Noble metal nanoparticles have been extensively studied to understand and apply their plasmonic responses, upon coupling with electromagnetic radiation, to research areas such as sensing, photocatalysis, electronics, and biomedicine. The plasmonic properties of metal nanoparticles can change significantly with changes in particle size, shape, composition, and arrangement. Thus, stabilization of the fabricated nanoparticles is crucial for preservation of the desired plasmonic behavior. Because plasmonic nanoparticles find application in diverse fields, a variety of different stabilization strategies have been developed. Often, stabilizers also function to enhance or improve the plasmonic properties of the nanoparticles. This review provides a representative overview of how gold and silver nanoparticles, the most frequently used materials in current plasmonic applications, are stabilized in different application platforms and how the stabilizing agents improve their plasmonic properties at the same time. Specifically, this review focuses on the roles and effects of stabilizing agents such as surfactants, silica, biomolecules, polymers, and metal shells in colloidal nanoparticle suspensions. Stability strategies for other types of plasmonic nanomaterials, lithographic plasmonic nanoparticle arrays, are discussed as well.

Stabilization of Silver and Gold Nanoparticles: Preservation and Improvement of Plasmonic Functionalities.

Plasmonic effects have been proposed as a solution to overcome the limited light absorption in thin-film photovoltaic devices, and various types of plasmonic solar cells have been developed. This review provides a comprehensive overview of the state-of-the-art progress on the design and fabrication of plasmonic solar cells and their enhancement mechanism. The working principle is first addressed in terms of the combined effects of plasmon decay, scattering, near-field enhancement, and plasmonic energy transfer, including direct hot electron transfer and resonant energy transfer. Then, we summarize recent developments for various types of plasmonic solar cells based on silicon, dye-sensitized, organic photovoltaic, and other types of solar cells, including quantum dot and perovskite variants. We also address several issues regarding the limitations of plasmonic nanostructures, including their electrical, chemical, and physical stability, charge recombination, narrowband absorption, and high cost. Next, we ...

Plasmonic Solar Cells: From Rational Design to Mechanism Overview.

Surface plasmons have recently been harnessed to carry out processes such as photovoltaic current generation, redox photochemistry, photocatalysis, and photodetection, all of which are enabled by separating energetic (hot) electrons and holes—processes that, previously, were the domain of semiconductor junctions. Currently, the power conversion efficiencies of systems using plasmon excitation are low. However, the very large electron/hole per photon quantum efficiencies observed for plasmonic devices fan the hope of future improvements through a deeper understanding of the processes involved and through better device engineering, especially of critical interfaces such as those between metallic and semiconducting nanophases (or adsorbed molecules). In this review, we focus on the physics and dynamics governing plasmon-derived hot charge carrier transfer across, and the electronic structure at, metal–semiconductor (molecule) interfaces, where we feel the barriers contributing to low efficiencies reside. We ...

Hot Charge Carrier Transmission from Plasmonic Nanostructures

Novel self-powered nanoscale photodetectors that can work without an external power source, which have great application potential in next-generation nanodevices that operate wirelessly and independently, are being widely studied. This review aims to give a comprehensive summary of the state-of-the-art research results on self-powered nanoscale photodetectors. An introduction of recent progress on Schottky junction photodetectors is provided. Two types of Schottky junctions are discussed in detail: metal-semiconductor and semiconductor-graphene junctions. Next, recent developments of p-n junction photodetectors are highlighted, including homojunction and heterojunction photodetectors. Then, piezo-phototronic effect enhanced photodetection performances of Schottky junctions and p-n junctions are discussed. Then, significant results on the photoelectrochemical-cell-based photodetector and integrated self-powered nanosystem are presented, followed by a systematic comparison of different types of photodetectors. Finally, a summary of the previous results is given, and the major challenges that need to be addressed in the future are outlined. The hope is that this review can provide valuable insights into the current status of self-powered photodetectors and spur new structure and device designs to further enhance photodetection performance.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/smll.201701848

Self-Powered Nanoscale Photodetectors.

