Search Results (43)

As part of a systematic study on the structures of the mixed halide isothiocyanates, Sn^IIHal(NCS), their single crystals were grown and structurally characterized. For Hal = F (1), the SnClF structure type was confirmed, while with Hal = Cl (2), Br (3), and I (4), there are three isostructural compounds of a new structure type, and for Hal = Cl (5), there is a second modification of a third structure type. These structure types have been described with respect to the composition and coordination geometry of the first, second, and van der Waals crust coordination spheres and their dependence on the halogen size and thiocyanate binding modes. With respect to the first coordination spheres, all three structure types constitute one-dimensional coordination polymers. In 1, “ladder”-type double chains result from μ₃-bridging fluorine atoms, and in 2–4, single-chains built up from μ₂-halogen atoms are pairwise “zipper”-like interconnected via κ²NS-bridging NCS ligands, which manage the halogen-linked chain assembly in the double chains of 5. Based on the octet rule, short atom distances are interpreted in terms of 2c-2e and various (symmetrical, quasi-symmetrical, and asymmetrical) kinds of 3c-4e bonds. Weak contacts, the topology of which suggests the extension of the latter bonding concept, are identified as electron-deficient, bifurcated tetrel bonds. Full article

Lead halide perovskites (LHPs) have superior luminescent properties, but their toxicity hinders their commercialization, arousing interests in tin halide perovskites as environmentally friendly substitutes for LHPs. Herein, we synthesized a series of two-dimensional tin halide perovskite ODASnBr_4-xI_x (ODA denotes 1,8-octanediammonium, X = 0, 1, 2, 3, 4) microcrystals via an aqueous-phase method. The differences between ODASnI₄ and ODASnBr₄ in luminescent properties and morphological characteristics were systematically discussed for the first time and attributed to light-driven ligand-to-metal charge transfer. The prepared ODASnBr₄ has a PL peak at 567 nm and a PL QY of 99%, and the white light-emitting diodes fabricated with ODASnBr₄ and commercial blue phosphors realized a luminous efficacy of up to 96.27 lm/W, which demonstrated the remarkable potential of ODASnBr₄ microcrystals for high-efficiency white light-emitting diode applications. Full article

The rapid advancement of wearable electronics and the Internet of Things (IoT) has driven the demand for sustainable power sources to replace conventional batteries. In this study, we developed a high-performance, lead-free triboelectric nanogenerator (TENG) using methylammonium tin chloride (MASnCl₃) perovskite–poly(methyl methacrylate) (PMMA) composite films. MASnCl₃ was synthesized via an anti-solvent-assisted collision technique and incorporated into a flexible PMMA matrix to enhance dielectric properties, thereby improving triboelectric output. The optimized 10 wt% MASnCl₃–PMMA composite-based TENG exhibited a maximum output voltage of 525 V, a current of 13.6 µA, and of power of 2.5 mW, significantly outperforming the many halide perovskite-based TENGs. The device demonstrated excellent pressure sensitivity, achieving 7.72 V/kPa in voltage detection mode and 0.2 μA/kPa in current detection mode. The device demonstrated excellent mechanical stability and was successfully used to power a small electronic device. The findings highlight the potential of halide perovskite–polymer composites in developing eco-friendly, efficient mechanical energy harvesters for next-generation self-powered electronics and sensor applications. Full article

At present, lead halide PVSKSCs are promising photovoltaic cells but have some limitations, including their low stability in ambient conditions and the toxicity of lead. Thus, it will be of great significance to explore lead-free perovskite materials as an alternative absorber layer. In recent years, the numerical simulation of perovskite solar cells (PVSKSCs) via the solar cell capacitance simulation (SCAPS) method has attracted the attention of the scientific community. In this work, we adopted SCAPS for the theoretical study of lead (Pb)-free PVSKSCs. A cesium bismuth iodide (CsBi₃I₁₀; CBI) perovskite-like material was used as an absorber layer. The thickness of the CBI layer was optimized. In addition, different electron transport layers (ETLs), such as titanium dioxide (TiO₂), tin oxide (SnO₂), zinc oxide (ZnO), and zinc selenide (ZnSe), and different hole transport layers, such as spiro-OMeTAD (2,2,7,7-tetrakis(N,N-di(4-methoxyphenylamine)-9,9′-spirobifluorene), poly(3-hexylthiophene-2,5-diyl) (P₃HT), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine (PTAA), and copper oxide (Cu₂O), were explored for the simulation of CBI-based PVSKSCs. A device structure of FTO/ETL/CBI/HTL/Au was adopted for simulation studies. The simulation studies showed the improved photovoltaic performance of CBI-based PVSKSCs using spiro-OMeTAD and TiO₂ as the HTL and ETL, respectively. An acceptable PCE of 11.98% with a photocurrent density (J_sc) of 17.360258 mA/cm², a fill factor (FF) of 67.10%, and an open-circuit voltage (V_oc) of 1.0282 V were achieved under the optimized conditions. It is expected that the present study will be beneficial for researchers working towards the development of CBI-based PVSKSCs. Full article

