Search

Many investigations have revealed that PbI2 plays a passivated role to reduce the charge recombination in the perovskite films. However, due to the random distribution of PbI2 in perovskite films, the passivation effect is blanketed to some extent. In this work, we use the argon ions bombardment to deliberately induce the PbI2 layer at the surface of perovskite films and investigate the photoelectric performance of samples. It is found that the PbI2 layer at the surface can passivate the defects effectively, leading to an improvement of the photoconduction by an order of magnitude as well as the responsivity by >4 times under the irradiation of 405 nm light. The bombardment provides an effective method for perovskite surface passivation and optimizing the performances of perovskite-based photoelectric devices.

Layers of tungsten were deposited on two types of graphite substrates at three different angular position by a low energy plasma focus device. First series of substrates included only raw graphite while carbon interlayers were used for the second type. Tungsten deposition process was carried out at 0°, 15°, and 30° angular location with respect to the device anode axis during 40 focus shots at optimum argon gas pressure. The characterization of the deposited tungsten coatings was verified by X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy and Nanoindentation analyses. Tungsten-carbon structures such as WC1-X, W2C, WC, and W2(C, O) were detected by XRD analysis. Compounds such as WC1-X, W2C and W2(C, O) were identified on raw graphite substrate while WC1-X, WC, W2C were formed on the graphite substrates with carbon interlayer. For both types of samples positioned at 30 degrees with respect to device axis, the WC1-X phase, which is a high temperature structure with high melting point, was detected more than other tungsten-carbon structures. The coating of carbon interlayer on substrates changes surface morphologies and leads to homogenous deposition of tungsten layer on the surface. The increase in angular position of substrates led to creation of flat and smooth surfaces. Raman spectroscopy shows the presence of WO3 and amorphous carbon structures in both types of prepared samples. Nanoindentation analysis indicates that the hardness of samples increases after tungsten deposition process. The substrate angular position with respect to anode axis is an effective parameter in deposition process of tungsten layers.

The chemical bath deposition process of depositing CdS buffer layer was replaced with electron-beam evaporation method, full vacuum preparation process, which is more environmentally friendly and non-solution contact, was achieved to prepare Cu2ZnSnS4 (CZTS) solar cells. First, the influence of growth rate on the structural, optical, morphological, electrical properties of electron-beam evaporated CdS films was investigated. CdS thin films were deposited at growth rates of about 3, 6, 9, 12 A/s, respectively. The results revealed that CdS thin films deposited at lower rate showed better crystallinity, higher transmittance, lower carrier concentrations, preferred for the application in CZTS solar cells. Then, kesterite Cu2ZnSnS4 thin film solar cells using the optimal CdS thin films as a buffer layer are fabricated, and a best efficiency of 4.87% was demonstrated. The statistical distribution of device performance parameters of 150 solar cells using electron-beam evaporated CdS buffer layer was also demonstrated.

This work reports the structure, growth rate, dielectric response, and capacitance properties of (100)-oriented Ba0.67Sr0.33TiO3 (BST)/LaNiO3 (LNO) hetero-structure thin films with varied BST layer thicknesses from 34 nm to 342 nm. The BST/LNO hetero-structure thin films were prepared by radiofrequency magnetron sputtering technique on Pt/SiO2/Si substrates. The XRD results showed that the compressive stress is relaxed at around 73 nm of BST layer, and above 119 nm of the BST layer thickness, the tensile stress has a significant effect on the crystal structure of the BST/LNO hetero-structure film. The growth rate of the BST films was thickness-dependent which was strongly related to the minimization of the strain energy. The dielectric constant of BST layer with the compressive stress increase from 177 to 2640 with the increase of BST layer thickness. The BST layer with the tensile stress showed a comparably stable dielectric constant of 2400. In addition, the capacitance properties and the electrical breakdown strength of BST/LNO hetero-structure thin films are also thickness-dependent, respectively. The electrical breakdown strength reached a maximum value of 1237 kV/cm in the BST/LNO hetero-structure thin film with ~73 nm BST layer.

Electronic properties of a CdTe solar cell are reported using temperature-dependent capacitance spectroscopy and current-voltage characteristics, the latter in dark and illuminated conditions. The baseline solar cell material stack investigated is comprised of soda-lime-glass/SnO2:F/SnO2/CdS:O-buffer/CdTe-absorber/Cu/Au. Device properties are compared with CdTe solar cells in which the back surface was hydroiodic acid etched, before the back-contact formation, and a CdTe device in which Mg-doped ZnO (MZO) replaces buffer layers. Reduced back-contact barrier height and grain boundary barrier height are observed in the hydroiodic acid treated CdTe cell. Improved device performance in the MZO-based CdTe device is attributed to reduced emitter/absorber interface recombination when using the MZO window layer.

We have previously reported that phosphine (PH 3 ) surface treatment of a p-type crystalline germanium (c-Ge) substrate improves the c-Ge heterojunction solar cell performance. In this study, the effects of the heterointerface properties of the c-Ge heterojunction solar cell were investigated. We found that the deposition temperature of the heterojunction layer and O 2 surface treatment before the PH 3 surface treatment influence the interface phase structure and band structure. Consequently, a conversion efficiency of 7.61% with a high open-circuit voltage of 0.270 V was obtained.

Polarity-controlled epitaxial ZnO films with two types of surface morphologies were prepared using pulsed laser deposition, and their gas sensing responses to several reductive gases were determined. Gas response measurements of high-temperature-grown (HT) c(+)- and c(−)-polar ZnO films having large, densely packed grains with flat surfaces indicated that the selectivity for ethanol of the c(−)-polar film was lower than that of the c(+)-polar film. This is due to the absence of Zn ions, which facilitate the adsorption and reaction of ethanol, in the topmost layer of the surface. In the case of low-temperature-grown (LT) c(−)- and c(+)-polar ZnO films consisting of densely packed grains with diameters of several tens of nm, the c(−)-polar ZnO film had a higher selectivity for ethanol. The gas response behavior of the LT c(−)-polar film differed from that of the HT c(−)-polar film because the surface of the former can feature the h 0 h ¯ l crystal plane, which is terminated with undercoordinated Zn ions. The presence of undercoordinated Zn ions on the surface can greatly enhance the ethanol gas response of the LT c(−)-polarity film.

