Annealing characteristics of amorphous silicon alloy solar cells irradiated with 1.00 MeV protons

Amorphous Si:H and amorphous Si sub x, Ge sub (1-x):H solar cells were irradiated with 1.00 MeV proton fluences in the range of 1.00E14 to 1.25E15 cm (exp -2). Annealing of the short circuit current density was studied at 0, 22, 50, 100, and 150 C. Annealing times ranged from an hour to several days. The measurements confirmed that annealing occurs at 0 C and the initial characteristics of the cells are restored by annealing at 200 C. The rate of annealing does not appear to follow a simple nth order reaction rate model. Calculations of the short-circuit current density using quantum efficiency measurements and the standard AM1.5 global spectrum compare favorably with measured values. It is proposed that the degradation in J sub sc with irradiation is due to carrier recombination through the fraction of D (o) states bounded by the quasi-Fermi energies. The time dependence of the rate of annealing of J sub sc does appear to be consistent with the interpretation that there is a thermally activated dispersive transport mechanism which leads to the passivation of the irradiation induced defects

Theoretical Study of Electronic Properties of Pyridine, Pyrimidine, Pyrazine and Pyridazine via Density Functional Theory

Theoretical studies on pyridine, pyrimidine, pyrazine and pyridazine molecules were performed using DFT. Based on B3LYP with 6-31(d, p)basis sets was used to investigate the effect of different position of nitrogen atom on the electronic and structure properties of benzene. The optimized structure, total energies, electronic states, energy gaps, ionization potentials, electron affinities, chemical potential, global hardness, softness, global electrophilicity, dipole moment and dipole polarizability were calculated. The harmonic vibration frequencies calculated and compared with available experimental data. The results showed a decrease in gap energies and improve the electronic properties. Keywords: B3LYP, DFT, optimization, energy gap, and vibration frequency

Study of Geometrical Optimization and Some Electronic Properties of D-B-A Molecular System

This work deals with designing donor - bridge - acceptor molecular system depending on Aviram – Ratner model and calculating the geometrical parameters and energies for the D- B-A and it is components. Benzene ring is the basic part for all the components of such molecular system. The LUMO-HOMO energy gap for the studied structures showed that the D-B-A molecular system has a suitable small energy gap. The results showed that this new molecular system is more reactive in charge transfer process and has good semiconductor properties. Keywords:B3LYP , DFT, , energy gap, HOMO ,LUMO and polarizability

A minimal integer automaton behind crystal plasticity

Power law fluctuations and scale free spatial patterns are known to characterize steady state plastic flow in crystalline materials. In this Letter we study the emergence of correlations in a simple Frenkel-Kontorova (FK) type model of 2D plasticity which is largely free of arbitrariness, amenable to analytical study and is capable of generating critical exponents matching experiments. Our main observation concerns the possibility to reduce continuum plasticity to an integer valued automaton revealing inherent discreteness of the plastic flow.Comment: 4 pages, 5 figure