/pdf/metal-oxide-nanostructures-for-sensor-applications-3fe10u79mn.pdf

Metal oxide nanostructures for sensor applications

Solution-processed solar cells are particularly suited to benefit from absorption enhancement by plasmonic nanoparticles, due to their transport-limited film thicknesses and the ease with which metal nanoparticles can be integrated into the materials. Despite practical demonstrations of performance enhancements, the overall benefits have so far been limited in scope to photocurrents well below the theoretical limits. In this Perspective, we critically evaluate the prospects for plasmonic enhancements in solution-processed thin-film solar cells. We give an overview of recent work, focusing on embedded plasmonic nanoparticles in organic, perovskite, and colloidal quantum dot solar cells. We then develop an intuitive effective medium model for embedded plasmonic nanostructures in photovoltaic thin films, evaluate the model in the context of previous results in the field, and use the model to provide a framework for identifying the most promising avenues for realizing plasmonic performance enhancements in sol...

http://pubs.acs.org/doi/pdf/10.1021/acsphotonics.5b00428

Plasmonic Nanoparticle Enhancement of Solution-Processed Solar Cells: Practical Limits and Opportunities

We report on the significant performance enhancement of SnO2 thin film ultraviolet (UV) photodetectors (PDs) through incorporation of CuO/SnO2 p-n nanoscale heterojunctions. The nanoheterojunctions are self-assembled by sputtering Cu clusters that oxidize in ambient to form CuO. We attribute the performance improvements to enhanced UV absorption, demonstrated both experimentally and using optical simulations, and electron transfer facilitated by the nanoheterojunctions. The peak responsivity of the PDs at a bias of 0.2 V improved from 1.9 A/W in a SnO2-only device to 10.3 A/W after CuO deposition. The wavelength-dependent photocurrent-to-dark current ratio was estimated to be ∼592 for the CuO/SnO2 PD at 290 nm. The morphology, distribution of nanoparticles, and optical properties of the CuO/SnO2 heterostructured thin films are also investigated.

/pdf/high-performing-visible-blind-photodetectors-based-on-sno2-4sqbavteur.pdf

High-performing visible-blind photodetectors based on SnO2/CuO nanoheterojunctions

Colloidal quantum dots (CQDs), are a promising candidate material for realizing colored and semitransparent solar cells, due to their band gap tunability, near infrared responsivity and solution-based processing flexibility. CQD solar cells are typically comprised of several optically thin active and electrode layers that are optimized for their electrical properties; however, their spectral tunability beyond the absorption onset of the CQD layer itself has been relatively unexplored. In this study, we design, optimize and fabricate multicolored and transparent CQD devices by means of thin film interference engineering. We develop an optimization algorithm to produce devices with controlled color characteristics. We quantify the tradeoffs between attainable color or transparency and available photocurrent, calculate the effects of non-ideal interference patterns on apparent device color, and apply our optimization method to tandem solar cell design. Experimentally, we fabricate blue, green, yellow, red and semitransparent devices and achieve photocurrents ranging from 10 to 15.2 mA/cm2 for the colored devices. We demonstrate semitransparent devices with average visible transparencies ranging from 27% to 32%, which match our design simulation results. We discuss how our optimization method provides a general platform for custom-design of optoelectronic devices with arbitrary spectral profiles.

Color-tuned and transparent colloidal quantum dot solar cells via optimized multilayer interference.

Dopant-Dependent Increase in Seebeck Coefficient and Electrical Conductivity in Blended Polymers with Offset Carrier Energies

Although record efficiencies in colloidal quantum dot (CQD) solar cells continue to increase, they are still demonstrated on impractically small-area devices. Concentrators can effectively enlarge the active area, allowing scaled-up energy harvesting. Here, we present an economical and scalable method to fabricate compact concentrators made from polydimethylsiloxane using 3D-printed molds, which are directly bonded to CQD solar cells. The resulting integrated systems deliver more than a 20-fold increase in photocurrent and power, as well as significant open circuit voltage enhancements, over the original cells. We use the integrated systems to identify limiting factors in CQD solar cell operation under high irradiance. Our method could pave the way to making practical high-power solution-processed solar cells.

Botong Qiu

Papers

Plasmonic Nanoparticle Enhancement of Solution-Processed Solar Cells: Practical Limits and Opportunities

High-performing visible-blind photodetectors based on SnO2/CuO nanoheterojunctions

Color-tuned and transparent colloidal quantum dot solar cells via optimized multilayer interference.

Dopant-Dependent Increase in Seebeck Coefficient and Electrical Conductivity in Blended Polymers with Offset Carrier Energies

Integrated Concentrators for Scalable High-Power Generation from Colloidal Quantum Dot Solar Cells