Plasmon-enhanced performance of an ultrathin silicon solar cell using metal-semiconductor core-shell hemispherical nanoparticles and metallic back grating

Plasmon-enhanced parabolic nanostructures for broadband absorption in ultra-thin crystalline Si solar cells

Sub-wavelength plasmonic light trapping nanostructures are promising candidates for achieving enhanced broadband absorption in ultra-thin silicon (Si) solar cells. In this work, we use finite-difference time-domain (FDTD) simulations to demonstrate the light harvesting properties of periodic and parabola shaped Si nanostructures, decorated with metallic gold (Au) nanoparticles (NPs). The active medium of absorption is a 2 μm thick crystalline-silicon (c-Si), on top of which the parabolic nanotextures couple incident sunlight into guided modes. The parabola shape provides a graded refractive index profile and high diffraction efficiencies at higher order modes leading to excellent antireflection effects. The Au NPs scatter light into the Si layer and offer strong localized surface plasmon resonance (LSPR) resulting in broadband absorption with high conversion efficiency. For wavelengths (λ) ranging between 300 nm and 1600 nm, the structure is optimized for maximum absorption by adjusting the geometry and periodicity of the nanostructures and the size of the Au NPs. For parabola coated with 40 nm Au NPs, the average absorption enhancements are 7% (between λ = 300 nm and 1600 nm) and 28% (between λ = 800 nm and 1600 nm) when compared with bare parabola. Furthermore, device simulations show that the proposed solar cell can achieve a power conversion efficiency (PCE) as high as 21.39%, paving the way for the next generation of highly efficient, ultra-thin and low-cost Si solar cells.

A novel plasmonic metal-semiconductor-insulator-metal (MSIM) color sensor compatible with CMOS technology

Color detection is one of the top interests in both biological and industrial applications. Specifically, the Determination of the light wave characteristics is vital in photonic technology. One of the features in the color sense that should be found out is its wavelength or color. In this work, we propose a structure that can be used to detect RGB colors separately in an efficient way. The proposed detector consists of the plasmonic filter sensing desired wavelength (red, green, and blue) and the PN diode to convert the received photons to the electrical current. At the input intensity of 1 mW × cm-2, the current density for blue, green, and red colors are 27, 35, and 48 µA × cm-2, respectively. It is shown that the intensities needed to obtain the current densities of 0.1 µA × cm-2 are 3.94, 2.98, and 2.25 µW × cm-2 for the blue, green, and red spectra respectively. It should mention that by using high-precision photodetector structures such as PIN diode, the minimum detectable level can be decreased. Simple adjusting for desired wavelength and linear operation for different input intensities are the characteristics of the designed structure. This detector is compatible with CMOS technology and can be easily utilized in numerous applications, such as charge-coupled devices, displays, and cameras.

Cutting sinusoidal gratings to enhance light trapping in thin-film silicon solar cells

A crystalline silicon thin-film solar cell with a three-layer sinusoidal grating structure is studied. The structure has a double-layer antireflection layer, and the three-layer grating is located in the double-layer antireflection layer and the passivation layer, respectively. The related parameters of the grating structure are optimized by scanning using finite-difference time-domain. The optimization results show that cutting the sinusoidal grating structure can significantly improve the light absorption efficiency of the cell for near-infrared light (750-1100 nm), and the enhancement effect is mainly in the transverse electric (TE)-polarized light. This is because the localized surface plasmon resonance and optical waveguide mode under TE-polarized light can be fully excited after the sinusoidal structure is cut. The short-circuit current density (J _{S C} ) of the optimized three-layer sinusoidal grating structure is 19.82m A/c m ², which is 112.43% higher than that of the planar structure with the same parameters and 23.18% higher than that of the uncut sinusoidal grating structure with the same parameters.

Dimensional Optimization of TiO2 Nanodisk Photonic Crystals on Lead Iodide (MAPbI3) Perovskite Solar Cells by Using FDTD Simulations

Perovskite solar cells (PSC) are currently exhibiting reproducible high efficiency, low-cost manufacturing, and scalable electron transport layers (ETL), which are becoming increasingly important. The application of photonic crystals (PC) on solar cells has been proven to enhance light harvesting and lead solar cells to adjust the propagation and distribution of photons. In this paper, the optimization of a two-dimensional nanodisk PC introduced in ETL with an organic-inorganic lead-iodide perovskite (methylammonium lead-iodide, MAPbI3) as the absorber layer was studied. A finite-difference time-domain (FDTD) simulation was used to evaluate the optical performance of PSC with various lattice constants and a radius of nanodisk photonic crystals. According to the simulation, the optimum lattice constant and PC radius applied to ETL are 500 nm and 225 nm, respectively. This optimum design enhances PSC absorption performance by more than 94% of incident light.

