Showing papers on "Evaporation (deposition) published in 2020"

Isothermally crystallized perovskites at room-temperature

Abstract: The solution processability of photoactive halide perovskites differentiates them from traditional inorganic semiconducting materials that require multiple post-processing steps such as thermal/vacuum/blowing- and solvent-assisted treatment. Here we report a technical breakthrough of isothermally crystallizing high-quality perovskite films at room-temperature (RT) without the necessity of any post-processing. This process takes advantage of our discovery of a metastable intermediate of lower-dimensionality formed by amine-assisted crystallographic lattice expansion from an initial three-dimensional perovskite. Using in situ optoelectrical/chemical and ex situ structural characterizations, a detailed understanding of the low-dimensional metastable intermediate is developed. In conjunction with the metastable intermediate, the rapid evaporation of the solvent and amine facilitates ultra-fast crystallization at RT within seconds. This RT rapidly synthesized perovskite film exhibits a carrier diffusion length of 2.9 μm and {00} preferred orientation with an ultrahigh Lotgering factor of 97%. These films are highly compatible to conventional or inverted devices, demonstrating 22.3% and 23.1% power conversion efficiencies, respectively.

Characterization of e-beam evaporated Ge, YbF3, ZnS, and LaF3 thin films for laser-oriented coatings.

Abstract: Thin films of Ge, ZnS, YbF3, and LaF3 produced using e-beam evaporation on ZnSe and Ge substrates were characterized in the range of 0.4–12 µm. It was found that the Sellmeier model provides the best fit for refractive indices of ZnSe substrate, ZnS, and LaF3 films; the Cauchy model provides the best fit for YbF3 film. Optical constants of Ge substrate and Ge film as well as extinction coefficients of ZnS, YbF3, LaF3, and ZnSe substrate are presented in the frame of a non-parametric model. For the extinction coefficient of ZnS, the exponential model is applicable. Stresses in Ge, ZnS, YbF3, and LaF3 were estimated equal to (−50)MPa, (−400)MPa, 140 MPa, and 380 MPa, respectively. The surface roughness does not exceed 5 nm for all films and substrates.

Blackbody-Inspired Array Structural Polypyrrole-Sunflower Disc with Extremely High Light Absorption for Efficient Photothermal Evaporation.

Abstract: The three-dimensional (3D) structural design of solar evaporators has been considered as one of the most promising approaches toward enhancing photothermal performance by improving light absorption...

A new type low-cost, flexible and wearable tertiary nanocomposite sensor for room temperature hydrogen gas sensing.

Abstract: This paper reports on reduced graphene oxide (rGO), tin oxide (SnO2) and polyvinylidene fluoride (PVDF) tertiary nanocomposite thick film based flexible gas sensor. The nanocomposite of 0.90(PVDF) − 0.10[x(SnO2) − (1 − x)rGO] with different weight percentages (x = 0, 0.15, 0.30, 0.45, 0.6, 0.75, 0.90 and 1) have been prepared by the hot press method. Chromium (Cr) has been deposited on the surface by using E-beam evaporation system, which is used as electrode of the device. Crystal structure, morphology, and electrical characteristics of the device have been explored for the technological application. A correlation between crystallinity, morphology, and electrical properties with these thick films has also been established. The device has been tested at different hydrogen (H2) gas concentration as well as at different response times. A superior response of 0.90(PVDF) − 0.10[0.75(SnO2) − 0.25 rGO] nanocomposite thick film has been observed. Hence, this composition is considered as optimized tertiary nanocomposite for the hydrogen gas sensor application. The sensor response of 49.2 and 71.4% with response time 34 sec and 52 sec for 100 PPM and 1000 PPM H2 gas concentration respectively have been obtained. First time a new kind of low cost and flexible polymer based nanocomposite thick film gas sensor has been explored.

Laser-Synthesized Rutile TiO2 with Abundant Oxygen Vacancies for Enhanced Solar Water Evaporation

Abstract: Titanium dioxide (TiO2) as a common photothermal material usually faces with low photothermal conversion efficiency, mainly owing to the little utilization of visible (Vis) and near-infrared (NIR) ...

TiN, ZrN, and HfN Nanoparticles on Nanoporous Aluminum Oxide Membranes for Solar-Driven Water Evaporation and Desalination

Abstract: Water desalination via thermal evaporation using plasmonic nanostructures which harness and convert solar irradiation to provide the requisite heat input is gaining interest as a scalable and susta...

