The Impact of parasitic loss on solar cells with plasmonic nano-textured rear reflectors

Feline eye-inspired artificial vision for enhanced camouflage breaking under diverse light conditions

Biologically inspired artificial vision research has led to innovative robotic vision systems with low optical aberration, wide field of view, and compact form factor. However, challenges persist in object detection and recognition against complex backgrounds and varied lighting. Inspired by the feline eye, which features a vertically elongated pupil and tapetum lucidum, this study introduces an artificial vision system designed for superior object detection and recognition in a monocular framework. Using a slit-like elliptical aperture and a patterned metal reflector beneath a hemispherical silicon photodiode array, the system reduces excessive light and enhances photosensitivity. This design achieves clear focus under bright light and enhanced sensitivity in dim conditions. Theoretical and experimental analyses demonstrate the system's ability to filter redundant information and detect camouflaged objects in diverse lighting, representing a substantial advancement in monocular camera technology and the potential of biomimicry in optical innovations.

Efficiency improvement of thin film solar cell using silver pyramids array and antireflective layer

In recent years, plasmonics has been widely employed to improve light trapping in solar cells. Silver nanospheres have been used in several research works to improve the capability of solar absorption. In this paper, we use silver pyramid-shaped nanoparticles, a noble plasmonic nanoparticle, inside thin-film silicon and InP solar cells to increase light absorption compared to previously published topologies. The proposed structure consists of a TiO₂ pyramid structure placed at the top of the surface working as an anti-reflective layer, silicon/indium phosphate as an absorption layer, silver pyramid-shaped nanoparticles incorporated inside the absorption layer, and an aluminum reflecting layer at the bottom. In this research, we used finite difference time domain (FDTD) simulation to model the thin-film solar cell (TFSC). Optimizing the shape and placement of the silver pyramids, we have achieved an efficiency of 17.08% and 18.58% using silicon and InP as the absorbing layers respectively, which is significantly better than previously reported studies. The open-circuit voltages are 0.58 V and 0.92 V respectively, which is the highest among other configurations. To conclude, the findings of this study laid the foundation to create an efficient thin-film solar cell utilizing the light-trapping mechanism of noble plasmonic nanoparticles.

Modified transmission line model for grating solar cells

Due to the wide range of applications of plasmonic diffraction gratings, it has become essential to provide an analytical method for modeling performance of the devices designed based on these structures. An analytical technique, in addition to greatly reducing the simulation time, can become a useful tool for designing these devices and predicting their performance. However, one of the major challenges of the analytical techniques is to improve the accuracy of their results compared to those of the numerical methods. So, here, a modified transmission line model (TLM) has been presented for the one-dimensional grating solar cell considering diffracted reflections in order to improve the accuracy of TLM results. Formulation of this model has been developed for the normal incidence of both TE and TM polarizations taking into account diffraction efficiencies. The modified TLM results for a silicon solar cell consisting of silver gratings considering different grating widths and heights have shown that lower order diffractions have dominant effects on the accuracy improvement in the modified TLM, while the results have been converged considering higher order diffractions. In addition, our proposed model has been verified by comparing its results to those of the finite element method-based full-wave numerical simulations.

The impact of plasmonic electrodes on the photocarrier extraction of inverted organic bulk heterojunction solar cells

Nano-patterning the semiconducting photoactive layer/back electrode interface of organic photovoltaic devices is a widely accepted approach to enhance the power conversion efficiency through the exploitation of numerous photonic and plasmonic effects. Yet, nano-patterning the semiconductor/metal interface leads to intertwined effects that impact the optical as well as the electrical characteristic of solar cells. In this work we aim to disentangle the optical and electrical effects of a nano-structured semiconductor/metal interface on the device performance. For this, we use an inverted bulk heterojunction P3HT:PCBM solar cell structure, where the nano-patterned photoactive layer/back electrode interface is realized by patterning the active layer with sinusoidal grating profiles bearing a periodicity of 300 nm or 400 nm through imprint lithography while varying the photoactive layer thickness (L _PAL ) between 90 and 400 nm. The optical and electrical device characteristics of nano-patterned solar cells are compared to the characteristics of control devices, featuring a planar photoactive layer/back electrode interface. We find that patterned solar cells show for an enhanced photocurrent generation for a L _PAL above 284 nm, which is not observed when using thinner active layer thicknesses. Simulating the optical characteristic of planar and patterned devices through a finite-difference time-domain approach proves for an increased light absorption in presence of a patterned electrode interface, originating from the excitation of propagating surface plasmon and dielectric waveguide modes. Evaluation of the external quantum efficiency characteristic and the voltage dependent charge extraction characteristics of fabricated planar and patterned solar cells reveals, however, that the increased photocurrents of patterned devices do not stem from an optical enhancement but from an improved charge carrier extraction efficiency in the space charge limited extraction regime. Presented findings clearly demonstrate that the improved charge extraction efficiency of patterned solar cells is linked to the periodic surface corrugation of the (back) electrode interface.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s00339-023-06492-6.

