Davood Fathi

Tarbiat Modares University | TMU · Faculty of Electrical and Computer Engineering

So far, remarkable achievements have been obtained by optimizing the device architecture and modeling of solar cells is a precious and very effective way to comprehend a better description of the physical mechanisms in solar cells. As a result, this study has inspected two-dimensional simulation of perovskite solar cells (PSCs) to achieve a precise...

Light absorption process is a key factor in improving the performance of perovskite solar cells (PSCs). Using arrays of metal nanostructures on semiconductors such as perovskite (CH3NH3PbI3), the amount of light absorption in these layers is significantly increased. Metal nanostructures have been considered for their ability to excite plasmons (col...

In this research study, the effects of different parameters on the electron transfer rate from three quantum dots (QDs), CdSe, CdS, and CdTe, on three metal oxides (MOs), TiO2, SnO2, and SnO2, in quantum-dot-sensitized solar cells (QDSSCs) with porous structures in the presence of four types of blocking layers, ZnS, ZnO, TiO2, and Al2O3, are modele...

In this work, we propose a new liquid refractive index (RI) sensor based on one-dimensional (1D) regular array of multi-walled carbon nanotubes (MWCNTs) for sensing oil derivatives (ODs), for the first time. The proposed sensor is a ribbon consisting of 10 MWCNTs grown inside an AAO (Al2O3) template as the host material, which can sense the change...

In this brief opinionated article, we present a critical look at metamaterial dimensionality which is published in many articles and literatures these days. We try to discuss space and time as dimensions and the future of the degrees of freedom regarding dimensional spacetime metamaterials. In the following, we propose a practical common procedure...

Although assisted reproductive technology has been very successful for the treatment of infertility, its steps are still dependent on direct human opinion. An important step of assisted reproductive treatments in lab for women is choosing an oocyte that has a better quality. This step would predict which oocyte has developmental competence leading...

The development potential for oocytes can be predicted by their mechanical properties. One important parameter that is measured to calculate oocyte hardness is Cortical Tension (CT). In this work, for the first time, we present the design, simulation, and fabrication of a new aspiration microfluidic chip to measure the CT of oocytes and then predic...

Utilizing photonic nanostructures is a very efficient technique to capture light in broadband as well as a cheap and flexible method in photovoltaic devices. In this article, the finite element method (FEM) is applied to investigate the novel structures for perovskite solar cells (PSCs) aiming to find methods to enhance light absorption in the acti...

In this paper, we present a set of optimal graphene-based multilayer surface plasmon resonance (SPR) biosensors for highly sensitive detection of biomolecules. To optimize the biosensor structure, we employed a multi-objective gray wolf optimizer (MOGWO) to maximize the sensitivity and minimize the structure full width at half maximum (FWHM). The m...

We present a tunable planar guided-mode resonance (GMR) filter using time-varying permittivity along grating nanobars. Results show that the effective medium concept in the temporal state is exactly the same as the spatial state. Furthermore, the structure has spatial periodicity to save the resonance peak of the passive GMR in addition to the temp...

We present a general approach for numerical mode analysis of the multilayer slab waveguides using the scattering matrix (SM) instead of the conventional numerical methods. To calculate the global scattering matrix of multilayer structures, we apply the concept used in the transfer matrix method (TMM), which entails working through the device one la...

We present an emulation design method for converting asymmetrical transmitters to nonreciprocal isolators equipped with time-varying metasurfaces. To illustrate the model, we design a structure using a combination of the photonic crystal (PhC) and time-varying metasurface. Moreover, we propose a general approach for numerical analysis of the time-m...

The aim of this dissertation is to provide a numerical method for numerical investigating spatial, temporal and spatio-temporal periodic structures. The proposed method includes polarization with any elevation and azimuth angle, field calculation, reflection and transmission in each layer, input wave selection, better accuracy and speed than differ...

We present a general approach for numerical mode analysis of the multilayer slab waveguides using the scattering matrix (SM) instead of the conventional numerical methods. To calculate the global scattering matrix of multilayer structures, we apply the concept used in the transfer matrix method (TMM), which entails working through the device one la...

In recent years, have been seen a leap at the opportunity of investigation tandem solar cells. This due to the complementary bandgap energies of various layers which leads to enhancement of the light absorption and the power conversion efficiency (PCE) of this type of solar cells. In this numerical based study, a new hole transport material (HTM) f...

