Reactive Deposition Method Research Articles

Synergistic Enhancement of Efficient Perovskite/Quantum Dot Tandem Solar Cells Based on Transparent Electrode and Band Alignment Engineering

AbstractPerovskite‐based tandem solar cells have demonstrated high potential for overcoming the Shockley–Queisser limit. Routine bandgap (RBG, ≈1.55 eV) perovskites have achieved a perfect balance between efficiency and stability. The narrow bandgap (NBG) candidates for RBG perovskite‐based tandem devices are very limited. Lead sulfide (PbS) colloidal quantum dots (CQDs) are a promising partner due to their broad absorption spectra. However, the efficiency of RBG perovskite/QD tandem devices still lags behind. Herein, efficient RBG perovskite/QDs four‐terminal tandem photovoltaics are successfully implemented through synergistic enhancement from transparent electrode and band alignment Engineering. For tin doped indium oxide (ITO) electrodes, their conductivity and near‐infrared transparency are leveraged using magnetron sputtering and reactive plasma deposition (RPD) methods. Furthermore, instead of traditional zinc oxide, aluminum‐doped zinc oxide (AZO) is developed to enhance the carrier extraction capability of PbS QD bottom cells. Based on the above enhancements, ≈0.95 eV PbS solar cells achieve a record efficiency of 14.14%. Integrated with the front semi‐transparent perovskite solar cells, the four‐terminal perovskite/QD tandem device reaches a record efficiency of 26.12%. The synergistic combination of the RBG perovskite and NBG QD devices provides promising prospects for tandem photovoltaics.

Electron transport layer of tin dioxide deposited by reactive plasma and its application in perovskite solar cells

The electron transport layer is very important for the device efficiency and stability of perovskite solar cells. Tin dioxide is a common electron transport layer in high-efficiency solar cells and has good carrier extraction and transport capability. However, using the solution method to prepare tin dioxide, a large number of defects are generated on its surface during high-temperature annealing in air, which can degrade the electrical properties of the film, so the solution method is not conducive to preparing large-area film. In this paper, the reactive plasma deposition method is used to prepare tin dioxide thin film, and the performance of the thin film is optimized by adjusting the glow discharge time and working current. The film is applied to small-area N-I-P type perovskite solar cells, the efficiency reaching to 21.24%. The hysteresis of the device is improved by introducing stannous isooctanoate and tin dioxide as a double electron transport layer, the open circuit voltage of the solar cell increases from 1.11 to 1.15 V, the efficiency rises from 21.27% to 22.15%, and the hysteresis factor decreases from 24.04% to 3.69%. This work presents a new preparation method and effective optimization strategy to prepare tin dioxide electron transport layer, which will promote the development of planar heterojunction perovskite solar cells and provide a new research idea for preparing high-efficiency and stable perovskite solar cells.

Comparative study of the photocatalytic effects of pulsed laser deposited CoO and NiO nanoparticles onto TiO2 nanotubes for the photoelectrochemical water splitting

Hybrid structures combining a photo-active material and non noble metal oxide co-catalyst nanoparticles are of strong interest to produce efficient photoelectrodes for hydrogen production while limiting the cost due to noble metals (Pt, Ru …). In order to get some insight on the mechanism change induced by such co-catalyst nanoparticles (NPs), we conducted a comparative study between cobalt and nickel oxide nanoparticles deposited onto TiO2 nanotubes (NTs) prepared through anodization. The TiO2-NTs were decorated with CoO and NiO nanoparticles using the reactive pulsed laser deposition (PLD) method. The oxygen atmosphere used during the PLD process, ensures the in-situ oxidation of the metal nanoparticles into CoO and NiO. The surface loadings of CoO or NiO NPs were controlled by the number of laser ablation pulses (NLP). The efficiency of CoO and NiO NPs as co-catalysts for photo-electrochemical water splitting was studied by cyclic voltammetry, as a function of NLP, under both simulated sunlight and visible light illuminations and by external quantum efficiency (EQE) measurements. We determined an optimal catalyst loading at NLP = 2000, allowing to almost triple the photoconversion efficiency (PCE) for both TiO2-NTs/CoO-NPs and TiO2-NTs/NiO-NPs nanohybrid photoanodes, in comparison with bare TiO2-NTs. Moreover, CoO-NPs were found to be the best co-catalyst under visible light illumination, with a PCE almost 10 times higher than for TiO2. This significant enhancement of the visible light activity is ascribed to the narrower band gap of CoO and to the formation of a heterojunction with TiO2 that is more favorable for charge transfer than in the case of NiO co-catalyst.

