Defect Levels Research Articles

Influence of zinc on electrochemical and photoluminescence properties of yttrium chromate nanoparticles

YCrO4: Zn (1-9 mol %) nanoparticles were synthesized using Aloe vera gel via a solution combustion method and subsequently calcined at 600 °C for 3 h. X-ray diffraction analysis confirmed a pure tetragonal crystal structure, indicative of high material quality, while surface morphology revealed irregularly shaped and sized nanoparticles that varied with dopant concentration. The crystallite size, calculated using Scherrer’s method, decreased from 14 nm to 9 nm, and the optical energy band gap narrowed from 2.93 eV to 2.75 eV with increasing zinc doping. Photoluminescence emission spectra, recorded under 310 nm excitation, displayed peaks centered at 483, 525, and 628 nm, with the violet-blue emission attributed to the recombination of zinc interstitial (Zni) and zinc vacancy (VZn) energy levels. The presence of oxygen vacancies contributed to the green emission peak, while red emissions resulted from band transitions between zinc interstitial and oxygen interstitial (Oi) defect levels within the host matrix. The CIE coordinates fell within the 1713 K region, with an average color-correlated temperature of 1730 K, indicating a warm LED output. Electrochemical studies demonstrated that the specific capacitance of YCrO4:Zn (1-9 mol%) nanoparticles ranged from 86.94 to 130.27 F/g at a scan rate of 10 mV/s, underscoring the significant influence of dopant concentration on the material’s electrochemical properties, as higher concentrations of Zn2+ in YCrO4 enhanced the charge storage capability, suggesting its potential for improved performance in energy storage applications.

First-principles study on defect levels of transition metal ions in near-inverse MgGa2O4

First-principles study on defect levels of transition metal ions in near-inverse MgGa2O4

Structural and electronic properties of interstitial oxygen defect in amorphous indium gallium oxide (IGO) semiconductors: a theoretical study

Abstract We elucidate the role of gallium (Ga) in the structural and electronic properties of amorphous indium gallium oxide(a-IGO) for different Ga concentrations with oxygen interstitial defects by using hybrid density functional methods. Ab initio molecular dynamic simulations reveal that Ga substitution significantly affects the structural characteristics and that Ga-O coordination is particularly sensitive to changes in oxygen stoichiometry. The electronic structure indicates the formation of an O-O dimer in the neutral state. The stability of this dimer upon capturing electrons is influenced by the local atomic structure around the dimer. When the bond breaks, the dimer's antibonding defect level is significantly lowered from the conduction band, approaching the valence band. This makes it more energetically advantageous for the dimer to capture two electrons. We statistically studied the Ga concentration dependence on the impact of O2 dimer generation in a-IGO. Formation transition energy indicates that O-O bond is broken easily with more Ga, which acts as an electron trap identifying the origin of positive bias stress (PBS) observed in the transistor behavior.

Modification of Gallium Nitride Defect Structure by Microwave Radiation Treatment

GaN has incredible potential for applications in high‐electron‐mobility transistors, ultraviolet light‐emitting diodes, and gas sensor systems. Herein, the results of the study of modification of the structure of GaN films formed on sapphire substrates by microwave radiation treatment (MRT) are presented. In particular, the influence of the MRT (2.45 GHz) on the defect concentration in this material is investigated. Moreover, features of the long‐term evolution of the defect subsystem are tracked as well. Both spectral (photoluminescence (PL)) and structural (X‐ray) methods of investigation are applied to obtain reliable results about the concentration of defects in particular dislocations. PL and X‐ray diffraction spectra are measured to achieve this goal. These measurements are repeated after several days to estimate the temporal evolution of the defect level resulted from the MRT. It is found that the concentration of screw dislocations changes nonmonotonously after the MRT, while the concentration of edge dislocations almost does not change. The obtained results advance the understanding of the processes, which may be useful for defect engineering by MRT.