We reported the fabrication and optical analysis of titanium dioxide (TiO2) nanostructures by a glancing angle deposition (GLAD) method using an electron-beam evaporator with various incident vapor flux angles (θα). The GLAD TiO2 layers were grown on silicon and glass substrates. The GLAD TiO2 films with nano-columnar structures were formed at various θα = 0, 40, 60, and 80°. The structural properties of the GLAD TiO2 layers were evaluated, creating slanted porous columnar structures due to the self-shadow effect. As the θα was increased during the evaporation, the effective refractive index of the GLAD TiO2 layers was decreased and their average transmittance was increased in the wavelength range of 300–1000 nm due to the decreased average reflectance, together with theoretical calculations. For photovoltaic device applications, one pair of TiO2 layers with θα = 0 and 80° was produced using optical quarter wavelength thicknesses, exhibiting the lowest reflectance value of 6.67% at the wavelength of 540 nm. The highest solar weighted transmittance was also calculated to be 89.6% for the GLAD TiO2 layer at θα = 80° in the wavelength range of 300–1100 nm.

Inorganic-organic multilayer systems are ubiquitous in many important technological applications and have received considerable attention recently. Although the mechanics, structures, materials and performances of multilayer devices under room temperature have been extensively investigated, the effect of heat on the inorganic-organic composite systems remains unclear. Here we report on the fracture and wrinkle behaviors of metal/elastomer (silver/polydimethylsiloxane(PDMS)) bilayers resting on glass slides induced by high temperature annealing. It is found that as the annealing temperature is beyond a critical value, the PDMS layer is fractured and detaches from the glass slide due to the thermal contraction during cooling. The fractured PDMS layer bends upward and places the silver film under a compressive stress, which is relieved by formation of multiple wrinkle patterns. The morphological characteristics, evolutional behaviors and potential mechanisms of both fracture and wrinkle patterns are discussed in detail. The report in this work could promote better understanding of the effect of heat on the mechanical durability of metal/elastomer/solid multilayer systems.

The article presents crystal structure, composition, optical, electrical and thermoelectric properties of semi-transparent CuI films produced in different modes of the cost-effective and large scalable method Successive Ionic Layer Adsorption and Reaction (SILAR) on flexible poly(ethylene terephthalate) (PET) substrates. The obtained data together with the analysis of output thermoelectric characteristics of p-type thermolegs based on these CuI films are used to select the SILAR mode to create semi-transparent p-type thermolegs for a new flexible wearable thin film thermoelectric generator (TEG). The best obtained flexible p-CuI thin film single thermoleg demonstrates output power 17.1 μW/m2 at the temperature gradient ∆T = 35 K at near-room temperatures. Therefore, CuI films produced in such mode of the SILAR method on the flexible PET substrates can be used as a part of a new lightweight low cost flexible wearable thin film TEG for a production of electrical energy for low-power devices due to absorption of low-potential heat.

Dual-layer photoanode thin films for dye sensitized solar cells (DSSCs) has garnered great attention, due to its excellent scattering property, dye loading capacity, superior electron transfer and simple device fabrication processing. Here, we report a ZnO nanorod/ZnO-SnO2 mesoporous (ZZS) composite film as an efficient electron extraction layer for dye sensitized solar cells. The DSSCs exhibit a maximum power conversion efficiency (PCE) of 5.10% and a short-circuit current density (Jsc) of 12.94 mA·cm−2 due to the improved light scattering, absorption and interface bonding, which controlled by varying the processes of hydrothermal reaction and solid state reaction. The results further demonstrated that the ZnO/ZnO-SnO2 photoanode structure is a promising strategy with effective electron extract efficiency for efficient DSSCs.

To develop high-efficiency multijunction solar cells onto inexpensive substrates, an innovative technique for growing a large-grained Ge layer on glass is strongly desired. We investigated the epitaxial growth of a light absorbing Ge film (500-nm thickness) on a large-grained (>100 μm) Ge seed layer (50-nm thickness) formed on glass by Al-induced layer exchange. After examining molecular beam epitaxy (MBE) and solid-phase epitaxy (SPE) for both methods, Ge layers with a low Al concentration were epitaxial grown at 350 °C. Microwave photoconductivity decay revealed that the MBE-Ge layer exhibited a short minority carrier lifetime owing to the rough surface. Conversely, the SPE-Ge layer was relatively flat and exhibited a long bulk minority carrier lifetime (5.6 μs), which is close to that of a single-crystal Ge. Therefore, the seed layer concept that combines SPE with Al-induced layer exchange is a promising way for fabricating ideal bottom cells for high-efficiency multijunction solar cells based on inexpensive substrates.

The outstanding strength-to-weight performance of 7075 aluminum alloy (AA 7075) has prompted its wide-scale application to light-weight sport equipment, automobile bodies, and airframe design. However, the fatigue performance of AA 7075 cannot match that of steel. In this study, we used direct current sputtering to coat AA 7075 substrates with (Zr53Cu30Ni9Al8)99.5Si0.5 (Zr-based) metallic glass thin film (MGTF) coupled to a 50-nm titanium thin-film buffer layer. The Zr-based MGTF coating was applied at thicknesses of 200, 300, 400, and 500 nm. The fatigue characteristics of as-polished and coated AA 7075 samples were then tested in accordance with ASTM-C1161-02c specifications. The 200-nm-thick Zr-based MGTF coating was shown to extend the fatigue life of the AA 7075 by 26 times at a stress level of 250 MPa. The application of 200-nm-thick Zr-based MGTF coating also extended the fatigue limit from 150 MPa (as-polished sample) to 235 MPa, which represents an improvement of 56.7%. Transmission electron microscopy analysis revealed that the Zr-based MGTF coating restricted the formation of offsets and cracks beneath the surface of specimen. This can be attributed to the high strength, good flexibility, and strong adhesion of the Zr-based MGTF coating, which provided sufficient compressive stress to suppress slip band protrusions. The increases in fatigue life and fatigue limit were proportional to the thickness of the MGTF coating, due to changes in surface roughness and adhesion capability. A coating thickness of 200 nm was found to provide the best resistance to fatigue, due to its superior flexibility. These results demonstrate the outstanding potential of Zr-based MGTF coatings to improve the fatigue resistance of AA 7075.

