptor. The PSC device with an active layer of P4:PCBM (1:1 by weight) exhibits the best power-conversion efficiency.

Demand for green and renewable energy is stimulating research into future materials for energy production. Thin films of materials possessing both electron accepting and donating functions play a unique role in solar energy technology because of their light weight, flexibility, and economical, low-temperature, and large-area fabrication. A [60]fullerene derivative, [6,6]-2-selenyl-C 61 -butyric acid methyl ester (SeCBM), has been synthesized in three steps, namely through Friedel–Crafts acylation of selenophene, hydrazone formation and Bamford-Steven reaction. Organic photovoltaic device incorporating SeCBM and the conducting polymer P3HT exhibited an average power conversion efficiency of 3.26% and a champion efficiency as high as 3.81% under AM 1.5G irradiation.

We present an antireflection structure consisted of tapered nanopillars to simultaneously increase light extraction efficiency and image contrast of flexible organic light-emitting devices. The nanopillars were made by imprinting the anodized aluminum oxide on polycarbonate substrates. The thermal viscosity effect formed the nanopillars with tapered shapes. Such tapered nanopillars show excellent antireflection properties for a wide range of incident angles and wavelengths. The transmittance was greatly improved from 52.8% to 89.1% at 60° incident angle for 150-nm-height nanopillars. With this antireflection structure, the device efficiency was improved 69% as compared to devices with flat substrates. Due to wide-angle antireflection, the ANSI image contrast ratio was also significantly improved.

Two b-cyano-thiophenevinylene-based polymers containing cyclopentadithiophene (CPDT-CN) and dithienosilole (DTS-CN) units were synthesized via Stille coupling reaction with Pd(PPh3)4 as a catalyst. The effects of the bridged atoms (C and Si) and cyano-vinylene groups on their thermal, optical, electrochemical, charge transporting, and photovoltaic proper- ties were investigated. Both polymers possessed the highest occupied molecular orbital (HOMO) levels of about � 5.30 eV and the lowest unoccupied molecular orbital (LUMO) levels of about � 3.60 eV, and covered broad absorption ranges with narrow optical band gaps (ca. 1.6 eV). The bulk heterojunction polymer solar cell (PSC) devices containing an active layer of

In this study, we used a transferring process to fabricate a simple light-harvesting system featuring 2D periodic granular-like electrodes for polymer solar cells (PSCs). This transferring technique, which was based on nanosphere lithography, could be used to fabricate periodic nanostructures on both the photoactive layers and the Al electrodes in the normal PSC device configuration (indium tin oxide glass/PEDOT:PSS/photoactive layer/Al). We investigated the properties of the PSC devices featuring periodic nanostructures in the photoactive layers using reflection UV–vis spectra and in terms of their external quantum efficiency (EQE) and photocurrent–voltage characteristics. In addition, we used numerical simulations to evaluate the electromagnetic field distributions in the devices. The light trapping efficiency in the PSCs featuring periodic nanostructures was enhanced as a result of light scattering and surface plasmon resonance effects. Relative to conventional devices featuring a flat geometry, the po...

Two kinds of novel conjugated polymers containing 2,7-carbazole, thiophene, and fused-dithienothiophene rings as backbones bearing acid-protected and benzoic acid pendants ( PC1 and PC2 , respectively) were utilized for organic solar cell applications. The absorption spectra of these polymers (in both solutions and solid films) showed an absorption range at 300–580 nm. Furthermore, ZnO nanoparticles were synthesized and surface-modified with pyridyl surfactants ( ZnOpy ) to be ca. 3–4 nm. The pyridyl surfactants of ZnOpy nanoparticles (as electron acceptors to partially replace expensive electron acceptor PCBM) not only induce supramolecular interactions with benzoic acid pendants of polymer PC2 via H-bonds, but also enhance the homogeneous dispersions of ZnOpy nanoparticles in polymer PC2 . Thus, the ternary systems of PC1–PC2 / ZnOpy /PCBM in weight ratios of 1:0.05:1 and 1:0.1:1 were investigated in bulk heterojunction polymer solar cells (PSCs). Under the standard illumination of AM 1.5, 100 mW/cm 2 , the best power conversion efficiency (PCE) of the PSC cell containing a polymer blend of PC2 / ZnOpy /PCBM = 1:0.05:1 reached PCE = 0.55%, with J sc = 2.11 mA/cm 2 , V oc = 0.88 V, and FF = 29.4%.