Effect of crystalline structure on optical and electrical properties of IWOH films fabricated by low-damage reactive plasma deposition at room temperature

Tungsten and water co-doped indium oxide (IWOH) films were deposited via a low-damage reactive plasma deposition method at room temperature followed by air atmosphere annealing. The structural, electrical, and optical properties of IWOH films with different water flow rates (F H2O ) were systematically investigated before and after annealing. Despite the lower mobility (43.7 cm 2 /V) of IWOH films with high water flow rate (H-F H2O , F H2O ≥ 1.5 sccm) in the as-deposited state, it has increased to 65.2 cm 2 /V, which surpassed IWOH films with low water flow rate (L-F H2O , F H2O < 1.5 sccm) after annealing. Meanwhile, a significant increase in average optical transmittance from 80.9% to 88.8% and from 92.2% to 95.2% in the short wavelength of visible (350–500 nm) and near-infrared region (800–2500 nm), respectively, was obtained for H-F H2O films after annealing. The variation of the optical and electrical properties for IWOH films with different F H2O was attributed to the crystalline structure with a larger crystallite size and lower density of grain boundary. X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy analysis revealed that high water flow rate impeded crystallization of IWOH films during reactive plasma deposition, leading to an amorphous structure in the as-deposited state. After annealing, however, the H-F H2O films crystallized and exhibited larger grains than both tungsten-doped indium oxide (IWO) and L-F H2O films. The modified crystalline properties of IWOH films with larger grains hence reducing grain-boundary scattering, which was realized by H-F H2O and annealing treatment, gave rise to enhanced electrical properties without deteriorating optical properties. • Hydrogen-doped indium tungsten oxide was fabricated by reactive plasma deposition at room temperature. • Structural, optical and electrical properties were studied as a function of water flow rate. • Proper water flow rate can enhance the crystalline quality with fewer grain boundary scattering. • The modified crystalline properties with reduced grain boundary led to enhanced mobility.

(CH3NH3)3Bi2I9 perovskite films fabricated via a two-stage electric-field-assisted reactive deposition method for solar cells application

Methylammonium bismuth iodide ((CH3NH3)3Bi2I9, MBI) is a promising alternative to perovskite solar cells (PSCs) due to its air stability and low-toxicity. Herein, a two-stage electric-field-assisted reactive deposition method has been introduced to prepare MBI films for the first time. PSCs based on MBI films were fabricated and characterized. The influences of electric parameters (applied voltage mode, pulse and time, etc.) on the morphology and crystal structure of MBI film correlated with the photovoltaic performance of PSCs have also been investigated systematically in detail. Through adjusting the voltage mode, crystal growth can be completely controlled, leading to a compact MBI film with large grain size. Moreover, the MBI film prepared by electrochemical deposition required no annealing. This work determined that the optimal performance of PSCs is based on the MBI film deposited by square-wave (AC) voltage mode (−7.3 V/+1 V, 5 Hz, 5 min). All devices exhibited long-term stability in ambient air (humidity of >50%) for more than 300 h. This study will inspire further research on the application of electrochemical deposition technique for other lead-free PSCs.