Effect of dopants and surface oxides on the electronic properties of dislocations in p-type SiC

Abstract Understanding the electronic properties of dislocations is key to tailoring the properties of silicon carbide (SiC)-based electronic devices. By combining the Kelvin probe force microscopy (KPFM) analysis and first-principles calculations, we investigate the effect of aluminum (Al) dopants and surface oxides on the electronic properties of dislocations in p-type SiC. It is found that dislocations, including threading screw dislocations (TSDs), threading edge dislocations (TEDs), and basal plane dislocations (BPDs) create deep acceptor-like states in p-type SiC. The defect levels move upwards in the order of BPD, TED and TSD, which closely relates with the lattice distortion of dislocations. Interestingly, we find that the defect levels of dislocations are higher than that of Al in p-type SiC. First-principles calculations indicate that the defect formation energies of Al dopants at the cores of dislocations are higher than those in the perfect region of p-type SiC, as a result of the steric effect. This indicates that the concentration of Al acceptors at the dislocation cores is lower than that in the perfect region, resulting in the higher defect level positions of dislocations in p-type SiC. Additionally, we find that surface oxidation reduces the difference of defect-level positions between dislocations and the perfect region of p-type SiC, which paves the way for tailoring the electronic properties of dislocations in p-type SiC.

Superior Multimodal Luminescence in a Stable Single-Host Nanomaterial with Large-Scale Synthesis for High-Level Anti-Counterfeiting and Encryption.

Multimode luminescent materials exhibit tunable photon emissions under different excitation or stimuli channels, endowing them high encoding capacity and confidentiality for anti-counterfeiting and encryption. Achieving multimode luminescence into a stable single material presents a promising but remains a challenge. Here, the downshifting/upconversion emissions, color-tuning persistent luminescence (PersL), temperature-dependent multi-color emissions, and hydrochromism are integrated into Er3+ ions doped Cs2NaYbCl6 nanocrystals (NCs) by leveraging shallow defect levels and directed energy migration. The resulting NCs display strong static and dynamic colorful luminescence in response to ultraviolet, 980-nm laser, and X-ray. Additionally, the NCs exhibit distinct luminescent colors as the temperature increases from 330 to 430 K. Surprisingly, it also demonstrates the ability of the reversible emission modal and color in response to water. Theoretical calculations and experimental characterizations reveal that self-trapped exciton state (STEs), chlorine vacancy defects, and ladderlike 4f energy levels of Er3+ ions contribute to multimodal luminescence. More importantly, it has extremely remarkable environmental stability, which can be stored in the air for more than 18 months, showing promising commercial prospects. This work not only gives new insights into lanthanide-based metal halide NCs but also provides a new route for developing multimodal luminescent nanomaterials for anti-counterfeiting and encryption.

Sub-bandgap charge harvesting and energy up-conversion in metal halide perovskites: ab initio quantum dynamics

Metal halide perovskites (MHPs) exhibit unusual properties and complex dynamics. By combining ab initio time-dependent density functional theory, nonadiabatic molecular dynamics and machine learning, we advance quantum dynamics simulation to nanosecond timescale and demonstrate that large fluctuations of MHP defect energy levels extend light absorption to longer wavelengths and enable trapped charges to escape into bands. This allows low energy photons to contribute to photocurrent through energy up-conversion. Deep defect levels can become shallow transiently and vice versa, altering the traditional defect classification into shallow and deep. While defect levels fluctuate more in MHPs than traditional semiconductors, some levels, e.g., Pb interstitials, remain far from band edges, acting as charge recombination centers. Still, many defects deemed detrimental based on static structures, are in fact benign and can contribute to energy up-conversion. The extended light harvesting and energy up-conversion provide strategies for design of novel solar, optoelectronic, and quantum information devices.

