Although the concept of using local surface plasmon resonance based nanoantenna for photodetection well below the semiconductor band edge has been demonstrated previously, the nature of local surface plasmon resonance based devices cannot meet many requirements of photodetection applications. Here we propose the concept of deep-trench/thinmetal (DTTM) active antenna that take advantage of surface plasmon resonance phenomena, three-dimensional cavity effects, and large-area metal/semiconductor junctions to effectively generate and collect hot electrons arising from plasmon decay and, thereby, increase photocurrent. The DTTM-based devices exhibited superior photoelectron conversion ability and high degrees of detection linearity under infrared light of both low and high intensity. Therefore, these DTTM-based devices have the attractive properties of high responsivity, extremely low power consumption, and polarization-insensitive detection over a broad bandwidth, suggesting great potential for use in photodetection and on-chip Si photonics in many applications of telecommunication fields.

In this paper, we report the optical constants (refractive index, extinction coefficient) of self-assembled hollow gold nanoparticle (HGN) monolayers determined through spectroscopic ellipsometry (SE). We prepared a series of HGNs exhibiting various morphologies and surface plasmon resonance (SPR) properties. The extinction coefficient (k) curves of the HGN monolayers exhibited strong SPR peaks located at wavelengths that followed similar trends to those of the SPR positions of the HGNs in solution. The refractive index (n) curves exhibited an abnormal dispersion that was due to the strong SPR extinction. The values of Δn and k max both correlated linearly with the particle number densities. From a comparison of the optical constant values of HGNs with those of solid Au nanoparticles (NPs), we used SE measurements to demonstrate a highly sensitive Si-based chemical sensor. HGNs display a slightly lower value of k at the SPR peak but a much higher sensitivity to changes in the surrounding medium than do solid Au NPs.

In this paper, we demonstrate the strong influence of the regioregularity (RR) of poly-(3-hexylthiophene) (P3HT) on the optical anisotropy of hybrid P3HT/fullerene films before and after thermal annealing. We determined the conversion efficiency and characterized the optical anisotropy of P3HT/6,6-phenyl-C61-butyric acid methyl ester (PCBM) blends featuring various values of RR. Unlike grazing-incidence X-ray diffraction analysis, optical anisotropic measurement provides a clear and convenient view of the polymer orientation and the device anisotropic absorption at the same time. By calculating the in-plane and out-of-plane optical constants (extinction coefficients and refractive indices), we determined that the optical anisotropy of P3HT/PCBM films was improved in both orientations upon increasing the RR. Upon increasing the thermal annealing temperature, the main chains of high-RR P3HT were converted from an amorphous structure to an alignment parallel to the substrate, resulting in higher optical anisotropy. The degree of anisotropy of the high-RR P3HT/ PCBM blend was up to six times higher than that of the low-RR sample. This strong RR effect on optical anisotropy was also evident in the power conversion efficiency of large-area P3HT/PCBMbased organic solar cells.

Convenient, rapid, and accurate detection of chemical and biomolecules would be a great benefit to medical, pharmaceutical, and environmental sciences. Many chemical and biosensors based on metal nanoparticles (NPs) have been developed. However, as a result of the inconvenience and complexity of most of the current preparation techniques, surface plasmon-based test papers are not as common as, for example, litmus paper, which finds daily use. In this paper, we propose a convenient and practical technique, based on the photothermal effect, to fabricate the plasmonic test paper. This technique is superior to other reported methods for its rapid fabrication time (a few seconds), large-area throughput, selectivity in the positioning of the NPs, and the capability of preparing NP arrays in high density on various paper substrates. In addition to their low cost, portability, flexibility, and biodegradability, plasmonic test paper can be burned after detecting contagious biomolecules, making them safe and eco-friendly.

In this study, the phenomenon of light trapping in Si solar cells coated with metal (Au) and dielectric (TiO 2 , SiO 2 ) nanoparticles (NPs) is systematically investigated. In contrast to previous reports, herein it is proposed that the photocurrent enhancement of solar cells should be attributed to the limited antirefl ection ability of the Au NP arrays. In other words, the Au NP arrays might not enhance the absorption of the active layer in cells when no light is refl ected from the air-substrate interface. Therefore, the Au NPs are replaced with dielectric NPs, which possess lower extinction coeffi cients, and then the antirefl ection property of the TiO 2 NP arrays is optimized. A simple, rapid, and cheap solution-based method is used to prepare close-packed TiO 2 NP fi lms on Si solar cells; these devices exhibit a uniform and remarkable increase (ca. 30%) in their photocurrents. To the best of the authors' knowledge, this uniform photocurrent enhancement is greater than those obtained from previously reported metal and dielectric NP-enhanced Si wafer-based solar cells.