Manipulating the Edge of a Two-Dimensional MgO Nanoisland

We investigate the morphology evolution and electronic properties of MgO islands grown on the Ag(001) substrate by the reactive deposition method using low-temperature scanning tunneling microscopy...

Some of Electrical and Detection properties of nano silver oxide

Micro and Nano Ag2O3 thin films have been deposited using the Reactive Pulse Laser Deposition (RPLD) method. N-type silicon wafer was used as substrates. The prepared films were annealed at (400 -600) °C to produce the oxide films. Spectral Responsivity had been sensed more optically for green (560nm) and near IR (840nm). Response time reveals an enhancement with annealing temperatures.

Study of temperature effect on carbide layer formation behaviour of dual elements thermal reactive deposition on SUJ2 steel substrate

In this research, the formation of carbide layer coating on SUJ2 steel by pack Thermal Reactive Deposition method was studied. Mixture of 35/65 weight percent of ferrochromium/ferrovanadium (FeCr/FeV) powder was applied as coating elements. The process was carried out at temperatures of 900, 950, and 1000 °C for 6 hours for each temperature. The effects of temperature on layer thickness, microstructures, homogeneity, hardness, and wear resistance were analyzed. The result showed that the higher the temperature, the thicker the layer formed on substrate surface. The higher percentage of vanadium in the coating layer compared to chromium found by EDS Linescan results indicate that vanadium has higher affinity to carbon than chromium. This result also means the possibility of vanadium carbide formation will be higher than chromium carbides, due to the lower Gibbs energy for vanadium carbide formation. XRD results showed that the layer formed in this process consists of vanadium carbide (V8C7 and V6C5), chromium carbide (Cr23C6 and Cr7C3), and complex carbides. The average micro hardness and wear rate of all coatings with three different temperature variations were 2100 HV, and 3 × 10−4 mm3/m respectively. This hardness was close to FeV hardness as single carbide former at approximately 2400 HV.

The Effects of Gd-Free Impurity Phase on the Aging Behavior for the Microwave Surface Resistance of Ag-coated GdBa2Cu3O7−δ at Cryogenic Temperatures

High-TC GdBa2Cu3O7−δ (GdBCO) superconductor has been popular for making superconductive tapes that have much potential for various fields of large-scale applications. We investigated aging effects on the microwave surface resistance (RS) of Ag-coated GdBCO layer on Hastelloy substrate, so called GdBCO coated conductors (CCs), and Ag-coated GdBCO films on LaAlO3 (LAO) single-crystal substrates at cryogenic temperatures and compared them with each other. Unlike the RS of Ag-coated GdBCO films showing significant degradation in 4 weeks, no significant aging effects were found in our Ag-coated GdBCO CCs aged 85 weeks. The reactive co-evaporation deposition and reaction (RCE-DR) method was used for preparing the Ag-coated GdBCO CCs. Such durability of the Ag-coated GdBCO CCs in terms of the RS could be explained by existence of a protective impurity phase, i.e., Gd-free Ba–Cu–O phase as confirmed by transmission electron microscopy study combined with the energy-dispersive X-ray spectroscopy measurements. Although the scope of this study is limited to the Ag-coated GdBCO CCs prepared by using the RCE-DR method, our results suggest that a solution for preventing the aging effects on transport properties of other kinds of Ag-coated GdBCO CCs could be realized by means of an artificially-grown protective impurity layer.

A Novel Approach to Realize Si-Based Porous Wire-In-Tube Nanostructures for High-Performance Lithium-Ion Batteries.