Heterojunctions between different graphitic nanostructures, including fullerenes, carbon nanotubes and graphene-based sheets, have attracted significant interest for light to electrical energy conversion. Because of their poor solubility, fabrication of such all-carbon nanocomposites typically involves covalently linking the individual constituents or the extensive surface functionalization to improve their solvent processability for mixing. However, such strategies often deteriorate or contaminate the functional carbon surfaces. Here we report that fullerenes, pristine single walled carbon nanotubes, and graphene oxide sheets can be conveniently coassembled in water to yield a stable colloidal dispersion for thin film processing. After thermal reduction of graphene oxide, a solvent-resistant photoconductive hybrid of fullerene-nanotube-graphene was obtained with on-off ratio of nearly 6 orders of magnitude. Photovoltaic devices made with the all-carbon hybrid as the active layer and an additional fullerene block layer showed unprecedented photovoltaic responses among all known all-carbon-based materials with an open circuit voltage of 0.59 V and a power conversion efficiency of 0.21%. The ease of making such surfactant-free, water-processed, carbon thin films could lead to their wide applications in organic optoelectronic devices.

A bilayer polymer solar cell is demonstrated with the device configuration ITO/PEDOT:PSS/poly(3-hexylthiophene)/C70/Al. In this article, we highlight the importance of polymer surface morphology, its crystallinity and mobility on device output parameters. The solvent used for polymer processing plays a major role in deciding these parameters and it was observed that high boiling point solvents are desirable for achieving large surface roughness of the polymer layer, which in turn provide more interface area in the bilayer device structure. Due to the increased interface area for exciton dissociation, these bilayer devices resulted in a maximum power conversion efficiency of 3.65% under one sun radiation.

Understanding the effects of conjugated polymer structures on exciton lifetimes and morphologies within bulk heterojunction (BHJ) films is a necessary step toward the development of better organic solar cells. Studying the impact of a polymer’s structure on the optical, morphological, and performance characteristics of a device can lead to advances in the design of new polymers. In this study, we synthesized carbon- and silicon-bridged cyclopentadithiophene- (CPDT-) based polymers and determined their photophysical properties and morphologies by measuring the exciton lifetime distributions in their BHJ films. The silicon-bridged CPDT-based polymer/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) BHJ exhibited a higher degree of luminescence quenching, suggesting that thermodynamically favorable mixing on the molecular scale and nanoscale phase separation occurred simultaneously in the blend film. We attribute this favorable morphology to the presence of strong π−π stacking in the silicon-bridged CPDT-bas...

A series of π-conjugated bis-terpyridyl ligands (M1–M3) bearing various benzodiazole cores and their corresponding main-chain Ru(II) metallo-polymers were designed and synthesized. The formation of metallo-polymers were confirmed by NMR, relative viscosity, and UV-visible titration measurements. The effects of electron donor and acceptor interactions on their thermal, optical, electrochemical, and photovoltaic properties were investigated. Due to the strong intramolecular charge transfer (ICT) interaction and metal to ligand charge transfer (MLCT) in Ru(II)-containing polymers, the absorption spectra covered a broad range of 260–750 nm with the optical band gaps of 1.77–1.63 eV. In addition, due to the broad sensitization areas of the metallo-polymers, their bulk heterojunction (BHJ) solar cell devices containing [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an electron acceptor exhibited a high short-circuit current (Jsc). An optimum PVC device based on the blended polymer P1:PCBM = 1:1 (w/w) achieved the maximum power conversion efficiency (PCE) value up to 0.45%, with Voc = 0.61 V, Jsc = 2.18 mA cm−2, and FF = 34.1% (under AM 1.5 G 100 mW cm−2), which demonstrated a novel family of conjugated polyelectrolytes with the highest PCE value comparable with BHJ solar cells fabricated from ionic polythiophene and C60.

