Russell Gaudiana

Solar Power Wires Based on Organic Photovoltaic Materials

Organic photovoltaics in a flexible wire format has potential advantages that are described in this paper. A wire format requires long-distance transport of current that can be achieved only with conventional metals, thus eliminating the use of transparent oxide semiconductors. A phase-separated, photovoltaic layer, comprising a conducting polymer and a fullerene derivative, is coated onto a thin metal wire. A second wire, coated with a silver film, serving as the counter electrode, is wrapped around the first wire. Both wires are encased in a transparent polymer cladding. Incident light is focused by the cladding onto to the photovoltaic layer even when it is completely shadowed by the counter electrode. Efficiency values of the wires range from 2.79% to 3.27%.

Highly efficient organic solar cells based on a poly(2,7-carbazole) derivative

We have studied the utilization of PCDTBT, an alternating poly(2,7-carbazole) derivative, in organic bulk heterojunction solar cells. The effect of polymer molecular weight, PCDTBT:[60]PCBM ratio, and active layer thickness on the device performance is reported. The best performance was obtained when the number-average molecular weights (Mn) are around 20 kDa with a polydispersity index around 2.2. Both PCDTBT:[60]PCBM ratio and active layer thickness affect the light absorption and the charge transport properties. By optimizing these two parameters, power conversion efficiency (PCE) up to 4.35% was reached under calibrated AM1.5G illumination of 100 mW cm−2. When blended with [70]PCBM, PCDTBT exhibited a PCE up to 4.6%.

Morphology control in polycarbazole based bulk heterojunction solar cells and its impact on device performance

Incremental increase in dimethyl sulfoxide (or dimethyl formamide) in ortho-dichlorobenzene solution of poly[N-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) gradually reduces the polymer-solvent interaction, the attraction forces between polymer chains become more dominant, and the polymer chains adopt a tight and contracted conformation with more interchain interactions, resulting in a progressive aggregation in both solutions and films. This was used to fine tune the morphology of PCDTBT/PC71BM based solar cells, leading to improved domain structure and hole mobility in the active layer, and significantly improved photovoltaic performance. The power conversion efficiency increased from 6.0% to 7.1% on devices with an active area of 1.0 cm2.

Highly efficient polycarbazole-based organic photovoltaic devices

We combined experimental and computational approaches to tune the thickness of the films in poly(N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole) (PCDTBT)-based organic solar cells to maximize the solar absorption by the active layer. High power-conversion efficiencies of 5.2% and 5.7% were obtained on PCDTBT-based solar cells when using [6,6]-phenyl C61-butyric acid methyl ester (PC60BM) and [6,6]-phenyl C71-butyric acid methyl ester (PC70BM) as the electron acceptor, respectively. The cells are designed to have an active area of 1.0 cm2, which is among the largest organic solar cells in the literature, while maintaining a low series resistance of 5 Ω cm2.

Amorphous rigid-rod polymers

Synthese de tels polyamides, polyesters et polyesteramides influence de la structure moleculaire sur les proprietes optiques et morphologiques

Stabilization of film morphology in polymer-fullerene heterojunction solar cells

Abstract The fixation of film morphology is essential for the long‐term stability of heterojunction polymer photovoltaic (PV) cells. An epoxy‐functionalized fullerene C60 derivative was synthesized for this purpose. This material can be polymerized at acidic conditions and was found to stabilize the phase‐separated morphologies within blended polythiophene–fullerene heterojunction films. The phase stability of the films was characterized by UV‐VIS spectroscopy and optical microscope. Crosslinkable polythiophene derivatives were also prepared but these materials were much less effective in stabilizing film morphology when mixed into PCBM (C61‐butyric acid methyl ester). Heterojunction polymer PV cells were prepared from these materials and their performance was compared with cells made from conventional materials.

Design and Synthesis of High Refractive Index Polymers. II

Abstract The synthesis, physical and optical properties of a series of high molecular weight, colorless, nonbirefringent, amorphous polymethacrylates (and acrylates) comprising brominated and iodinated carbazole rings that are connected to the backbone by short hydrocarbon spacers are described. The refractive indices exhibited by these homopolymers are in the range of 1.67 to 1.77. A ternary mixture of brominated monomers has a low melting point (<50°C); the refractive index of the corresponding polymer = 1.72.

High Refractive Index Polymers

Ethylenically unsaturated polymerizable acrylic (or methacrylic) monomers having pendant halogenated carbazole moieties, useful for the production of high refractive index polymers, are disclosed. The monomers are useful for the bonding of optical elements in the fabrication of optical devices.

Study of Tails in Smectic Liquid Crystals. I. The Effect of Fluorocarbon/Hydrocarbon Ether Tails on Phenyl Ester Biphenyl Cores

Abstract The use of the mixed fluorocarbon/hydrocarbon ether sequence [1H,1H,5H-octafluoro-1-pentoxy-]ethoxy in place of aliphatic or aliphatic ether sequences significantly enhances the temperature range of the chiral smectic C (Sc*) liquid crystalline phase. Considerations derived from the literature, supported by computer modeling, suggested that stabilization of the Sc* phase results from enhancement of the population of gauche conformers. These considerations have led to liquid crystal molecules with the widest range of Sc* phase thus far reported.

Synthesis and modeling of acridine dyes as potential photosensitizers for dye-sensitized photovoltaic applications

We have synthesized novel aromatic amine‐substituted acridine dyes as potential candidates for the photosensitizers in dye sensitized nanocrystalline semiconductor based solar cells (DSSC) cells. The protonation and quaternization of the acridine nitrogen led to acridine dyes with extended absorption from 400–800 nm. Computational modeling was used to evaluate a variety of structures to achieve insights for correlating these types of molecular structures with predicted absorption spectra. Pertinent dihedral angles as well as bond lengths were evaluated to assess and compare planarity and conjugation for these dyes. Other predictions include plots of the HOMO and LUMO levels to qualitatively examine electron distributions and the potential for electron injection. The results from modeling along with the experimental data consisting of synthesis, characterization and UV‐visible absorption properties of the selected dyes are presented. †Dedicated to the memory of Professor Sukant K. Tripathy.