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The progressive enhancements in solar-to-electrical conversion within the past decade have allowed organic–inorganic lead halide perovskite-based solar cell (PSC) technology to become a competitive candidate for creating affordable and sustainable electricity. This review highlights the developments in fabricating advanced precursor inks of organic–inorganic lead halide perovskite-based light harvesters for large-area perovskite solar cell technology. One of the key characteristics of this promising photovoltaic technology includes solution processing, which offers possibilities to scale up lab-sized solar cell devices into large-area perovskite solar modules comprising unique device architectures. These have been realized in recent years for their deployment in various applications such as building-integrated photovoltaics or internet of things (IoT) devices. In this regard, the presented overview highlights the recent trends that have emerged in the research and development of novel perovskite precursor ink formulations, and it also discusses their contribution toward demonstrating efficient, scalable, and durable PSC technology to create electricity and energize futuristic applications. Various reports were included aiming to showcase the robust photovoltaic performance of large-area perovskite solar modules in a variety of device configurations, hence providing a brief overview of the role of state-of-the-art scalable precursor ink development in transforming unstable lab-sized solar cells into robust, low-cost perovskite solar cell technology that can be scaled up to cover much larger areas.

The asymmetric transmission has fascinated wide interest because of its novel applications. In this paper, we propose and present the design procedure and the simulation results of the tunable dual-band polarization-sensitive graphene chiral metasurface. The resonance wavelength depends on and is controlled by the graphene chemical potential. The two-dimensional chiral response of the structure, circular conversion dichroism (CCD), is tunable and is reached to 0.2. As an application of the tunable chiral structure, a novel tunable polarization-sensitive refractive index sensor with the maximum sensitivities of 7000–10000 nm/RIU is proposed and analyzed. For different kinds of the circularly polarized incident electromagnetic waves, the sensitivities are high and noticeable. This paper exposes a new way to propose other polarization-sensitive structures, such as switches and absorbers in the terahertz (THz) region. In addition, the proposed structure and its application could be useful in polarization-sensitive devices and systems.

An enhanced graphene-based refractive index sensor with high sensitivity composed of two vertical layers, asymmetric double graphene layers, that act as a resonator and also two horizontal layers that act as input/output waveguides is designed and proposed. Performance of the sensor is based on the alternation of the resonance wavelength of the resonator. The two-dimensional-finite difference time-domain (2D-FDTD) simulation results show a linear relation between the resonance wavelengths and the refractive index of the material under sense (MUS). This feature makes it easy to identify the injected material in the resonator. The mid-infrared (MIR) wavelength range of the sensor structure can be tuned by applying the bias voltage to graphene to change its chemical potential. The sensitivity value can be obtained as high as 1900 nm per refractive index unit (nm/RIU). The performance of the proposed sensor is studied theoretically and confirmed numerically. The proposed plasmonic refractive index sensor would have useful applications in nano devices and circuits in MIR.

In this paper, the periodic arrays of multi-layer graphene disks placed near a metallic ground coated by dielectric spacers are proposed and analyzed by the Circuit Model (CM) based on the reflected fields to predict the perfect absorption response in the terahertz (THz) region. As numerical examples, single-, dual-, and triple-band absorbers with perfect absorption at three different THz frequencies are designed and proposed. The design is done by usage of a simple MATLAB code analytically and the numerical results are obtained by the Finite Element Method (FEM) to verify the accuracy and validity of the CM approach. The metallic ground restricted the transmission of the incident wave and all incident electromagnetic wave is confined between graphene disks and the metallic ground. As a result, a narrowband perfect absorption peak with full width at half maximum (FWHM) of ˜0.1 THz is obtained. The position of the absorption peak and also the number of peaks could be altered by control of the chemical potential of graphenes, indicating the tunability of the proposed structure. This structure supports the fabrication of THz devices such as optical filters, sensors, and active THz metamaterial devices.

Dye-sensitized solar cells (DSSCs) are an efficient photovoltaic technology for powering electronic applications such as wireless sensors with indoor light. Their low cost and abundant materials, as well as their capability to be manufactured as thin and light-weight flexible solar modules highlight their potential for economic indoor photovoltaics. However, their fabrication methods must be scaled to industrial manufacturing with high photovoltaic efficiency and performance stability under typical indoor conditions. This paper reviews the recent progress in DSSC research towards this goal through the development of new device structures, alternative redox shuttles, solid-state hole conductors, TiO2 photoelectrodes, catalyst materials, and sealing techniques. We discuss how each functional component of a DSSC has been improved with these new materials and fabrication techniques. In addition, we propose a scalable cell fabrication process that integrates these developments to a new monolithic cell design based on several features including inkjet and screen printing of the dye, a solid state hole conductor, PEDOT contact, compact TiO2, mesoporous TiO2, carbon nanotubes counter electrode, epoxy encapsulation layers and silver conductors. Finally, we discuss the need to design new stability testing protocols to assess the probable deployment of DSSCs in portable electronics and internet-of-things devices., Dye-sensitized solar cells (DSSCs) are an efficient photovoltaic technology for powering electronic applications such as wireless sensors with indoor light.

