Bistable organic materials in optoelectrical switches: Two-electrode devices vs. organic field effect transistors

The paper presents a short overview of research into properties of organic materials and structures that could be used in optoelectrical switches, i.e., switches in which changes in electrical properties are triggered by light of appropriate wavelengths. In particular, described are the structures acting by virtue of reversible photochemical reactions occurring in photochromic molecular materials

Electrolytic simulation of airfloil flow

Airfoil flow simulation tests were carried out in a 20-inch diameter double layer circular electrolytic tank. Results of the tests indicate that the tank very closely approximates ideal conditions. The double layer circular electrolytic tank is shown to generate a very large rectangular tank. Formulas were derived to show that this double layer tank is valid for the analogy between fluid velocity and voltage gradient. Tests were performed on a five inch diameter cylindrical model. The first series of tests was performed with the ground plane very far from the model surface. Electrical current to the model was adjusted so that circulation and lift could be calculated for different angles of stagnation point on the model. The second series of tests was performed with suitable electrodes so the model would be near the ground plane. The purpose of these tests was to investigate how circulation, lift, and effective velocity varied when model to ground plane distance was varied. The appendix contains data in a format similar to that in which it was used in the ALWAC IIIE computer to obtain numerical results. AIso in the appendix are results of investigations on circular airfoils made by other investigators using conducting sheets and a wind tunnel. A discussion of equipment used and improvements that could be made is included

Bias-Dependent Generation and Quenching of Defects in Pentacene

We describe a defect in pentacene single crystals that is created by bias stress and persists at room temperature for an hour in the dark but only seconds with 420nm illumination. The defect gives rise to a hole trap at Ev + 0.38eV and causes metastable transport effects at room temperature. Creation and decay rates of the hole trap have a 0.67eV activation energy with a small (108 s-1) prefactor, suggesting that atomic motion plays a key role in the generation and quenching process.Comment: 10 pages, 3 figure

Photovoltaic and optical properties of a polymer - PbS nanocomposite

Photovoltaic and optical properties of a polymer-PbS nanoparticles in polyvinyl alcohol (PVA) films and the effect of annealing in air at various temperatures on these properties are studied in this work. In the range of 1.0 to 3.7 eV, absorption spectra of PbS nanocomposite films are correctly fitted by five Gaussian bands peaking at 1.5, 1.84, 2.41, 3.06, and 3.58 eV. A characteristic feature of the films is the presence of green and blue luminescence with intensity maxima at 2.25 and 3.02 eV, respectively. The luminescence intensity strongly depends on the excitation energy and the annealing temperature in air. The highest intensity of the green luminescence is observed under the excitation with 2.35 eV radiation, whereas the intensity of the blue luminescence peaks under 3.46 eV excitation. After annealing at 370 K, the intensity of the green luminescence decreases a few times whereas the intensity of the blue emission increases. The photovoltaic sensitivity of the PbS nanocomposite films depends on the annealing conditions, attaining the maximum after annealing in air at approximately glass transition temperature of PVA (370 K). The spectral range of the photosensitivity of PbS nanocomposite films is wider than that of CdSe- and CuInS₂-polymer nanocomposite films

Non-Exponential Decays in First-Order Kinetic Processes. The Case of"Squeezed Exponential"

Kinetics of processes, in which the reaction rate increases with conversion, is discussed and illustrated with an example of the chemical reaction of isomerization of an azobenzene derivative in a liquid crystalline matrix. A simple phenomenological model is put forward explaining the effect by dynamic changes of interactions between the reacting species and the matrix