Hollow inorganic nanostructures have drawn great attention due to their fascinating features, such as large surface area, high loading capacity, and high permeability. The formation, characterization, and application of partially and entirely hollow structure by applying a Si-based reactive ion deposition and etching method on silicon nanowire as a template are reported. This fabrication technique is extended to a stainless steel substrate to be used as the binder-free anode for high capacity and high rate lithium-ion batteries. The electrochemical analyses exhibit that in addition to the high initial discharge capacity of 4125 mAh g-1 at a rate of C/16, the best performing electrode shows discharge/charge capacity of as high as 3302.14/2832.1 mAh g-1 , respectively, with an excellent charge capacity retention of 96.7% over 100 cycles at a rate density of 1 C. Even at a rate of 12 C, the as-designed structure is still able to deliver an impressive 1553 mAh g-1 , which probably is attributed to fast lithium diffusion in its hollow part and high porosity of Si and alumina layer. It is proved that the change in hollowness ratio significantly affects capacity retention and average coulombic efficiency of the lithium-ion cells.

Surface scattering effect on the electrical mobility of ultrathin Ce doped In2O3 film prepared at low temperature

Electrical conduction behavior of ultrathin cerium doped In2O3 (ICO) films fabricated by reactive plasma deposition (RPD) method at low temperature is investigated. It is found that both carrier density and mobility of ICO film are dependent on the film thickness strongly. When the film thickness is increased from 5 nm to 300 nm, carrier density improved gradually from 0.5 × 1020 cm−3 to 2.1 × 1020 cm−3, while carrier mobility increased from 35.1 cm2/Vs to 153.7 cm2/Vs and then decreased slightly to 121.5 cm2/Vs. The limited carrier mobility is theoretically discussed from analyzing the counterplay between grains boundary scattering-limited and surface scattering-limited mechanism.

Magnetization enhancement due to incorporation of non-magnetic nitrogen content in (Co84Zr16)Nx nano-composite films

We report the magnetic, electronic, and structural properties of nano-composite (Co84Zr16)Nx or CZN films prepared by reactive co-sputter deposition method. As-deposited CZN films have shown enhancement in magnetization (Ms) with incorporation of nitrogen content, which is related to the evolution of nano-composite phase. X-ray diffraction study has confirmed poly-crystalline growth of CZN films with fcc(331) and fcc(422) phases. High-resolution transmission electron microscope study reveals that CZN films are composed of ordered and crystalline ferromagnetic Co nano-clusters, which are embedded in the nano-composite matrix. Photoemission measurements show the change in the intensity near the Fermi level most likely due to defects and shift in the core-levels binding energy with nitrogen concentration. Raman spectroscopy data show an increase in the intensity of the Raman lines with nitrogen concentration upto 20%. However, the intensity is significantly lower for 30% sample. This indicates that less nitrogen or defect states are being substituted into the lattice above 20% and is consistent with the observed magnetic behavior. Our studies indicate that defects induced due to the incorporation of non-magnetic nitrogen content play a key role to enhance the magnetization.

Epitaxial formation of Ni germanide on Ge(0 0 1) substrate by reactive deposition

We investigated the crystalline structure of a NiGe layer grown on Ge(001) substrate through the reactive deposition method. NiGe layers grown at 350°C are a single crystalline, provided that they are thin enough—below 22nm. The epitaxial relationship with the Ge(001) substrate is then as follows: NiGe(111)//Ge(001), and NiGe[01¯1]//Ge[110]. However, the NiGe layer becomes polycrystalline when the thickness reaches 22nm or thicker. We proposed a two-step deposition method combined with solid-phase reaction to suppress the polycrystalline formation and successfully achieved an epitaxial NiGe layer over 22nm-thick with an atomically flat interface. We also clarified that the Ge atom is the dominant diffusion species during the reactive deposition and that the Ni atom dominates during the solid-phase reaction.