In this paper, we report the design, simulation, and some applications of a tunable graphene-based cylindrical resonator by analytical and numerical two-dimensional finite-difference time-domain methods. The base structure operates as a bandpass filter in the mid-infrared region. The tunability of the filter is achieved by changing the radius and/or the chemical potential of the graphene cylinder. Based on the proposed cylindrical resonator, a two-channel wavelength selector and some novel linear plasmonic logic gates are designed and proposed. The even- and the odd-order resonance modes are separated in the two-channel wavelength selector and are transmitted to the output graphene waveguides. Moreover, the plasmonic logic gates including XOR, XNOR, NAND, and NOT having the significant features such as linearity, compact size, and low loss are proposed. The analytical approach and the numerical simulations prove the excellent performance of the logic gates in comparison to the reported ones in the literature. The simulation results demonstrate that the maximum ON/OFF ratios for these plasmonic logic gates are 29.09, 28.78, 28.78, and 29.09 dB, respectively. The proposed functional ultra-compact nano-scale graphene-based structures offer potential basic blocks for mid-infrared optical computing and signal processing.

Terahertz frequency band has become one of the most interesting fields of research these days and the necessity of various modern applications in this area is THz absorbers. In this paper, we have proposed and investigated a novel ultra-wideband terahertz absorber by using periodic arrays of graphene disks and ribbons. Analytical circuit model of graphene arrays besides a developed transmission line theory is used to obtain analytical expressions for the input impedance of the proposed structure. The input impedance is adjusted to be closely matched to the free space impedance in a wide frequency range. Using three layers of patterned graphene, bandwidth of 90% absorption reached to 131% of central frequency. Regarding excellent performance of the proposed method in terms of computation time (showing more than 5 orders of magnitude reduction in runtime) and memory sources, this method with producing results with an acceptable agreement (with an error less than 5%) compared to the results of full-wave numerical modeling can be utilized in design of other graphene-based sub-wavelength devices.

A graphene-based slot cavity is proposed and investigated numerically by using two-dimensional finite-difference time-domain method. The structure can be used as a tunable midinfrared multichannel bandpass filter, mode separator, multi/demultiplexer, and logic gates. Passbands of the designed filters can be tuned by varying the length and/or the chemical potential of the graphene slot cavity. The filter can be promoted to a mode separator by using another graphene output waveguide in the middle of the slot cavity filter. The even and odd order resonance modes can be separated and transmitted to the outputs. The proposed mode separator can also be used to design a wavelength multi/demultiplexer with minimum number of the slot cavities. We also proposed and simulated an ultracompact nanoscale logic gates of xor , or , and not with graphene slot cavity resonators, especially in the midinfrared wavelengths with an extinction ratio of 19.85 dB, which can be utilized for design of the nanoscale photonic integrated circuits (PICs). The gates behaviors are based on the suppression or enhancement of the resonance modes in the slot cavity due to the place of the input and output waveguide ports. These components are efficient and can be utilized in the design of midinfrared nanoscale devices and PICs.

Two parallel graphene sheet waveguides and a graphene cylindrical resonator between them is proposed, analyzed, and simulated numerically by using the finite-difference time-domain method. One end of each graphene waveguide is the input and output port. The resonance and the prominent mid-infrared band-pass filtering effect are achieved. The transmittance spectrum is tuned by varying the radius of the graphene cylindrical resonator, the dielectric inside it, and also the chemical potential of graphene utilizing gate voltage. Simulation results are in good agreement with theoretical calculations. As an application, a multi/demultiplexer is proposed and analyzed. Our studies demonstrate that graphene based ultra-compact, nano-scale devices can be designed for optical processing and photonic integrated devices.

In this study, we have designed an equivalent circuit model (ECM) by use of a simple MATLAB code to analyze a single-layered graphene chiral multi-band metadevice absorber which is composed of U-shaped graphene resonator array in terahertz (THz) region. In addition, the proposed metadevice absorber is analyzed numerically by the finite element method (FEM) in CST Software to verify the ECM analysis. The proposed device which is the first tunable graphene-based chiral metadevice absorber can be used in polarization sensitive devices in THz region. It is single-layered, tunable, and it has strong linear dichroism (LD) response of 94% and absorption of 99% for both transverse electric (TE) and transverse magnetic (TM) electromagnetic waves. It has four absorption bands with absorption >50% in 0.5-4.5 THz : three absorption bands for TE mode and one absorption band for TM mode. Proposed ECM has good agreement with the FEM simulation results. ECM analysis provides a simple, fast, and effective way to understand the resonance modes of the metadevice absorber and gives guidance for the analysis and design of the graphene chiral metadevices in the THz region.