Two-dimensional tin halide perovskites are of significant interest for light emitting applications. Here, we investigate the effect of organic cation A on the stability of different Dion–Jacobson tin-based halide perovskites. The ASnBr₄ materials using diammonium cation A with shorter alkyl chains are found to exhibit improved stability, exhibiting dramatic stability difference between the most stable HDASnBr₄, where HDA denotes 1,6-hexanediammonium, and two materials with 8- and 10-carbon alkyl chain ammonium cations. The HDASnBr₄ powders were thermally stable at 100 °C in an argon environment but exhibited decreasing photoluminescence with time in ambient air at 100 °C. The sample degradation at 100 °C is accelerated compared to room temperature, but it proceeds along similar pathways, namely phase transformation followed by perovskite decomposition. Light emission from HDASnBr₄ thin films could be further enhanced by methanol vapor treatment, and warm white emission with Commission Internationale de l’Eclairage (CIE) coordinates (0.37, 0.34) could be obtained by combining HDASnBr₄ with a blue-emitting polymer film, while direct mixing of blue phosphor and HDASnBr₄ powder yields white emission with CIE coordinates of (0.34, 0.32). Full article

The integration of perovskite materials in solar cells has garnered significant attention due to their exceptional photovoltaic properties. However, achieving a bandgap energy below 1.2 eV remains challenging, particularly for applications requiring infrared absorption, such as sub-cells in tandem solar cells and single-junction perovskite solar cells. In this study, we employed a doping strategy to engineer the bandgap and observed that the doping effects varied depending on the A-site cation. Specifically, we investigated the impact of bismuth (Bi³⁺) incorporation into perovskites with different A-site cations, such as cesium (Cs) and methylammonium (MA). Remarkably, Bi³⁺ doping in MA-based tin-lead perovskites enabled the fabrication of ultra-narrow bandgap films (~1 eV). Comprehensive characterization, including structural, optical, and electronic analyses, was conducted to elucidate the effects of Bi doping. Notably, 8% Bi-doped Sn-Pb perovskites demonstrated infrared absorption extending up to 1360 nm, an unprecedented range for ABX₃-type single halide perovskites. This work provides valuable insights into further narrowing the bandgap of halide perovskite materials, which is essential for their effective use in multi-junction tandem solar cell architectures. Full article

Metal oxide core–shell fibrous nanostructures are promising gas-sensitive materials for the detection of a wide variety of both reducing and oxidizing gases. In these structures, two dissimilar materials with different work functions are brought into contact to form a coaxial heterojunction. The influence of the shell material on the transportation of the electric charge carriers along these structures is still not very well understood. This is due to homo-, hetero- and metal/semiconductor junctions, which make it difficult to investigate the electric charge transfer using direct current methods. However, in order to improve the gas-sensing properties of these complex structures, it is necessary to first establish a good understanding of the electric charge transfer in ambient air. In this article, we present an impedance spectroscopy study of networked SnO₂/Ga₂O₃ core–shell nanobelts in ambient air. Tin dioxide nanobelts were grown directly on interdigitated gold electrodes, using the thermal sublimation method, via the vapor–liquid–solid (VLS) mechanism. Two forms of a gallium oxide shell of varying thickness were prepared via halide vapor-phase epitaxy (HVPE), and the impedance spectra were measured at 189–768 °C. The bulk resistance of the core–shell nanobelts was found to be reduced due to the formation of an electron accumulation layer in the SnO₂ core. At temperatures above 530 °C, the thermal reduction of SnO₂ and the associated decrease in its work function caused electrons to flow from the accumulation layer into the Ga₂O₃ shell, which resulted in an increase in bulk resistance. The junction resistance of said core–shell nanostructures was comparable to that of SnO₂ nanobelts, as both structures are likely connected through existing SnO₂/SnO₂ homojunctions comprising thin amorphous layers. Full article

Zero-dimensional tin-based halide perovskites have garnered considerable interest owing to their remarkable optical properties, including broad-band emission, high photoluminescence (PL) efficiency, and low self-absorption. Nevertheless, enhancing the PL efficiency and stability of these materials remains a pressing challenge. In this study, the enhancement of PL and stability in Cs₄SnBr₆ zero-dimensional perovskite was investigated through Ce³⁺ doping. Our experimental results demonstrate that the incorporation of Ce³⁺ can significantly boost the light emission intensity from self-trapped excitons (STEs) in Cs₄SnBr₆, achieving over a 150% increase compared to the undoped sample, with a PL quantum yield of approximately 64.7%. Moreover, the thermal stability of the corresponding doped sample is markedly enhanced. Through comprehensive analyses, including X-ray diffraction, energy-dispersive spectroscopy, time-resolved PL, and temperature-dependent PL measurements, we elucidate that the enhanced light emission is attributed to the distortion of the [SnBr₆]⁴⁻ octahedral structure induced by Ce³⁺ doping, which strengthens electron–phonon coupling and elevates the binding energy of STEs. Full article

