Synergetic Exterior and Interfacial Approaches by Colloidal Carbon Quantum Dots for More Stable Perovskite Solar Cells Against UV.

The achievement of both efficiency and stability in perovskite solar cells (PSCs) remains a challenging and actively researched topic. In particular, among different environmental factors, ultraviolet (UV) photons play a pivotal role in contributing to device degradation. In this work, by harvesting simultaneously both the optical and the structural properties of bottom-up-synthesized colloidal carbon quantum dots (CQDs), a cost-effective means is provided to circumvent the UV-induced degradation in PSCs without scarification on their power conversion efficiencies (PCEs).

Luminescence enhancement effects on nanostructured perovskite thin films for Er/Yb-doped solar cells.

Recent attempts to improve solar cell performance by increasing their spectral absorption interval incorporate up-converting fluorescent nanocrystals on the structure. These nanocrystals absorb low energy light and emit higher energy photons that can then be captured by the solar cell active layer. However, this process is very inefficient and it needs to be enhanced by different strategies.

Long-Term Stable Near-Infrared-Short-Wave-Infrared Photodetector Driven by the Photothermal Effect of Polypyrrole Nanostructures.

Polypyrrole (PPy) is a conductive polymer and widely applied in different applications owing to its broadband absorption in the UV-visible, near-infrared (NIR), and short-wave-infrared (SWIR) spectrum, excellent conductivity, and strong photothermal effect. In this work, we explored for the first time the photothermal effect of PPy nanoparticles (PPy-NPs) in a photothermal-induced detector structure and developed a new type of air-stable hybrid PPy-NPs/Pt photodetector (PD) with NIR/SWIR sensitivity. By combining PPy-NPs with a platinum (Pt)-resistive pattern, we fabricated PPy-NPs/Pt PDs that are sensitive to illumination in the wavelength range from 800 to 2000 nm.

TiO Nanocolumn Arrays for More Efficient and Stable Perovskite Solar Cells.

Organic-inorganic hybrid perovskite solar cells have attracted much attention due to their high power conversion efficiency (>25%) and low-cost fabrication. Yet, improvements are still needed for more stable and higher-performing solar cells. In this work, a series of TiO nanocolumn photonic structures have been intentionally fabricated on half of the compact TiO-coated fluorine-doped tin oxide substrate by glancing angle deposition with magnetron sputtering, a method particularly suitable for industrial applications due to its high reliability and reduced cost when coating large areas.

Heavy-Metal-Free Flexible Hybrid Polymer-Nanocrystal Photodetectors Sensitive to 1.5 μm Wavelength.

Photodetection in the short-wave infrared (SWIR) wavelength window represents one of the core technologies allowing for many applications. Most current photodetectors suffer from high cost due to the epitaxial growth requirements and the ecological issue due to the use of highly toxic heavy-metal elements. Toward alternative SWIR photodetection strategies, in this work, high-performance heavy-metal-free flexible photodetectors sensitive to λ = 1.

Hybrid plasmonic gold-nanorod-platinum short-wave infrared photodetectors with fast response.

Short-wave infrared (SWIR) photodetectors, sensitive to the wavelength range between 1 and 3 μm, are essential components for various applications, which constantly demand devices with a lower cost, a higher responsivity and a faster response. In this work, a new hybrid device structure is presented for SWIR photodetection composing a coupling between solution-processed colloidal plasmonic gold (Au) NRs and a morphology-optimized resistive platinum (Pt) microwire. Pt microwires harvest efficiently the photothermal effect of Au NRs and in return generating a change of device resistance.

Mapping plasmon-enhanced upconversion fluorescence of Er/Yb-doped nanocrystals near gold nanodisks.

Fluorescence enhancement effects have many potential applications in the domain of biochemical sensors and optoelectronic devices. Here, the emission properties of up-converting nanocrystals near nanostructures that support surface plasmon resonances have been investigated. Gold nanodisks of various diameters were illuminated in the near-infrared (λ = 975 nm) and a single fluorescent nanocrystal glued at the end of an atomic force microscope tip was scanned around them.

Short-Wave Infrared Sensor by the Photothermal Effect of Colloidal Gold Nanorods.