A series of novel hydrogen-bonded (H-bonded) cross-linking polymers were generated by complexing various proton-donor (H-donor) solar cell dyes containing 3,6- and 2,7-functionalized electron-donating carbazole cores bearing symmetrical thiophene linkers and cyanoacrylic acid termini with a proton-acceptor (H-acceptor) side-chain homopolymer carrying pyridyl pendants (with 1/2 M ratio of H-donor/H-acceptor). The supramolecular H-bonded structures between H-donor dyes and the H-acceptor side-chain polymer were confirmed by FTIR measurements. The effects of the supramolecular architecture on optical, electrochemical, and organic photovoltaic (OPV) properties were investigated. From DFT (density functional theory) calculations, the optimized geometries of organic dyes reflected that the carbazole cores of H-donor dyes were coplanar with the conjugated thiophenes and cyanoacrylic acids, which is essential for strong conjugations across the donor-acceptor units in D1–D4 dyes. Under 100 mW/cm2 of AM 1.5 white-light illumination, bulk heterojunction (BHJ) OPV cell devices containing an active layer of H-bonded polymers (PDFTP/D1–D4) as an electron donor blended with [6,6]-phenyl C61-butyric acid methyl ester (PCBM) as an electron acceptor in a weight ratio of 1:1 were explored. From the preliminary investigations, the OPV device containing 1:1 weight ratio of H-bonded polymer PDFTP/D2 and PCBM showed the best power conversion efficiency (PCE) value of 0.31% with a short-circuit current (Jsc) of 1.9 mA/cm2, an open-circuit voltage (Voc) of 0.55 V, and a fill factor (FF) of 29%, which has a higher PCE value than the corresponding H-donor D2 dye (PCE = 0.15%) or H-acceptor PDFTP homopolymer (PCE = 0.02%) blended with PCBM in 1:1 weight ratio.

A series of novel low-bandgap triphenylamine- based conjugated polymers (PCAZCN, PPTZCN, and PDTPCN) consisting of different electron-rich donor main chains (N-alkyl- 2,7-carbazole, phenothiazine, and cyclopentadithinopyrol, respectively) as well as cyano- and dicyano-vinyl electron- acceptor pendants were synthesized and developed for poly- mer solar cell applications. The polymers covered broad absorption spectra of 400-800 nm with narrow optical band- gaps ranging 1.66-1.72 eV. The highest occupied molecular or- bital and lowest unoccupied molecular orbital levels of the polymers measured by cyclic voltammetry were found in the range of � 5.12 to � 5.32 V and � 3.45 to � 3.55 eV, respectively. Under 100 mW/cm 2 of AM 1.5 white-light illumination, bulk heterojunction photovoltaic devices composing of an active

A series of low-band-gap (LBG) donor-accepor con- jugated main-chain copolymers (P1-P4) containing planar 2,7- carbazole as electron donors and bithiazole units (4,4 0 -dihexyl- 2,2 0 -bithiazole and 4,4 0 -dihexyl-5,5 0 -di(thiophen-2-yl)-2,2 0 -bithia- zole) as electron acceptors were synthesized and studied for the applications in bulk heterojunction (BHJ) solar cells. The effects of electron deficient bithiazole units on the thermal, optical, electrochemical, and photovoltaic (PV) properties of these LBG copolymers were investigated. Absorption spectra revealed that polymers P1-P4 exhibited broad absorption bands in UV and visible regions from 300 to 600 nm with opti- cal band gaps in the range of 1.93-1.99 eV, which overlapped with the major region of the solar emission spectrum. More- over, carbazole-based polymers P1-P4 showed low values of the highest occupied molecular orbital (HOMO) levels, which provided good air stability and high open circuit voltages (Voc) in the PV applications. The BHJ PV devices were fabricated using polymers P1-P4 as electron donors and (6,6)-phenyl-C61- butyric acid methyl ester (PC61BM) or (6,6)-phenyl-C71-butyric acid methyl ester (PC71BM) as electron acceptors in different weight ratios. The PV device bearing an active layer of polymer blend P4:PC71BM (1:1.5 w/w) showed the best power conver- sion efficiency value of 1.01% with a short circuit current den- sity (Jsc) of 4.83 mA/cm 2 , a fill factor (FF) of 35%, and Voc ¼ 0.60 V under 100 mW/cm 2 of AM 1.5 white-light illumination.

