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Currently, research is being actively conducted aimed at developing materials and devices for obtaining and storing energy from renewable sources. In particular, attention is paid to the conversion of solar energy with a view to its subsequent storage in lithium-ion current sources or hydrogen storage devices. In this regard, the possibility of electrochemical synthesis of photoelectroactive thin silicon films on glassy carbon from the low-melting LiCl-KCl-CsCl-K2SiF6 electrolyte at a temperature of 540 °C was studied in this article. Experimental samples of thin silicon films were obtained from the studied electrolyte depending on the electrolysis parameters; their morphology and elemental composition have been studied by means of scanning electron microscopy and energy-dispersive X-ray analysis. The pulsed mode of electrodeposition of the densest film was chosen, including: an anode treatment of the surface of the working electrode at a current density of 14.3 mA/cm2 during 5 s, after which pulsed electrolysis was carried out at a cathode current density of 28.5 mA/cm2 for 30 min with periodic current interruptions. The photoelectric effect of obtained silicon film was studied. A relatively high photosensitivity of the sample was shown due to an increased specific surface area and its energy inhomogeneity. Then, the base properties of the obtained sample were determined by means of atomic emission spectroscopy, visual photoelectron microscopy with plasma treatment of the sample with argon, laser atomic emission spectrometry, and atomic force electron microscopy. Highlights: • Electrochemical synthesis. • Silicon thin films were deposited. • Films were tested. [ABSTRACT FROM AUTHOR]

The crystal volume ratios of silicon thin films vary depending on the substrate material and production conditions. The difference in crystal volume fraction also affects the types of electronic defects in the band gap of thin films. Electronic defects occur in silicon thin films due to atmospheric conditions or prolonged light exposure. Conductivity values changes can occur due to the change of electronic defects. In this study, silicon thin films were grown on three different substrates at the same time using the PECVD technique. The crystal volume ratios and surface morphology of the grown films were determined by Raman Spectroscopy and scanning electron microscopy (SEM) respectively. The grown silicon thin films intentionally were exposed to different atmospheric conditions (such as laboratory atmosphere, light soaking and UV aging) and electronic defects were created in the structure of the thin films. The behavior of these defects were investigated by electrical conductivity methods, which are time dependent dark conductivity, photoconductivity and mobility-lifetime calculations. As a result of the findings, it was determined that there were significant differences in the crystal volume ratios and thicknesses of the materials due to the different base materials, and that the materials were affected by different electronic defect states in the same atmospheric conditions due to these differences. [ABSTRACT FROM AUTHOR]

Based on the finite-difference time domain (FDTD) method, this paper has studied the absorption characteristics of the all-dielectric absorbers composed of silicon thin film with a multilayer dielectric stack. Broadband absorption was achieved in this paper. For instance, one-dimensional planar structure composed of 60nmSiO2–30nmMgF2–60nmGaN–3000nmSi maintains a broadband absorption ≥ 95% over a wavelength range from 440 to 770 nm. And the whole absorptance maintains 90% in the above spectral band, at an oblique incidence angle of 0.25π, while compared to the absorption property of pure silicon film in the same thickness but less than 70%, the new structure shows the greatly improving. [ABSTRACT FROM AUTHOR]

See-through, light-through, and color modules are developed for large-area (1.3 m × 1.1 m) tandem amorphous/microcrystalline silicon thin-film solar modules for building-integrated photovoltaic (BIPV) applications. Key technologies for achieving these BIPV functionalities are developed and introduced into the 60 MW production line. These key technologies include post-scribing passivation of nano-size thin-films, large-area film uniformity, front reflective layers, 4-step laser scribing, transverse laser scribing, and peripheral pen-type junction boxes. This paper demonstrates and discusses the potential and versatility of these silicon thin-film modules in BIPV applications. It also shows that the BIPV modules' specifications and performance mainly depend on the key technologies and their associated manufacturing processes in the production line. The electrical and optical performances of the BIPV modules are presented and important issues about their use in BIPV applications are also discussed. • See-through, light-through, and color a-Si/μ-Si BIPV modules are developed. • Key technologies are developed and introduced into the 60 MW production line. • Post-scribing passivation, large-area film uniformity, front reflective layers. • 4-step laser scribing, transverse laser scribing, peripheral pen-type junction boxes. [ABSTRACT FROM AUTHOR]

