KEYWORDS: Hot carriers, Nanowires, Solar cells, Semiconductors, Photovoltaics, Diseases and disorders, Crystals, Beam diameter, Time resolved spectroscopy, Spectroscopes
III-V nanowire structures have shown promising results in mitigating hot carrier thermalization rates suitable for hot carrier solar cell applications. This effect is attributed to the spatial confinement of charged particles and the adjustment of material properties in these nanostructures. Furthermore, by designing vertically standing nanowires, it is possible to improve photo-absorption by increasing internal surface reflection. Investigating the properties of hot carriers in core-shell InGaAs nanowires has shown evidence for a strong diameter dependence of these nanostructures. Determining the origin of this effect provides valuable information for the development of efficient hot carrier absorbers for 3rd generation solar cells.
This theoretical work shows that ultra-thin InGaAs solar cells can have the operation of a hot carrier solar cell. Considering a quantum modeling of the electronic transport we show that the open circuit voltage Voc increases with an energy-selective contact considered between the absorber and the reservoir. Moreover, we do not observe the feared corresponding current degradation. The Voc improvement agrees with a simple and general expression based on the isentropic carrier extraction, confirming the link between the voltage and the carrier temperature. Concerning the current, as already shown in a precedent work, if carriers are confined in the absorber the current across an energy-selective contact is of the same order of magnitude as that obtained without selectivity. This advantageous behavior is explained by the hybridation of states in the absorber and in the reservoir.
The remarkable experimental discovery of femtosecond scale laser pulse-driven demagnetization process in ferromagnetic nickel in mid ’90s spurred a flurry of experimental and theoretical research activities in ultrafast magnetization dynamics. Standard theoretical description of magnetization dynamics based on Landau-Lifshitz-Gilbert equation is justified only for slow enough spin phenomena while those occurring at very short time scales are much less understood. The past two decades have observed a remarkable theoretical development predicting the emergence of dynamical inertia in magnetization dynamics at very short time scale, focusing mostly on the dynamics of a single spin, leading to the prediction of a new type of spin motion called nutation. We advance this theoretical progress by considering inertial effect on the dynamics of a system of interacting spins. We demonstrate the occurrence of a new type of collective mode referred to as nutation wave, shown to have massive relativistic dispersion relation with characteristic speed and frequency well exceeding those of the more familiar spin wave. These excellent properties make nutation wave a prospective candidate to be a platform for optically-driven ultrafast spintronic devices.
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