In the present article, potential of a bilayer organic solar cell has been investigated. We utilize newly synthesized small molecules, namely dibenzo[f,h]thieno[3,4-b]quinoxaline as electron donors for solar cells in heterojunction bilayer configuration. These small molecules with a narrow absorption band in the range 400–450 nm provide a complementary spectrum for the fullerene C70, thereby leading to an overall power conversion efficiency of 2.670.2% under 100 mW/cm 2 incident radiation. Thermal annealing seems to impact the charge separation at the donor–acceptor interface, which eventually affects device performance. This work demonstrates that carefully optimized bilayer devices are comparable to the bulk heterojunction counterparts.

A series of soluble donor-acceptor conjugated poly- mers comprising of phenothiazine donor and various benzodia- zole acceptors (i.e., benzothiadiazole, benzoselenodiazole, and benzoxadiazole) sandwiched between hexyl-thiophene linkers were designed, synthesized, and used for the fabrication of polymer solar cells (PSC). The effects of the benzodiazole acceptors on the thermal, optical, electrochemical, and photo- voltaic properties of these low-bandgap (LBG) polymers were investigated. These LBG polymers possessed large molecular weight (Mn) in the range of 3.85� 5.13 � 10 4 with high thermal decomposition temperatures, which demonstrated broad absorption in the region of 300� 750 nm with optical bandgaps of 1.80� 1.93 eV. Both the HOMO energy level (� 5.38 to � 5.47 eV) and LUMO energy level (� 3.47 to � 3.60 eV) of the LBG polymers were within the desirable range of ideal energy level. Under 100 mW/cm 2 of AM 1.5 white-light illumination, bulk heterojunction PSC devices containing an active layer of elec- tron donor polymers mixed with electron acceptor (6,6)-phe- nyl-C61-butyric acid methyl ester (PC61BM) or (6,6)-phenyl-C71- butyric acid methyl ester (PC71BM) in different weight ratios were investigated. The best performance of the PSC device was obtained by using polymer PP6DHTBT as an electron do- nor and PC71BM as an acceptor in the weight ratio of 1:4, and a power conversion efficiency value of 1.20%, an open-circuit voltage (Voc) value of 0.75 V, a short-circuit current (Jsc) value of 4.60 mA/cm 2 , and a fill factor (FF) value of 35.0% were achieved. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4823-4834, 2010

In this study, we synthesized a new polymer, PCTDBI, containing alternating carbazole and thiadiazole-benzoimidazole (TDBI) units. This polymer (number-average molecular weight = 25,600 g mol−1), which features a planar imidazole structure into the polymeric main chain, possesses reasonably good thermal properties (Tg = 105 °C; Td = 396 °C) and an optical band gap of 1.75 eV that matches the maximum photon flux of sunlight. Electrochemical measurements revealed an appropriate energy band offset between the polymer's lowest unoccupied molecular orbital and that of PCBM, thereby allowing efficient electron transfer between the two species. A solar cell device incorporating PCTDBI and PCBM at a blend ratio of 1:2 (w/w) exhibited a power conversion efficiency of 1.20%; the corresponding device incorporating PCTDBI and PC71BM (1:2, w/w) exhibited a PCE of 1.84%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