Highlights • Novel method of synthesis of Si nano porous thin film with laser plasma ionization. • Study of effect of ionization temperature and process overlap on thin film thickness and its resistive behavior. • Effect of such variation in topological structure of the fabricated thin film. Abstract Considering abundance of silicon on earth with its known acceptance in semiconductor industries and increasing applications of nano porous thin films in various sensors, electrical circuits, new generation batteries, and capacitors, it is essential to comprehend the resistive behavior offered by Silicon Nano-fibrous (SiNf) thin films. We present a novel approach of laser plasma processing of silicon surface to fabricate SiNf thin films with diverse range of resistivity. Parallel plate electrode configuration was employed to measure the resistance offered by SiNf thin film fabricated using various laser parameters. Pulsation width of laser was varied to affect the plasma temperature causing variation in suitable ablation conditions. In addition, scanning parameter of leading(i.e.distance between two consecutive scan with laser beam) was modified to change the extent of silicon surface covered under direct laser gaussian beam causing variation in process overlap. Along with the resistive nature of the thin films, topological changes were also studied for the sound understanding and validation of respective resistive behavior. Significant difference was noticed in terms thickness, structure and resistivity of SiNf thin film when such variation was performed. Also, successful correlation was attained with sound support of various analysis and surface characterization tests. [ABSTRACT FROM AUTHOR]

We study light trapping and parasitic losses in hydrogenated amorphous silicon thin film solar cells fabricated by plasma-enhanced chemical vapor deposition on nanostructured back reflectors. The back reflectors are patterned using polystyrene assisted lithography. By using O2 plasma etching of the polystyrene spheres, we managed to fabricate hexagonal nanostructured back reflectors. With the help of rigorous modeling, we study the parasitic losses in different back reflectors, non-active layers, and last but not least the light enhancement effect in the silicon absorber layer. Moreover, simulation results have been checked against experimental data. We have demonstrated hexagonal nanostructured amorphous silicon thin film solar cells with a power conversion efficiency of 7.7% and around 34.7% enhancement of the short-circuit current density, compared with planar amorphous silicon thin film solar cells. [ABSTRACT FROM AUTHOR]

We study light trapping in hydrogenated amorphous silicon thin film solar cells fabricated by plasma-enhanced chemical vapor deposition on various nanostructured back reflectors. The back reflectors are patterned using polystyrene assisted lithography. We have investigated the correlation between the back reflector optical properties and the corresponding solar cell performance. We have introduced double size polystyrene sphere patterned back reflectors and have provided experimental evidence for improved light trapping performance compared to single size polystyrene sphere patterned back reflectors. We have achieved high performing nanostructured amorphous silicon solar cells with an initial power conversion efficiency of 7.53% and over 20% enhancement of the short-circuit current compared with the reference flat solar cell. [ABSTRACT FROM AUTHOR]

A continuous‐wave blue laser annealing (BLA) system (λ ~ 440 nm) is applied to delineate the physical phenomenon of low‐temperature crystallization from amorphous Si (a‐Si) thin film to poly‐Si film on glass substrates for potential industrial application. At various scanning speeds and laser intensities, crystallization mechanism of BLA has been studied. It shows that BLA can achieve high quality, smooth poly‐Si film with laterally grown grains with sizes of 4×10 µm, as studied by optical microscopy, Raman spectroscopy, and AFM. The p‐channel poly‐Si TFT on glass exhibited the field‐effect mobility of 120.82 cm2/Vs and subthreshold swing of 284mV/dec. Therefore, it proves that BLA can substitute conventional annealing processes as a reliable, scalable, and economical tool. [ABSTRACT FROM AUTHOR]

