In this paper, we use a polarization independent phase gradient metasurface to trap sunlight inside a thin film solar cell. In this method, the metasurface is placed at the bottom of the solar cell to anomalously reflect light rays of Sun and prevent them from escaping the cell. The performance of the proposed structure is numerically studied at different wavelengths as well as different angles of incidence, for both TM and TE polarizations. The numerical results show absorption enhancement in a wide range of wavelengths, and short circuit current improvement for both TM and TE polarizations.
A shape reconstruction method for microwave imaging of perfect electric conductor objects based on contour deformations exploiting the level set method is presented. The calculation of the method of moments impedance matrix in the direct scattering part is done in a single step using the relation of the original and adjoint systems. In the inverse scattering part the fast marching method is used in the re-initialization process which has drastically improved the velocity of the reconstruction. Based on the simulation results the inverse scattering method presented in this paper has proved to be efficient and accurate, giving highly accurate reconstructions in relatively short computational times for single or multiple objects and also in the presence of noise. The accuracy and efficiency of the method suggest that it could usefully be extended to the three-dimensional case.
This paper presents a design and fabrication of an ultra-wideband bandpass filter with two notched (rejection) bands. Ultra-wideband (UWB) systems are systems with the electromagnetic spectrum from 3.1 GHz to 10.6 GHz. The designed filter removes WLAN and satellite signals which are 5.8 GHz and 8 GHz. For designing filter, we use a stepped-impedance stub-loaded resonator (SISLR). To provide two notched bands, a radial stub loaded resonator with a defected microstrip structure (DMS) is used. The presented filter has more analytic relations and simpler structure than prior works. This filter is fabricated on an RO4003 substrate with dielectric constant of 3.55. The dimensions of the filter are 10 × 25 mm 2 which are more compact than prior structures. The measurements have a good agreement with predicted results which verifies the feasibility of the UWB filter.
In this paper, using a deep neural network and a genetic algorithm, an optimized digital metasurface is designed to trap sunlight in thin-film solar cells. The deep neural network is trained using full-wave numerical simulation results as the training dataset, and it is designed to predict the electromagnetic response of thin-film solar cells whose active layers are shaped as a digital metasurface. The developed neural network can predict the results much faster than full-wave solvers and therefore can be used for optimization purposes. Using the results generated by the trained neural network, an evolutionary procedure based on the genetic algorithm is developed to find the optimum structure for the digital metasurface, which provides the highest short circuit current inside the thin-film solar cell. The performance of the resultant optimum design is validated using full-wave numerical simulation illustrating a short circuit current of
15.39
m
A
/
c
m
2
and
13.30
m
A
/
c
m
2
for TE and TM polarization of the incident light, respectively. The resultant short circuit current is 2.47 and 2.13 times higher than a simple thin-film solar cell with the same amount of silicon inside, for TE and TM polarization of the incident light, respectively. To have a more comprehensive comparison, the designed optimum structure is compared with several standard shapes for the metasurface, such as star and plus sign. This comparison showed that the optimum structure provides a short circuit current which is much higher than the current achieved by standard shapes.
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