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Fullerene Derivative‐Doped Zinc Oxide Nanofilm as the Cathode of Inverted Polymer Solar Cells with Low‐Bandgap Polymer (PTB7‐Th) for High Performance

Modification of a ZnO cathode by doping it with a hydroxyl-containing derivative - giving a ZnO-C60 cathode - provides a fullerene-derivative-rich surface and enhanced electron conduction. Inverted polymer solar cells with the ZnO-C60 cathode display markedly improved power conversion efficiency compared to those with a pristine ZnO cathode, especially when the active layer includes the low-bandgap polymer PTB7-Th.

Single Junction Inverted Polymer Solar Cell Reaching Power Conversion Efficiency 10.31% by Employing Dual-Doped Zinc Oxide Nano-Film as Cathode Interlayer

We present high efficiency and stable inverted PSCs (i-PSC) by employing sol-gel processed simultaneously doped ZnO by Indium and fullerene derivative (BisNPC60-OH) (denoted as InZnO-BisC60) film as cathode interlayer and PTB7-Th:PC71BM as the active layer (where PTB7-Th is a low bandgap polymer we proposed previously). This dual-doped ZnO, InZnO-BisC60, film shows dual and opposite gradient dopant concentration profiles, being rich in fullerene derivative at the cathode surface in contact with active layer and rich in In at the cathode surface in contact with the ITO surface. Such doping in ZnO not only gives improved surface conductivity by a factor of 270 (from 0.015 to 4.06 S cm−1) but also provides enhanced electron mobility by a factor of 132 (from 8.25*10−5 to 1.09*10−2 cm2 V−1 s−1). The resulting i-PSC exhibits the improved PCE 10.31% relative to that with ZnO without doping 8.25%. This PCE 10.31% is the best result among the reported values so far for single junction PSC.

WHITE LIGHT EMISSION FROM EXCIPLEX IN A BILAYER DEVICE WITH TWO BLUE LIGHT-EMITTING POLYMERS

Bilayer polymer light-emitting diodes with two blue light-emitting materials, poly(N-vinylcarbazole) (PVK) and poly(2-dodecyl-p-phenylene) (C12O-PPP), can emit blue or white light, depending on the solvent used in the fabrication of the second layer, C12O-PPP. If hexane (the nonsolvent for PVK) is used, the device emits blue light as a single layer device with C12O-PPP. However, if toluene (the cosolvent for the two polymers) is used, the device emits white light originating from an exciplex emission at the bilayer interface in addition to the exciton emission from C12O-PPP. At low temperatures, the intensity of the exciplex emission drops and that of the exciton emission becomes dominant.

White-light emission from electroluminescence diode with polyaniline as the emitting layer

Abstract A light-emitting diode (LED) with emeraldine base polyaniline (PAn) as the emitting layer, indium—tin oxide coated glass plate as the hole injector and deposited aluminum (or magnesium) thin film as the electron injector was fabricated, which can emit nearly white light covering the full range of visible light (380–750 nm). It is found that the white light is emitted from the phase with reduced repeat units (amine form), while the phase with oxidized repeat units (quinoid form) has no contribution to the emitting light. The turn-on voltage for eye-observable light intensity is 13 and 6 V for the LEDs with aluminum and magnesium electrodes, respectively, at a thickness of the emitting layer of 800 A. The range of the electroluminescence (EL) spectrum covering the range 300–800 nm is much broader than that of the photoluminescence (PL) spectrum, 350–510 nm.

Multiple Functionalities of Polyfluorene Grafted with Metal Ion-Intercalated Crown Ether as an Electron Transport Layer for Bulk-Heterojunction Polymer Solar Cells: Optical Interference, Hole Blocking, Interfacial Dipole, and Electron Conduction

We present a novel electron transport (ET) polymer composed of polyfluorene grafted with a K(+)-intercalated crown ether involving six oxygen atoms (PFCn6:K(+)) for bulk-heterojunction polymer solar cells (PSCs) with regioregular poly(3-hexylthiophene) (P3HT) as the donor and indene-C(60) bisadduct (ICBA) or indene-[6,6]-phenyl-C(61)-butyric acid methyl ester (IPCBM) as the acceptor in the active layer and with Al or Ca/Al as the cathode. A remarkable improvement in the power conversion efficiency (PCE) (measured in air) was observed upon insertion of this ET layer, which increased the PCE from 5.78 to 7.5% for a PSC with ICBA and Ca/Al (5.53 to 6.63% with IPCBM) and from 3.87 to 6.88% for a PSC with ICBA and Al (3.06 to 6.21% with IPCBM). This ET layer provides multiple functionalities: (1) it generates an optical interference effect for redistribution of light intensity as an optical spacer; (2) it blocks electron-hole recombination at the interface with the cathode; (3) it forms an interfacial dipole that promotes the vacuum level of the cathode metal; and (4) it enhances electron conduction, as evidenced by (1) the increase in total absorption of 1:1 w/w P3HT:ICBA by a factor of 1.3; (2) the reduction in the hole-only current density profile by a factor of 3.3 at 2.0 × 10(5) V/cm; (3) the decrease of 0.81 eV in the work function of Al from 4.28 to 3.47 eV, as determined by UV photoelectron spectroscopy; and (4) the decrease in the series resistance of PSCs with ICBA and Al by a factor of 4.5, as determined by the current-voltage characteristic under dark conditions; respectively. The PSC of 7.5% is the highest among the reported values for PSC systems with the simplest donor polymer, P3HT.