In this paper, using finite element method (FEM) as a three-dimensional simulation, the light trapping mechanism due to the use of plasmonic core/shell nanorod (PLCS-NR) array as well as its effect on absorption, generation, transfer of carriers and power conversion efficiency (PCE) in a perovskite solar cell (PSC) has been investigated. The short-...

We present an emulation design method for converting asymmetric isolators to nonreciprocal ones using time-varying metasurfaces. To illustrate the model, we design a structure using a combination of the photonic crystal (PhC) and time-varying metasurface. Moreover, we propose a general approach for numerical analysis of the time-modulated proposed...

We introduce two-dimensional space plus time (2D+1) structure and numerically investigate it using a developed multilayer simulation framework, for the first time. The new structure is consisting of crossed grating with time-varying permittivity which is inspired from 1D+1. In this regard, we extend Fourier Modal Method (FMM) in a general approach...

We present a general approach for numerical mode analysis of the multilayer slab waveguides using the Transfer Matrix Method (TMM) instead of the Finite Difference Frequency Domain (FDFD) method. TMM consists of working through the device one layer at a time and calculating an overall transfer matrix. Using the scattering matrix technique, we devel...

We present a general approach for numerical mode analysis of the multilayer slab waveguides using the Transfer Matrix Method (TMM) instead of the Finite Difference Frequency Domain (FDFD) method. TMM consists of working through the device one layer at a time and calculating an overall transfer matrix. Using the scattering matrix technique, we devel...

Despite the wide range of applications and versatility, actively Q-switched fiber lasers (AQS-FLs) suffer from the multi-peak phenomenon or stepwise pulse generation under certain conditions. As such, the advantage of the stepwise tendency in AQS-FL to modify the pulse shape and create a temporal profile that minimizes the power of stimulated Brill...

In this paper, we propose a new all-optical sensor based on a two-dimensional (2D) regular array of multi-walled carbon nanotubes (MWCNTs) for the refractive index sensing of oil derivatives, for the first time. The interaction of optical wave with the desirable oil derivatives is enhanced using the slow light effect that makes the group velocity g...

Perovskite solar cells (PSCs) based on lead halide and solution process face issues such as low efficiency and high manufacturing costs. Recently, the emerging field of plasmonics as a branch of photonics has been utilized in electronic, optic and electro-optic devices, which deals with optical phenomena in metallic nanostructures like Au, Ag and C...

Organometal halide perovskite has a vast variety of facilities and possibilities that makes them emerge in perovskite solar cell (PSC) technology. Interaction of incident light with plasmonic nanoparticles (NPs) leads to the formation of an electric field around the NPs. The electric field from plasmonic NPs can enhance the possibility of incident...

Perovskite Solar Cells (PSC) have been elicited much interest within the photovoltaic industry due to their many performance advantages. One of the effective ways to enhance the Power Conversion Efficiency (PCE) of PSCs is to minimize light and electrical losses. To this end, we have focused on the use of nanostructured light absorbers in PSCs and...

Design and analysis of a silicon waveguide with embedded pin diode are proposed here for the realization of second harmonic generation (SHG). The reverse-biased pin structure is employed to apply a DC field across an intrinsic silicon region which gives rise to electric-field induced (EFI) second-order nonlinearity χ(2)EFI in silicon. The resulted...

In this paper, a nanostructured perovskite solar cell (PSC) on a textured silicon substrate is examined, and its performance is analyzed. First, its configuration and the simulated unit cell are discussed, and its fabrication method is explained. In this proposed structure, poly-dimethylsiloxane (PDMS) is used instead of glass. It is shown that the...

In recent years, investigation on utilizing perovskite solar cells (PSCs) has become widespread and much researches have been conducted to increase the power conversion efficiency (PCE) and sustainability of this type of solar cell. In this research, the effects of graphene (Gr) and TiO2/Gr nanocomposite as the electron transport layer (ETL) on the...

In this paper, coupled optical and electrical simulations of perovskite solar cells (PSCs) are performed to optimize their basis output parameters and obtain the best power conversion efficiency (PCE) based on both the light absorption and carrier transport mechanisms. Due to the limitation of the perovskite absorption in longer wavelengths, we use...