Ion beam irradiation dramatically enhances the sensing response of a graphene gas sensor by producing defects on the graphene layer. The number of defects depends on the ion size, energy, and dose. In addition, by using different gases such as ammonia (NH3), nitrogen dioxide (NO2), and carbon monoxide (CO), we were able to compare the sensing response of graphene with that of ion-irradiated graphene. The sensing response of ion-irradiated graphene is 15 times larger than pristine graphene. For the other gases, the sensing responses are also enhanced. The sensing response ratios for the different gases are closely related to the theoretically expected adsorption energy between the graphene and the gas molecules.

Silicon nitride (SiNx:H) films are generally used as passivation and anti-reflection layers in solar cells, and they are usually made by plasma-enhanced chemical vapor deposition (PECVD). Silicon nitride could act as a hydrogen diffusion source, and it also plays a role in chemical passivation. In this study, we investigated the improvement of the passivation characteristics of the passivated contact structure by a PECVD SiNx:H hydrogenation process and the characteristics of SiNx:H for improving the passivation characteristics. It was confirmed that the passivation characteristics cannot be predicted only by the mass density of the SiNx:H film, and the chemical bonding ratio in the SiNx:H thin film is also important. In addition, higher passivation characteristics can be obtained when SiNx:H thin films with higher S H bond concentration and dominant N2Si H2 bonds are used.

We propose to utilize a giant nanomembrane as a substrate for an ultra-thin lightweight device. The giant nanomembrane used in this research is a robust nanometer thick film consisting of highly cross-linked epoxy resins. We fabricated organic thin-film solar cells on the nanomembrane, and monitored the performance of the cells. Successful solar cell fabrication on a nanomembrane by just a sequential lamination of thin films proved that nanomembranes showed enough physical stability, chemical resistance, and surface wettability, to be utilized as a substrate for an ultra-lightweight device. In addition, we tried to detach the nanomembrane solar cell from a solid substrate by dissolving an expendable nanomembrane layer, which had been created solely for this purpose, and scooped it up with our fingers. The total thickness and weight of the detached device were less than 500 nm and 0.8 g·m−2 respectively, which are comparable to the corresponding characteristics of the thinnest and lightest devices in the world. This demonstration will expand the possibility of nanomembranes as substrates for various wearable electronic and optical devices.

In this paper, we report results on the processing of cadmium zinc sulfide (CdxZn1-xS) ternary compound starting from the deposition of cadmium sulfide (CdS)/zinc sulfide (ZnS) bi-layers buffer configuration and a subsequent thermal annealing for its application to thin film solar cells. The impact of different CdS/ZnS bi-layers buffer configurations as effective alternative to the single CdS buffer layer, as well as the physical and chemical properties of the equivalent CdxZn1-xS ternary compound are presented and discussed. Results on physical properties optimization of CdxZn1-xS ternary compound for future applications to thin film solar cells are presented.

Dry plasma reduction under atmospheric pressure is a unique approach for stably, continuously, easily, and uniformly fabricating Ag layer on the metal seeds-polyethylene terephthalate (PET) substrate. In this study, effects of particle size, surface uniformity, surface coverage, and film thickness of metal seeds such as Ag, Cu, Fe and Ni on the formation of uniform Ag layer were studied on the basis of their surface free energies and critical radius, which further leads to variations in the sheet resistance levels of the silver layers. The root mean square roughness and sheet resistance of the Ag layer PET substrate were decreased with the deposition of metal seeds. Among the added seed metals, Ni seed has shown best uniformity. Furthermore, the fabricated films were applied for electromagnetic interference (EMI) shielding. Among the added seed metals, Ni has shown the highest electromagnetic interference shielding effectiveness. The present study will be useful for the development of various low-cost metal films in the field of EMI shielding.

Single layer Mo and Si thin films deposited for different deposition times on c-Si substrates by Ion beam sputtering technique have been characterized by Grazing Incidence X-ray Reflectivity (GIXRR) measurements. Subsequently, few Mo/Si multilayers having 5 bi-layers with different Mo to bi-layer thickness ratio (Γ) at a fixed bi-layer thickness have been deposited and characterized by GIXRR measurements. Investigation has been carried out on the different behaviors of the interfaces and also variation of the interface width with Γ has been studied. Finally, 25 bi-layer Mo/Si multilayer samples having the lowest Γ value and with and without carbon diffusion barrier layer at both the Mo/Si interfaces are deposited and the interfaces have been characterized by hard X-ray and soft X-ray reflectivity measurements. The study shows improvement in reflectivities of the multilayer with carbon diffusion barrier layer from 38% to 54% at 130 A wavelength. To have further insight into the modification of the interface due to introduction of the carbon barrier layer, depth selective study of both the multilayers have been carried out by Grazing Incidence Extended X-ray Absorption Fine Structure measurements using synchrotron radiation and thereby investigating the local structures around Mo atoms in Si bulk region and Si-on-Mo interface. This study confirms the reduction of diffusion of Mo and Si layer into each other when the carbon buffer layers are present at the interfaces, thus reducing the chance of formation of MoSi2.

Electronic devices such as solar cells and thin-film transistors can be fabricated using thin-film deposition. Low-cost, low-temperature and high-speed deposition methods are required to ensure that the production of devices using thin-film deposition is affordable. Herein, we report the development of a low-cost and simple thin-film deposition method using microwave-excited atmospheric pressure plasma jet (MWAPPJ). MWAPPJ produces a low-temperature (several hundred degrees) plasma under atmospheric conditions, does not require expensive vacuum equipment, and it enables high-speed deposition of thin-films. Zinc acetylacetonate sol-gel precursors that were adhered to stainless steel mesh targets were irradiated by MWAPPJ with oxygen, which resulted in zinc oxide (ZnO) nanosheet thin-films with diameters of 100–200 nm on silicon substrates. We used 50-nm-thick ZnO thin-films that were processed using MWAPPJ as the electron collection layer in organic photovoltaic (OPV) cells. This work represents an important contribution to the design and production of low-cost OPV solar cells.