SiO x N y is an innovative material that has recently attracted a lot of attention in different and new applications, ranging from photovoltaics, conductive oxide, carbon capture; nevertheless, due to its complex and multiphase nature, the understanding of its electrical properties is still ongoing. In this framework, the present manuscript presents the investigation of electrical transport properties of nanocrystalline (nc-) SiO x N y . In fact, non-stoichiometric nc-SiO x N y films deposited by Plasma Enhanced Chemical Vapor Deposition have been studied by conductive Atomic Force Microscopy (AFM). The analyses of samples subjected to different thermal treatments conditions and the comparison with nc-Si:H films have allowed us to clarify the role of crystallization and O content on the local conductivity of the layers. We show that the annealing treatment promotes an enhancement of conductance, a redistribution of the conductive grains in the layers and the activation of B doping. Current-voltage characteristics locally performed using the conductive AFM-tip as a nanoprobe have been modelled with thermionic emission transport mechanism. [ABSTRACT FROM AUTHOR]

To obtain an optimum absorption layer based on hydrogenated polymorphous and nanocrystalline silicon thin films in a plasma-enhanced chemical vapor deposition, radio frequency (RF) power was varied from 25W to 100W using a mixture of dichlorosilane and hydrogen. By Raman spectroscopy, the crystalline fraction was found to be varied from 7% to 69%, and RF power value of 75W was found to be suitable with an appropriate mixture of amorphous and crystalline phases, respectively. Thickness measurements performed by profilometry were cross-checked with the value obtained from the cross-sectional scanning electron microscopy micrographs. Micrographs obtained using high-resolution transmission electron microscopy confirmed the presence of silicon nanocrystals in the range of 2-5nm with a strong probability of confinement effect. B and gap value of 1.55eV at 75W upheld the suitability of this particular RF power for active absorption layer, which has also shown maximum photosensitivity. By varying the RF power in a plasma-enhanced chemical vapor deposition (PECVD) system, control over the morphology and phase transition (a-Si to nc-Si) of silicon thin films has shown. Furthermore, control over the size of nanoparticles and hence, effective band gap (absorption coefficient) of the material is also reported. Overall, the use of the present material as a proficient absorption layer in silicon solar cells shown excellent optoelectronic properties. [ABSTRACT FROM AUTHOR]

The thermal unimolecular decomposition of SiH ion and its related reverse reactions, SiH + H and SiH + H, have been investigated by ab initio molecular orbital and quantum statistical variational RRKM theory calculations. The potential energy surface has been calculated at different levels of theory; the results at the highest level, CCSD(T)/CBS//CCSD(T)/6-311++G(3df,2p), show that the decomposition of SiH can mainly occur via a barrierless channel giving SiH + H lying 11.8 kcal/mol above the reactant, or via a transition state forming SiH ···H complex to be followed by a barrierless decomposition yielding SiH + H lying 23.5 kcal/mol above the reactant. Barrierless processes were calculated using the CASPT2 and CASSCF methods with the 6-311++G(3df,2p) basis set and fitted with Morse potentials. The rate constants were predicted by solving master equations based on the RRKM theory at the E,J-resolved level; the results show that the channel SiH → SiH + H is predominate under PEVCD conditions. For H- and H-capturing by SiH and SiH ions, respectively, the rate constants were found to be weakly dependent on temperature at the high-pressure limit and decrease rapidly with pressure. The calculated heats of formation of the SiH (x = 2-4) ions are in close agreement with available thermochemical data. [ABSTRACT FROM AUTHOR]