In this study, a portable optical instrument was designed and developed for real-time non-destructive determination of fruit ripeness. A prototype of the instrument using inexpensive parts, was developed and calibrated for apple ripeness detection based on moisture content, Soluble Solids Content, pH and firmness. An array of 6 optical point source...

In this paper, a coupled optical-electrical modeling method is applied to simulate perovskite solar cells (PSCs) to find ways to improve light absorption by the active layer and ensure that the generated carriers are collected effectively. Initially, a planar structure of the PSC is investigated and its optical losses are determined. To reduce the...

Si3N4 has emerged as a prominent material for expanding the capability of silicon photonics to wavelengths below < 1 μm. However, realizing an efficient optical modulator, a key building block for any integrated optics platform, remains a major challenge in Si3N4 mainly because this material has a vanishing Pockels coefficient. Here, we propose a...

Design of the guided-mode resonance (GMR) grating filter, as one of the most important optical components, using the cultural algorithm (CA) is presented, for the first time. CA is an evolutionary algorithm (EA) which is easy-to-implement, flexible, inspired by the human cultural evolution, upon using the domain knowledge for reducing the search sp...

In an actively Q-switched fiber laser (AQS-FL) a type of acousto-optic modulator (AOM) or (potentially) electro-optic modulator (EOM) controls the generation of output nanosecond wide pulses. An integrated Gaussian pulse shape is desirable in many applications such as material processing, microfabrication, ultrasound generation, gold photothermal t...

In this paper, we propose the design and analyze a plasmonic-organic-hybrid (POH) waveguide structure for efficient forward and backward second harmonic generation (SHG) to bridge the mid-infrared (IR) to near-IR. The required phase matching is satisfied by quasi-phase matching (QPM) technique through periodically altering the material of the metal...

In this paper, the copper sulfide/copper selenide (Cu2S/Cu2Se) composite is presented as a new counter electrode (CE) in the quantum-dot-sensitized solar cells (QDSSCs), for the first time. This novel CE shows a higher electrocatalytic performance towards the polysulfide electrolyte. The obtained results show that, with the change of the CE materia...

We propose and design a nonlinear-polymer-filled asymmetric silicon slot waveguide (SSW) for efficient second-harmonic generation. The distinct modal dispersion of the designed asymmetric SSW is used to achieve phase matching between the zeroth-order waveguide mode at the fundamental frequency (𝜆=3.1µm) and the second-order mode at the second-harmo...

We propose an optimized method for the inverse design of guided-mode resonance (GMR) filters using one- and two- dimensional (1D & 2D) grating structures. This work for 2D state is based on developing the effective permittivity of 1D grating structures along three orthogonal axes to predict the physical dimensions of the structure, for the first ti...

Dielectric metasurfaces have opened promising possibilities to enable a versatile platform in the miniaturization of optical elements at visible and infrared frequencies. Due to high efficiency and compatibility with CMOS fabrication technology, silicon-based metasurfaces have a remarkable potential for a wide variety of optical devices. Adding tun...

Thermophotovoltaic (TPV) devices via efficient emitter are used to convert the thermal radiation into electricity. We propose a new nanostructure to reach the broadband high efficient TPV emitter. The performance of the model is enhanced by more interaction between the excited surface plasmon polaritons (SPPs) and the magnetic polaritons (MPs) base...

Thermophotovoltaic (TPV) devices via efficient emitter are used to convert the thermal radiation into electricity. We propose a new nanostructure to reach the broadband high efficient TPV emitter. The performance of the model is enhanced by more interaction between the excited surface plasmon polaritons (SPPs) and the magnetic polaritons (MPs) base...

Quality assessment of fruits and vegetables is important for all involved in production, processing, trading and even consumption of the products. This study was conducted for non-destructive estimation of moisture content (MC), soluble solids content (SSC), pH and firmness of Gala apple samples using near-infrared spectroscopy in the 350–2500 nm r...

In this study, Na-montmorillonite (MMT) was intercalated with the cerium cations. The Ce3+ cations intercalated sodium montmorillonite (Ce-MMT) nanoreservoirs were incorporated into the epoxy coating. The active inhibitive performance of the synthesized nanoreservoirs and their effect on the protective behavior of the epoxy coating was investigated...

