Lead-free Materials Research Articles

A-Site Cations Impact on Nonradiative Recombination, Mobility, and Defect Dynamics in Sn-Based Perovskites.

Sn-based perovskites with different cations in the A-site exhibit distinct electronic structures and dynamic properties. By utilizing time-dependent density functional theory and nonadiabatic molecular dynamics, we demonstrate that larger FA cations decrease wave function overlap between initial and final states and slow down nuclear motion. In the case of FASnI3, this alteration decreases the nonadiabatic coupling and increases the nonradiative electron-hole recombination time by 130% and 76%, respectively, compared to CsSnI3 and MASnI3 (CH3NH3SnI3). Furthermore, A-site modification significantly improves electron mobility and changes the properties of defects in FASnI3 (HC(NH2)2SnI3), which achieves higher electron mobility through a polar optical phonon-dominated scattering mechanism and exhibits higher defect formation energy and migration barriers of A-site cations due to increased steric hindrance, relative to CsSnI3 and MASnI3. These results emphasize the critical function of A-site cation substitution in controlling nonradiative recombination dynamics, electron mobility, and defect characteristics in Sn-based perovskites and provide theoretical insights for the advancement of novel lead-free perovskite materials.

Mechanical and Tribological properties of the Lead-Free Composite-A review

In recent years, there has been a growing demand for materials that are both eco-friendly and cost-effective while maintaining high performance levels. Design engineers and researchers are increasingly turning to advanced materials as substitutes for traditional metals and alloys. Journal bearings, integral components of machinery and engines, play a crucial role in their operation, significantly impacting efficiency, operational costs, system longevity, and reliability. The pursuit of eco-friendly and high-performance materials has spurred notable progress in tribological research, particularly concerning journal bearings. This study offers a comprehensive examination of lead-free composite materials for journal bearings, delving into various types such as polymers, ceramics, and metallic alloys. It meticulously evaluates their mechanical and tribological properties, as well as their microstructural characteristics. The insights gleaned from this review are invaluable for engineers and researchers seeking to enhance the design and performance of journal bearings while aligning with environmental regulations and sustainability objectives.

Physical Properties of CaTiO3-Modified NaNbO3 Thin Films.

NaNbO3(NN)-based lead-free materials are attracting widespread attention due to their environment-friendly and complex phase transitions, which can satisfy the miniaturization and integration for future electronic components. However, NN materials usually have large remanent polarization and obvious hysteresis, which are not conducive to energy storage. In this work, we investigated the effect of introducing CaTiO3((1-x)NaNbO3-xCaTiO3) on the physical properties of NN. The results indicated that as x increased, the surface topography, oxygen vacancy and dielectric loss of the thin films were significantly improved when optimal value was achieved at x = 0.1. Moreover, the 0.9NN-0.1CT thin film shows reversible polarization domain structures and well-established piezoresponse hysteresis loops. These results indicate that our thin films have potential application in future advanced pulsed power electronics.

Investigation of structural, dielectric and electrical properties of lead-free bismuth-based layered multifunctional material: CaBiGdNbVO9 for device fabrication

Investigation of structural, dielectric and electrical properties of lead-free bismuth-based layered multifunctional material: CaBiGdNbVO9 for device fabrication

Bismuth (Bi3+) and Tellurium (Te4+) doped Cs2ZrCl6 lead-free halide perovskite phosphors for white LEDs

Lead-free halide double-perovskite materials have been given extensive attention due to the charming fluorescent property and simple synthesis process. Their strong electro-acoustic coupling effects endow the materials with wideband emission properties and the tremendous potential application in white light emitting diodes (w-LEDs). Herein, the blue (456 nm) and yellow (578 nm) light emitting phosphors with broad band emission were synthesized by introducing the Bi3+ and Te4+ into the structure-stable and low toxicity Cs2ZrCl6 materials, respectively. The blue and yellow emission from 3P1 → 1S0 transitions of Bi3+ and Te4+ were achieved in Cs2ZrCl6: 7%Bi3+ and Cs2ZrCl6: 3%Te4+, where the large full width at half maximum (FWHM) values of 45 and 101 nm were attributed to the large Huang-Rhys factor and electro-acoustic coupling strength. The white LED fabricated through combining the 365 nm chip with the prepared blue and yellow phosphors exhibited wideband white light emission ranging from the 400–750 nm with correlated color temperature (CCT) 5028 K and good color rendering index (CRI) 84.