Optimizing solar performance of CFTSe-based solar cells using MoSe2 as an innovative buffer layers

In this study, we explore the photovoltaic performance of an innovative high efficiency heterostructure utilizing the quaternary semiconductor Cu2FeSnSe4 (CFTSe). This material features a kesterite symmetrical structure and is distinguished by its non-toxic nature and abundant presence in the earth’s crust. Utilizing the SCAPS simulator, we explore various electrical specifications such as short circuit current (Jsc), open circuit voltage (Voc), the fill factor (FF), and power conversion efficiency (PCE) were explored at a large range of thicknesses, and the acceptor carrier concentration doping (NA). Our results demonstrate that optimized parameters yield a remarkable PCE of 26.47%, accompanied by a Voc of 1.194 V, Jsc of 35.37 mA/cm2, and FF of 62.65% at a CFTSe absorber thickness of 0.5 μm. Furthermore, the performance of the photovoltaic cell is assessed for the defect levels in the CFTSe absorber and MoSe2 buffer layers. Results indicate that deep defect levels above 1 × 1017 cm− 3 lead to a decrease in Jsc. The study also investigates the effect of operating temperature on cell performance within the 300–500 K range. A notable decline in Voc is observed, likely due to an increase in saturation current, suggesting an interaction between temperature and cell behavior. In this work, we propose a practical CFTSe-based structure that replaces conventional buffer layers, such as CdS, with MoSe2 TMDC as a promising alternative buffer layer, paving the way for more sustainable solar technology.

Hydrothermal growth and characterization of large Rb2SnBr6 double perovskite crystals: a promising semiconductor material for photocatalysis and optoelectronics.

In this study, we present the growth of large (millimeter- and centimeter-scale) crystals of Rb2SnBr6 double perovskite via a hydrothermal process. The crystals and powders were successfully synthesized, yielding light-yellow products, and subjected to comprehensive characterization using powder and single crystal X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS) point analysis, and UV-Vis diffuse reflectance spectroscopy. Previously, methods such as solution growth, evaporation, and gel techniques have been employed to synthesize Rb2SnBr6. However, none of these approaches have successfully yielded large crystals on the millimeter- or centimeter-scale. Our experimental results reveal that Rb2SnBr6 is a semiconductor with a bandgap of 2.97 eV. This wide bandgap not only suggests high stability and low defect levels but also positions Rb2SnBr6 as a highly promising candidate for advanced applications in photocatalysis, photovoltaics, and optoelectronics. The ability to grow large-sized crystals with such favorable electronic properties highlights the material's potential for integration into scalable technologies, paving the way for further research and development in energy conversion and optoelectronic devices.

Calcium level and autophagy defect in GNE mutants of rare neuromuscular disorder.

Rare genetic disorders are low in prevalence and hence there is little or no attention paid to them in the mainstream medical industry. One of the ultra-rare neuromuscular disorders, GNE myopathy is caused due to biallelic mutations in the bifunctional enzyme, GNE (UDP N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase). It catalyses the rate-limiting step in sialic acid biosynthesis. There are no effective treatments for GNE myopathy as the pathomechanism is poorly understood. Pathologically, the disease is characterized by the formation of rimmed vacuoles that contain aggregates of β-amyloid, tau, presenilin etc proteins in muscle biopsy samples. Accumulation of aggregated proteins in the cells may occur due to the failure of the regulated autophagy phenomenon. In the present study, we aim to understand the effect of GNE mutations on autophagy. The cytosolic calcium levels in GNE mutant cells were found to be altered in a GNE mutation-specific manner. The chaperone levels, such as HSP70 and PDI, as well as autophagic markers (LC3II/I ratios) were altered in the GNE mutant cells. Treatment with BAPTA-AM, calcium chelator, significantly restored cytosolic calcium levels in some GNE mutant cells as well as autophagic marker levels and autophagic punctae formation. The effect on the calcium signalling cascade involving CaMKKβ/AMPK/mTOR was studied in the GNE mutant cells. Our study provides insights into the role of calcium in autophagic vacuole formation in the cells with GNE mutations that will have significance towards understanding the pathomechanism of GNE Myopathy and drug target identification for the rare disease.