In this work, we extend the multiscale cohesive zone model (MCZM) (Zeng and Li in Comput Methods Appl Mech Eng 199:547-556, 2010), in which interatomic potential is embedded into constitutive relation to express cohesive law in fracture process zone, to include the hierarchical Cauchy-Born rule in the process zone and to simulate three dimensional fracture in silicon thin films. The model has been applied to simulate fracture stress and fracture toughness of single-crystal silicon thin film by using the Tersoff potential. In this study, a new approach has been developed to capture inhomogeneous deformation inside the cohesive zone. For this purpose, we introduce higher order Cauchy-Born rules to construct constitutive relations for corresponding higher order process zone elements, and we introduce a sigmoidal function supported bubble mode in finite element shape function of those higher order cohesive zone elements to capture the nonlinear inhomogeneous deformation inside the cohesive zone elements. Benchmark tests with simple 3D models have confirmed that the present method can predict the fracture toughness of silicon thin films. Interestingly, this is accomplished without increasing of computational cost, because the present model does not require quadratic elements to represent heterogeneous deformation, which is the inherent weakness of the previous MCZM model. Quantitative comparisons with experimental results are performed by computing crack propagation in non-notched and initially notched silicon thin films, and it is found that our model can reproduce essential material properties, such as Young's modulus, fracture stress, and fracture toughness of single-crystal silicon thin films. [ABSTRACT FROM AUTHOR]

Hybrid solar cells have been fabricated from solution processing of poly-(3-hexylthiophen-2,5-diyl) onto planar poly-crystalline thin film silicon (poly-Si) absorbers on glass. The poly-Si layers were prepared by laser crystallization. Methyl passivation of the poly-Si surface by a one-step grafting process via methyl-Grignard enabled open circuit voltages of up to 552 mV and an overall power conversion efficiency of 6.6% for this device type. The solar cell exhibited significant advantages compared to the wafer-based counterparts. The inverted device structure of the thin film cell lead to an enhancement of the quantum efficiency since the back side contacted cell had less light absorption and reflection losses due to the gold layer which was used as front contact for the c-Si-based hybrid solar cell. As a result, a photo current of 24.3 mA cm−2 was obtained for a 10 μm thin poly-Si layer on glass. Furthermore, the inverted device structure showed a pronounced increase in stability due to the much thicker gold back contact that reduces the diffusion of water and oxygen toward the polymer layer. After 3 months in ambient air, this type of solar cell operated with 86% of its initial efficiency. [ABSTRACT FROM AUTHOR]

A surface plasmon resonance based biosensor consisting of SF10 prism, silicon layer, gold thin film and MoS 2 enhanced nanosheet is presented. We systematically investigated the SPR reflectivity and resonance angle through the transfer matrix method. Furthermore, with the optimized thickness of gold, silicon and MoS 2 , we calculated the change of resonance angle to a fixed refractive index change of sample solutions and the full width at half maximum of the reflectivity curves. The excitaition wavelengths of light sources that we use range from 600 nm to 1024 nm which covers both visible and near infrared light. In addition, the optimum configuration for MoS 2 -enhanced SPR biosensors are monolayer MoS 2 and 7 nm silicon layer coated on 50 nm Au thin film with 633 nm as the excitation wavelength. With these optimized parameters we can efficiently increase the sensitivity by ∼10%. Even without the silicon layers, the pure MoS 2 enhanced nanosheet can also improve the sensitivity by ∼8%. The performance of MoS 2 enhanced nanosheet is almost 3-fold higher than that of graphene. [ABSTRACT FROM AUTHOR]

In this work, phosphorus and boron doped silicon films were deposited on monocrystalline silicon substrates by plasma enhanced chemical vapour deposition. Microstructure and net doping concentration were investigated using Raman spectroscopy and secondary ion mass spectrometer, and the dark conductivity, carrier concentration and mobility of the films were measured using semiconductor characterisation system. The results indicated that the structure of the films were all amorphous despite of the different doping gas flow ratios, and the dark conductivity and carrier density changed by only one order of magnitude with the increase in [PH3]/[SiH4] and [B2H6]/[SiH4] gas flow ratios. The best flow ratios of [PH3]/[SiH4] and [B2H6]/[SiH4] were obtained to be 1·5 and 1% respectively, and then the optimised samples were annealed. After annealing, the film expressed a tendency of transition to crystalline from amorphous according to the Raman results, and the dark conductivity and carrier concentration increased by two to three orders of magnitude for both doped film series. The structure has more significant influence on the electrical properties of doped silicon thin film than the doping concentration. [ABSTRACT FROM AUTHOR]

