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Device Operation (device + operation)

Distribution by Scientific Domains

Polymers and Materials Science	60%

Selected Abstracts

Control of Solid-State Dye-Sensitized Solar Cell Performance by Block-Copolymer-Directed TiO2 Synthesis

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2010
Pablo Docampo
Abstract Hybrid dye-sensitized solar cells are typically composed of mesoporous titania (TiO2), light-harvesting dyes, and organic molecular hole-transporters. Correctly matching the electronic properties of the materials is critical to ensure efficient device operation. In this study, TiO2 is synthesized in a well-defined morphological confinement that arises from the self-assembly of a diblock copolymer,poly(isoprene- b -ethylene oxide) (PI- b -PEO). The crystallization environment, tuned by the inorganic (TiO2 mass) to organic (polymer) ratio, is shown to be a decisive factor in determining the distribution of sub-bandgap electronic states and the associated electronic function in solid-state dye-sensitized solar cells. Interestingly, the tuning of the sub-bandgap states does not appear to strongly influence the charge transport and recombination in the devices. However, increasing the depth and breadth of the density of sub-bandgap states correlates well with an increase in photocurrent generation, suggesting that a high density of these sub-bandgap states is critical for efficient photo-induced electron transfer and charge separation. [source]

Influence of Electric Field on Microstructures of Pentacene Thin-Films in Field-Effect Transistors,

ADVANCED FUNCTIONAL MATERIALS, Issue 2 2008
L. Cheng
Abstract We report on electric-field-induced irreversible structural modifications in pentacene thin films after long-term operation of organic field-effect transistor (OFET) devices. Micro-Raman spectroscopy allows for the analysis of the microstructural modifications of pentacene in the small active channel of OFET during device operation. The results suggest that the herringbone packing of pentacene molecules in a solid film is affected by an external electric field, particularly the source-to-drain field that parallels the a,b lattice plane. The analysis of vibrational frequency and Davydov splitting in the Raman spectra reveals a singular behavior suggesting a reduced separation distance between pentacene molecules after long-term operations and, thus, large intermolecular interactions. These results provide evidence for improved OFET performance after long-term operation, related to the microstructures of organic semiconductors. It is known that the application of large electric fields alters the semiconductor properties of the material owing to the generation of defects and the trapping of charges. However, we first suggest that large electric fields may alter the molecular geometry and further induce structural phase transitions in the pentacene films. These results provide a basis for understanding the improved electronic properties in test devices after long-term operations, including enhanced field-effect mobility, improved on/off current ratio, sharp sub-threshold swing, and a slower decay rate in the output drain current. In addition, the effects of source-to-drain electric field, gate electric field, current and charge carriers, and thermal annealing on the pentacene films during OFET operations are discussed. [source]

Transparent and Photo-stable ZnO Thin-film Transistors to Drive an Active Matrix Organic-Light- Emitting-Diode Display Panel

ADVANCED MATERIALS, Issue 6 2009
Sang-Hee K. Park
Transparent ZnO thin-film transistors (TFTs) with a defect-controlled channel and channel/dielectric interface maintain good photo-stability during device operation. The figure shows a cross-sectional view of a top-gate ZnO-based transparent TFT/storage capacitor cell structure, connected to front-panel organic-light-emitting-diode pixels to operate in bottom emission mode. [source]

Pseudo Crosstalk Behavior in a Patient with Atrio-ventricular Block and Implanted Biventricular Defibrillator

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2007
REGINALD T. HO M.D.
We present a 59-year-old man with a dilated cardiomyopathy (ejection fraction = 20%), congestive heart failure and atrio-ventricular (AV) block who underwent implantation of a biventricular defibrillator (BiV ICD). While undergoing cardiac transplant evaluation for drug-refractory ventricular fibrillation, his telemetry recorded findings resembling crosstalk inhibition. Device interrogation was normal. All episodes occurred at 1:00 a.m. suggesting a routine device operation. Left ventricular capture management, a new feature that automatically measures left ventricular pacing thresholds at 1:00 a.m., had been programmed to Monitor. Understanding this sophisticated pacing algorithm might avoid confusion when operative in patients with AV block. [source]

Electronic Studies on Oligothienylenevinylenes: Understanding the Nature of Their Ground and Excited Electronic States

CHEMPHYSCHEM, Issue 11 2009
Rocío Ponce Ortiz
Abstract The electronic and molecular structures of a family of oligothienylenevinylenes for organic solar cells are studied by means of UV/Vis, fluorescence and Raman spectroscopy, aided by quantum chemical calculations. By using different anchoring groups, the alteration of the electronic properties upon inserting electron-withdrawing groups into different positions on the oligothienylenevinylene backbone is determined. In addition, a thorough study of the photophysical properties is carried out to understand their potential use in optoelectronic devices. The charge defect of one of these systems is analysed to elucidate the possible charge carriers photogenerated during device operation. [source]