Photoexcited charge-carrier transport in monolayer and bulk bismuth oxyiodide: the impact of the polaronic effect and deep-level defects

Bismuth oxyiodide (BiOI), in monolayer and bulk forms, is a lead-free semiconductor material that has sparked increased interest for applications in perovskite solar cells and x-ray detectors. It is vital to clarify the transport nature of photoexcited charge-carriers to improve device performance. However, the transport scattering mechanisms remain poorly understood, and a detailed explanation of the measured charge-carrier mobilities in this material system is still under scrutiny. Herein, we implement transport scattering models that include LO phonon scattering based on the polaronic effect and ionized impurity scattering due to deep-level defects to elucidate photoexcited charge mobilities. We found that large polarons produced by photoexcited charge carriers coupled with LO phonon modes of 86 cm−1 and 156 cm−1 play a key role in the transport process of the BiOI system. Large polaron mobility provides a good explanation for the measured mobilities in single crystal samples between 26–83 cm2V−1s−1 at 295 K. The estimated results from both transport scattering models agree with the temperature-dependent mobilities measured in thin-film samples, between 13 cm2V−1s−1 at 5 K and 3 cm2V−1s−1 at 295 K. This work provides important insights into a band-like transport feature in the BiOI system.

Theoretical Design of Tellurium-Based Two-Dimensional Perovskite Photovoltaic Materials.

In recent years, the photoelectric conversion efficiency of three-dimensional (3D) perovskites has seen significant improvements. However, the commercial application of 3D perovskites is hindered by stability issues and the toxicity of lead. Two-dimensional (2D) perovskites exhibit good stability but suffer from low efficiency. Designing efficient and stable lead-free 2D perovskite materials remains a crucial unsolved scientific challenge. This study, through structural prediction combined with first-principles calculations, successfully predicts a 2D perovskite, CsTeI5. Theoretical calculations indicate that this compound possesses excellent stability and a theoretical efficiency of up to 29.3%, showing promise for successful application in thin-film solar cells. This research provides a new perspective for the design of efficient and stable lead-free 2D perovskites.

Comprehensive investigation of oxidation behavior on ternary In–Zn–Sn lead-free solder electronic materials

Comprehensive investigation of oxidation behavior on ternary In–Zn–Sn lead-free solder electronic materials

Investigation of the shielding properties against γ-radiation of (Cu–Ba–Y–O)-x(Zn–Fe–O) ceramics

The search for lead-free radiation shielding materials has become a matter of great demand, especially with the increase in the use of ionizing radiation, including X-rays and γ-rays, in various vital fields. In the present work, the shielding potential against γ-radiation of lead-free (Cu–Ba–Y–O)-x(Zn–Fe–O) samples (x = 0.1–2.0 wt%) was evaluated. The samples are polycrystals and showed an orthorhombic crystal structure. The orthorhombicity was progressively reduced with the effect of Zn–Fe–O addition. The introduction of Zn–Fe–O into Cu–Ba–Y–O altered also the density values of the samples. The density values followed the order x = 2.0 <x = 1.0 <x = 0.5 <x = 0.1 wt%. The structural, and physical properties results were correlated with radiation shielding properties. The shielding efficiency against γ-radiation of different proposed ceramics was evaluated using Monte Carlo Simulation. The analysis revealed that the introduction of Zn–Fe–O into Cu–Ba–Y–O decreases the linear attenuation coefficient of the samples. The Linear attenuation coefficient over the γ-ray energy interval between 0.015 and 2.506 MeV varied between 322.560 and 0.243 cm−1, 322.41–0.243 cm−1, 290.799–0.220 cm−1, and 263.769–0.199 cm−1 for x = 0.1, 0.5, 1.0, and 2.0 wt%, respectively.

Design and numerical simulation of lead-free inorganic perovskites (Cs2BiAgI6) solar cell through computation method

Cs2BiAgI6 is a lead-free inorganic perovskite material exhibits exceptional photoelectric characteristics and great environmental stability. HTL/Cs2BiAgI6is/ETLs solar cells was investigated numerically by using SCAPS 1-D Capacitance Simulator. IGZO, TiO2, WO3, MoO3, and SnO2 have been chosen as ETLs, while CuO, CuI, and MoO3 are as HTLs. The values of electrical parameters were calculated as function of thickness of the absorber layer, ETLs, HTLs, interface defect densities, doping densities, and working temperature. Comparative study shows that best configuration of obtain solar cell is MoO3/Cs2BiAgI6/IGZO. The obtain value of Jsc, Voc, FF and PCE are 23.80 mA/cm2, 1.193 V, 83.46 %, 23.711 % respectively. The value of quantum efficiency is 80–90 % in the range of 350–750 nm. These results will open the door for the widespread use of stable and environmentally friendly perovskite solar cells by providing theoretical recommendations for high performance of Cs2BiAgI6 based photovoltaic solar cells (PSCs).

