Search results for "Energy Conversion"
showing 10 items of 134 documents
Hole transporting materials based on benzodithiophene and dithienopyrrole cores for efficient perovskite solar cells
2018
The development of highly efficient hole transporting materials (HTMs) for perovskite solar cells (PSCs) is still one of the most thrilling research subjects in the development of this emerging photovoltaic technology. Inner ring engineering of the aromatic core of new HTMs – consisting of three fused rings endowed with four triarylamine units – reveals major performance effects over the fabricated devices. In particular, substitution of the central pyrrole ring in dithienopyrrole (DTP) by a benzene ring – benzodithiophene (BDT) – allows enhancing the power conversion efficiency from 15.6% to 18.1%, in devices employing mixed-perovskite (FAPbI3)0.85(MAPbBr3)0.15 (MA: CH3NH3+, FA: NHCHNH3+) …
Quantification of spatial inhomogeneity in perovskite solar cells by hyperspectral luminescence imaging
2016
Vacuum evaporated perovskite solar cells with a power conversion efficiency of 15% have been characterized using hyperspectral luminescence imaging. Hyperspectral luminescence imaging is a novel technique that offers spectrally resolved photoluminescence and electroluminescence maps (spatial resolution is 2 micrometer) on an absolute scale. This allows, using the generalized Planck’s law, the construction of absolute maps of the depth-averaged quasi-Fermi level splitting (Δμ), which determines the maximum achievable open circuit voltage (Voc) of the solar cells. In a similar way, using the generalized reciprocity relations the charge transfer efficiency of the cells can be obtained from the…
Near-unity third-harmonic circular dichroism driven by a quasibound state in the continuum in asymmetric silicon metasurfaces
2021
We use numerical simulations to demonstrate third-harmonic generation with near-unity nonlinear circular dichroism (CD) and high conversion efficiency $({10}^{\ensuremath{-}2}\phantom{\rule{4pt}{0ex}}{\text{W}}^{\ensuremath{-}2})$ in asymmetric Si-on-$\mathrm{Si}{\mathrm{O}}_{2}$ metasurfaces. The working principle relies on the spin-selective excitation of a quasibound state in the continuum, characterized by a very high $(g{10}^{5})$ quality factor. By tuning multimode interference with the variation of the metasurface geometrical parameters, we show the possibility to control both linear CD and nonlinear CD. Our results pave the way for the development of all-dielectric metasurfaces for …
High-order harmonic generation in fullerenes using few- and multi-cycle pulses of different wavelengths
2012
We present the results of experimental and theoretical studies of high-order harmonic generation (HHG) in plasmas containing fullerenes using pulses of different duration and wavelength. We find that the harmonic cutoff is extended in the case of few-cycle pulses (3.5 fs, 29th harmonic) compared to longer laser pulses (40 fs, 25th harmonic) at the same intensity. Our studies also include HHG in fullerenes using 1300 and 780 nm multicycle (35 and 40 fs) pulses. For 1300 nm pulses, an extension of the harmonic cutoff to the 41st order was obtained, with a decrease in conversion efficiency that is consistent with theoretical predictions based on wave packet spreading for single atoms. Theoreti…
Investigations on the photoelectron conversion efficiency of NaI(Tl) counters
1988
Abstract The photoelectron conversion efficiency of NaI(Tl) detectors has been measured by counting single photoelectron pulses of the detector output pulse train on a very fast storage oscilloscope. This result is compared with those obtained by the measurement of the achievable time resolution using the first photoelectron triggering technique.
Solar Nanoantennas energy based characterization
2016
Solar nanoantennas appear a very interesting solution to exploit solar radiation, as a matter of fact, their operating principle allows heat losses to be lessened compared to traditional photovoltaic cells and efficiency to be increased. Anyway, some technological issues are to be overcome. Literature often proposes a characterization by radiation efficiency typical of traditional antennas. Since the aim of solar nanoantennas is to harvest energy, in this paper the most promising devices are characterized by the upper bound of deliverable power density calculated in the whole operating wavelengths range.
The role of nonlinear optical absorption in narrowband difference-frequency terahertz-wave generation
2010
We present a general analysis of the influence of nonlinear optical absorption on terahertz generation via optical difference frequency generation, when reaching for the quantum conversion efficiency limit. By casting the equations governing the process in a suitably normalized form, including either two-photon- or three-photon-absorption terms, we have been able to plot universal charts for phase matched optical-to-terahertz conversion for different values of the nonlinear absorption coefficients. We apply our analysis to some experiments reported to date, in order to understand to what extent multiphoton absorption could have played a role and also to predict the maximum achievable conver…
Innovative Computational Approach to Harmonic Mitigation for Seven-level Cascaded H-Bridge Inverters
2020
Low frequency modulation strategies are a good solution to increase the energy conversion efficiency in high power applications. The paper is devoted to presents an innovative way to low order harmonics mitigation for seven-level Cascaded H-Bridge Inverters. In particular, this approach is based on the mitigation of selected harmonics without solve non-linear equations for an extended range of the fundamental amplitude. In fact, in real-Time operation to evaluate the control angles the polynomial equations have been identified. Through circuit simulation analysis in MatLab/PLECS environment, the effectiveness of the harmonic mitigation method has been tested and compared with theoretical re…
Strategies and Techniques for Powering Wireless Sensor Nodes through Energy Harvesting and Wireless Power Transfer
2019
The continuous development of internet of things (IoT) infrastructure and applications is paving the way for advanced and innovative ideas and solutions, some of which are pushing the limits of state-of-the-art technology. The increasing demand for Wireless Sensor Nodes (WSNs) able to collect and transmit data through wireless communication channels, while often positioned in locations that are difficult to access, is driving research into innovative solutions involving energy harvesting (EH) and wireless power transfer (WPT) to eventually allow battery-free sensor nodes. Due to the pervasiveness of radio frequency (RF) energy, RF EH and WPT are key technologies with the potential to power …
Evaluation of the optimal renewable electricity mix for Lampedusa island: The adoption of a technical and economical methodology
2020
Abstract Worldwide, the majority of small islands not connected to the main grid is still dependent on fossil fuels. From an economic and environmental point of view, this condition is no more sustainable given the high costs for electricity generation and the high level of pollutant emissions. Furthermore, the dependence on fossil fuel represents a risk for the security of the supply of several small developing Countries since they are obliged to import those resources from foreign Countries. The introduction of renewable energy sources in small islands represents a valid solution to solve these problems. In this context, the paper investigates the case of Lampedusa, a small Italian island…