Sol-gel processed niobium oxide (Nb2O5) thin-film was synthesized for a scaffold layer (SL) of methylammonium lead iodide-based perovskite film. Complementary characterizations, including scanning electron microscopy, X-ray diffraction, optical absorption spectroscopy have revealed that the Nb2O5 SL facilitates efficient crystallization of the perovskite film compared to the conventional mesoporous titanium oxide (m-TiO2) SL. Also, photoluminescence spectroscopy revealed the higher electron-extraction capability at the perovskite/Nb2O5 interface than the perovskite/m-TiO2 interface. The present sol-gel processed Nb2O5 SL and the superior optoelectronic properties of the overlying perovskite film suggest a promising avenue for high-performance and cost-effective perovskite solar cells.

In this paper recent results on monitoring and control of plasma ion assisted deposition (PIAD) processes are presented. An industrial PIAD system equipped with diagnostics for deposition rate and optical thickness was augmented by active plasma resonance spectroscopy to access electron density near the substrate. A series of experiments implementing different schemes to control the level of plasma assistance, while depositing a model 5-layer quarterwave stack SiO2/TiO2, were conducted. Data on in situ spectral transmission of the coatings was used to reconstruct optical properties and the thickness of each layer. Conventional control of anode voltage of the assist source Advanced Plasma Source (APS) was found to exhibit remarkable variations of electron density as drifts during deposition and shifts between separate runs. We demonstrate that measuring the electron density and using that signal in the feedback loop control of the APS greatly improves the layer-to-layer repeatability and run-to-run reproducibility of coating performance. Best results were obtained combining electron density control with optical monitoring for endpoint detection.

In this study, lithium fluoride (LiF) was deposited on lithium (Li) metal by thermal evaporation in order to reduce degradation of Li metal batteries caused by growth of Li dendrites. Li | Li symmetric cells were used to measure impedance changes, overvoltage after cycling at 1 mA/cm2 and 1 mAh/cm2, and surface images after 100 cycles. In addition, the residual capacity and Coulombic efficiency after 0.5C charge/discharge cycling were confirmed using LiCoO2|Li cells. Based on electrochemical impedance spectroscopy measurements, Li | Li symmetric cells made of LiF-coated Li showed no impedance changes, even 12 h after fabrication. During the overvoltage test with Li | Li symmetric cells, the cell with a 300 nm thick LiF layer showed highest stability under repeated cycling. The surface of the 300 nm LiF-coated Li was relatively smooth and almost no abnormal growth of Li was observed. In the LiCoO2|Li cells, 200 nm and 300 nm LiF-coated cells showed the best performance in terms of residual capacity. The 300 nm LiF-coated Li cell exhibited close to 100% Coulombic efficiency and remained more stable than the bare Li cell.

The effects of introducing a passivation layer at the rear of ultrathin Copper Indium Gallium di-Selenide Cu(In,Ga)Se2 (CIGS) solar cells is studied. Point contact structures have been created on 25 nm Al2O3 layer using e-beam lithography. Reference solar cells with ultrathin CIGS layers provide devices with average values of light to power conversion efficiency of 8.1% while for passivated cells values reached 9.5%. Electronic properties of passivated cells have been studied before, but the influence of growing the CIGS on Al2O3 with point contacts was still unknown from a structural and morphological point of view. Scanning Electron Microscopy, X-ray Diffraction and Raman spectroscopy measurements were performed. These measurements revealed no significant morphological or structural differences in the CIGS layer for the passivated samples compared with reference samples. These results are in agreement with the similar values of carrier density (~8 × 1016 cm-3) and depletion region (~160 nm) extracted using electrical measurements. A detailed comparison between both sample types in terms of current-voltage, external quantum efficiency and photoluminescence measurements show very different optoelectronic behaviour which is indicative of a successful passivation. SCAPS simulations are done to explain the observed results in view of passivation of the rear interface., P.M.P. Salomé acknowledges the funding of Fundação para a Ciência e a Tecnologia (FCT) through the project IF/00133/2015. The European Union's Horizon 2020 research and innovation programme ARCIGS-M project (grant agreement no. 720887) is acknowledged. J. M. V. Cunha acknowledges the funding of Fundação para a Ciência e a Tecnologia (FCT) through the project PD/BD/142780/2018. J. P. Teixeira and J. P. Leitão acknowledge the funding of FCT through the project UID/CTM/50025/2013.

Recent published literature dealing with FeS pyrite (thin films and single crystals) faces a few and relevant issues: the low photovoltage presented by pyrite (mainly related to the singular nature of its surface), the not yet clearly defined way of making available n and p type reliable samples and the relevance of their stoichiometry. To address the second and third issues, Fe thin films, Ti/Fe and Co/Fe bilayers deposited on sodalime glass and amorphous quartz substrates have been sulfurated at different temperatures (T) (T ≲ 600C) during 20 h to obtain pyrite thin films. Seebeck coefficient and Hall Effect measurements have been carried out at room temperature with the sulfurated samples. It has been found that sulfurated Ti/Fe on sodalime glass presents a change of the Seebeck coefficient sign (from negative to positive) due to a strong interaction of the Ti layer with the substrate, which is not present in the Ti/Fe samples deposited on amorphous quartz. As a consequence of the interaction, a new TiO layer is formed between the sodalime glass substrate and the pyrite layer. Sulfurated Co/Fe bilayers on sodalime glass show a coherent behavior according to the obtained results and previously published works. They all appear to be n-type semiconductors when T ≳ 175C. Non-intentionally doped Fe thin films on sodalime glass behave in a non-conclusive fashion from the point of view of their electrical transport characterization. The Seebeck coefficient (S) of the sulfurated films appear to be S > 0 for all values of T. However, the value and sign of the Hall constant behave in a non-reproducible way. Results are discussed on the light of present knowledge of synthetic pyrite thin films growth and doping., The authors thank technical support from Mr. F. Moreno. Financial support by MINECO-FEDER (MAT2015-65203R) is acknowledged and the project INFANTE (PIE 201550E072) is also recognized. Carlos Morales thanks the Ministerio de Educación Cultura y Deporte of Spain for the FPU grant.