Local Characterization of Ultrathin ZnO Layers on Ag(111) by Scanning Tunneling Microscopy and Atomic Force Microscopy

We have studied the local structure of ultrathin ZnO layers grown on Ag(111) by the reactive deposition method using low-temperature scanning tunneling microscopy (STM) and noncontact atomic force microscopy (nc-AFM) at 5 K. The characteristic Moiré patterns arising from the lattice mismatch between the ZnO(0001) layers and Ag(111) appear in STM, but it is not pronounced in nc-AFM images. This indicates an atomically flat geometrical structure of the ZnO layer and a dominant contribution of the electronic state to the Moiré patterns imaged by STM. We found that the apparent height of STM for the ZnO layers strongly depends on the bias voltage and becomes comparable with that of nc-AFM when the bias voltage is below the conduction band edge of the ZnO layers. The ZnO layers with the STM (AFM) apparent height of 3.8 (4.0) ± 0.3 and 5.8 (6.1) ± 0.3 Å were observed. On the other hand, mapping the onset of the resonance state of the ZnO layer by scanning tunneling spectroscopy provides a basis for determining its thickness. Our results suggest that the ZnO layers on Ag(111) grow predominantly as bi- and trilayers under the conditions used.

Tribological coatings with a chromium-based composite structure obtained by reactive deposition in vacuum

The peculiarities inherent to the chemical and phase compositions, microstructure, and tribological behavior of Cr-O, Cr-C-O, Cr-C-H and Cr-C-N-H coatings, obtained by plasma-assisted physical vapor deposition in a chemically active gas atmospheres (activated reactive deposition and magnetron sputtering methods), have been studied. It has been demonstrated that all coatings have a micro- and/or nanocomposite structure comprising nanoscale chromium-based domains, as well as chromium oxide, carbide and nitride phases with different stoichiometries. The tribological properties of the coatings investigated in a broad temperature range under unlubricated friction contact conditions, as well as their correlation with microstructures and reactive-deposition technology parameters, are discussed.

Platinum containing amorphous hydrogenated carbon (a-C:H/Pt) thin films as selective solar absorbers

We have investigated a double-cermet structured thin film in which an a-C:H thin film was used as an anti-reflective (AR) layer and two platinum-containing amorphous hydrogenated carbon (a-C:H/Pt) thin films were used as the double cermet layers. A reactive co-sputter deposition method was used to prepare both the anti-reflective and cermet layers. Effects of the target power and heat treatment were studied. The obtained films were characterized using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy. The optical absorptance and emittance of the as deposited and annealed films were determined using UV–vis-NIR spectroscopy. We show that the optical absorptance of the resulting double-cermet structured thin film is as high as 96% and remains to be 91% after heat treatment at 400 °C, indicating the thermal stability of the film.

Excimer laser treatment of TiO2/WO3 thin films for self-cleaning gasochromic applications: Preparation and characterization

Surface poisoning of gasochromic tungsten oxide layers is one of the most challenging effects, which needs to be resolved. In this paper, first amorphous TiO2/WO3/glass thin films have been prepared by reactive pulsed laser deposition (PLD) method. Then they were irradiated by a single-pulse of excimer laser (λ=248nm) with different incident energies (110, 140, 170 and 200mJ) in order to obtain a thin top layer of anatase TiO2 (a-TiO2) with high photocatalytic activity. By means of X-ray diffraction (XRD), it was observed that by excimer laser treatment (ELT) at 110mJ, a-TiO2 phase is forming while a mixture of a-TiO2 and monoclinic WO3 (m-WO3) is forming at higher energies. X-ray photoelectron spectroscopy (XPS) revealed that laser treatment removes surface contaminants and hydroxyl groups, increases the W/Ti ratio, shifts surface tungsten oxidation states to lower binding energies and leads to the formation of TiC compound on the surface. The surface morphology of samples was investigated by atomic force microscope (AFM) and field emission scanning electron microscope (FESEM). It was revealed that the surface roughness increases with the laser energy, which is due to an increase in the height of surface granular particles. The films hydrophilicity, measured by water contact angle, was found to increase with the incident laser energy. The photocatalytic activity was investigated by methylene orange (MO) degradation test. It was observed that the sample irradiated at 110mJ has the most increased photocatalytic activity. The variation of optical transmittance was investigated by UV–vis spectrophotometer. The gasochromic properties of samples with and without laser treatment were compared in the presence of diluted hydrogen (10%H2/90%Ar) gas.

