state of the art and perspectives of inorganic photovoltaics

In the last decade, the fast increase of the global energy consumption, mainly related to the strong economic growth in the Far East, and the progressive depletion of the fossil fuels induced a run-up in the world oil price. Both these economic concerns and the growing global pollution pointed out that a transition toward renewable energies is mandatory. Among renewables, the conversion of sunlight into electricity by photovoltaic (PV) devices is a reliable choice to cope the growing energy consumption, due to the huge potentially extractable power (up to 120000 TW). The most important classes of inorganic PV devices developed in the last sixty years will be reviewed in this paper, in order to depict the state of the art of the technologies which dominate the PV market. Some novel concepts which could have an important role in the future of PV will be also described

Hybrid sputtering/evaporation deposition of Cu(In,Ga)Se2 thin film solar cells

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The Missing Piece: The Structure of the Ti3C2TxMXene and Its Behavior as Negative Electrode in Sodium Ion Batteries

The most common MXene composition Ti3C2Tx (T = F, O) shows outstanding stability as anode for sodium ion batteries (100% of capacity retention after 530 cycles with charge efficiency >99.7%). However, the reversibility of the intercalation/deintercalation process is strongly affected by the synthesis parameters determining, in turn, significant differences in the material structure. This study proposes a new approach to identify the crystal features influencing the performances, using a structural model built with a multitechnique approach that allows exploring the short-range order of the lamella. The model is then used to determine the long-range order by inserting defective elements into the structure. With this strategy it is possible to fit the MXene diffraction patterns, obtain the structural parameters including the stoichiometric composition of the terminations (neutron data), and quantify the structural disorder which can be used to discriminate the phases with the best electrochemical properties

Pentanol isomer synthesis in engineered microorganisms

Pentanol isomers such as 2-methyl-1-butanol and 3-methyl-1-butanol are a useful class of chemicals with a potential application as biofuels. They are found as natural by-products of microbial fermentations from amino acid substrates. However, the production titer and yield of the natural processes are too low to be considered for practical applications. Through metabolic engineering, microbial strains for the production of these isomers have been developed, as well as that for 1-pentanol and pentenol. Although the current production levels are still too low for immediate industrial applications, the approach holds significant promise for major breakthroughs in production efficiency

On the instability tongues of the Hill equation coupled with a conservative nonlinear oscillator

We study the asymptotics for the lengths of the instability tongues L_N(q) of Hill equations that arise as iso-energetic linearization of two coupled oscillators around a single-mode periodic orbit. We show that for small energies, i.e. q->0, the instability tongues have the same behavior that occurs in the case of the Mathieu equation: L_N(q)=O(q^N). The result follows from a theorem which fully characterizes the class of Hill equations with the same asymptotic behavior. In addition, in some significant cases we characterize the shape of the instability tongues for small energies. Motivation of the paper stems from recent mathematical works on the theory of suspension bridges

Asymmetric invariants for a class of strictly hyperbolic systems including the Timoshenko beam

We introduce a set of conserved quantities of energy-type for a strictly hyperbolic system of two coupled wave equations in one space dimension. The system is subject to mechanical boundary conditions. Some of these invariants are asymmetric in the sense that their defining quadratic form contains second order derivatives in only one of the unknowns. We study their independence with respect to the usual energies and characterize their sign. In many cases, our results provide sharp well-posedness and stability results. Finally, we apply some of our conservation laws to the study of a singular perturbation problem previously considered by J. Lagnese and J. L. Lions

On the Timoshenko beam vibrating under an obstacle condition

The dynamic impact problem for the Timoshenko beam against a rigid frictionless obstacle is studied. The unknown reaction is modeled as a positive measure with support contained in the contact set and acting on the centroid of the beam in the vertical direction. Three independent invariant quantities of energy type for the free beam are derived. These quantities turn out to be useful in the description of the impact lines, the crucial assumption being the conservation of the local energies in order to model the perfectly elastic impact. The problem of extending the solution after the first influence line is considered. The strict hyperbolicity of the system leads to a free-boundary problem similar to a previous one studied by L. AMERIO for the impact of two strings with different propagation velocities. In a ``generic'' case, a necessary and sufficient condition for the solvability of the free-boundary problem is provided