In this study, we have constructed the first organic field effect sensor based on an electrolyte-insulator-semiconductor structure (OEIS) and applied this novel device to pH and DNA sensing. Variations in the insulator-electrolyte surface potential, which originate from either the change of the ionization states of the insulator surface groups or the binding of charged molecules to the insulator surface, modify the flat band voltage (V(FB)) of the OEIS sensor. The pH sensing experiments of OEIS sensor showed that the output signal linearly depended on pH solution in the range from pH 2 to pH 12, and an average sensitivity of 44.1 mV/pH was obtained. In the biosensing experiments, the absorption of positively charged poly-L-lysine on the insulator surface resulted in the reduction of the V(FB) value, whereas the subsequent binding of negatively charged single-stranded DNA probe (ssDNA) via electrostatic interaction increased the V(FB) value. Furthermore, the ssDNA-immobilized OEIS device was successfully used for the detection of DNA hybridization. The detection limit of complementary DNA was as low as 1 microM, and the output signal of OEIS biosensor linearly increased with the logarithm of complementary DNA concentration in the range from 5x10(-5) to 10(-7) M. The easy and inexpensive fabrication of the OEIS device allows to be served as a potentially disposable and sensitive biosensor.

Lithium-sulfur (Li-S) battery with high theoretical energy density of 2600 Wh/kg, expected to be next generation battery. In reality Li-dendrite growth, polysulfide formation, shuttling effect, low conductivity of sulfur and low active material loading become major challenges to develop Li-S battery technology. To overcome these problems we have tried a bilayer separator, which consists of low dimensional molybdenum oxide (MoO3) nanorods on one side and polymer on other side to prevent the migration of polysulfides. The low dimensional transition metal oxide was prepared by simple physical grinding process. 10 wt% solution was prepared in isopropyl alcohol (IPA) and spray coated onto one side of the celgard. Initial capacity of 1185 mAh/g was achieved at 0.5 C (1C=1675mAh/g) and at the end of 500 cycles 80% initial discharge capacity was retained with degradation rate of 0.04% per cycle. Rate capability of the Li-S battery using MoO3 coated separator was measured starting with 0.5 C rate followed by 1 C, 2 C, 3 C, 4 C and finally, return to 0.5 C and the test illustrates that the Li-S battery possesses very good rate capability by showing 93.21% retention of initial discharge capacity. Figure 1

we describe a modified activated expanded graphite chitosan (AEG/CH) coated separator for Li–S batteries in which the shuttling phenomenon of the lithium polysulfides is restrained through two types of interactions: activated expanded graphite (AEG) flakes having a high surface area of 368 m2g-1interacted physically with the lithium polysulfides, while chitosan (CH), was used to bind the AEG flakes on the separator, interacted chemically through its abundance of amino and hydroxyl functional groups. Moreover, the AEG flakes facilitated ionic and electronic transfer during the redox reaction. Live H-cell discharging experiments revealed that the modified separator was effective at curbing polysulfide shuttling; moreover, XPS analysis of the cycled separator confirmed the presence of lithium polysulfides in the AEG/CH matrix. Using this dual functional interaction approach, the lifetime of the pure sulfur-based cathode was extended to 1000 cycles at 1C-rate (1C = 1670 mA/g), decreasing the decay rate to 0.021% per cycle—a value that is among the best reported to date. A flexible battery based on this modified separator exhibited stable performance and could turn on multiple light emitting diodes. Such modified membranes with good mechanical strength, high electronic conductivity, and anti-self-discharging shield appear to be a scalable solution for future high-energy battery systems.