FTIR characterization analysis of BaTiO3 nanoparticles synthesized using Terminalia catappa leaf extract

Ferroelectric materials are materials that are in great demand in high-density memory applications, such as ferroelectric random access memory, ferroelectric field effect transistors, negative capacitance field effect transistors, and ferroelectric tunnel junctions. Barium titanate (BaTiO3) is a lead-free ferroelectric material with a high dielectric constant and low dielectric loss. The method used is sol gel for the synthesis of BaTiO3 solution, extract for ketapang (Terminalia catappa) leaves, and characterized by FTIR. The FTIR spectrum synthesized with ketapang leaf extract displays several characteristic peaks in the mid-infrared region (4000 – 400 cm-1). These peaks can be determined by the specific vibration mode of the structure and organic compounds contained in the ketapang leaf extract. BaTiO3 has a cubic perovskite structure with a peak wave number of 600 cm-1. Ketapang leaf extract is incorporated into the BaTiO3 structure. BaTiO3 has a Ti–O functional group. Ketapang leaf extract has C–O, C=O, C–H, and O–H functional groups.

Ligand-free Cs2PdBr6 perovskite microcrystals with narrow bandgap and high photoelectrochemical performance in aqueous solution

The exploration of efficient lead-free perovskite photoelectric active materials to develop high-performance photoelectrochemical (PEC) systems in aqueous solution is crucial to expand their PEC applications. Herein, we successfully constructed a high-performance PEC platform using ligand-free perovskite Cs2PdBr6 microcrystals (MCs) as the photoactive substance. The Cs2PdBr6 MCs showed narrow bandgap, wide absorption range, high electronic mobility and good stability in aqueous solutions. Particularly, the Cs2PdBr6 MCs exhibited an excellent photoresponse, the photocurrent density could reach as high as 98 μA/cm2 under 10.18 mW/cm2 light irradiation in the absence of other electron acceptors. In addition of the extremely wide range of response wavelength, wide pH range and accelerated interfacial carrier transfer, the Cs2PdBr6 MCs demonstrated the significant potential of photocathode active material for applications in PEC sensors and optoelectronic devices. Therefore, this work indicates that Cs2PdBr6 MCs design is a highly efficient way to solve the intrinsic issues of perovskite material, predicting a promising strategy for high performance PEC application in aqueous ambience.

Self-Powered Visible-Blind Ultraviolet Photodetector Based on Organic-Inorganic Hybrid Copper Halide [N(C2H5)4]2[Cu2Br4

Organic-inorganic hybrid ternary copper halides offer a broader spectrum of structural possibilities for finely tuning their optoelectronic properties. Herein, we demonstrate for the first time the potential of [N(C2H5)4]2[Cu2Br4], a zero-dimensional hybrid copper halide [(TEA)2Cu2Br4], for ultraviolet (UV) photodetection. A self-powered, visible-blind UV photodetector based on a (TEA)2Cu2Br4/GaN heterojunction architecture is developed, exhibiting a high responsivity, a high detectivity, and fast response speeds. The device demonstrates exceptional stability against environmental oxygen/moisture, heat, and UV light illumination, surpassing the stability of reported copper-based UV photodetectors. Our work highlights the significant potential of (TEA)2Cu2Br4 as a lead-free, stable, and efficient material for next-generation UV photodetection technology.

Effect of temperature on joint quality in wave soldering of Sn-9Zn-2.5Bi-1.5In lead-free solder alloy