Perspectives on weak interactions in complex materials at different length scales

Nanocomposite materials consist of nanometer-sized quantum objects such as atoms, molecules, voids or nanoparticles embedded in a host material. These quantum objects can be exploited as a super-structure, which can be designed to create material properties targeted for specific applications. For electromagnetism, such targeted properties include field enhancements around the bandgap of a semiconductor used for solar cells, directional decay in topological insulators, high kinetic inductance in superconducting circuits, and many more. Despite very different application areas, all of these properties are united by the common aim of exploiting collective interaction effects between quantum objects. The literature on the topic spreads over very many different disciplines and scientific communities. In this review, we present a cross-disciplinary overview of different approaches for the creation, analysis and theoretical description of nanocomposites with applications related to electromagnetic properties.

Light management in ultra-thin photonic power converters for 1310 nm laser illumination

We designed and optimized ultra-thin single junction InAlGaAs photonic power converters (PPC) with integrated back reflectors (BR) for operation at the telecommunications wavelength of 1310 nm and numerically studied the light trapping capability of three BR types: planar, cubic nano-textured, and pyramidal nano-textured. The PPC and BR geometries were optimized to absorb a fixed percentage of the incident light at the target wavelength by coupling finite difference time-domain (FDTD) calculations with a particle swarm optimization. With 90% absorptance, opto-electrical simulations revealed that ultra-thin PPCs with 5.6- to 8.4-fold thinner absorber layers can have open circuit voltages (V_oc) that are 9-12% larger and power conversion efficiencies (PCE) that are 9-10% (relative) larger than conventional thick PPCs. Compared to a thick PPC with 98% absorptance, these ultra-thin designs reduce the absorber layer thickness by 9.5-14.2 times while improving the V_oc by 12-14% and resulting in a relative PCE enhancement of 3-4%. Of the studied BR designs, pyramidal BRs exhibit the highest performance for ultra-thin designs, reaching an efficiency of 43.2% with 90% absorptance, demonstrating the superior light trapping capability relative to planar and cubic nano-textured BRs.

An empirical investigation on the correlation between solar cell cracks and hotspots

In recent years, solar cell cracks have been a topic of interest to industry because of their impact on performance deterioration. Therefore, in this work, we investigate the correlation of four crack modes and their effects on the temperature of the solar cell, well known as hotspot. We divided the crack modes to crack free (mode 1), micro-crack (mode 2), shaded area (mode 3), and breakdown (mode 4). Using a dataset of 12 different solar cell samples, we have found that there are no hotspots detected for a solar cell affected by modes 1 or 2. However, we discovered that the solar cell is likely to have hotspots if affected by crack mode 3 or 4, with an expected increase in the temperature from 25\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ $$\end{document}∘C to 100\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ $$\end{document}∘C. Additionally, we have noticed that an increase in the shading ratio in solar cells can cause severe hotspots. For this reason, we observed that the worst-case scenario for a hotspot to develop is at shading ratios of 40% to 60%, with an identified increase in the cell temperature from 25\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ $$\end{document}∘C to 105\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ $$\end{document}∘C.

Enhanced Performance of Nanotextured Silicon Solar Cells with Excellent Light-Trapping Properties

Light-trapping nanostructures have been widely used for improving solar cells’ performance, but the higher surface recombination and poor electrode contact introduced need to be addressed. In this work, silicon nanostructures were synthesized via silver-catalyzed etching to texturize solar cells. Atomic-layer-deposited Al2O3 passivated the nanotextured cells. A surface recombination velocity of 126 cm/s was obtained, much lower than the 228 cm/s of the SiNX-passivated one. Additionally, the open-circuit voltage (VOC) of the nanotextured cells improved significantly from 582 to 610 mV, as did the short-circuit current (JSC) from 25.5 to 31 mA/cm2. Furthermore, the electrode contact property was enhanced by light-induced plating. A best efficiency of 13.3% for nano-textured cells was obtained, which is higher than the planar cell’s 12%.