Structure and Magnetic Properties Investigation of CoZr and CoZrN Thin Films

nanocomposite [(Co91.5Zr8.5)- or CZN films has been prepared by reactive co-sputter deposition method. Nitrogen content plays key role to tune soft magnetic properties. Experimental observation shows that, non-magnetic nitrogen content enhances magnetization and reduces coercivity. The nanostructure is composed of Co nanoclusters embedded in CoN/ZrN matrix, revealed by high resolution transmission electron microscope study. The d-spacing of single Co nanocluster was found to be ~0.22nm corresponding to (002) phase of Cobalt. X-ray diffraction result is in agreement with cubic (400) and (622) phase of CoZr. High electrical resistivity ρs~108μΩ-cm attained corresponding to 16% N2content films. Hysteresis loop squareness depends on film thickness and coercivity squareness (S*)~0.84, obtained for ~250nm film thickness. A correlated composite nanostructure evolution is responsible for nitrogen induced magnetization and, suggests that film properties can tuned by controlling nitrogen content, in CoN/ZrN composite matrix.

Reactive growth of MgO overlayers on Fe(0 0 1) surfaces studied by low-energy electron diffraction and atomic force microscopy

Ultra-thin MgO films grown reactively on the Fe(001) surface by evaporation of magnesium in an atmosphere of molecular oxygen have been investigated by low energy electron diffraction and non-contact atomic force microscopy. Preparation of structurally stable crystalline films requires a protocol that prevents an excessive interfacial reaction between oxygen and the Fe(001) surface, but at the same time provides a sufficient amount of oxygen in order to grow a stoichiometric MgO film. The proper ratio between the magnesium deposition rate and the oxygen pressure has been determined, as well as measures to prevent initial interfacial oxidation of the substrate. The effect of both post-annealing and an increased substrate temperature during the growth has been studied. We demonstrate that the reactive deposition method, which gives full control over the gaseous species that reach the surface, can produce terraces that have an average size of 10nm (on an 8 monolayer thick film), which is a significant improvement compared to other preparation methods, such as thermal or electron beam evaporation of MgO.

Photon synthesis of iron oxide thin films for thermo-photo-chemical sensors

Ultraviolet photons of KrF-laser (248nm) and of photodiode (360nm) were used for the synthesis of iron oxide thin films with variable thickness, stoichiometry and electrical properties. The reactive pulsed laser deposition (RPLD) method was based on KrF-laser and photon-induced chemical vapor deposition (PCVD) was based on a photodiode. Deposited films demonstrated semiconductor properties with variable band gap (Eg). The film thickness (50–140nm) and Eg depended on the laser pulse number, oxygen and iron carbonyl vapor pressure in the deposition chamber, and exposure time to the substrate surface with ultraviolet (UV) radiation. Sensing characteristics strongly depended on electrical and structural properties of such thin films. Iron oxide films were deposited on 〈100〉 Si substrate and had large thermo electromotive force (e.m.f.) coefficient (S) and high photosensitivity (F). The largest value of the S coefficient obtained by RPLD was about 1.65mV/K in the range 270–290K and by PCVD was about 1.5mV/K in the range 280–322K. The largest value F obtained by RPLD and PCVD was about 44Vc/W and 40Vc/W, accordingly, for white light at power density (I≅0.006W/cm2). It was shown that the S coefficient and F strongly depended on Eg. Moreover, these films were tested as chemical sensors: the largest sensitivity of NO molecules was at the level of 3×1012cm−3. Our results showed that RPLD and PCVD were used to synthesize semiconductor iron oxide thin films with different sensing properties. So iron oxide thin films synthesized by UV photons are up-to-date materials for multi-parameter sensors: thermo-photo-chemical sensors operating at moderate temperature.