SnZn (tin‑zinc) solder has been regarded as a promising lead-free solder material with a low melting point of 198 °C, serving as a suitable alternative to both SnPb solder due to its lack of hazardous substances and Sn-Ag-Cu solder because of the high cost associated with silver. Nonetheless, its susceptibility to oxidation hinders solderability and increases soldering defects such as bridging, insufficient fillings, and voids, limiting its use in commercial production. Devices designed with through-hole technology, in contrast to surface-mounted ones, continue to exhibit superior interconnection reliability in such applications. In this investigation on wave soldering, a newly developed lead-free solder, composed of 87% tin, 9% zinc, 2.5% bismuth, and 1.5% indium by weight, was employed under two conditions related to nitrogen content: 1) Ensuring that static oxygen content remained below 3000 ppm. 2) Maintaining soldering section oxygen content below 600 ppm at a conveyor speed of 1200 mm/min. The soldering results were examined at various temperatures of preheating and soldering. It proves that the measured peak temperature of liquid solder TpL over 230 °C makes the bridging defect rate lower than 0.30%. Additionally, setting the peak temperature of solder joint TpZ above 220 °C, along with specific preheating temperatures (105/115/135/145 °C), archives 100% vertical filling without significant voids in the solder joints. Moreover, optimizing wave soldering settings, specifically adjusting the wave soldering setting temperature Ts to 235 °C, conveyor speed vc to 1000 mm/min, resolves soldering defects associated with Sn-9Zn-2.5Bi-1.5In alloy in wave process. Relevance summary1.TpL surpasses 230 °C, the total number of bridging defects per board decreases to fewer than 6, approximately 0.30%. TpZ values of 220 °C or higher results in 100% vertical fill and no significant large voids, demonstrating optimal filling effects2.Under the conditions of TS = 235 °C and vc = 1000 mm/min yield TpL > 230 °C and TpZ > 210.9 °C, it leads to a reduction in bridging defects.3.To maintain flux efficiency and minimize internal voids, an optimal selection of preheating temperatures (105/115/135/145 °C) is demonstrated.4.An integrated nitrogen content-controlled system is utilized to eliminate oxygen from the solder pot, aiming to prevent oxidation.

The investigation of piezoelectric features of lead-free barium titanate ceramic materials at different initial temperatures in the tetragonal phase using molecular dynamics simulation

This study used molecular dynamics simulation to investigate how temperature changes the piezoelectric properties of crystal barium titanate in its tetragonal form. Consistent with the results, the oxygen diffusion coefficient in the simulated sample increased to 0.35 Å2/ns (expansion mode) and 0.56 Å2/ns (contraction mode) by increasing the temperature from 300 to 400 K. Moreover, the piezoelectric coefficient of samples decreased from 267.22 to 162.56 in an expansion mode and from 189.96 to 145.21 in a contraction mode by increasing temperature. On the other hand, increasing the temperature decreased saturation polarization (from 0.372 to 0.290 C/m2), coercivity field (from 0.259 to 0.155 MV/m), and residual polarization (from 0.154 to 0.084). This decrease may be due to approaching the critical temperature and changing the structure from tetragonal to cubic. Finally, the results show that the dielectric coefficients were found by raising the temperatures to 400 K (expansion mode) and getting 73, 70, 68, and 64. For the contraction mode, they were 70, 66, 55, and 63.

Ultra-small cesium silver bismuth bromide quantum dots fabricated by modified hot-injection method for highly efficient degradation of contaminants in organic solvent

Lead-free halide perovskite material has drawn fast-growing interest due to its superior solar-conversion efficiency and nontoxic nature. In this work, we have successfully fabricated cesium silver bismuth bromide (Cs2AgBiBr6) quantum dots utilizing the hot injection method. The as-synthesized quantum dots were characterized by combined techniques, which showed remarkable visible-light photocatalytic activity for organic dyes and antibiotic degradation in ethanol. Specifically, about 97% of rhodamine B and methyl orange may be removed within 10 min and 30 min, respectively. Additionally, 60% of antibiotic residue of tetracycline hydrochloride is degraded in 30 min which is 7 times more than that on commercial titania (P25). The reactive species for the photodegradation are determined through capture experiments, and a reaction mechanism is proposed accordingly. This work provides a novel photocatalyst for the selective removal of diverse organic contaminants in ethanol and an alternative for the potential application of lead-free halide perovskites.

Ion migration and dark current suppression in quasi-2D perovskite-based X-ray detectors.