We have synthesized a low-bandgap polymer, bithiazole-based polymer (PCPDTTBT) containing cyclopentadithiophene and thiophene units, and studied its opticophysical properties and morphologies in bulk heterojunction films after annealing. We used confocal optical microscopy in conjunction with a fluorescence module to record exciton lifetime images within photoactive layers of PCPDTTBT and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). These images, which were consistent with those recorded using atomic force microscopy and transmission electron microscopy, revealed that phase separation of PCPDTTBT and PCBM occurred during slow solvent evaporation. This phase separation not only provided bicontinuous pathways for carrier transport to the respective electrodes but also enhanced the degree of polymer chain stacking, thereby improving the absorption and balancing the electron and hole mobilities. We tested the performance of solar cells incorporating PCPDTTBT and various fullerene derivatives. Under AM 1...

Flexible indium tin oxide (ITO)-free poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester (P3HT:PC61BM) solar cells with a spin-coated silver nanowire transparent electrode are demonstrated. The solution-processed silver nanowire thin film not only exhibits high transmission (~87%), but also shows low sheet resistance R s (~25 Ω/sq). For solar cells with a conventional structure, the power conversion efficiency (PCE) of devices based on silver nanowires can reach around 2.29%. For the inverted structure, the PCE of devices can reach 3.39%. Conventional and inverted flexible ITO-based P3HT:PC61BM solar cells are also fabricated as a reference for comparison. For both types of solar cells, the PCE of ITO-free devices is very close that of an ITO-based polymer solar cell.

We have synthesized a narrow-bandgap conjugated polymer (PCTDPP) containing alternating cyclopentadithiophene (CT) and diketo-pyrrolo-pyrrole (DPP) units by Suzuki coupling. This PCTDPP exhibits a low band gap of 1.31 eV and a broad absorption band from 350 to 1000 nm, which allows it to absorb more available photons from sunlight. A bulk heterojunction polymer solar cell incorporating PCTDPP and C70 at a blend ratio of 1:3 exhibited a high short-circuit current of 10.87 mA/cm2 and a power conversion efficiency of 2.27%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1669–1675, 2010

In this study, the exciton lifetime images within the photoactive layers of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are revealed by confocal optical microscopy combined with the fluorescence module. The images reveal that the active layers during slow solvent evaporation provide 3D pathways for charge transport and the concentration gradient through the film which reflects the better cell performance. This technique offers a great help to investigate the 3D optical-physical property without destroying the blends.

In this article, we demonstrate the effect of donor−acceptor (D-A) interface on the performance of bilayer organic solar cells. Solution processing was used to develop liquid crystal poly(9,9′-dioctylfluorene-co-bithiophene) (F8T2) polymer films and variable morphology of the films was achieved by varying the annealing temperature. The morphology of the annealed active layers signature a well-aligned nanodomain feature with an interdegitated structure at 200 °C. The devices with bilayer configuration, ITO/PEDOT:PSS/F8T2/C70/Al, have yielded a power conversion efficiency (PCE) of 3.4(±0.2)% under 1 sun incident radiation. We attribute the high PCE to the increased D-A junction interface and balanced charge transport between electron/hole transport layers.

In this article, low temperature processed, reactively evaporated titanium oxide layers were utilized as gate dielectrics for achieving low voltage driven transistors and complementary inverters. The surface of the gate dielectric was modified by an ultra thin (∼30 nm) fluoropolymer Cytop® layer which partially helped to reduce the leakage in the dielectric films and also enhanced the organic transistor performance. The current investigation demonstrates the ability of these high capacitance bi-layer dielectrics (k ∼ 20). The combined p-type and n-type field-effect transistors show similar saturation mobility ∼0.3 cm2/V s−1 to achieve low voltage driven complementary circuits with output gain of 22. Low temperature processing of these dielectric layers make them easily integrated.

We have fabricated organic photovoltaic devices with blends of poly[9,9′-dioctyl-fluorene- co -bithiophene] (F8T2) and fullerene as an electron donor and electron acceptor, respectively. A significant improvement of the photovoltaic efficiency was found in device by using active materials with complementary spectra. The different weight ratios of composite film were also performed to correlate between morphology and the device performance. A power conversion efficiency (PCE) up to 2.0% with an open-circuit voltage of 0.85 V and a short-circuit current ( J SC ) of 5.3 mA/cm 2 , was achieved by blending the F8T2 with [6,6]-phenyl-C71-butyric acid methyl ester (PC[70]BM).