• SiO x thin film was obtained by electron beam deposition of Si and subsequent annealing. • The annealed SiO x thin film electrode exhibits a long-term cycle stability. • The inter-layer between Si film and substrate enhances cyclability of the electrode. Silicon (Si) is a promising material as anode electrode because of its high theoretical capacity of 3579 mAh g−1 and low electrode potential (< 0.4 V vs. Li/Li+). In this paper, the Si thin film electrodes were fabricated by using electron beam evaporation on the stainless steel (SS) foil at room temperature. The structural and electrochemical characterization were investigated for the Si thin film electrodes before and after annealing at 700 ˚C. X-ray photoelectron spectroscopy analysis revealed that the annealed film layer consisted of SiO x containing about 30 at.% oxygen. The annealed Si thin film electrode resulted in improved electrochemical performance compared to as-deposited Si thin film electrode. The Si thin film electrode after annealing exhibited an initial discharge capacity of 2270 mAh g−1, and sustained excellent cycle stability with retention capacity about 95 % for 100 cycles at 0.5 C-rate. The improvement in cyclability for the annealed Si thin film electrode can be attributed to the enhanced adhesion of Si thin film to SS substrate through interdiffuion at the Si/SS interface owing to the post-annealing process. [ABSTRACT FROM AUTHOR]

Silicon thin films were deposited on a sapphire and a highly oriented pyrolytic graphite (HOPG), which have atomically flat and chemically inert surfaces. The electronic and geometrical structures of the films were analyzed by X-ray photoelectron spectroscopy (XPS) and polarization-dependent X-ray absorption fine structure (XAFS). It was found that the silicon K- edge XAFS spectra for ultra-thin silicon films thinner than 0.2 monolayer exhibited two distinct resonance peaks which were not observed for bulk silicon. The peaks were assigned to the resonance excitations from the Si 1 s into the valence unoccupied orbitals with π ∗ and σ ∗ characters. The average tilted angle of the π ∗ orbitals was determined by the polarization dependencies of the peak intensities. It was demonstrated that direction of a part of the π ∗ orbitals in silicon film is perpendicular to the surface. These results support the existence of quasi-freestanding single-layered silicon films with sp 2 configuration. [ABSTRACT FROM AUTHOR]

In this paper, non-equilibrium molecular dynamics simulations (NEMD) are employed to study the effects of isotope and in-plane strain on the thermal conductivity of silicon thin film. The results show that the thermal conductivity of silicon thin film decreases with the isotope concentration at the lower concentration and increases with the isotope concentration at the higher concentration, respectively. In addition, simulations on the strained film indicate that the thermal conductivity decreases monotonously with the applied strain. To achieve a fundamental understanding of the physical mechanisms, phonon density of states (DOS) and phonon dispersion are analyzed in details. High frequency phonons are found to be sensitive to the impurity, which leads to the reduction of phonon group velocity. For the strained thin film, high frequency phonons, especially of transverse optical (TO) phonon branch, play an important role in the change of thermal conductivity. Our findings suggest the great potential of tailoring the thermal properties by isotope and mechanical strain. [ABSTRACT FROM AUTHOR]

Abstract: The study of high energy density electrode materials is central to the development of Li+-ion batteries. Si is among the most promising anode materials for next generation Li+-ion batteries. Model composite electrodes of self-organized, conductive titania (TiO2−x –C) nanotubes coated with silicon (Si) via plasma enhanced chemical vapor deposition (PECVD) are produced and studied in terms of their lithiation/delithiation characteristics. The nanotube array provides direct one dimensional electron transport to the current collector, without the need of adding binders or conductive additives. Both components of the composite can be lithiated delivering 120 μAh cm−2 total capacity for a film thickness of 1 μm and a Si loading of ∼10 wt.%. 86% capacity retention upon 88 cycles at a rate of C/5 and 60 μAh cm−2 total capacity at a rate of 10 C are achieved owing to the low lateral expansion and thus good adhesion of the thin Si coating to the TiO2−x –C nanotubes, and due to the formation of a stable solid electrolyte interface (SEI) in ethylene-carbonate (EC), dimethyl-carbonate (DMC), vinylene-carbonate (VC) electrolyte with 1 M LiPF6. [Copyright &y& Elsevier]