Photodetection in the short-wave infrared (SWIR) spectrum is a challenging task achieved often by costly low bandgap compound semiconductors involving highly toxic elements. In this work, an alternative low-cost approach is reported for SWIR sensors that rely on the plasmonic-induced photothermal effect of solution-processed colloidal gold nanorods (Au NRs). A series of uniform solution-processed Au NRs of various aspect ratios are prepared exhibiting a strong and well-defined longitudinal localized surface plasmon resonance (L-LSPR) maximum from 900 nm to 1.

Compact layer free mixed-cation lead mixed-halide perovskite solar cells.

Thickness-tunable and compact FACsPb(IBr) perovskite thin films are achieved with a large grain size up to 12 microns. They are then employed to fabricate functional solar cells with a simplified planar structure without the use of electron-transport (ETL) layers. These results are highly encouraging for the future large-scale fabrication of FACsPb(IBr)-based solar cells.

Plasmonic-enhanced perovskite-graphene hybrid photodetectors.

The surface plasmonic effect of metal nanostructures is a promising method to boost the performance of optoelectronic devices such as solar cells and photodetectors. In this report, gold nanoparticles with surface plasmon resonance localized at about 530 nm were synthesized and integrated into graphene/methylammonium lead iodide perovskite (CH3NH3PbI3) hybrid photodetectors. Compared with pristine graphene-CH3NH3PbI3 devices, a device with gold nanoparticles embedded has a doubly higher photo-responsivity as well as a faster photoresponse speed.

Parallel collective resonances in arrays of gold nanorods.

In this work we discuss the excitation of parallel collective resonances in arrays of gold nanoparticles. Parallel collective resonances result from the coupling of the nanoparticles localized surface plasmons with diffraction orders traveling in the direction parallel to the polarization vector. While they provide field enhancement and delocalization as the standard collective resonances, our results suggest that parallel resonances could exhibit greater tolerance to index asymmetry in the environment surrounding the arrays.

Note: A scanning thermal probe microscope that operates in liquids.

We have developed a scanning thermal probe microscope that operates in liquid environments. The thermal sensor is a fluorescent particle glued at the end of a sharp tungsten tip. Since light emission is a strongly thermally sensitive effect, the measurement of the particle fluorescence variations allows the determination of the temperature.

Tuning temperature and size of hot spots and hot-spot arrays.

By using scanning thermal microscopy, it is shown that nanoscale constrictions in metallic microwires deposited on an oxidized silicon substrate can be tuned in terms of temperature and confinement size. High-resolution temperature maps indeed show that submicrometer hot spots and hot-spot arrays are obtained when the SiO(2) layer thickness decreases below 100 nm. When the SiO(2) thickness becomes larger, heat is less confined in the vicinity of the constrictions and laterally spreads all along the microwire.

Scanning thermal imaging by near-field fluorescence spectroscopy.

A scanning thermal microscope that uses a fluorescent particle as a temperature probe has been developed. The particle, made of a rare-earth ion-doped fluoride glass, is glued at the extremity of a sharp tungsten tip and scanned on the surface of an electronic device. The temperature of the device is determined by measuring the fluorescence spectrum of the particle at every point on the surface and by comparing the intensity variations of two emission lines.

Near-field scattered by a single nanoslit in a metal film.

Using a scanning near-field optical microscope, we visualize, in three dimensions, the electromagnetic field distribution near an isolated slit aperture in a thin gold film. At the metal-air interface and for a TM incident polarization, we confirm some recently observed results and show that the slit generates two kinds of surface waves: a slowly decaying surface plasmon polariton and a quasi-cylindrical wave that decreases more rapidly when moving away from the slit. These waves are not generated for a TE incident polarization.

Fabrication and characterization of fluorescent rare-earth-doped glass-particle-based tips for near-field optical imaging applications.

Fluorescent rare-earth-doped glass particles glued to the end of an atomic force microscope tip have been used to perform scanning near-field optical measurements on nanostructured samples. The fixation procedure of the fluorescent fragment at the end of the tip is described in detail. The procedure consists of depositing a thin adhesive layer on the tip.

Interference effect in apertureless near-field fluorescence imaging.

Apertureless scanning near-field optical microscopy has been used to image fluorescent latex spheres with a resolution of a few tens of nanometers and good signal-to-noise ratio. The near-field fluorescence images reveal optical interference with several highly contrasted fringes located around the spheres. The origin of the interference is discussed in detail, and models are used to explain their formation.

Comparison of test images obtained from various configurations of scanning near-field optical microscopes.

The characteristics of a few experimental near-field optical microscopes, located in different laboratories, have been compared on the basis of their ability to image a well-defined submicrometer test object.