Effect of film thickness and evaporation rate on co-evaporated SnSe thin films for photovoltaic applications

Abstract: SnSe thin films were deposited by a co-evaporation method with different film thicknesses and evaporation rates. A device with a structure of soda-lime glass/Mo/SnSe/CdS/i-ZnO/ITO/Ni/Al was fabricated. Device efficiency was improved from 0.18% to 1.02% by a film thickness of 1.3 μm and evaporation rate of 2.5 A S−1 via augmentation of short-circuit current density and open-circuit voltage. Properties (electrical, optical, structural) and scanning electron microscopy measurements were compared for samples. A SnSe thin-film solar cell prepared with a film thickness of 1.3 μm and evaporation rate of 2.5 A S−1 had the highest electron mobility, better crystalline properties, and larger grain size compared with the other solar cells prepared. These data can be used to guide growth of high-quality SnSe thin films, and contribute to development of efficient SnSe thin-film solar cells using an evaporation-based method.

Ultrathin sputter-deposited plasmonic silver nanostructures

Abstract: In this study, ultrathin silver plasmonic nanostructures are fabricated by sputter deposition on substrates patterned by nanoimprint lithography, without additional lift-off processes. Detailed investigation of silver growth on different substrates results in a structured, defect-free silver film with thickness down to 6 nm, deposited on a thin layer of doped zinc oxide. Variation of the aspect ratio of the nanostructure reduces grain formation at the flanks, allowing for well-separated disk and hole arrays, even though conventional magnetron sputtering is less directional than evaporation. The resulting disk–hole array features high average transmittance in the visible range of 71% and a strong plasmonic dipole resonance in the near-infrared region. It is shown that the ultrathin Ag film exhibits even lower optical losses in the NIR range compared to known bulk optical properties. The presented FDTD simulations agree well with experimental spectra and show that for defect-free, ultrathin Ag nanostructures, bulk optical properties of Ag are sufficient for a reliable simulation-based design.

Morphological, Optical, and Electrical Properties of p-Type Nickel Oxide Thin Films by Nonvacuum Deposition

Abstract: In this study, a p-type 2 at% lithium-doped nickel oxide (abbreviation L2NiO) solution was prepared using Ni(NO3)2·6H2O, and LiNO3·L2NiO thin films were deposited using an atomizer by spraying the L2NiO solution onto a glass substrate. The sprayed specimen was heated at a low temperature (140 °C) and annealed at different high temperatures and times. This method can reduce the evaporation ratio of the L2NiO solution, affording high-order nucleating points on the substrate. The L2NiO thin films were characterized by X-ray diffraction, scanning electron microscopy, UV-visible spectroscopy, and electrical properties. The figure of merit (FOM) for L2NiO thin films was calculated by Haacke's formula, and the maximum value was found to be 5.3 × 10-6 Ω-1. FOM results revealed that the L2NiO thin films annealed at 600 °C for 3 h exhibited satisfactory optical and electrical characteristics for photoelectric device applications. Finally, a transparent heterojunction diode was successfully prepared using the L2NiO/indium tin oxide (ITO) structure. The current-voltage characteristics revealed that the transparent heterojunction diode exhibited rectifying properties, with a turn-on voltage of 1.04 V, a leakage current of 1.09 × 10-4 A/cm2 (at 1.1 V), and an ideality factor of n = 0.46.

Scalable All‐Evaporation Fabrication of Efficient Light‐Emitting Diodes with Hybrid 2D–3D Perovskite Nanostructures

Abstract: Quasi-2D (Q2D) lead halide perovskites have emerged as promising materials for light-emitting diodes (LEDs) due to their tunable emission, sloweddown carrier diffusion, and improved stability. However, they are primarily fabricated through solution methods, which hinders its large-scale manufacture and practical applications. Physical-vapor-deposition (PVD) methods have well demonstrated the capability for reproducible, scalable, and layerby-layer fabrication of high quality organic/inorganic thin films. Herein, for the first time, the full-evaporation fabrication of organic–inorganic hybrid ((BA)2Csn−1PbnBr3n+1) Q2D–3D PeLEDs is demonstrated. The morphology and crystal phase of the perovskite are controlled from 3D to 2D by modulating material composition, annealing temperature, and film thicknesses. The confinement of carriers in 3D layers and the energy funnel effect are discovered and discussed. Importantly, a record high external quantum efficiency (EQE) of 5.3% based on evaporation method is achieved. Moreover, a centimeterscale PeLED (1.5 cm × 2 cm) is obtained. Furthermore, the T50 lifetime of the device with an initial brightness of 100 cd m−2 is found to be 90 min with a thin layer PMMA passivation, which is among the longest for all PVD processed PeLEDs. Overall, this work casts a solid stepping stone towards the fabrication of high-performance PeLEDs on a large-scale.