Nanostructures for Light Trapping in Thin Film Solar Cells

Thin film solar cells are one of the important candidates utilized to reduce the cost of photovoltaic production by minimizing the usage of active materials. However, low light absorption due to low absorption coefficient and/or insufficient active layer thickness can limit the performance of thin film solar cells. Increasing the absorption of light that can be converted into electrical current in thin film solar cells is crucial for enhancing the overall efficiency and in reducing the cost. Therefore, light trapping strategies play a significant role in achieving this goal. The main objectives of light trapping techniques are to decrease incident light reflection, increase the light absorption, and modify the optical response of the device for use in different applications. Nanostructures utilize key sets of approaches to achieve these objectives, including gradual refractive index matching, and coupling incident light into guided modes and localized plasmon resonances, as well as surface plasmon polariton modes. In this review, we discuss some of the recent developments in the design and implementation of nanostructures for light trapping in solar cells. These include the development of solar cells containing photonic and plasmonic nanostructures. The distinct benefits and challenges of these schemes are also explained and discussed.

Using a Neural Network to Improve the Optical Absorption in Halide Perovskite Layers Containing Core-Shells Silver Nanoparticles

Core-shells metallic nanoparticles have the advantage of possessing two plasmon resonances, one in the visible and one in the infrared part of the spectrum. This special property is used in this work to enhance the efficiency of thin film solar cells by improving the optical absorption at both wavelength ranges simultaneously by using a neural network. Although many thin-film solar cell compositions can benefit from such a design, in this work, different silver core-shell configurations were explored inside a Halide Perovskite (CH₃NH₃PbI₃) thin film. Because the number of potential configurations is infinite, only a limited number of finite difference time domain (FDTD) simulations were performed. A neural network was then trained with the simulation results to find the core-shells configurations with optimal optical absorption across different wavelength ranges. This demonstrates that core-shells nanoparticles can make an important contribution to improving solar cell performance and that neural networks can be used to find optimal results in such nanophotonic systems.

Optical Management with Nanoparticles for a Light Conversion Efficiency Enhancement in Inorganic γ-CsPbI3 Solar Cells

Recently, γ-CsPbI₃ perovskite solar cells (PSCs) have shown potential applications in optoelectronic devices, due to their high thermal stability. However, the incomplete utilization of the solar spectra especially in the near-infrared (ca. 46%) range significantly limits the power conversion efficiency (PCE). Herein, core-shell-structured NaLuF₄:Yb,Er@NaLuF₄ upconversion nanoparticles (UCNPs) have been successfully synthesized and integrated into the hole transport layer for improving PCE in γ-CsPbI₃ PSCs. Compared with the reference one, the short-circuit current density ( J_SC) and PCE of the optimized device reached up to 19.17 mA/cm² (18.81 mA/cm²) and 15.86% (15.51%), respectively. Actually, due to the ultralow photoluminescence quantum yield (PLQY, < 1%) obtained in UCNPs now, we proved the generally recognized upconversion effect of UCNPs in solar cells (adjusting the light absorption edge from the visible toward NIR range for extending the spectral absorption) was negligible. A further study found the UCNPs in the PSCs primarily served as scattering centers, which is beneficial to extend the sunlight optical path by combining with scattering and reflecting sunlight, leading to producing more photoelectric current. This study suggests a new insight into understanding the underlying mechanism of UCNPs in the PSCs and provides a promising strategy via light scattering effect to enhance the device performance.

Nonnoble-Metal-Based Plasmonic Nanomaterials: Recent Advances and Future Perspectives

The application scope of plasmonic nanostructures is rapidly expanding to keep pace with the ongoing development of various scientific findings and emerging technologies. However, most plasmonic nanostructures heavily depend on rare, expensive, and extensively studied noble metals such as Au and Ag, with the limited choice of elements hindering their broad and practical applications in a wide spectral range. Therefore, abundant and inexpensive nonnoble metals have attracted attention as new plasmonic nanomaterial components, allowing these nonnoble-metal-based materials to be used in areas such as photocatalysis, sensing, nanoantennas, metamaterials, and magnetoplasmonics with new compositions, structures, and properties. Furthermore, the use of nonnoble metal hybrids results in newly emerging or synergistic properties not observed from single-metal component systems. Here, the synthetic strategies and recent advances in nonnoble-metal-based plasmonic nanostructures comprising Cu, Al, Mg, In, Ga, Pb, Ni, Co, Fe, and related hybrids are highlighted, and a discussion and perspectives in their synthesis, properties, applications, and challenges are presented.