Period-mismatched sine dual-interface grating for optical absorption in silicon thin-film solar cells

Crystalline silicon thin-film solar cells with period-mismatched sine dual-interface gratings are proposed. Several structural parameters of the front and rear gratings, such as heights, periods, and duty ratios, are optimized using the finite-difference time-domain method. The mechanisms of absorption enhancement are also illustrated by analyzing the optical and electrical performance in thin-film solar cells with different grating arrangements. Numerical results indicate that the period-mismatched sine dual-interface grating structure shows obvious improvement in absorption efficiency and is more suitable for grating structures with small period. The short-circuit current density of the period-mismatched dual-interface sine grating structure is improved to 18.89mA/cm², an increase of 41.39% as compared with the planar structure. The research findings can be utilized to guide the design of grating structures for thin-film solar cells.

Plasmonic and photonic enhancement of photovoltaic characteristics of indium-rich InGaN p-n junction solar cells

In this paper, we demonstrate via Finite-difference time-domain (FDTD) simulations that the performance of indium-rich In_xGa_1-xN (x = 0.6) p-n junction thin-film solar cells is improved by incorporating an integrated structure of a 2-dimensional (2D) array of ITO nanodiscs on the top surface and a 2D array of Ag nanodiscs in the active layer above the Ag back reflector of the solar cell. The bottom Ag nanodiscs primarily enhance the absorption of longer wavelengths by coupling incident light into surface plasmon resonance (SPR) and waveguide modes. The top ITO nanodiscs enhance the middle wavelengths (400 nm to 800 nm) by coupling the incident light to photonic modes in the active layer. Thus, the integrated structure of nanodisc arrays leads to a very high absorption in the active region in broad spectral range (> 0.85 for wavelengths lying between 350 nm and 800 nm), significantly increasing the short circuit current density (J_sc) and power conversion efficiency (PCE) of the solar cell. In the proposed solar cells, the geometries of the silver and ITO nanodiscs were optimized to obtain the maximum possible values of the J_sc. The highest enhancements in J_sc and PCE of ∼25% and ∼26%, respectively, were obtained in a solar cell containing the integrated structure of ITO and Ag nanodisc arrays. Moreover, the performance of these cells was examined under oblique light incidence and it was observed that the solar cells containing the integrated structure of nanodisc arrays have a significantly larger value of J_sc when compared to the cells having no nanostructures or having only the top ITO nanodisc array or only the bottom Ag nanodisc array.

Light-trapping schemes for silicon thin-film solar cells via super-quadratic subwavelength gratings

We systematically investigate the light-trapping schemes of crystalline silicon thin-film solar cells (TFSCs) for three common grating layouts via one-dimensional super-quadratic subwavelength gratings. The effects of antireflective coating, absorber layer thickness, and grating geometry on the light-trapping performance of TFSCs are numerically studied using the finite-difference time-domain method. The results suggest that the conformal aluminum-doped zinc oxide (AZO) coatings have better optical properties than the plane AZO coatings. For the case of only top Si gratings, the grating geometry of degree $n={4}$n=4 can achieve a good trade-off between the shape-dependent light-trapping and antireflection properties, showing the best light-trapping effect; for the case of only bottom Ag gratings, the optical performance of TFSCs is significantly degraded as the degree $n$n increases from $n={1}$n=1 to $n\to\infty$n→∞. The above findings are analyzed and demonstrated in detail from the optical and electrical perspectives, and they can be utilized to guide the design of light-trapping structures for TFSCs.

Enhanced light trapping in thin-film silicon solar cells with concave quadratic bottom gratings

We present a theoretical crystalline silicon thin-film solar cell with concave quadratic bottom gratings using parametric design of the gratings and systematically perform optoelectronic simulations of the proposed grating structures. Numerical results reveal that the concave quadratic grating structure leads to a desirable enhancement of light absorption in the near-IR region (750-1100 nm), and this enhancement is dominated by TE-polarized light. The mechanisms of light absorption enhancement under TE-polarized light are based on the hybrid effect of optical waveguide modes and Fabry-Perot modes. Moreover, research results indicate that the concave quadratic grating structure has excellent light-focusing effects, which is conducive to the excitation of optical waveguide modes. The study findings can be utilized to improve the efficiency of thin-film solar cells based on grating structures.

Photovoltaic absorber with different grating profiles in the near-infrared region

We theoretically introduce a Si-based photovoltaic absorber with different grating profiles, which demonstrates a desirable enhancement of light absorption in the near-infrared region by increasing the degree of the grating's profile function. The mechanisms of light absorption enhancement originate from the synergetic effect of optical waveguide modes, light scattering, and Fabry-Perot resonances. Moreover, numerical results indicate that the convex grating structure is more conducive to the excitation of optical waveguide modes compared with the concave grating structure. The research findings can be utilized to guide the design of thin-film solar cells based on grating structures.

Metal-enhanced fluorescence of single shell-isolated alloy metal nanoparticle

A single silica-shell isolated Au-Ag alloy nanoparticle is used for investigating a metal-enhanced fluorescence effect. Well-dispersed alloy nanoparticles are prepared by the facile chemical method, and the property of local surface plasmon resonance is controlled by adjusting the metal component of the alloy and shell thickness. The distance dependence of fluorescence enhancement for a single Au-Ag alloy nanoparticle is studied systematically with different silica shell thickness ranging from 2 to 35 nm. The isolation shell not only adjusts the distance between metal surface and fluorophore emitters but also improves the chemical stability of the metal particle.