In this study, a tunable graphene plasmonic filter and a two-channel demultiplexer are proposed, simulated, and analyzed in the mid-infrared (MIR) region. We discuss the optical transmission spectra of the proposed cross-shaped resonator and the two-channel demultiplexer. The transmission spectra of the proposed MIR resonator are tunable by change of its dimensional parameters and the Fermi energy of the graphene. Our proposed structures have a single mode in the wavelength range of 5&ndash, 12 &micro, m. The minimum full width at half maximum (FWHM) and the maximum transmission ratio of the proposed resonator respectively reached 220 nm and 55%. Simulations are performed by use of three-dimensional finite-difference time-domain (3D-FDTD) method. Coupled mode theory (CMT) is used to investigate the structure theoretically. The numerical and the theoretical results are in good agreement. The performance of the proposed two-channel demultiplexer is investigated based on its crosstalk. The minimum value of crosstalk reaches &minus, 48.30 dB. Our proposed structures are capable of providing sub-wavelength confinement of light waves, useful in applications in MIR region.

In this paper, a plasmonically induced transparency (PIT)-like phenomenon in a metasurface composed of a periodic graphene ring and ribbon arrays is studied in the terahertz region. We used the Lorentz oscillator model to analyze the metasurface physically and theoretically. This PIT-like effect can be tuned by alternation of the chemical potential and dimension of the nano-graphene ring and ribbon. The resonance frequency of the PIT-like phenomenon is not sensitive to the incident lightwave angle. As an application of the structure, a refractive index sensor is proposed and simulated. Furthermore, we propose a metasurface composed of a double ring and graphene ribbon to realize the PIT-like effect with three dips. Our results express an appropriate approach for the expansion of mid-infrared absorbers and sensors.

A plasmonic refractive index sensor based on a metal-insulator-metal waveguide coupled with a double concentric square ring resonator is proposed and analyzed both theoretically and numerically. The theoretical and the numerical results are based on the transmission-line model and the finite difference time domain method, respectively. The theoretical results agree well with the numerical ones. A maximum sensitivity of 1250 nm per refractive index unit with a high figure of merit of 32.8 for the double concentric square ring resonator with one stub is obtained in the near-infrared region. Also, the double concentric square ring resonator with three stubs is simulated, and has a maximum sensitivity of 1270 nm per refractive index unit with a high figure of merit of 58. Our proposed plasmonic structures could find useful applications in sensing systems and integrated circuits in the near-infrared region.

In this research, a three-dimensional (3D) graphene intrinsically chiral metastructure in terahertz (THz) region was proposed and analyzed. The unit cell consists of bi-layer cross-shaped graphene ribbons in which the back layer is rotated compared to the front layer. Parameter retrieval method and Kramers–Kronig relations are used for theoretical analysis and derivation of the right-handed and left-handed electromagnetic effective refractive indices of the proposed structure. Based on our analysis, the proposed meta-structure has a tunable and controllable chiral response due to the tunability of graphene and circular dichroism (CD) was reached to 0.2. In order to evaluate the performance of the THz device in biosensor application, its characteristics in chiral biomolecule (collagen) sensing was analyzed. With an optimum design, our simulations show that the refractive index sensitivity value can be obtained as high as 0.96 THz per refractive index unit (THz/RIU) for the CD spectra. Proposed graphene chiral metastructure is promising enabler for controllable polarization-sensitive devices and systems such as tunable polarization filters, rotators, polarizers, biosensors, phase shifters, operating in the THz region.

A method for designing a metalens with electrically tunable focal length is proposed and analyzed. Metasurfaces are defined as low-thickness devices to initiate and generate the abrupt electromagnetic wavefront variation. However, there is no way to control them actively. Our research proposes the design of a metalens that consists of cross-shaped apertures (CSAs) in a gold film and a graphene layer. The CSAs have different lengths and rotation angles. By applying bias voltage to graphene, the focal length can be varied and controlled electrically. When the Fermi energy of the graphene changes from 0.1 to 0.5 eV, the focal length changes from 10.5 to 12.67 mm. The structure is simulated by the finite-difference time-domain numerical method. By splitting graphene layers to several parts and biasing each of them with different bias voltages, the transmitted focused beam could be rotated up to 35 deg. As an application of the metalens device, a refractive index sensor with sensitivity of 80 μm per refractive index unit (μm / RIU) is proposed.

The asymmetric transmission (AT) has attracted wide attention due to its novel applications. In this paper, we propose and investigate a tunable polarization-dependent intrinsically chiral graphene metasurface composed of split ring arrays in terahertz (THz) region. The resonance frequency of the structure is sensitive to the graphene chemical potential. Circular conversion dichroism (CCD) of the proposed structure is tunable and is reached to 0.36. Our work paths a new approach to propose some other compact and on-chip polarization-dependent structures in THz region. Furthermore, our proposed structure could be a useful segment in polarization-dependent systems.

A parallel graphene layer pair arranged in an antisymmetric configuration coupled through a cavity resonator is proposed and analyzed by the analytical method and the numerical finite-difference time-domain method. The structure operates as a bandpass filter in the midinfrared region. The feature, as the result of the wavelength selective property of the cavity resonator, can be tuned by varying the length of the resonator, the lateral coupling distance between the graphene layers, the dielectric refractive index of material inside the resonator, and, the most interesting, the chemical potential of the graphene layers. The proposed structure can be promoted to power splitters and refractive index sensors by proper designs. Various power division ratios can be realized by changing the relative positions and/or the chemical potentials of the output waveguides. The investigated components can be utilized in the design of midinfrared nanoscale photonic integrated circuits.