In this study, we investigated the influence of a buffer layer of molybdic oxide (MoO 3 ) at the metal/organic junction on the behavior of organic base-modulation triodes. The performance of devices featuring MoO 3 /Al as the emitter electrode was enhanced relative to that of corresponding devices with Au and Ag, presumably because of the reduced in the contact barrier and the prevention of metal diffusion into the organic layer. The device exhibited an output current of −16.1 μA at V B = −5 V and a current ON/OFF ratio of 10 3 . Using this architecture, we constructed resistance–load inverters that exhibited a calculated gain of 6.

In this work, the hemocompatibility of a sulfobetaine-like copolymer brush resulting from a mixed-charge copolymerization of the positively charged 11-mercapto-N,N,N-trimethylammonium chloride (TMA) and negatively charged 11-mercaptoundecylsulfonic acid (SA) was studied. Mixed charge distribution in the prepared poly(TMA-co-SA) copolymer brushes was controlled by the regulation of the reaction rate of the surface-initiated atom transfer radical polymerization (ATRP). The adsorption behavior of plasma proteins on a surface grafted with poly(TMA-co-SA) was measured by a surface plasmon resonance (SPR) sensor. The effects of varying temperature, solution pH, and ionic strength on the antifouling characteristics of the mixed-charge copolymer brushes were systematically evaluated, and the protein-fouling resistance was discussed in detail, especially with respect to the effect of ionic strength on the intra- and intermolecular interactions of the poly(TMA-co-SA) with proteins. The adhesion and activation of blood cells on the poly(TMA-co-SA)-grafted surface in contact with human whole blood was also demonstrated. The results suggest that mixed-charge copolymer brushes of poly(TMA-co-SA), which, like zwitterionic homopolymer brushes, have overall charge neutrality, can be used in similar applications for protein-fouling resistance and have excellent hemocompatibility with human whole blood at physiologic temperatures.

Novel supramolecular side-chain polymers were constructed by complexation of proton acceptor (H-acceptor) polymers, i.e., side-chain conjugated polymers P1–P2 containing pyridyl pendants, with low-band-gap proton donor (H-donor) dyes S1–S4 (bearing terminal cyanoacrylic acids) in a proper molar ratio. Besides unique mesomorphic properties confirmed by DSC and XRD results, the H-bonds of supramolecular side-chain structures formed by pyridyl H-acceptors and cyanoacrylic acid H-donors were also confirmed by FTIR measurements. H-donor dyes S1–S4 in solid films exhibited broad absorption peaks located in the range of 471–490 nm with optical band-gaps of 1.99–2.14 eV. Furthermore, H-bonded polymer complexes P1/S1–P1/ S4 and P2/S1–P2/S4 exhibited broad absorption peaks in the range of 440–462 nm with optical band-gaps of 2.11–2.25 eV. Under 100 mW/cm2 of AM 1.5 white-light illumination, the bulk heterojunction polymer solar cell (PSC) devices containing an active layer of H-bonded polymer complexes P1/S1–P1/S4 and P2/S1–P2/S4 (as electron donors) mixed with [6,6]-phenyl C61 butyric acid methyl ester (i.e., PCBM, as an electron acceptor) in the weight ratio of 1:1 were investigated. The PSC device containing H-bonded polymer complex P1/S3 mixed with PCBM (1:1 w/w) gave the best preliminary result with an overall power conversion efficiency (PCE) of 0.50%, a short-circuit current of 3.17 mA/cm2, an open-circuit voltage of 0.47 V, and a fill factor of 34%. VVC 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5998–6013, 2009

A low-bandgap polymer (PF-PThCVPTZ) consisted of fluorene and phenothiazine was designed and synthesized. With the donor–acceptor segment, the partial charge transfer can be built in the polymer backbone leading to a wide absorbance. The absorption spectrum of PF-PThCVPTZ exhibits a peak at 510 nm and an absorption onset at 645 nm in the visible range. As blended with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an electron acceptor, narrow bandgap PF-PThCVPTZ as electron donor shows significant solar cell performance. Under AM 1.5 G, 100 mA/cm 2 illumination, a power conversion efficiency (PCE) of 1.85% was recorded, with a short circuit current ( J SC ) of 5.37 mA/cm 2 , an open circuit voltage ( V OC ) of 0.80 V, and a fill factor (FF) of 43.0%.

