Photon Management in Two-Dimensional Disordered Media

Elaborating reliable and versatile strategies for efficient light coupling between free space and thin films is of crucial importance for new technologies in energy efficiency. Nanostructured materials have opened unprecedented opportunities for light management, notably in thin-film solar cells. Efficient coherent light trapping has been accomplished through the careful design of plasmonic nanoparticles and gratings, resonant dielectric particles and photonic crystals. Alternative approaches have used randomly-textured surfaces as strong light diffusers to benefit from their broadband and wide-angle properties. Here, we propose a new strategy for photon management in thin films that combines both advantages of an efficient trapping due to coherent optical effects and broadband/wide-angle properties due to disorder. Our approach consists in the excitation of electromagnetic modes formed by multiple light scattering and wave interference in two-dimensional random media. We show, by numerical calculations, that the spectral and angular responses of thin films containing disordered photonic patterns are intimately related to the in-plane light transport process and can be tuned through structural correlations. Our findings, which are applicable to all waves, are particularly suited for improving the absorption efficiency of thin-film solar cells and can provide a novel approach for high-extraction efficiency light-emitting diodes

Status report on emerging photovoltaics

\ua9 2023 Society of Photo-Optical Instrumentation Engineers (SPIE).This report provides a snapshot of emerging photovoltaic (PV) technologies. It consists of concise contributions from experts in a wide range of fields including silicon, thin film, III-V, perovskite, organic, and dye-sensitized PVs. Strategies for exceeding the detailed balance limit and for light managing are presented, followed by a section detailing key applications and commercialization pathways. A section on sustainability then discusses the need for minimization of the environmental footprint in PV manufacturing and recycling. The report concludes with a perspective based on broad survey questions presented to the contributing authors regarding the needs and future evolution of PV

Toxicity and cellular uptake of gold nanoparticles: what we have learned so far?

Gold nanoparticles have attracted enormous scientific and technological interest due to their ease of synthesis, chemical stability, and unique optical properties. Proof-of-concept studies demonstrate their biomedical applications in chemical sensing, biological imaging, drug delivery, and cancer treatment. Knowledge about their potential toxicity and health impact is essential before these nanomaterials can be used in real clinical settings. Furthermore, the underlying interactions of these nanomaterials with physiological fluids is a key feature of understanding their biological impact, and these interactions can perhaps be exploited to mitigate unwanted toxic effects. In this Perspective we discuss recent results that address the toxicity of gold nanoparticles both in vitro and in vivo, and we provide some experimental recommendations for future research at the interface of nanotechnology and biological systems

Optical Rotation Reversal in the Optical Response of Chiral Plasmonic Nanosystems: The Role of Plasmon Hybridization

Chirality is an important molecular property for structural analysis. Similarly, it has been shown that plasmonic chiral systems exhibit strong circular dichroism (CD) responses that can be used to determine the relative positions of their constituent plasmonic elements. Here we show that the sign of the circular dichroism spectrum in a plasmonic system can be controllably changed through small geometric perturbations that change the energetic ordering of the hybridized modes. This mechanism is distinct from geometrical changes that explicitly change the handedness of the system. In a simple system composed of two stacked L-shaped resonators we observe a reversal of the optical rotation spectral signature for small relative shifts, and we show through electromagnetic modeling and experiments on lithographically patterned samples that this is due to a rearrangement of the relative energies between modes. The plasmonic system allows for geometric perturbation along controlled directions and therefore offers more control than corresponding molecular examples. Interestingly, this strong sensitivity in the optical response encodes more spatial information into the optical spectrum, emphasizing the importance of chiral plasmonic assemblies for structural investigations on the nanoscale

Symmetry Breaking in Tetrahedral Chiral Plasmonic Nanoparticle Assemblies

Self-assembled plasmonic structures combine the specificity and tunability of chemical synthesis with collective plasmonic properties. Here we systematically explore the effects of symmetry breaking on the chiroptical response of an assembly of plasmonic nanoparticles using simulation. The design is based on a tetrahedral nanoparticle frame with two different types of nanoparticles, where chirality is induced by targeted stimuli that change the distance along one edge of the assembly. We show that the intensity, spectral position, and handedness of the CD response are tunable with small structural changes, making it usable as a nanoscale plasmonic ruler. We then build upon this initial design to show that the symmetry breaking principle may also be used to design a chiral pyramid using a mixture of different nanoparticle materials, which affords tunability over a broad spectral range, and retrieves nanoscale conformational changes over a range of length scales. (Figure Presented)