Halide perovskite materials have broad prospects for applications in various fields such as solar cells, LED devices, photodetectors, fluorescence labeling, bioimaging, and photocatalysis due to their bandgap characteristics. This study compiled experimental data from the published literature and utilized the excellent predictive capabilities, low overfitting risk, and strong robustness of ensemble learning models to analyze the bandgaps of halide perovskite compounds. The results demonstrate the effectiveness of ensemble learning decision tree models, especially the gradient boosting decision tree model, with a root mean square error of 0.090 eV, a mean absolute error of 0.053 eV, and a determination coefficient of 93.11%. Research on data related to ratios calculated through element molar quantity normalization indicates significant influences of ions at the X and B positions on the bandgap. Additionally, doping with iodine atoms can effectively reduce the intrinsic bandgap, while hybridization of the s and p orbitals of tin atoms can also decrease the bandgap. The accuracy of the model is validated by predicting the bandgap of the photovoltaic material MASn_1−xPb_xI₃. In conclusion, this study emphasizes the positive impact of machine learning on material development, especially in predicting the bandgaps of halide perovskite compounds, where ensemble learning methods demonstrate significant advantages. Full article

Tin oxide (SnO₂) has been recognized as one of the beneficial components in the electron transport layer (ETL) of lead–halide perovskite solar cells (PSCs) due to its high electron mobility. The SnO₂-based thin film serves for electron extraction and transport in the device, induced by light absorption at the perovskite layer. The focus of this paper is on the heat treatment of a nanoaggregate layer of single-nanometer-scale SnO₂ particles in combination with another metal-dopant precursor to develop a new process for ETL in PSCs. The combined precursor solution of Li chloride and titanium(IV) isopropoxide (TTIP) was deposited onto the SnO₂ layer. We varied the heat treatment conditions of the spin-coated films comprising double layers, i.e., an Li/TTIP precursor layer and SnO₂ nanoparticle layer, to understand the effects of nanoparticle interconnection via sintering and the mixing ratio of the Li-dopant on the photovoltaic performance. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) measurements of the sintered nanoparticles suggested that an Li-doped solid solution of SnO₂ with a small amount of TiO₂ nanoparticles formed via heating. Interestingly, the bandgap of the Li-doped ETL samples was estimated to be 3.45 eV, indicating a narrower bandgap as compared to that of pure SnO₂. This observation also supported the formation of an SnO₂/TiO₂ solid solution in the ETL. The utilization of such a nanoparticulate SnO₂ film in combination with an Li/TTIP precursor could offer a new approach as an alternative to conventional SnO₂ electron transport layers for optimizing the performance of lead–halide perovskite solar cells. Full article

Tin oxide (SnO₂) is a technologically important semiconductor with versatile applications. In particular, attention is being paid to nanostructured SnO₂ materials for use as a part of the constituents in perovskite solar cells (PSCs), an emerging renewable energy technology. This is mainly because SnO₂ has high electron mobility, making it favorable for use in the electron transport layer (ETL) in these devices, in which SnO₂ thin films play a role in extracting electrons from the adjacent light-absorber, i.e., lead halide perovskite compounds. Investigation of SnO₂ solution synthesis under diverse reaction conditions is crucial in order to lay the foundation for the cost-effective production of PSCs. This research focuses on the facile catalyst-free synthesis of single-nanometer-scale SnO₂ nanocrystals employing an aromatic organic ligand (as the structure-directing agent) and Sn(IV) salt in an aqueous solution. Most notably, the use of an aromatic amino acid ester hydrochloride salt—i.e., phenylalanine methyl ester hydrochloride (denoted as L hereafter)—allowed us to obtain an aqueous precursor solution containing a higher concentration of ligand L, in addition to facilitating the growth of SnO₂ nanoparticles as small as 3 nm with a narrow size distribution, which were analyzed by means of high-resolution transmission electron microscopy (HR-TEM). Moreover, the nanoparticles were proved to be crystallized and uniformly dispersed in the reaction mixture. The environmentally benign, ethanol-based SnO₂ nanofluids stabilized with the capping agent L for the Sn(IV) ions were also successfully obtained and spin-coated to produce a SnO₂ nanoparticle film to serve as an ETL for PSCs. Several SnO₂ ETLs that were created by varying the temperature of nanoparticle synthesis were examined to gain insight into the performance of PSCs. It is thought that reaction conditions that utilize high concentrations of ligand L to control the growth and dispersion of SnO₂ nanoparticles could serve as useful criteria for designing SnO₂ ETLs, since hydrochloride salt L can offer significant potential as a functional compound by controlling the microstructures of individual SnO₂ nanoparticles and the self-assembly process to form nanostructured SnO₂ thin films. Full article

