Broadband Metamaterial Absorbers for Organic Solar Cells

This paper presents the design, simulation and parametric analysis of a concentric continuous and split rings resonator (CCRR, CSRR) structure for a dual broadband metamaterial (MM) absorber. The MM structure unit cell consists of concentric circular split rings of same width and different radii and concentric continuous rings of different width and different radii arranged in four different quadrants. The three layered proposed MM absorber design has upper layer comprising of concentric continuous and split rings structured sub-cells separated by bottom laminated copper layer of FR-4 substrate. The proposed MM absorber is insensitive to any polarization state of incident EM waves due to highly symmetrical circular and split ring structures. The scattering parameter and absorption coefficient are obtained for the present MM absorber. The magnetic and electric fields are monitored to realize the behavior of MM structure. The dual broadband MM absorber has absorbance of 99% from 7.785 GHz – 8.475 GHz and absorbance of 98% from 11.835 GHz – 12.81 GHz. The absorption peaks for this MM absorber are obtained as 99.5%, 99.6%, 98.4% and 98.8% at 7.785 GHz, 8.475 GHz, 11.835 GHz and 12.81 GHz frequencies respectively for the normal incidence of EM waves. The high absorbance makes this MM absorber suitable for various microwave applications including airborne and radar signal absorption.

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Broadband metamaterial absorber (MA) in the whole visible regime has attracted an enormous amount of attention for its potential applications in thermophotovoltaic cells, thermal emitters, and other optoelectronic devices. Nonetheless, complicated device configuration is still involved in achieving broadband, polarization-independent MA and it results in a cost-ineffective fabrication process. In this paper, a novel MA composed of a periodic array of dielectric cylinder sandwiched by the non-noble metal of nickel (Ni) film is demonstrated. Experimental results show that the proposed MA exhibits strong absorptive behavior independent of polarization in the whole visible regime (400-700 nm). The absorption still remains 80% when the incident angle is 60°. The proposed fabrication method is well compatible with the conventional soft nano-imprinting lithography technique, thus it is economic and scalable for a large-format substrate. These results provide an alternative method for the realization of high-performance visible light absorber and offer new opportunities for potential applications in related fields.

We present a broadband and polarization-insensitive metamaterial absorber (MA) composed of a dielectric substrate sandwiched with double-circle rings (DCRs) and welded with lumped resistances and continuous metal film. The structure is designed with thickness of 3 mm and investigated by simulation, fabrication, and experiment. The results show that the composite MA loaded with lumped resistances has wider absorptivity compared with a structure with only DCRs. The simulation results indicate that the proposed absorber achieves 7.60-GHz-wide absorption from 8.87 GHz to 16.47 GHz with absorptivity greater than 90%, in excellent agreement with experimental results. Further simulations indicate that there exist optimal values for the lumped resistances for which the absorptivity is the highest and the bandwidth widest. Additionally, the proposed MA is polarization insensitive at normal incidence. Simulation results for wide angles of incidence of both transverse electric and transverse magnetic waves are also investigated.

A broadband metamaterial (MM) absorber based on water droplets is proposed and investigated in this paper. The proposed MM absorber is composed of a periodic array of holes drilled in the dielectric substrate which are then filled with water droplets. The absorption property of such water absorber can be tuned by manipulating the volume of the water droplets. Through optimized design, a broadband water electromagnetic (EM) wave absorber is achieved in microwaves regime, which obtains 90% absorption efficiency across the frequency band from 7.63 to 14.94 GHz. The physical mechanism of the proposed MM absorber is investigated. The absorption performance of such MM absorber is verified through both full-wave simulation and experimental measurement which coincide with each other.

