Ab initio electronic structure calculations of solid, solution-processed metallotetrabenzoporphyrins

An ab initio study of the electronic structures of solid metallotetrabenzoporphyrins (MTBPs) utilized in organic transistors and photovoltaics is presented. Bandstructures, densities of states, and orbitals are calculated for H2, Cu, Ni, and Zn core substitutions of the unit cell of solid TBP, as deposited via soluble precursors that are thermally annealed to produce polycrystalline, semiconducting thin-films. While the unit cells of the studied MTBPs are nearly isomorphous, substitution of the core atoms alters the structure of the bands around the energy bandgap and the composition of the densities of states. Cu and Ni core substitutions introduce nearly-dispersionless energy bands near the valence and conduction band edges, respectively, that form acceptor or deep generation/recombination states.Comment: 7 pages, 3 figures, 4 table

P‐64: UV‐Light‐Modified Polyimide Films for Liquid‐Crystal Alignment

Infrared, UV‐visible and X‐ray photoelectron spectroscopy measurements indicate that bond‐breaking and oxidation occur during broadband UV‐illumination of the polyimide film in the air. Surface tension and polarity are increased based on the measurements of contact angles. No obvious morphology change has been observed through atomic force microscopy analysis. While the polarized UV‐light generates a relatively small pretilt angle on a nonrubbed surface, it reduces the pretilt angle to some degree on a rubbed surface, depending upon the UV‐light polarization direction relative to the rubbing direction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92039/1/1.1833863.pd

Angular dependence of the luminance and contrast in medical monochrome liquid crystal displays

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134850/1/mp6449.pd

Ultraviolet light induced changes in polyimide liquid‐crystal alignment films

Ultraviolet light induced changes in polyimide liquid‐crystal alignment films were investigated. Infrared, UV‐visible, x‐ray photoelectron spectroscopy, and electron‐spin‐resonance measure‐ ments indicated that bond breaking and subsequent oxidation reactions occur in polyimide films (SE7210, OCG284, DuPont 2555 and 2540) during the broadband UV illumination in air. Mechanical rubbing has no effect on the optical and magnetic properties but it causes the removal of the UV‐exposed film. Capacitance–voltage measurements indicate that there is a slight decrease in dielectric constant and creation of net negative charges in the film after UV exposure. Sur‐ face tension of polyimide films before and after UV illumination and changes in the pretilt angle of the polyimide surface following UV exposure have also been studied. The decrease in pretilt angle following UV illumination is attributed to an increase in surface tension. Our results indicate that a simple UV technique can be used to achieve domain divided liquid‐crystal pixel electrode design with improved viewing characteristics. © 1996 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70453/2/JAPIAU-80-9-5028-1.pd

The low-field conductivity of zeolite-encapsulated molecular wires

The first measurements of an upper bound for the low-field conductivity of a molecular wire are presented here. We were able to encapsulate polypyrrole with chain lengths more than 10 monomers within the channels of different zeolites. Although the chains are fully oxidized by intrazeolite Fe3 + ions, and should conduct (when included in a bulk polymer), they do not exhibit, in the zeolite, significant ac conductivity up to 1 GHz. This suggests that other strategies than low field conductivity are needed to inject charges and transmit information through isolated molecular wires

25.1: Luminance Probes for Contrast Measurements in Medical Displays

We report on a comparative study that examines four conic luminance probes in their ability to measure small‐spot display contrast. We performed linear scans of a slit using a computer‐controlled stage. We found that, although the probes were assembled according to the same design, small differences in their performance due to minor variations in materials and surfaces can be measured.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92056/1/1.1832436.pd

Three-dimensional cascaded system analysis of a 50 µm pixel pitch wafer-scale CMOS active pixel sensor x-ray detector for digital breast tomosynthesis

High-resolution, low-noise x-ray detectors based on the complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been developed and proposed for digital breast tomosynthesis (DBT). In this study, we evaluated the three-dimensional (3D) imaging performance of a 50 ��m pixel pitch CMOS APS x-ray detector named DynAMITe (Dynamic Range Adjustable for Medical Imaging Technology). The two-dimensional (2D) angle-dependent modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) were experimentally characterized and modeled using the cascaded system analysis at oblique incident angles up to 30��. The cascaded system model was extended to the 3D spatial frequency space in combination with the filtered back-projection (FBP) reconstruction method to calculate the 3D and in-plane MTF, NNPS and DQE parameters. The results demonstrate that the beam obliquity blurs the 2D MTF and DQE in the high spatial frequency range. However, this effect can be eliminated after FBP image reconstruction. In addition, impacts of the image acquisition geometry and detector parameters were evaluated using the 3D cascaded system analysis for DBT. The result shows that a wider projection angle range (e.g. ��30��) improves the low spatial frequency (below 5 mm-1) performance of the CMOS APS detector. In addition, to maintain a high spatial resolution for DBT, a focal spot size of smaller than 0.3 mm should be used. Theoretical analysis suggests that a pixelated scintillator in combination with the 50 ��m pixel pitch CMOS APS detector could further improve the 3D image resolution. Finally, the 3D imaging performance of the CMOS APS and an indirect amorphous silicon (a-Si:H) thin-film transistor (TFT) passive pixel sensor (PPS) detector was simulated and compared

REVIEW OF CONDUCTOR-POLYMERIC SEMICONDUCTOR SOLAR CELLS

La propriétés photovoltaiques d'une barrière de Schottky, d'une héterojonction et d'une cellule photoélectrochimique impliquant les polymères organiques sont discutées dans cet article.The photovoltaic properties of Schottky barrier, heterojunction and photo-electrochemical cell involving organic polymers are reviewed in this paper