Low-Threshold Optical Bistability in the Graphene-Oxide Integrated Asymmetric Nanocavity at Visible Light Frequencies.

Here, we propose an optical bistable device structure with a few layers of graphene oxide integrated in the metal-dielectric-metal based asymmetric nanocavity. Through the light confinement in the nanocavity, the third order nonlinear absorption of graphene oxide can be significantly enhanced, which experimentally delivers low-threshold optical bistability at the visible wavelength of 532 nm with only 267 KW/cm intensity. In addition, the switching threshold can be further reduced via increasing the graphene oxide thickness, hence paving a new way for achieving tunable optical bistable devices at visible light frequencies.

Improving the Photovoltage of Blade-Coated MAPbI Perovskite Solar Cells via Surface and Grain Boundary Passivation with π-Conjugated Phenyl Boronic Acids.

High-density electronic defects at the surfaces and grain boundaries (GBs) of perovskite materials are the major contributor to suppressing the power conversion efficiency (PCE) and deteriorating the long-term stability of the solar devices. Hence, the judicious selection of chemicals for the passivation of trap states has been regarded as an effective strategy to enhance and stabilize the photovoltaic performance of solar devices. Here, we systematically investigated the passivation effects of four organic π-conjugated phenylboronic acid molecules: phenylboronic acid, 2-amino phenylboronic acid (2a), 3-amino phenylboronic acid (3a), and 4-amino phenylboronic acid (4a) by adding them into the methylammonium lead iodide (MAPbI) precursor solution.

Temperature-Assisted Crystal Growth of Photovoltaic α-Phase FAPbI Thin Films by Sequential Blade Coating.

Formamidinium lead triiodide (FAPbI) exhibits the smallest band gap among lead halide perovskites, which is more desirable for solar cell applications compared to methylammonium-based counterparts. However, it remains a big challenge to prepare phase-pure α-FAPbI in addition to controlling the crystal morphology during film formation. Herein, we developed a temperature-assisted crystal growth to prepare high-quality thin films of α-FAPbI by sequential blade coating.

A Critical Review on Crystal Growth Techniques for Scalable Deposition of Photovoltaic Perovskite Thin Films.

Although the efficiency of small-size perovskite solar cells (PSCs) has reached an incredible level of 25.25%, there is still a substantial loss in performance when switching from small size devices to large-scale solar modules. The large efficiency deficit is primarily associated with the big challenge of coating homogeneous, large-area, high-quality thin films via scalable processes.

Ultra-broadband all-dielectric metamaterial thermal emitter for passive radiative cooling.

Passive radiative cooling, which pumps heat to outer space via thermal radiation, has been a promising energy free technology to maintain the earth surface temperature. Nighttime radiative cooling technology is quite mature, while daytime radiative cooling still poses many challenges due to the requirement of minimization of incident solar absorption and maximization of the mid-infrared emissivity in the atmospheric transparency windows. However, the mid-infrared emissivity efficiency of natural materials is usually poor, providing a low cooling efficiency and the realization of a high performance daytime radiative cooler is still quite challenge.

A Generalized Crystallization Protocol for Scalable Deposition of High-Quality Perovskite Thin Films for Photovoltaic Applications.

Metal halide perovskite solar cells (PSCs) have raised considerable scientific interest due to their high cost-efficiency potential for photovoltaic solar energy conversion. As PSCs already are meeting the efficiency requirements for renewable power generation, more attention is given to further technological barriers as environmental stability and reliability. However, the most major obstacle limiting commercialization of PSCs is the lack of a reliable and scalable process for thin film production.

Laser-Splashed Three-Dimensional Plasmonic Nanovolcanoes for Steganography in Angular Anisotropy.

Planar optics constructed from subwavelength artificial atoms have been suggested as a route to the physical realization of steganography with controlled intrinsic redundancy at single-pixel levels. Unfortunately, two-dimensional geometries with uniform flat profiles offer limited structural redundancy and make it difficult to create advanced crypto-information in multiplexed physical divisions. Here, we reveal that splashing three-dimensional (3D) plasmonic nanovolcanoes could allow for a steganographic strategy in angular anisotropy, with high resolution, full coloration, and transient control of structural profiles.

Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate.

Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency.

Intrinsically core-shell plasmonic dielectric nanostructures with ultrahigh refractive index.

Topological insulators are a new class of quantum materials with metallic (edge) surface states and insulating bulk states. They demonstrate a variety of novel electronic and optical properties, which make them highly promising electronic, spintronic, and optoelectronic materials. We report on a novel conic plasmonic nanostructure that is made of bulk-insulating topological insulators and has an intrinsic core-shell formation.

Significant light absorption enhancement in silicon thin film tandem solar cells with metallic nanoparticles.

Enhancing the light absorption in microcrystalline silicon bottom cell of a silicon-based tandem solar cell for photocurrent matching holds the key to achieving the overall solar cell performance breakthroughs. Here, we present a concept for significantly improving the absorption of both subcells simultaneously by simply applying tailored metallic nanoparticles both on the top and at the rear surfaces of the solar cells. Significant light absorption enhancement as large as 56% has been achieved in the bottom subcells.

Ultraviolet Plasmonic Aluminium Nanoparticles for Highly Efficient Light Incoupling on Silicon Solar Cells.

Plasmonic metal nanoparticles supporting localized surface plasmon resonances have attracted a great deal of interest in boosting the light absorption in solar cells. Among the various plasmonic materials, the aluminium nanoparticles recently have become a rising star due to their unique ultraviolet plasmonic resonances, low cost, earth-abundance and high compatibility with the complementary metal-oxide semiconductor (CMOS) manufacturing process. Here, we report some key factors that determine the light incoupling of aluminium nanoparticles located on the front side of silicon solar cells.

4-fold photocurrent enhancement in ultrathin nanoplasmonic perovskite solar cells.

Although perovskite materials have been widely investigated for thin-film photovoltaic devices due to the potential for high efficiency, their high toxicity has pressed the development of a solar cell structure of an ultra-thin absorber layer. But insufficient light absorption could be a result of ultra-thin perovskite films. In this paper, we propose a new nanoplasmonic solar cell that integrates metal nanoparticles at its rear/front surfaces of the perovskite layer.

Graphenized carbon nanofiber: a novel light-trapping and conductive material to achieve an efficiency breakthrough in silicon solar cells.

An innovative 1D material--graphenized carbon nanofiber--is designed and synthesized. The nanofiber exhibits superior light-scattering properties, ultralow absorption loss, and high electrical conductivity, and enables a wide range of applications. Simply integrating the nanofibers with the state-of-the-art silicon solar cells leads to a leaping efficiency boost of 3.

Broadband enhancement in thin-film amorphous silicon solar cells enabled by nucleated silver nanoparticles.

Recently plasmonic effects have gained tremendous interest in solar cell research because they are deemed to be able to dramatically boost the efficiency of thin-film solar cells. However, despite of the intensive efforts, the desired broadband enhancement, which is critical for real device performance improvement, has yet been achieved with simple fabrication and integration methods appreciated by the solar industry. We propose in this paper a novel idea of using nucleated silver nanoparticles to effectively scatter light in a broadband wavelength range to realize pronounced absorption enhancement in the silicon absorbing layer.