Two-dimensional Nanosheets by Liquid Metal Exfoliation.

Liquid exfoliation is a scalable and effective method for synthesizing 2D nanosheets (NSs) but often induces contamination and defects. Here, liquid metal gallium (Ga) is used to exfoliate bulk layered materials into 2D NSs at near room temperature, utilizing the liquid surface tension and Ga intercalation to disrupt Van der Waals (vdW) forces. In addition, the process can transform the 2H-phase of transition metal dichalcogenides into the 1T'-phase under ambient conditions. This method produces high aspect ratio, surfactant-free 2D-NSs for more than 10 types of 2D materials that include h-BN, graphene, MoTe2, MoSe2, layered minerals, etc. The subsequent Ga separation via ethanol dispersion avoids the formation of additional defects and surfactant contamination. By adjusting initial defect levels of the layered materials, customize the metallicity and/or defectiveness of 2D NSs can be customized for applications such as birefringence-tunable modulators with exfoliated h-BN, and enhanced hydrogen evolution with defective MoS2. This approach offers a strategy to optimize liquid metal/2D interfaces, preserving intrinsic properties and enabling practical applications, potentially transforming optics, energy conversion, and beyond.

Defective UIO66 metal-organic framework nanoparticles assisted by cascade isothermal amplification technology for the detection of aflatoxin B1.

Aflatoxin B1 (AFB1) exhibits significant toxicity and pose a serious threat to food safety, environmental hygiene, and public health even in trace amounts. Hence, the development of a rapid, accurate, and sensitive detection technology has become a pivotal aspect of ensuring control standards. In this study, we introduce the UIO66 and two defective dichloroacetic acid@UIO66 (DCA@UIO66, DU) metal-organic framework nanoparticles, named DU1 and DU2, characterized by different defect levels. It is noteworthy that DU1 exhibits superior DNA sensing capability compared to UIO66 and DU2. With a fluorescence quenching efficiency of 92.66% and a recovery efficiency of 1256.75%, DU1 demonstrates the substantial potential in the detection field. Furthermore, we employ cascade isothermal amplification to assist DU1-mediated fluorescence sensors in detecting AFB1. AFB1 is efficiently identified through an aptamer competition process facilitated by magnetic nanoparticles, which initiates the exponential amplification triggered rolling circle amplification reaction, and converts trace amounts of toxin signal into a large number of long single-stranded DNA molecules. Upon recognition of the amplification product by the fluorescent probe on DU1, a more stable double-stranded DNA is formed and leaves the surface of DU1, leading to a significant change in fluorescence intensity. This method exhibits acceptable sensitivity, with a detection limit of 0.09pgmL-1 and a wide detection range spanning from 0.2pgmL-1 to 20pgmL-1. Additionally, this assay exhibits satisfactory specificity and high accuracy in practical sample applications. Our proposed method offers a solid theoretical framework and technical backing, thereby facilitating the establishment of a new generation of mycotoxin detection standards.

Anorectal manometry and urodynamics in children with spina bifida: can we predict the colonic dysmotility from bladder dysfunction?