Thermoresponsive statistical copolymers of zwitterionic sulfobetaine methacrylate (SBMA) and nonionic N-isopropylacrylamide (NIPAAm) were prepared with an average molecular weight of about 6.0 kDa via homogeneous free radical copolymerization. The aqueous solution properties of poly(SBMA-co-NIPAAm) were measured using a UV--visible spectrophotometer. The copolymers exhibited controllable lower and upper critical solution temperatures in aqueous solution and showed stimuli-responsive phase transition in the presence of salts. Regulated zwitterionic and nonionic molar mass ratios led to poly(SBMA-co-NIPAAm) copolymers having double-critical solution temperatures, where the water-insoluble polymer microdomains are generated by the zwitterionic copolymer region of polySBMA or nonionic copolymer region of polyNIPAAm depending on temperature. A high content of the nonionic polyNIPAAm in poly(SBMA-co-NIPAAm) exhibits nonionic aggregation at high temperatures due to the desolvation of polyNIPAAm, whereas relatively low content of polyNIPAAm in poly(SBMA-co-NIPAAm) exhibits zwitterionic aggregation at low temperatures due to the desolvation of polySBMA. Plasma protein adsorption on the surface coated with poly(SBMA-co-NIPAAm) was measured with a surface plasmon resonance (SPR) sensor. The copolymers containing polySBMA above 29 mol % showed extremely low protein adsorption and high anticoagulant activity in human blood plasma. The tunable and switchable thermoresponsive phase behavior of poly(SBMA-co-NIPAAm), as well as its high plasma protein adsorption resistance and anticoagulant activity, suggests a potential for blood-contacting applications.

Six novel conjugated copolymers (P1−P6) containing coplanar cyclopentadithiophene (CPDT) units (incorporated with bithiazole/thienyl-based monomers) were synthesized and developed for the applications of polymer solar cells (PSCs). Copolymers P1−P6 covered broad absorption ranges from UV to near-infrared (400−800 nm) with narrow optical band gaps of 1.70−1.94 eV, which are compatible with the maximum solar photon reflux. Partially reversible p- and n-doping processes of P1−P6 in electrochemical experiments were observed. Compared with those previously reported CPDT-based narrow band gap polymers, the proper molecular design for HOMO/LUMO levels of P1−P6 induced relatively high photovoltaic open-circuit voltages in the PSC devices. Powder X-ray diffraction (XRD) analyses suggested that these copolymers formed highly self-assembled π−π stackings. Under 100 mW/cm2 of AM 1.5 white-light illumination, bulk heterojunction PSC devices containing an active layer of electron donor copolymers P1−P6 blended with ele...

Control of blend morphology at the nanoscale and high charge mobility is essential for polymer photovoltaic devices in terms of their power conversion efficiencies (PCE). In the case of bulk heterojunctions solar cells, both blend morphology and charge mobility are influenced by thermal treatment. In this manuscript, we study the effects of annealing temperature on polymer PV devices with blends of poly[9,9’- dioctyl-fluorene-co-bithiophene] (F8T2) and [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM). The morphological changes of blended films were observed upon thermal annealing temperature near and above glass transition temperature (130 °C). Such microstructural transformations resulted in modified charge transport pathways and therefore greately influenced the device performance. The highest PCE of 2.14% with an open-circuit voltage ( V OC ) of 0.99 V and a short-circuit current ( J SC ) of 4.24 mA/cm 2 was achieved by device annealing at 70 °C for 20 min.