Cesium-based lead-free double perovskite materials (Cs2AgBiBr6) have garnered significant attention in the X-ray detection field due to their environment friendly characteristics. However, their substantial ion migration properties lead to large dark currents and detection limits in Cs2AgBiBr6-based X-ray detectors, restricting the detection performance of the device. In terms of process technology, ultrasonic spraying is more suitable than a spin-coating method for fabricating large-area, micron-scale perovskite thick films, with higher cost-effectiveness, which is crucial for X-ray detection. This work introduces a BA+ (BA+ = CH3CH2CH2CH2NH3 +, n-butyl) source into the precursor solution and employs ultrasonic spraying to fabricate quasi-two-dimensional structured polycrystalline (BA)2Cs9Ag5Bi5Br31 perovskite thick films, developing a low-cost, eco-friendly X-ray detector with low dark current density and low detection limit. Characterization results reveal that the ion migration activation energy of (BA)2Cs9Ag5Bi5Br31 reaches 419 meV, approximately 17% higher than that of traditional three-dimensional perovskites, effectively suppressing perovskite ion migration and subsequently reducing the dark current. The (BA)2Cs9Ag5Bi5Br31-based X-ray detectors exhibit high resistivity (about 1.75 × 1010 Ω cm), low dark current density (66 nA cm-2), minimal dark current drift (0.016 pA cm-1 s-1 V-1), and detection limit (138 nGyair s-1), holding considerable promise for applications in low-noise, low-dose X-ray detection.

Reply to comment on “Ferroelectric composite-based piezoelectric energy harvester for self-powered detection of obstructive sleep” by A. Tkach and O. Okhay

In this contribution, we reply to comments made by Tkach et al. in our publication J. Materiomics 2023; 9:609. The main interest of our work is to synthesize a lead-free material, SrTi2O5 (STO), and then utilize it in the formation of composites and finally design the piezoelectric nanogenerator (PENG) for self-powered sensor applications. The authors have observed the presence of piezoelectric voltage and current output from the PENG. The authors humbly indicate that the PENG devices were poled using a DC poling setup as conditions mentioned in J. Materiomics 2023; 9:609 (Panda et al., 2023) [1]. The doping of STO into the PDMS increased from 2% to 20% (in mass). In this process, the piezoelectric output of the PENG device was observed to be highest for 15% (in mass) STO-PDMS composite. Besides, we agree with the comment raised by Tkach et al., and further we have addressed the issues in a step-by-step response as follows.

Mechanism and simulation analysis of high electric field of NaNbO3 − based energy storage ceramics based on defect engineering design

Ceramic materials possessing high polarization and substantial breakdown electric fields represent a principal strategy for enhancing the performance of pulse power systems. To augment the energy storage capabilities of ceramic materials, numerous studies have suggested a variety of specific control methods. However, reports on the vacancy defects arising during the regulatory process and the relationship between these vacancy defects and energy storage performance are scarce. This paper introduces an optimal quantity of oxygen vacancy defects into the prepared NN–based ceramics for characterization and analysis, aiming to elucidate the impact of oxygen vacancy defects and their concentration on the structure and energy storage properties of ceramics. Through managing the content of oxygen vacancies, the 0.83NN–0.17SNS ceramic achieved a high energy storage density (Wrec) of 6.27 J/cm3 and an energy storage efficiency (η) of 82.79 % at 705 kV/cm. This work presents a novel approach to regulating the energy storage performance, offering a new method for optimizing the performance of lead-free energy storage materials.

An inclusive study of lead-free perovskite CsMI3 materials for photovoltaic and optoelectronic appliance explored by a first principles study

The prime objective of this study is to understand the lead-free CsMI3 (M = Pb, Mg, Ga, Ca, Ba, Sr) perovskites for photovoltaic and optoelectronic applications using first-principle calculations. This study considered the structural aspects along with the mechanical, electrical, optical, and thermal properties. The formation energy, phonon dispersion curve, and elastic constants were calculated to check the structural stability of the compounds. The computed Poisson ratios (ν) support the CsMI3 compounds' ductility; only the CsMgI3 compounds lie on the ductile-brittle transition line. However, the compounds' ductility is confirmed by the Cauchy pressure, which also reflects the materials' mechanism of mechanical failure. The band structure calculations confirmed the energy band gap, Eg, in the range of 1.63–3.26 eV, which makes them suitable for absorbing materials in solar cell applications. The optical properties calculations revealed strong photoconductivity, low reflectivity, and high absorption coefficient, all of which show photovoltaic properties given the materials use in the solar cell application. Among the titled compounds, CsMgI3 will be the best replacement of Pb-based perovskites for photovoltaic and optoelectronic appliances. The substitution of I by Br in the CsMgI3 causes a significant improvement (band gap is increased from 1.12 to 1.87 eV; absorption coefficient is also increased) in the photovoltaic properties. The Eg and α further increase due to doping into the CsMg(I1-xBrx)3 where x = (0.25) makes them apposite for solar cell materials. The best combination, CsMg(I0.75Br0.25)3, shows Eg ∼ 1.4 eV, which may be considered as the optimum band gap for the highest efficiency of a single solar cell according to the Shockley-Queisser limit.