We report on the interplay between surface morphology and the magnetic properties of Pt/Mn ultra-thin bilayers by measuring the temperature dependence of the resistivity of Hall bars cooled under application of an external magnetic field. The resistivity (ρ) versus temperature (T) curves measured under a magnetic field applied along the x-, y- and z- directions exhibit a clear difference between the zero-field-cooled (ZFC) and field-cooled (FC) traces. The disparity between the ZFC and FC traces allowed us to determine the direction of the magnetic easy-axis. The ρ vs. T characteristic of the Pt/Mn bilayers revealed the existence of antiferromagnetic (AF) order below 79 K, in agreement with the Neel temperature observed in temperature dependent susceptibility curves. We also investigated the morphological evolution of the Mn films as a function of Mn thickness by atomic force microscopy (AFM). We observed the formation of a Mn layered structure on a 2nm-thick Al2O3 buffer layer for films thicker than 2.5 nm. Our results suggest that bilayer structures consisting of non-magnetic noble metals on ultra-thin antiferromagnetic metals can be used as a probe to explore the complex magnetic properties of the AF layer.

A set of bottom-gate Zinc Oxide (ZnO) thin film transistors (TFTs) with active layers containing 1, 4 and 8 layers of spin-coated ZnO were fabricated and their electrical characteristics such as transistor transfer and capacitance-voltage characteristics were analyzed. The transconductance of the single-layered ZnO transistor shows a single peak. On the other hand, multiple peaks and humps were observed in the transconductance and capacitance-voltage characteristics of multi-layered ZnO transistors. The multi-layers were grown by reiteration of the spin-coating process, producing ZnO − ZnO interlayer-interfaces. The surface of the ZnO layer in contact with the ambient contains active sites, resulting in chemisorption of ambient gases such as oxygen prior to the deposition of subsequent layers. The chemisorbed species become negatively-charged and form charge sheets, depleting the surface/interface region. It was proposed that the formation of depletion layers at ZnO − ZnO interlayer-interfaces is the main cause for the observed anomaly.

Surface passivation effect with an aluminum nitride (AlN) thin film deposited by atomic layer deposition (ALD) on metal/gallium nitride (GaN) junctions were investigated using current–voltage and capacitance–voltage (C V) measurements. The sample with an AlN layer revealed higher barrier height and lower ideality factor compared to the sample without AlN layer. X-ray photoelectron spectroscopy measurement on bare GaN surface showed the presence of native oxide on the GaN surface. From C V measurements, it was found that the interface state density was reduced with an AlN layer. Hence, deposition of AlN layer by ALD can be used to improve the interface quality of metal/GaN junction.

Substoichiometric TiO2 films have been prepared by reactive magnetron sputtering. Employing an oxygen feedback loop has enabled a precise control of the sub-stoichiometry in the growing TiO2-x film as well as a high level of sample reproducibility. TiO2-x was deposited on unheated substrates and subsequently annealed at 300 °C. These films have been characterized by a variety of techniques to unravel the interplay between stoichiometry and optical as well as electronic properties. Capping the films by a Si3N4 layer was sufficient to prepare films with resistivities as low as 8 mΩcm showing a high mobility of up to 15 cm2/Vs. At the same time, a high transparency above 80% could be realized for these samples. The results verify that metal-like conductivity and high transparency can be realized simultaneously in undoped TiO2-x. Upon variation of the film stoichiometry a metal-insulator transition has been observed in temperature dependent electrical measurements performed down to 2 K.

Poly(2-hydroxyethyl methacrylate) brushes were grown from a gold substrate by Atom Transfer Radical Polymerization (ATRP) and the material was applied as the gate dielectric layer in Organic Thin Film Transistor (OTFT) devices. The ATRP method provided 120 nm thick layers with relatively low roughness, as characterized by Atomic Force Microscopy. The layers were also investigated by Fourier Transform Infrared Spectroscopy to confirm that the polymer layer was covalently bonded to the gold surface. The synthesized polymer had very low dispersity, Ð = 1.18, indicating the well-controlled polymerization process. Dielectric Spectroscopy was used to characterize dielectric properties of the layers for potential use as the gate dielectric in OTFTs. Then, an OTFT device was subsequently constructed by deposition of a pentacene derivative as the semiconductor on the dielectric layer. The OTFT exhibits a field-effect for a relatively low operational voltage range (VDS

Zn(O,S) thin films have attracted intensive attention for their potential application as Cd-free buffer layers in kesterite-based solar cells due to their desirable band alignment with Cu2ZnSnS4 (CZTS) or Cu2ZnSnSxSe4-x (CZTSSe) materials. In this work, Zn(O,S) thin films with controllable content of oxygen have been designed via ozone-assisted photochemical deposition processes. Results showed that the deposited Zn(O,S) thin films using various ozone flow rate are flat, compact and uniform with a thickness of ~ 40 nm, consisting of nanoparticles with a diameter of 30–50 nm. The introduction of ozone into synthesis processes can hardly impose any effect on the morphologies, but significantly modify and tune the oxygen contents in the deposited thin films. Moreover, optical absorption spectra indicate that the optical band-gap of Zn(O,S) films can be readily tuned from 3.3 to 3.7 eV by changing the ozone flow rates. Furthermore, it is confirmed that the solar cells with Zn(O,S)/CZTS structure has a higher conversion efficiency of 3.0% and a higher open circuit voltage of 0.516 V compared to those with ZnS/CZTS structure. Our research would open an easy and promising approach to prepare Cd-free buffer layer materials for kesterite-based thin film solar cells.

Inverted polymer/quantum-dots (QDs) hybrid white light emitting diodes with high efficiency and color stability were fabricated. The white devices show high luminous efficiency of 5.3 cd/A, external quantum efficiency of 3.0%, by using polyetherimide (PEI) to modify zinc oxide layer as the electron injection layer and blue emitting polymer of poly (dibenzothiophene-S,S-dioxide-co-9,9-dioctyl-2,7-fluorene) (PFSO) doped with green and red quantum-dots (G-QDs, R-QDs) as the emitting layer. Pure white emission at Commission Internationale de L'Eclairage coordinates of (0.31, 0.32) was achieved by adjusting weight ratio of PFSO: G-QDs: R-QDs to be 10.0: 3.6: 2.2. In addition, the electroluminescence (EL) spectra of the white device are quite stable in the wide brightness range between 1.0 × 102 cd/m2 and 1.0 × 104 cd/m2. The possible reason was that the PEI could reduce the energy barrier height between the cathode and emitting layer, and facilitate electron injection into the emitting layer. It's confirmed that both Forest energy transfer and charge trapping mechanisms work in the EL process and the latter is dominant.