We presented a numerical investigation of a metamaterial narrowband perfect absorber conducted via a finite element method based on commercially available COMSOL software. The periodic array of silicon meta-atoms (MAs) are placed on 80 nm thick gold layer. The broadband light at normal incidence is blocked by the gold layer and silicon MAs are used to excite the surface plasmon by scattering light through it. Maximum absorption of 95.7 % is obtained at the resonance wavelength of 1137.5 nm due to the perfect impedance matching of the electric and magnetic dipoles. The absorption is insensitive to the wide-angle of incidence ranging from 0 to 80 degrees. We believe that the proposed metamaterial device can be utilized in solar photovoltaic and biochemical sensing applications. Full Text: PDF ReferencesY. Cheng, X.S. Mao, C. Wu, L. Wu, R.Z. Gong, "Infrared non-planar plasmonic perfect absorber for enhanced sensitive refractive index sensing", Optical Materials, 53, 195-200 (2016). CrossRef S. S. Mirshafieyan, D.A. Gregory, "Electrically tunable perfect light absorbers as color filters and modulators", Scientific Reports,8, 2635 (2018). CrossRef D.M. Nguyen, D. Lee, J. Rho, "Control of light absorbance using plasmonic grating based perfect absorber at visible and near-infrared wavelengths", Scientific Reports, 7, 2611 (2017). CrossRef Y. Sun, Y. Ling, T. Liu, L. Huang, "Electro-optical switch based on continuous metasurface embedded in Si substrate", AIP Advances, 5, 117221 (2015). CrossRef H. Chu, Q. Li, B. Liu, J. Luo, S. Sun, Z. H. Hang, L. Zhou, Y. Lai, "A hybrid invisibility cloak based on integration of transparent metasurfaces and zero-index materials", Light: Science & Applications, 7, 50 (2018). CrossRef S. K. Patel, S. Charola, J. Parmar, M. Ladumor, "Broadband metasurface solar absorber in the visible and near-infrared region", Materials Research Express, 6, 086213 (2019). CrossRef Q. Qian, S. Ti, C. Wang, "All-dielectric ultra-thin metasurface angular filter", Optics Letters, 44, 3984 (2019). CrossRef P. Yu et al., "Broadband Metamaterial Absorbers", Advanced Optical Materials, 7, 1800995 (2019). CrossRef Y. J. Kim et al., "Flexible ultrathin metamaterial absorber for wide frequency band, based on conductive fibers", Science and Technology of advanced materials, 19, 711-717 (2018). CrossRef N.L. Kazanskiy, S.N. Khonina, M.A. Butt, "Plasmonic sensors based on Metal-insulator-metal waveguides for refractive index sensing applications: A brief review", Physica E, 117, 113798 (2020). CrossRef H. E. Nejad, A. Mir, A. Farmani, "Supersensitive and Tunable Nano-Biosensor for Cancer Detection", IEEE Sensors Journal, 19, 4874-4881 (2019). CrossRef

Balancing the thickness and bandwidth of electromagnetic wave–absorbing materials has been a challenging task. In this study, a thin and broadband metamaterial absorber consisting of a frequency selective surface (FSS) layer compounded with a magnetic dielectric layer was proposed. The changes in the wave absorbing properties of the absorbers with different numbers of openings in the open circular structure and combinations of open circular rings were analyzed. After obtaining the optimum combination of patterns, the effect of parameter variations on the microwave absorption properties of metamaterial wave absorbers was investigated. The test results show that the optimized metamaterial absorber has a thickness of 1.7 mm, a simulated absorption bandwidth of up to 10.0 GHz, and a microwave reflection loss of less than − 10 dB in the frequency band of 8.0–18.0 GHz. The absorber was prepared and its reflection loss was measured. It is found that these test results have the same trend as the simulation results, which verifies the feasibility of the metamaterial absorber structure design; the proposed two-layer magnetic dielectric composite FSS structure improves the overall impedance matching, avoids the electromagnetic wave being reflected in the surface, and makes the electromagnetic wave enter the interior more; when the resonant absorption peak generated by the introduction of FSS is close to the absorption peak generated by the magnetic dielectric layer, continuous absorption will be achieved, which is the reason for the wide absorption band of the metamaterial absorber. This novel structure takes into account the characteristics of thin layer, broadband absorption, and polarization insensitivity, which has a potential application prospect in stealth technology.