Thermophotovoltaic (TPV) devices via efficient emitter are used to convert thermal radiation into electricity. We propose new one-and two-dimensional (1D and 2D) nanostructures to reach the broadband highly efficient TPV emitters. The performance of the model is enhanced by more interaction between the excited surface plasmon polaritons and the mag...

Si3N4 has emerged as a prominent material for expanding the capability of silicon photonics to wavelengths below < 1 µm. However, realizing an efficient optical modulator, a key building block for any integrated optics platform, remains a major challenge in Si3N4 mainly because this material has a vanishing Pockels coefficient. Here, we propose a c...

A new multi-objective optimization framework is presented for designing large mode area photonic crystal fibers (LMA-PCFs) with effective single-mode operation in the bent state. For optimizing the structure, we utilize the Multi-Objective Gray Wolf Optimizer (MOGWO) to maximize the effective mode area (EMA) and the bending loss of higher order mod...

We propose and design a high-efficiency forward and backward second harmonic generation (SHG) in nonlinear polymer filled silicon slot waveguide known as silicon-organic hybrid (SOH) waveguides. The spatial distribution of second.order nonlinearity, $\mathcal{X^{(2)}}$ , of waveguide is altered by periodically poling of nonlinear polymer to achiev...

The quality of agricultural products is of high importance in terms of consumer interest, determining market acceptance, and thus, directly affects storage and post-harvest processing operations. Quality measurement of fruits, vegetables and food products is at the center of attention by the food industry. Non-destructive measurements of quality pa...

The present study is conducted to evaluate the spin polarization in two pyrene and Triphenylene graphene nanoflakes. All calculations are performed using non-equilibrium Green's function (NEGF) method. The obtained results show that, graphene has no magnetic property and using Pyrene nanoflake results in a better spin switching at extreme magnetic...

In this work, the performance of Quantum dot-sensitized solar cells (QDSSCs) is enhanced with the treatment of ZnO nanorods by magnesium acetate. A chemical solution method is used for decoration of magnesium acetate on the ZnO nanorods. Current density–voltage (J-V) results show short-circuit current density (Jsc), open circuit voltage (Voc), and...

In this research, the effect of treatment of the CdS/CdSe sensitized ZnO photoanode by ZnS, Al2S3, and ZnS/Al2S3 nanoparticles as a barrier layer on the performance of quantum dot sensitized solar cell is investigated. Current density–voltage (J–V) characteristics show that cell efficiency is enhanced from 3.62% to 4.82% with treatment of a CdS/CdS...

High-index silicon nanoblocks support excitation of both electric and magnetic resonance modes at telecommunication wavelengths. At frequencies where both electric and magnetic resonance modes are excited simultaneously, changing the geometrical dimensions of the silicon cubes creates a 2? full span over the phase of the transmitted light in differ...

In this paper we attempt to present a multilayered structure biosensor. A graphene-based surface plasmon resonance (SPR) biosensor is considered as a structure that offers enhancement of the sensitivity in comparison with conventional biosensors. The sensitivity improvement caused by the presence of graphene is discussed through monitoring of the b...

In this paper, a compact and CMOS compatible alloptical 1×2 switch based on directional coupler is proposed. One waveguide of directional coupler is a conventional silicon waveguide while else is a hybrid silicon/VO2 waveguide. By optically changing the phase of VO2 layer from insulating to metallic, dependent on VO2 thickness, a great effective re...

In this paper, the distinctive dispersion characteristic of hybrid plasmonic waveguides is exploited for designing ultra-wideband directional couplers. It is shown that by using optimized geometrical dimensions for hybrid plasmonic waveguides, nearly wavelength-independent directional couplers can be achieved. These broadband directional couplers a...

We report on fabrication of halide perovskite solar cells using a two-step spin-spray coating rout. The applied method is one of the most straight forward procedures for fabricating uniform stoichiometry and crystalline perovskite cells. To fabricate a high quality perovskite layer, various concentrations of methyl-ammonium iodide (CH3NH3I) were sp...

Electron transfer rate from quantum dot (QD) to metal oxide (MO) in quantum dot sensitized solar cells (QDSSCs) has an important role in the efficiency. In this work, we analyse the electron transfer rate from CdSe, CdS and CdTe QDs to TiO2, ZnO and SnO2 MOs by extending the related equations with considering various effects, based on the Marcus th...