We evaluated the performance of CeO2 as a buffer layer for emerging thin-film solar cells. Thin films of CeO2 were deposited via spin coating on transparent conductive oxide (TCO) glass substrates. The photovoltaic parameters of open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and conversion efficiency of the reference samples increased from 134 mV, 4.14 mA/cm2, 0.26, and 0.14% to 254 mV, 14.74 mA/cm2, 0.34, and 1.27%, respectively, by using the structure TCO/CeO2/Bi2S3/PbS. The crystallite size of the absorber layer (PbS) increased from 14 to 24 nm using a 130 nm CeO2 buffer layer.

Photostability of the polymer solar cells (PSCs) remains a challenge to attain, as number of factors including the electron transport layers contribute to the degradation of PSCs when they are tested under 1 sun illumination, along with heat and humidity. Especially electron transport layers (ETLs) have considerable contribution to the overall degradations in these solar cells. Most studied ETL into the fabrication of inverted PSCs is zinc oxide (ZnO) yet the photostability of these PSCs is limited. This degradation most probably occurred due to the direct contact of zinc metal with the photoactive layer. This interface between ZnO and photoactive layer results in the initiation of degradations in PSCs. Keeping in view of this issue, we have modified the ZnO ETL by mixing ZnO nano particles with ethoxylated polyethyleneimine (PEIE) and then passivating this modified ZnO (m-ZnO) with ultrathin PEIE buffer layer. The power conversion efficiency is not affected by this approach, but when PSCs were subjected to 1 sun illumination, these m-ZnO/PEIE based PSCs have shown the enhanced light soaking (LS) stability. These findings indicate that optimizing the interface between the photoactive layer and the electron transport layer can lead to enhanced LS stability.

The complex reaction cascade of 2-(3-amino-n-propyl)-2-methyl-4H-1,3,2-benzodioxasiline (APSI) with the tetra-functional epoxide reactant 4,4′-methylenebis(N,N-diglycidylaniline) (MDGA) has been applied to coat polyethylene terephthalate substrates with a nanostructured inorganic-organic hybrid layer. APSI is suitable to undergo twin polymerization and step growth polymerization processes to both poly(3-aminopropyl methyl)siloxane and phenolic resin as well as epoxy resin moieties, simultaneously. The molecular structure formation of the hybrid material formed is proven by solid state 13C and 29Si nuclear magnetic resonance spectroscopy of reference samples prepared as bulk materials. The formation of three polymer structures during one procedure allows the accurate adjustment of the surface morphology that is strongly determined by the ratio of reactant quantities used. In the coatings, at higher MDGA contents, increasingly larger areas of segregated polymer phases up to the micro scale occur. With increasing APSI amount, the surface becomes smoother and more homogeneous. This has a positive effect on the optical properties of the coatings. With a pure APSI layer, a transmission increase of 2% could be achieved.

Cu2SnS3 (CTS) absorber layer was deposited onto a Mo-coated soda-lime glass substrate by sulfurizing a co-evaporated Cu–SnS precursor thin film. Phase composition and quality of the layer were examined by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. A solar cell with such CTS absorber layer was characterized by current-voltage, external quantum efficiency, capacitance-voltage, and admittance spectroscopy. The CTS solar cell exhibited a maximum conversion efficiency of 2.01%. Capacitance-voltage measurement showed that CTS absorber had hole carrier concentration of 6.37 × 1016 cm−3 and depletion width of 82 nm at room temperature. Admittance spectroscopy showed capacitance steps that might have originated from a deep-level with activation energy and pre-exponential factor of about 0.11 eV and 8.31 × 104 s−1∙K−2, respectively. The concentration of the deep-level defects was estimated to be 5.23 × 1018 cm−3.

Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cells (TFSCs) have emerged as the most promising low-cost alternatives to well-established CuInGaS2 and CuInS2-based TFSCs technologies. The surface composition of the absorber layer and the interface quality between the absorber and buffer layers play a key role in the performance of CZTSSe TFSCs. In this study, we investigated the influence of different etchants namely potassium cyanide (KCN), hydrochloric acid (HCl) and ammonia on different properties such as structural, morphological, and compositional as well as the solar cell performance of CZTSSe TFSCs. The results revealed no significant changes in the film structural properties before and after etching with any of the tested etchants. However, the slight changes in the composition and microstructure were observed after etching treatment. The microstructure was improved after KCN treatment with larger grain size compared to absorber layer without etching, whereas the slightly distorted microstructure with several surface pinholes was observed after HCl and ammonia treatment. Surprisingly, HCl and ammonia treatments degraded the open circuit voltage and fill factor values and thereby decreasing the power conversion efficiency (PCE) of the CZTSSe TFSCs. On the other hand, KCN treatment slightly improved the PCE of CZTSSe TFSCs. The decreased PCE after HCl and ammonia treatments could be mainly attributed to the deteriorated absorber quality as well as poor formation of poor juction between the absorber layer and the CdS buffer layer.

A series of pyrite thin films were deposited in-situ in a monolayer-by-monolayer fashion using sequential evaporation of iron under high vacuum, followed by sulfidation at a sulfur pressure of 133 Pa, as a function of substrate temperature. The stoichiometry, crystallinity, topographic smoothness, and phase purity of the deposited pyrite thin films improve with increasing substrate temperature up to 420 °C, the highest temperature studied. Characterization of the films deposited at 420 °C using selected-area precession electron diffraction, Raman Spectroscopy, and conventional X-ray diffraction indicated that the pyrite layer is phase pure, with no evidence of a secondary marcasite phase, and grew in columnar grains with a preferential (100) orientation on the (100) silicon substrates. This novel sequential evaporation technique has the potential to make useful low-cost semiconducting pyrite materials for large-area electronic applications.