IntroductionSpina bifida is a condition that impacts the development of the neural tube leading to urological and gastrointestinal symptoms. Both systems are influenced together due to their shared innervation and embryological origin. Despite its impact on health and well-being there has been limited research on the relationship between manometry results and urodynamic tests, in this patient population. The aim of this study was to delineate the association of neurogenic bladder/bowel dysfunction with anorectal manometry and urodynamics.Materials and methodsUrodynamics and anorectal manometry were used to analyse the neurogenic bowel and bladder dysfunctions in 29 paediatric patients with spina bifida. Those children who had previous anorectal surgical interventions were excluded from the study. Patients were grouped according to the level of spinal defect to lower or upper defect. In this study, parameters such as bladder compliance, postvoid residual volume, detrusor activity, anorectal pressures, and rectal compliance were considered. Group comparison tests were performed using standardized paediatric protocols for data analysis as well as correlation tests. A p-value less than 0.05 was considered significant at all levels.ResultsA total of 29 patients with spina bifida were identified. Of these, 14 were male and 15 were female. Bladder function differed among the patients in the lower defect (LD, n:18) and upper defect (UD, n:11) groups. LD group exhibited lower bladder volumes (175.45 ± 106.19 mL) compared to the UD group (266.83 ± 102.54 mL, p < 0.05). All LD and 72.7% of UD had detrusor sphincter dyssynergia. There was positive correlation between functional bladder parameters and bowel dysfunction, such as rectoanal inhibitory reflex (RAIR) and maximum filling pressures of the bladder (rho = 0.569, p < 0.05). There was also a significant correlation between rectal compliance and bladder volumes.ConclusionsAssociation of neurogenic bowel and bladder dysfunction is a complex issue which requires personalized approach for managing the consequences. In children with neurogenic bladder dysfunction increased RAIR activity may be a sign for colonic dysmotility of neurogenic origin. This study may also pave the way for delineation of the mechanism under the generation of RAIR which is thought to be only intrinsic in origin. To optimize treatment modalities, full assessment with anorectal manometry and urodynamic studies should be done in patients with spina bifida.Clinical trial registrationThis study was not performed on volunteer patients. Clinical study enrolment is not required as this study was obtained from urodynamics and anorectal manometry performed in patients with neurogenic bladder/bowel and during clinical follow-up.

DLTS characterisation of 107 MeV krypton ion-irradiated nitrogen-doped 4H-silicon carbide

Swift heavy ions, such as krypton ions, play a significant role in developing and enhancing the performance of various devices. In this study, the influence of Kr2+ on nitrogen-doped 4H-silicon carbide has been investigated using deep level transient spectroscopy (DLTS). Krypton ions, with an energy of 107 MeV, were used to irradiate the Au/Ni/4H-SiC Schottky barrier diodes (SBDs) at a fluence of 1 × 1010 cm–2 at room temperature (300 K). Before the irradiation of the samples, the electrical measurements revealed good rectifying behaviour. However, rectification properties of the Au/Ni/4H-SiC SBDs were completely lost after irradiation at a fluence of 1 × 1010 cm–2. Annealing was performed at 300 °C in flowing argon, and the current–voltage (I–V) and capacitance–voltage (C–V) revealed partial rectification. DLTS of the as-grown devices analyses revealed the presence of four deep level defects. After annealing the irradiated device, the DLTS spectra showed a reduction in the intensity of the E0.10 and the disappearance of the E0.12 as well as the E0.16 defects compared to that as-grown. Two defects with energies of 280 and 410 meV showed inverted peaks, as would have been expected from minority carriers trap instead of majority carriers, which led to confusion as the peaks were inverted. It was concluded that the peculiar characteristics of DLTS measurements on SBDs may be due to the extremely high value of the series resistance as well as the low capacitance. The results of this study provide insight into the behaviour of SBDs under extreme irradiation and can be used to improve the radiation tolerance of electronic devices made from SiC.

Bifunctional Design of Ferroelectric-Order and Band-Engineering in Cu:KTN Crystal for Extended Self-Powered Photoelectric Response.