In this study, a highly crystalline and transparent indium-tin-oxide (ITO) thin film was prepared on a quartz substrate via RF sputtering to fabricate an efficient bottom-to-top illuminated electrode for an ultraviolet C (UVC) photodetector. Accordingly, the 26.6 nm thick ITO thin film, which was deposited using the sputtering method followed by post-annealing treatment, exhibited good transparency to deep-UV spectra (67% at a wavelength of 254 nm), along with high electrical conductivity (11.3 S/cm). Under 254 nm UVC illumination, the lead-halide-perovskite-based photodetector developed on the prepared ITO electrode in a vertical structure exhibited an excellent on/off ratio of 1.05 × 10⁴, a superb responsivity of 250.98 mA/W, and a high specific detectivity of 4.71 × 10¹² Jones without external energy consumption. This study indicates that post-annealed ITO ultrathin films can be used as electrodes that satisfy both the electrical conductivity and deep-UV transparency requirements for high-performance bottom-illuminated optoelectronic devices, particularly for use in UVC photodetectors. Full article

Lead-based halide perovskite nanocrystals (PeNCs) have demonstrated remarkable potential for use in light-emitting diodes (LEDs). This is because of their high photoluminescence quantum yield, defect tolerance, tunable emission wavelength, color purity, and high device efficiency. However, the environmental toxicity of Pb has impeded their commercial viability owing to the restriction of hazardous substances directive. Therefore, Pb-free PeNCs have emerged as a promising solution for the development of eco-friendly LEDs. This review article presents a detailed analysis of the various compositions of Pb-free PeNCs, including tin-, bismuth-, antimony-, and copper-based perovskites and double perovskites, focusing on their stability, optoelectronic properties, and device performance in LEDs. Furthermore, we address the challenges encountered in using Pb-free PeNC-LEDs and discuss the prospects and potential of these Pb-free PeNCs as sustainable alternatives to lead-based PeLEDs. In this review, we aim to shed light on the current state of Pb-free PeNC LEDs and highlight their significance in driving the development of eco-friendly LED technologies. Full article

Zero-dimensional (0D) tin halide perovskites, characterized by their broadband and adjustable emissions, high photoluminescence quantum yield, and absence of self-absorption, are crucial for the fabrication of high-efficiency optoelectronic devices, such as LEDs, solar cells, and sensors. Despite these attributes, boosting their emission efficiency and stability poses a significant challenge. In this work, Cr³⁺-doped Cs₄SnBr_6−xF_x perovskites were synthesized using a water-assisted wet ball-milling method. The effect of CrF₃ addition on photoluminescence properties of Cs₄SnBr_6−xF_x Perovskites was investigated. We found that Cr³⁺-doped Cs₄SnBr_6−xF_x Perovskites exhibit a broad emission band, a substantial Stokes shift, and an efficient green light emission centered at about 525 nm at ambient temperature. The derived photoluminescence quantum yield amounted to as high as 56.3%. In addition, these Cr³⁺-doped Cs₄SnBr_6−xF_x perovskites outperform their undoped counterparts in terms of thermal stability. Through a comprehensive analysis of photoluminescence measurements, our findings suggested that the elevated photoluminescence quantum yield can be attributed to the enhanced exciton binding energy of self-trapped excitons (STEs) and the suitable electron−phonon coupling resulting from the substantial distortion of [SnBr₆]⁴⁻ octahedra instigated by the addition of CrF₃. Full article

Tin-based perovskites are promising for realizing lead-free perovskite solar cells; however, there remains a significant challenge to achieving high-performance tin-based perovskite solar cells. In particular, the device fill factor was much lower than that of other photovoltaic cells. Therefore, understanding how the fill factor was influenced by device physical mechanisms is meaningful. In this study, we reported a method to improve the device fill factor using a thin cesium iodide layer modification in tin-based perovskite cells. With the thin passivation layer, a high-quality perovskite film with larger crystals and lower charge carrier densities was obtained. As a result, the series resistance of devices was decreased; the shunt resistance of devices was increased; and the non-radiative recombination of devices was suppressed. Consequently, the fill factor, and the device efficiency and stability were greatly enhanced. The champion tin-based perovskite cells showed a fill factor of 63%, an efficiency of 6.1% and excellent stability. Our study reveals that, with a moderate thin layer modification strategy, the long-term stability of tin-based PSCs can be developed. Full article