A method for the growth of high quality GaSb epilayer on GaAs (001) substrate is demonstrated in this study. It is found that a superior GaSb/GaAs interface can be obtained by depositing a thin Sb-precursor layer on the GaAs substrate containing a GaAs buffer layer. It is suggested that the growth occurs via the interface misfit (IMF) growth mode. Without this treatment, GaSb epilayer may grow according to the Stranski–Krastanov mechanism or via a blend of the Stranski–Krastanov and IMF mechanisms, leading to an inferior GaSb/GaAs interface. This could be due to the intermixing of anions, leading to the turbulent composition and misfit dislocation distribution at the heterointerface. It appears that with the addition of a Sb layer, IMF arrays can be formed at GaSb/GaAs interface resulting in superior GaSb layer without the need for changing the growth parameters.

Spatial stabilization of long-length structures under the space conditions is connected with a need for minimization of changes of their temperature fields during the non-stationary heating by solar radiation. One of the most effective ways of the solution to this problem is the use of the method of passive thermoregulation due to deposited special coatings on the construction surfaces. In case of deployable structures these coatings should possess a complex of properties, including a definite combination of an absorption coefficient of solar radiation and an emission coefficient, high adhesion to the construction surface in case of its technological and service deforming, as well as a sufficient erosion resistance in contact with other materials. Taking into account the above-mentioned requirements the present work deals with a feasibility of use of two-layer thin coatings, consisting of an inner layer of aluminum and outer layer of titanium dioxide TiO2, which were produced by the method of electron beam deposition. Mechanical and thermal radiation properties of two-layer coatings (Al/TiO2) on the surface of stainless steel were investigated in this work. It is shown that these coatings possess high adhesion strength and are characterized by an optimal combination of coefficients of radiation and absorption of solar radiation that will provide thermal stabilization of deployable steel structures under conditions of their non-stationary irradiation.

A novel technique with a ring-shaped water-cooled copper tube was used to study dynamic oxidation on melts of pure zinc, Zn4Al and ZA27. The thickness of the oxide layers was estimated by kinetic and thermodynamic calculations and measured using scanning electron microscopy on cross sections and energy-dispersive X-ray spectrometry (EDS). The most stable oxide phases on pure zinc, Zn4Al and ZA27 are ZnO, Al2O3 and again Al2O3, respectively. The theoretical thickness of the oxide layer (~5.3 nm) contradicts the experimental results. The dynamically formed oxide layers are an order of magnitude thicker. EDS analysis results in an oxide thickness of 50 nm, 60 nm and 36 nm for Zinc, Zn4Al and ZA27 alloys, respectively. Moreover, the measured thickness of oxide layers established upon cross section method in Zinc, Zn4Al and ZA27 are followed as 90 nm, 70 nm and 55 nm, correspondingly. Based on the appearance of the oxide layers, cracking of the layer which can provide uninterrupted contacts between gas phase and melt, considered as major factor responsible for the significant difference between experimental and theoretical results.

In this study, hetero-interface-structured Bi2Te3-nanoplate/Bi2Se3-electrodeposited films were prepared using all solution processes. Single-crystalline Bi2Te3 nanoplates were synthesized using a solvothermal method, and Bi2Te3 nanoplate films were prepared by drop-casting followed by thermal annealing. The electrodeposition time of the Bi2Se3 layer was tuned to obtain hetero-interface-structured films, wherein the gap between the Bi2Te3 nanoplates was filled. Cross-sectional scanning electron microscopy showed that the heterointerface structured films had a boundary between the composite layer and the Bi2Te3-nanoplate film. The X-ray diffraction patterns of the hetero-interface-structured films without thermal annealing exhibited peaks arising from Bi2Te3, as well as Bi2Se3 with and without antisite defects (SeBi), while those of the annealed film exhibited peaks from Bi2Te3, Bi2Se3, and the ternary alloys due to mutual diffusion. The annealed hetero-interface-structured film with an electrodeposition time of 40 min exhibited the highest power factor of 1.70 μW/(cm∙K2), which is 12-fold and 30% higher than that of the Bi2Te3-nanoplate and homo-interface-structured films (Bi2Te3-nanoplate/Bi2Te3-electrodeposited film), respectively. This enhancement was observed due to (a) increased electrical conductivity arising from the improved crystallinity of the Bi2Se3 electrodeposited layer and (b) increased Seebeck coefficient, resulting presumably from the combined effect of the heterostructured interface, decrease in the number of antisite defects, and formation of ternary alloys. Our findings provide a route for fabricating high-performance thermoelectric materials with low manufacturing costs.

Perylene diimide has been widely used as electron-transporting material due to its high electron affinity and high electron mobilities, therefore, it has been interesting as efficient electron transport for high performance perovskite solar cells. In this study, we introduce a bis (perylene diimide) derivative as a buffer layer of the electron transporting layer by the rapid convective deposition technique. The maximum power conversion efficiency of 13.38% with less hysteresis is achieved from the device with perylene diimide as the electron transporting layer. Further, we found that the performance of the perylene-based device is enhanced due to the lower transporting resistance and the increasing electron mobilities. These results suggest that the perylene diimide derivatives can play a crucial influence in the charge transporting enhancement of perovskite solar cells.

Recent developments in flexible circuits and optoelectronic materials have the potential to provide innovative solutions for wearable sensing. The presented work explores how materials from these developments can reduce the complexity of developing flexible optoelectronics. The work uses simplified fabrication methods to develop a large area thin film optoelectronic device using conjugated polymers and Quantum Dots, with the goal of providing evidence that such devices can be developed outside of a clean room facility. Electroluminescence testing using a power source and an imaging spectrometer show that both conductive polymers and Quantum Dots in the functional layer contribute to light emission. High voltages needed for light emission are likely a result of the observed uneven thicknesses in the active layer, which should be the main focus for improvement in continued work. To study flexibility, the effects of cyclic bending using an Instron machine is observed. Visual analysis identifies four main flaw features that can occur from the fabrication process, and that cyclic bending causes cracking only at these flaw features. This work serves as evidence that use of clean room facilities are not necessary to provide significant contributions towards flexible optoelectronic materials development.