Photoelectric conversion in ferroelectric crystals can support many important applications in modern on-chip technology, but suffering from two problems, low responsive current and narrow responsive range. Especially, wide-gap ferroelectric oxides are only active at short-wavelength ultraviolet region with weak photocurrent at nanoampere levels. Here, a bifunctional design strategy of ferroelectric-order and electronic-band to improve the photocurrent and extend the responsive range simultaneously, is proposed. In a Cu-doped KTa1- xNbxO3 (KTN) perovskite crystal, a conductive channel is constructed by "head-to-head" ferroelectric domains, associated with the emergence of micrometer-scale supercells. In addition, the introduction of Cu+ ion can induce defect levels, thus extending the responsive range beyond the inherent absorption of pure KTN. Through rational device optimization, a record self-powered responsivity of 5.23 mA W-1 is realized in Cu:KTN photodetector, which is two orders of magnitude higher than undoped KTN crystal. The temperature-dependent light diffraction and photocurrent show that the ferroelectric-order is dominated in this photoresponse behavior. Moreover, Cu:KTN detector is active in the broadband range from 390 to 1030 nm, covering ultraviolet, visible, and near-infrared regions. This work provides an effective method for the design of next-generation self-powered photodetectors with ultrahigh responsivity and ultrawide responsive range.

DETERMINATION OF PROCESS PARAMETER FOR INJECTION MOLDING : A REVIEW

One of the most suitable methods for mass production of complicated shapes is injection molding due to its superior production speed and quality. Plastic injection is the process of forming products from plastic materials with variations in shape and size. Controlling the quality of plastic products is an important aspect of the plastic injection molding process. To achieve high process effectiveness and desired product quality, correct and precise parameter settings are essential. One of the benchmarks for assessing the productivity and efficiency of an industry is to look at the level of product defects that occur in producing a product. This article aims to provide a brief review of the explanation of injection molding, types of molding, types of injection failure, experimental methods in determining injection molding parameters. Types of failure in the injection process such as short shot, weld mark, warpage, sink mark, air trap, black spot, flashing, hole, over molding, delamination. The experimental method determines parameters such as the Taguchi method, ANOVA method, hard computing techniques. The future will likely tend to use AI techniques as has happened with other methods in manufacturing processes to complement conventional techniques in determining injection molding process parameters.

Compositional engineering of phase-stable and highly efficient deep-red emitting phosphor for advanced plant lighting systems

Inorganic luminescent materials hold great promise for optoelectronic device applications, yet the limited efficiency and poor thermal stability of oxide-based deep-red emitting phosphors hinder the advancement of plant lighting technologies. Herein, a simple compositional engineering strategy is proposed to stabilize the phase, boost external quantum efficiency (EQE) and enhance thermal stability. The chemical modification of the PO4 tetrahedron in NaMgPO4:Eu by incorporating SiO4 lowers the formation energy, leading to the generation of pure olivine phase and increasing the EQE from 27% to 52%, setting a record for oxide deep-red phosphors. In parallel, the introduced deep defect level improves thermal stability at 150 °C from 62.5% to 85.4%. Besides, the excitation and emission peaks shifted to 440 nm and 675 nm, respectively, aligning precisely with the specific spectral absorption requirements of plant phytochromes. Moreover, the luminescent intensity showed nearly no decay after being exposed to 80% relative humidity and 80 oC for 6 h, and the pc-LED utilizing Na1.06MgP0.94Si0.06O4:Eu achieves a high output power of 780 mW at 300 mA. Our research demonstrates a facile method for optimizing the performance of inorganic luminescent materials and provides alternative solutions for low-cost plant lighting.

Identifying Key Parameters for Reducing Recombination Losses at the p - n Junction of Chalcopyrite Thin-Film Solar Cells

