Plasmonic Metamaterial Perovskite Solar Cells: Fundamental Tradeoffs, Limitations, and Opportunities

Whether dispersal of plasmonic nanoparticles (NPs) within a perovskite active layer can increase the efficiency of solar cells is a long-standing question. It is well known that inclusion of metallic NPs in an active layer can boost the surrounding near-field intensity around them owing to the dipolar localized surface plasmon resonance (LSPR, also called antenna effect), which can increase light absorption by solar cells. However, the use of plasmonic NPs in perovskite solar cells has been barely reported, and it is not known whether inserting plasmonic NPs into a perovskite active layer produces any performance advantage compared with a pure perovskite counterpart. We explore the fundamental and practical limits of plasmonic metamaterial perovskite solar cells by applying effective medium theory and a detailed balance analysis. Our results indicate that an increase in effective refractive index of perovskite through dispersed plasmonic NPs can in principle enhance the performance of solar cells

Practical Limits of Achieving Artificial Magnetism and Effective Optical Medium by Using Self-Assembly of Metallic Colloidal Clusters

The self-assembly of metallic colloidal clusters (so called plasmonic metamolecules) has been viewed as a versatile, but highly effective approach for the materialization of the metamaterials exhibiting artificial magnetism at optical frequencies (including visible and near infrared (NIR) regimes). Indeed, several proofs of concepts of plasmonic metamolecules have been successfully demonstrated in both theoretical and experimental ways. Nevertheless, this self-assembly strategy has barely been used and still remains an underutilized method. For example, the self-assembly and optical utilization of the plasmonic metamolecules have been limited to the discrete unit of the structure; the materialization of effective optical medium made of plasmonic metamolecules is highly challenging. In this work, we theoretically exploited the practical limits of self-assembly technology for the fabrication of optical magnetic metamaterials

Ultralow-Loss Substrate for Nanophotonic Dark-Field Microscopy

For the colloidal nanophotonic structures, a transmission electron microscope (TEM) grid has been widely used as a substrate of dark-field microscopy because a nanometer-scale feature can be effectively determined by TEM imaging following dark-field microscopic studies. However, an optically lossy carbon layer has been implemented in conventional TEM grids. A broadband scattering from the edges of the TEM grid further restricted an accessible signal-to-noise ratio. Herein, we demonstrate that the freely suspended, ultrathin, and wide-scale transparent nanomembrane can address such challenges. We developed a 1 mm by 600 μm scale and 20 nm thick poly­(vinyl formal) nanomembrane, whose area is around 180 times wider than a conventional TEM grid, so that the possible broadband scattering at the edges of the grid was effectively excluded. Also, such nanomembranes can be formed without the assistance of carbon support; allowing us to achieve the highest signal-to-background ratio of scattering among other substrates