A Theoretical Perspective of the Photochemical Potential in the Spectral Performance of Photovoltaic Cells

We present a novel theoretical approach to the problem of light energy conversion in thermostated semiconductor junctions. Using the classical model of a two-level atom, we deduced formulas for the spectral response and the quantum efficiency in terms of the input photons’ non-zero chemical potential. We also calculated the spectral entropy production and the global efficiency parameter in the thermodynamic limit. The heat transferred to the thermostat results in a dissipative loss that appreciably controls the spectral quantities’ behavior and, therefore, the cell’s performance. The application of the obtained formulas to data extracted from photovoltaic cells enabled us to accurately interpolate experimental data for the spectral response and the quantum efficiency of cells based on Si-, GaAs, and CdTe, among others.

Copper slag as a potential source of critical elements - A case study from Tsumeb, Namibia

SYNOPSIS At a time of resource consumption, it is important to study the chemical composition of mining and metallurgical wastes to prevent the dissipative loss of metals and metalloids from the mining value chain. In particular, the recovery of critical elements from wastes is an option to increase the resources of such materials that are economically significant and have an overall supply risk. In this paper we report on the chemical composition, in particular the critical element content, of granulated slag originating from historical smelting activities in the Tsumeb area, Namibia. Laboratory-based inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray fluorescence (XRF) analyses as well as portable X-ray fluorescence (pXRF) demonstrate that the slags are on average enriched in base metals (Cu 0.7 wt%, Pb 2.7 wt%, Zn 4.7 wt%), trace metals and metalloids (Cd approx. 50 mg/kg, Mo approx. 910 mg/kg) as well as critical elements (As approx. 6300 mg/kg, Bi approx. 3 mg/kg, Co approx. 200 mg/kg, Ga approx. 100 mg/kg, In approx. 9 mg/kg, Sb approx. 470 mg/kg). While metals and metalloids such as As, Mo and Pb can be determined reliably using pXRF instruments, the technique has inherent limitations in evaluating the contents of certain critical elements (Ga, Sb). However, there are positive correlations between the As, Mo, and Pb contents determined by pXRF and the Ga and Sb contents obtained through ICP-MS and XRF. Thus, quantitative pXRF analysis for As, Mo, and Pb allows calculation of Ga and Sb abundances in the slags. This work demonstrates that pXRF analysers are a valuable tool to screen smelting slags for their chemical composition and to predict the likely contents of critical elements. Keywords: base metal slag, portable XRF, critical elements, secondary resource.

Calculation of Site Attenuation for Calculable Dipole Antennas

This paper presents a method for calculating the site attenuation (SA) of an open-area test site (OATS) for a pair of calculable dipole antennas with a 3-dB hybrid balun in the frequency range of 30 MHz to 1 GHz. The SA was directly derived using the concept of power mismatch and dissipative loss from the SA measurement system instead of the concept of substitution loss. Two types of SA formulas using the power loss concept on the treatment of the OATS are presented. The first is the SA formula related to knowing only the value of the SA. The other is the SA formula that analyzed the effects of each part of the SA. Additionally, the constituent losses of the SA measurement system are discussed using the derived SA formula. The analysis of the results showed that the SA could be successfully characterized individually from the loss of the OATS. It also showed that SA is expressed as two kinds of losses: the balanced portmismatch losses of transmit and receive baluns and the half-space dissipative loss. The resultant SA showed good agreement with the results calculated from the S-parameters as well as with the measured results.

Low-frequency perfect sound absorption achieved by a modulus-near-zero metamaterial

We have analytically proposed a mechanism for achieving a perfect absorber by a modulus-near-zero (MNZ) metamaterial with a properly decorated imaginary part, in which the perfect absorption (PA) is derived from the proved destructive interference. Based on the analysis, an ultrathin acoustic metamaterial supporting monopolar resonance at 157 Hz (with a wavelength about 28 times of the metamaterial thickness) has been devised to construct an absorber for low-frequency sound. The imaginary part of its effective modulus can be easily tuned by attentively controlling the dissipative loss to achieve PA. Moreover, we have also conducted the experimental measurement in impedance tube, and the result is of great consistency with that of analytical and simulated ones. Our work provides a feasible approach to realize PA (>99%) at low frequency with a deep-wavelength dimension which may promote acoustic metamaterials to practical engineering applications in noise control.

What is a good conductor for metamaterials or plasmonics

We review conducting materials like metals, conducting oxides and graphene for nanophotonic applications. We emphasize that metamaterials and plasmonic systems benefit from different conducting materials. Resonant metamaterials need conductors with small resistivity, since dissipative loss in resonant metamaterials is proportional to the real part of the resistivity of the conducting medium it contains. For plasmonic systems, one must determine the propagation length at a desired level of confinement to estimate the dissipative loss.