Revealing the Interplay between Charge Transport, Luminescence Efficiency, and Morphology in Organic Light‐Emitting Diode Blends

Abstract: Phosphorescent emissive materials in organic light-emitting diodes (OLEDs) manufactured using evaporation are usually blended with host materials at a concentration of 3–15 wt% to avoid concentration quenching of the luminescence. Here, experimental measurements of hole mobility and photoluminescence are related to the atomic level morphology of films created using atomistic nonequilibrium molecular dynamics simulations mimicking the evaporation process with similar guest concentrations as those used in operational test devices. For blends of fac-tris[2-phenylpyridinato-C2,N]iridium(III) [Ir(ppy)] in tris(4-carbazoyl-9-ylphenyl)amine (TCTA), it is found that clustering of the Ir(ppy) (surface of the molecules within ≈0.4 nm) in the simulated films is directly relatable to the experimentally-measured hole mobility. Films containing 1–10 wt% of Ir(ppy) in TCTA have a mobility of up to two orders of magnitude lower (≈10 cm V s) than the neat TCTA film, which is consistent with the Ir(ppy) molecules acting as hole traps due to their smaller ionization potential. Comparison of the simulated film morphologies with the measured photoluminescence properties shows that for luminescence quenching to occur, the Ir(ppy) molecules have to have their ligands partially overlapping. Thus, the results show that the effect of guest interactions on charge transport and luminescence are markedly different for OLED light-emitting layers.

All-Inorganic CsPbBr3 Perovskite Films Prepared by Single Source Thermal Ablation.

Abstract: Hybrid organo-lead halide perovskites are becoming the benchmark material for next generation photovoltaics and a very important player for other applications such as photodetectors and light emitting diodes. Nevertheless, the most important issue hindering the large-scale application of these materials remains their intrinsic instability due to the organic cation. Although the substitution with inorganic cesium (Cs) enhances stability, in most cases solution deposition methods of fully inorganic perovskites result in high surface roughness and poor surface coverage. This work reports on the evaporation of the CsPbBr3 precursor by Single Source Thermal Ablation, showing that just after deposition films consist of a mixture of CsPbBr3, CsPb2Br5, and Cs4PbBr6 due to a vertical composition gradient. We point out that mild post deposition treatments lead to the conversion of CsPb2Br5 and Cs4PbBr6 into CsPbBr3 due to its higher thermodynamic stability. Conversion results into smooth and pinhole-free CsPbBr3 films with good light absorption and emission properties. We demonstrate the suitability of obtained films for planar devices by preparing perovskite-based pure-green light emitting diodes, thus promoting Single Source Thermal Ablation as a promising alternative deposition technique for all-inorganic perovskite-based devices.

Solution and Evaporation Hybrid Approach to Enhance the Stability and Pattern Resolution Characteristics of Organic Light-Emitting Diodes.

Abstract: The solution process and vacuum evaporation, both fabrication methods for conventional organic light-emitting diodes (OLEDs), are intrinsically restricted with regard to their ability to enhance pa...

Field evaporation and atom probe tomography of pure water tips.

Abstract: Measuring biological samples by atom probe tomography (APT) in their natural environment, i.e. aqueous solution, would take this analytical method, which is currently well established for metals, semi-conductive materials and non-metals, to a new level. It would give information about the 3D chemical structure of biological systems, which could enable unprecedented insights into biological systems and processes, such as virus protein interactions. For this future aim, we present as a first essential step the APT analysis of pure water (Milli-Q) which is the main component of biological systems. After Cryo-preparation, nanometric water tips are field evaporated with assistance by short laser pulses. The obtained data sets of several tens of millions of atoms reveal a complex evaporation behavior. Understanding the field evaporation process of water is fundamental for the measurement of more complex biological systems. For the identification of the individual signals in the mass spectrum, DFT calculations were performed to prove the stability of the detected molecules.

Vertically Aligned Al-Doped ZnO Nanowire Arrays as Efficient Photoanode for Dye-Sensitized Solar Cells

Abstract: In this communication, we report on the synthesis of vertically aligned aluminium (Al)-doped ZnO (ZnO:Al) nanowire (NW) thin films on FTO-coated glass substrates and their use as photoanode in dye-sensitized solar cells (DSSC). Very thin Al layers (∼3 nm, ∼6 nm and ∼10 nm) were deposited onto chemically synthesized ZnO nanowire film by electron-beam evaporation. The films were then subjected to rapid thermal annealing to incorporate different amounts of Al (∼0.98 at.%, 1.94 at.% and ∼2.89 at.%) into the ZnO nanowires. Optical, microstructural and compositional study of the films confirmed the growth of highly transparent and well-aligned ZnO:Al nanowires with a hexagonal crystal structure. The basic DSSC structure was fabricated using both undoped ZnO nanowire and ZnO:Al nanowire thin films as photoanode. In both cases, commercially available N3 dye was used as a photosensitizer, iodide/tri-iodide solution as electrolyte and FTO-coated glass as counter electrode. A significant increase in short-circuit current was observed, from 1.3 mA cm−2 for the pristine ZnO nanowire film-based DSSC to 4.4 mA cm−2 for the ZnO:Al (2.89 at.%) nanowire film-based DSSC. The overall power conversion efficiency (PCE) was also found to increase from 0.13% (for pristine ZnO nanowire thin film) to 0.49% for the ZnO:Al thin film-based DSSC.