Abstract: Internal monochromatic acoustic phonon emission has a distinct impact on temperature distribution, as well as transient heat dissipation, depending on the emitted phonon frequency and its polarization branch. A Monte Carlo simulation of phonon transport was used to study the impact of internal acoustic phonon emission on heat dissipation at nanoscale in a silicon thin film. The cause of the emission can be due to other energy carriers or by a direct external source. The simulation utilized parabolic phonon dispersion relations in longitudinal acoustic (LA) and transverse acoustic (TA) polarizations with three phonon–phonon scatterings. The Normal and Umklapp phonon scatterings were included in the simulation. All the scattering events scatter phonons isotropically. Results indicated that monochromatic TA-phonon emission within the film tends to create higher local peak temperature than that of LA-phonon emission with an identical volumetric power generation. [Copyright &y& Elsevier]

The parameters of a SiH4/H2 VHF plasma were measured as a function of silane gas concentration with a heated Langmuir probe. It was found that when the sailane gas concentration is increased, the nagative ion density increases. Here the negative ion density was estimated from the reduction of the electron saturation current. In addition, the dependence of the wall potential on the silane gas concentration agreed with the theoretical values derived from the Bohm sheath equation including negative ions. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Recently, Siemens et al. found that the Fourier law may overestimate the energy transported away from one hot spot in the thin film. In this work, the lattice Boltzmann method is employed to investigate phonon transport in silicon thin films. It is found that in the transitional or ballistic regime when the thermal waves initiated from temperature disturbances on two surfaces of the thin film meet in the inner region, the temperature rises significantly, which is different from the case when the heat conduction is induced by the temperature disturbance on one surface of the thin film. Therefore, the interaction of thermal waves induced by the thermal transport from two nanoscale hot spots separated by a nanoscale distance inside the thin film may temporarily cause a higher temperature in some regions between the two hot spots than that predicted by the Fourier law. [ABSTRACT FROM AUTHOR]

Abstract: The effect of vinylene carbonate (VC) as electrolyte additive on the properties of the silicon electrode / liquid electrolyte interface was studied in this paper. Galvanostatic cycling, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the SEI layer properties and the morphology at different stages of the cycling of thin film electrodes. The electrochemical performances were drastically improved by the introduction of a few per cent of VC additive. It was found that the SEI layer formed in VC-containing electrolyte has a different chemical composition and better resists to the stress caused by large volume variations associated with lithiation and delithiation reactions. The chemical and topographic modifications of the electrode surface at various stages of cycling are discussed in correlation with the evolution of the reversible capacity over cycling with and without VC. This study highlights the importance of the SEI which governs the electrochemical performances of Si thin film model electrodes. [Copyright &y& Elsevier]

We report on a comprehensive study of water jet guided laser cutting of polycrystalline silicon thin films using a pulsed 515nm disk laser. The optimization of the cutting process of polycrystalline silicon wafers having a thickness of 200-300μm is based on a Design of Experiments (DOE) approach taking into account process parameters such as laser power cutting speed laser repetition rate water pressure and nozzle diameter respectively. The targeted response of the DOE is defined by both the quality as well as the productivity of the cutting process. While the former is measured by the mechanical strength and the chipping of the wafers the latter is determined by the ablation depth and the cutting kerf cross-sectional area. Our analysis identifies the most influencing parameters on the cutting process provides insight into the interactions of these parameters and finally delivers an optimized process parameter window for water jet guided laser cutting of thin silicon films. [ABSTRACT FROM AUTHOR]