Molybdenum (Mo) thin films are widely used in microelectromechanical systems (MEMS) applications. Mo bilayer deposition by direct current (DC) magnetron sputtering has been proposed in order to attain the desired smooth surface, small in-plane tensile stress and high degree crystallisation of Mo thin film for the fabrication of MEMS actuators and electrodes. The influences of sputtering time (10 min–40 min) and sputtering DC power (100 W–250 W) on the physical and microstructural properties of single layer Mo thin film have been evaluated. The optimised sputtering conditions for bottom and top layer of Mo bilayer have been determined and the individual influence of each layer on the resulting Mo bilayer has been discussed. Our studies reveal that the deposition of top Mo layer with small surface roughness but high in-plane tensile stress has reduced the high surface roughness of bottom Mo layer and simultaneously retained the small in-plane tensile stress. Reducing the sputtering time and/or using similar sputtering power for bottom and top layers improved the crystallinity of Mo bilayer along the preferred 〈110〉 direction. Mo bilayer thin films of total thickness 19 nm, surface roughness

This paper discussed about the morphological and electrical properties of c-axis oriented aluminium nitride (AlN) thin films grown on Si (100) and Si (110) substrates by direct current (DC) reactive sputtering technique. Both the films showed intense (002) peak with the texture coefficient (γ) of 3.1 and 2.8 corresponding to Si (100) and (110) substrates. The AlN/Si (110) have grain sizes (20–30 nm) compared to the relatively denser grains (30–40 nm) of the film on Si (100) substrate. Both the films exhibited slanted columnar structures with slanting angle of 15° (Si (100) substrate) and 20° (Si (110) substrate). The dielectric constant values of the films at low frequency are found to be 7.4 and 8.8 corresponding to the Si (100) and Si (110) substrates respectively. The variation in dielectric constant values over the low frequency regime seems to be due to the presence of trapped charges present in the AlN layer and AlN‑silicon interface (interface trap density~1012 cm-2 eV−1). The flat band voltages are found to be 0.85 V and − 0.35 V corresponding to the Si (100) and (110) substrates respectively. The AlN/Si (100) film showed poor leakage current density ~ 10−4 A/cm−2 as compared to AlN/Si (110) (~ 10−5 A/cm−2). The AlN films exhibited dielectric breakdown field of 4.4 MV/cm and 6.6 MV/cm corresponding to the Si (100) and Si (110) substrates respectively.

Indium zinc oxide/silver/indium zinc oxide multilayer structures with a very low resistivity and high transmittance were deposited on a polyethylene terephthalate substrate by DC magnetron sputtering. The electrical, optical, mechanical, and thermal properties of the multilayer films were investigated at different Ag layer thicknesses (10–20 nm). The multilayers demonstrated relatively constant resistance change (∆R/ R0) over repeated bending tests with a radius of 8 mm. Efficient Joule heating could increase the operating temperature of the film heaters (7.3 Ω/□) to 73.7 °C in ~20 s at 3 V; moreover, the heat distribution remained uniform after bending tests. A high transmittance (84.7%) at a wavelength of 550 nm and low sheet resistance (7.3 Ω/□) of the optimized multilayer was obtained at an Ag layer thickness of 15 nm. These results indicate that the multilayers are promising as transparent film heaters for next-generation flexible applications.

Magnetron sputter deposited Mo thin films are frequently used as part of the metallization of thin film transistors. To ensure technological applications these Mo thin films are often combined with Al thin films, but are inherently brittle compared to the electrical charge carrying ductile Al thin films. To improve the fracture behavior of bilayered stacks containing Mo layers for future flexible devices like rollable or foldable displays, an optimum ductile/brittle layer thickness ratio is necessary. Within this work the electro-mechanical behavior of bilayered Al/Mo thin films grown by dc magnetron sputter deposition on polyimide substrates under tensile strain was investigated. Various Al/Mo layer thickness ratios (1:1, 3:1, 5:1 and 10:1), all with a base Mo film of 30 nm were tested. In situ tensile tests combining electrical 4-point probe resistance and optical measurements revealed an optimum thickness ratio between 5:1 and 10:1 for the crack onset strain. Post mortem analysis on the crack morphology revealed that higher thickness ratios better compensate cracks by leaving wider subsurface pathways for electron conduction of the layer stack than lower thickness ratios.

We investigated characteristics of TiN doped In2O3 (ITON)/Ag-Ti/ITON multilayer films prepared by using co-sputtering and thermal evaporation at room temperature to use as transparent and flexible electrodes. The optimized ITON(40 nm)/Ag-Ti(14 nm)/ITON(40 nm) multilayer film showed a sheet resistance of 4.136 Ohm/square and an average transmittance of 86.45% at visible range between 400 and 800 nm. In addition, the ITON/Ag-Ti/ITON multilayer film exhibited a constant resistance change (R/R0) below critical outer bending radius of 6 mm, which is smaller than typical Sn-doped In2O3 films. At dynamic fatigue tests, the ITON/Ag-Ti/ITON film showed a constant resistance change during 10,000 times repeated outer/inner bending cycles due to outstanding flexibility of the Ag-Ti interlayer and amorphous structure of the ITON layer. Low sheet resistance, high optical transmittance, and outstanding mechanical properties of ITON/Ag-Ti/ITON multilayer films indicate that ITON-based hybrid electrode is promising flexible and transparent electrodes for high performance flexible photovoltaics.

Atomic layer deposition of Al2O3 was used to fabricate rear surface passivation with lithographed point contact Cu(In,Ga)Se2 (CIGS) solar cells. We successfully demonstrated the use of photolithography to fabricate point contact holes of small size and fine pitch. The efficiency of the Al2O3 rear-surface-passivated ultra-thin CIGS solar cells with absorber layers of 1.89 μm and with a 5-nm-thick Al2O3 rear surface passivation layer and local point contact holes with a pitch of 1 μm and a diameter of 500 nm was 19.3% (total area = 0.519 cm2). The efficiency of the Al2O3 rear-surface-passivated ultra-thin CIGS solar cells with absorber layers of 380 nm was 11.3% (active area = 0.514 cm2) when an antireflection layer was used. Compare with unpassivated CIGS solar cells, higher efficiencies were found for the Al2O3 rear-surface-passivated CIGS solar cells, mainly due to the reduced carrier recombination and enhanced rear internal light reflection.