White-light electroluminescence from soluble oxadiazole-containing phenylene vinylene ether-linkage copolymer

We report a promising oxadiazole-containing phenylene vinylene ether-linkage copolymer, which can emit nearly white light from a single-layer light-emitting diode. The emission spectrum is composed of a red component originating from the new excited dimer in addition to the blue-green component from an individual lumophore and excimer. This excited dimer is formed under a strong electric field inside the diode and cannot be produced by photoexcitation, which is different from the excimer or exciplex that is often found both in photoluminescence and electroluminescence, and it is termed the “electromer.”

Polyaniline schottky barrier: effect of doping on rectification and photovoltaic characteristics

Abstract Schottky diodes of aluminium/polyaniline (PAn)/indium-tin oxide (ITO) with large area (0.3–1 cm2) are prepared using the casting technique. The PAns investigated involve undoped polyaniline (undoped PAn), polyacrylic acid-doped polyaniline (PAA-doped PAn) and toluene-4-sulfonic acid-doped polyaniline (TSA-doped PAn). The diodes, in which the undoped and doped PAns behave as p-type semiconductors, exhibit a moderate rectifying behaviour and low leakage current. Photovoltaic measurements on the the diodes at various light intensities from 1 to 40 mW/cm2 show power conversion efficiencies of about 0.04, 0.57 and 0.88%, respectively, at a light intensity of 1 mW/cm2 (which, for doped PAns, are comparable with that of HCl-doped (CH)x, 1% at 7 mW/cm2). The conversion efficiency decreases with increasing light intensity (1 to 40 mW/cm2). Acid-doping of PAn can cause a higher photovoltaic conversion efficiency.

Structures and properties of the soluble polyanilines, N-alkylated emeraldine bases

Abstract The N-alkylated emeraldine bases (N-butyl, N-hexyl, N-octyl, N-decyl, N-dodecyl, and N-hexadecyl) are synthesized by incorporation of flexible alkyl chains onto the polyaniline (PAn) through an N-alkylation method with the emeraldine base. The solubility of PAn in common organic solvents is improved remarkably with the alkylation and the oxidation level is maintained at 40–50 mol% (close to that of the original emeraldine base, 50%) allowing for an adequate acid doping. When carbon number of the alkyl side chain is six or more, the polymers can be dissolved in common organic solvents (such as tetrahydrofuran, dichloromethane, and chloroform) even in the presence of a protonic organic acid as dopant, such as dodecylbenzene sulfonic acid (DDBSA) and camphor sulfonic acid (CSA), and free-standing films can be obtained by casting from the solutions. When the carbon number is 12, the polymer film is flexible. DDBSA-doped N-alkylated emeraldine salt films cast from polymer solutions in dichloromethane in the presence of the acid dopant have maximum conductivities in the range 10−2– 10−4 S/cm, being two to three orders of magnitude higher than those of the reported HClO4-doped poly(N-alkylaniline)s.

Minimum end time policies for batchwise radical chain polymerization

Abstract For batchwise radical chain polymerization, the minimum end time problem is studied for the “optimal” process and “best” isothermal process by

Crystallization behavior, crystal transformation, and morphology of polypropylene/polybutene-1 blends

Abstract The effects of composition on crystallization behavior, crystal transformation, and morphology of crystalline/crystalline PP/PB-1 blends are complicated. The crystallization rate of PP decreases with increasing PB-1 content in the cooling or isothermal crystallization process. Avrami constants of the PP crystallization are, however, insignificantly dependent on the PB-1 content. The crystallization rate and spherulite size of PB-1 are both enhanced by PP in PB-1-rich blends. As prepared by the solution–precipitation method, pure PB-1 exhibits crystal forms I′ (or III) and II, whereas the PB-1 in the blends exhibits only crystal form I′; pure PP and PP in the blends both exhibit only crystal form α. Crystal transformation from form I′ to form II for PB-1 in the blends can occur upon dynamic heating and cooling, but the transformation is retarded with increasing PP content. The crystal form II of PB-1 can be transformed to form I upon aging at room temperature, and this transformation can be facilitated by the PP in PB-1-rich blends. The similar helix conformation, of crystal form α of PP and of crystal forms I′ and I of PB-1, is found to be a driving force in preventing crystal form I′ of PB-1 in PP-rich blends from transforming to form II upon dynamic heating and cooling, and in facilitating crystal transformation from form II to form I for PB-1 in PB-1-rich blends upon aging at room temperature.