With a record efficiency of 23.64% achieved in the past year, Cu(In,Ga)Se2 chalcopyrites are the absorbers of choice for thin-film solar cells. In these devices, the p-type chalcopyrite absorber and the n-type window layer form the p-n junction at the interface, which is mediated by a thin buffer layer. Due to its close proximity to the p-n junction, the defect electronic properties of the absorber surface and its interface with the buffer layer are of significant importance to limit recombination losses of photogenerated carriers. Furthermore, the recent surge in the efficiency gains have been achieved with the aid of heavy alkali-metal elements, which are implemented via a postdeposition treatment of the absorber surface. Due to the complex defect physics of chalcopyrite materials, the effects and involved processes of these alkali-metal treatments are so far not well understood. As a fundamental requirement, understanding the intrinsic defect physics of chalcopyrite absorbers and how it is influenced by various surface treatments is of significant importance. In fact, it can provide a basis to develop knowledge-based strategies to reduce recombination losses due to the presence of electronic defect levels in the vicinity of the p-n junction. To experimentally access such defects at the surface, it is essential that the chosen characterization techniques possess high surface sensitivity. Furthermore, due to the pronounced crystallographic lateral inhomogeneities of the polycrystalline chalcopyrite thin films, a high spatial resolution is desirable. A combined analytical approach using scanning probe microscopy and spectroscopy or Kelvin force microscopy and photoelectron spectroscopy methods can provide valuable insights. Despite the extensive literature available on related topics, a consolidated view of the various findings made in this regard and the direct consequences for the device efficiency is still lacking. Our review addresses the significant progress made in understanding the defect electronic properties of the chalcopyrite surface in the past decade. The findings are consolidated into five sections, which illuminate several external sources of electronic defects and surface-passivation procedures. This allows to develop specific strategies to reduce interface recombination losses for device optimization and improved solar-cell efficiencies. Published by the American Physical Society 2024

Search group control method of a batch of products

A brief overview of group control methods is given, which allow you to simultaneously control several products according to one or more parameters with one control tool. To reduce the time of control of a batch of products in comparison with its piece-by-piece control, a group control search method was developed and studied. It is based on an approach used to find hidden faults in radio equipment by dividing the circuit into parts and then monitoring them. The requirements that the controlled products must satisfy are determined, and the conditions for the advantage of the method are established. The influence of the volume and level of defectiveness of a batch, the distribution of defective products throughout the batch on the time of its inspection was studied. It has been proven: uniform distribution of defective products throughout the batch leads to the longest inspection time; the time of batch control by this method is significantly reduced with a decrease in the level of its defectiveness. The conditions for the feasibility of using the method in terms of batch volume and the level of its defectiveness have been established, under which it has an advantage over pieceby- piece inspection methods. A device for implementing the method is described. The efficiency of the search method of group control of a batch of products is calculated when applied in specific conditions. The obtained results can be used by technologists in various industries when developing processes for controlling batches of products.

Optical and photoelectric properties of nanostructured SnS films obtained by spraying ink using a nanoparticle suspension

Abstract In this work, SnS films were prepared using spraying ink with a nanoparticle suspension. The average size of the synthesized nanoparticles was (18-20) nm. The structural, optical and photoelectric properties of SnS films were investigated using different characterization techniques. XRD and EDX results show that the investigated films exhibited an orthorhombic SnS phase with a composition close to the stoichiometry (CS/CSn = 0.99) and low level of microdeformation (ε = 1.8×10-3). In addition, the hexagonal SnS2 and tetragonal SnO2 phases were also observed. The presence of SnS and SnS2 phases is confirmed by Raman characteristics. The band gap of the SnS, SnS2, and SnO2 phases was determined using the novel ACFD method based on the analysis of the spectra of the first derivative of the absorption coefficient, which directly determines the energy of both band-to-band optical transitions and transitions involving defect`s levels. These results correlate very well with data obtained using photoconductivity spectra. The nature of the electronic optical transitions as well as the type and energy position of various defect levels were established. It was shown that the energy of direct and indirect band-to-band optical transitions of SnS compound correspond to 1.72 eV and 1.16 eV, respectively. At the same time, the band gap of SnS2 phase equal to 2.05 eV. The ionization energy of the acceptor (233 meV) and donor (100 meV) levels that determine the p- and n-type conductivity of SnS and SnS2 compounds, respectively were defined. Due to its properties, SnS films may be suitable for the development of novel effective solar cells with SnS absorber layers.