This paper introduces the recent progress of incidence angle- and polarization-insensitive broadband metamaterial (MM) absorbers. The polarization insensitivity can be easily achieved by a symmetric geometry. In order to achieve incidence angle insensitivity, a unique unit cell must be designed. In this paper, we introduced three angle insensitive unit cells for metamaterial absorber applications. In order to achieve broadband absorption, we introduced two approaches such as multi-resonance and resistive patterns based on the angle- and polarization-insensitive MM absorbers. Therefore, we presented three angle- and polarization-insensitive broadband metamaterial (MM) absorbers.

In this paper, a broadband metamaterial (MM) absorber is presented for X-band applications. A novel eight-resistive-arm (ERA) cell is proposed as an MM unit cell to achieve both broadband absorption and wide incidence angles. The proposed ERA cell is designed using equivalent circuit model and full-wave analysis in order to achieve an absorption ratio higher than 90% in the range of 8.2–13.4 GHz. The experimental results indicate that the absorptivity was greater than 90% in the range of 8–13 GHz for all polarization angles under normal incidence. Under oblique incidence, the measured absorptivity was greater than 90% in the range of 8.2–12.2 GHz up to 60° and in the range of 9.2–12 GHz up to 65° in the transverse electric (TE) mode. In the transverse magnetic (TM) mode, the measured absorptivity was higher than 90% in the range of 9.5–12.4 GHz when the incidence angle was varied from 0° to 60° and remaining a 90% absorption bandwidth in the range of 10–12 GHz up to 65°. Compared to other broadband MM absorbers, the proposed MM absorber exhibited the widest incidence angles in both TE and TM modes.

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Optimization of the geometry of broadband metamaterial absorbers is crucial for improving the performance of optoelectronic devices. However, a large number of geometric parameters should be considered to achieve broad absorption, which is time-consuming. Herein, we propose a rapid and simple method for optimizing metamaterial absorbers dedicated to thermal radiation absorption using deep reinforcement learning. Deep reinforcement learning generated an ideal geometry for a broadband metamaterial absorber after 4 h, demonstrating the effectiveness of this technique for the rapid and effective optimization of metamaterial absorbers.

In this paper, based on split resonant ring (SRR) and NaCl solution (NS), a conformal and low thermal infrared radiation (LTIR) broadband metamaterial absorber (MA) with double SRRs and NS resonant cavity is proposed. Through simulation and measurement, it is proved that the proposed absorber has electromagnetic (EM) wave absorptivity of more than 90% under different polarization angles and different conformal conditions at 9.58–24.42 GHz. By introducing microfluidic channels, coupled electromagnetic thermal and coupled heat transfer simulations demonstrate that the design MA can maintain the thermal stability and LTIR characteristics under different power EM waves irradiation with low flow velocity (0.05 m s−1). Based on its good absorption performance and LTIR performance, it can be predicted that the proposed MA will have great application value in non-planar surface EM wave stealth and infrared stealth.

In this paper, a broadband metamaterial microwave absorber was designed and fabricated. Five unit cells of different geometrical dimensions which were designed using CST simulator, achieved at least 80% absorption of microwave at 11 GHz, 12 GHz, 13 GHz, 14 GHz and 15 GHz, respectively. The proposed metamaterial absorbers unit cell was composed of a split ring resonator and a microstrip slot structure, which was printed in repeated pattern on both sides of FR-4 substrate with 1.58 mm and (20×20) cm2 of thickness and area, respectively. In this study, the designed microstrip slot structure contains multi-width section compared to a conventional linear slot structure. Parametric studies of the geometrical dimensions for the metamaterial absorber were observed and analysed. The size of the unit cell decreased by 7% in average which caused the shifting of absorption peak from lower to higher frequency by 1 GHz. The metamaterial absorbers were experimentally tested using free-space measurement technique covering X-Ku band in which the planar surface of the metamaterial absorber was normal to the incident wave (in-plane). The S-parameters measurement results showed that the absorption properties of the metamaterial for normal incidence case (in-plane) were slightly deviate from the simulation results by shifting 0.3 GHz to higher frequency.

Broadband long-wave infrared metamaterial absorbers based on germanium resonators

Composite structure design of a broadband metamaterial absorber based on magnetic composites