Lead-based Perovskites Research Articles

Recent Advances and Future Perspectives of Lead-Free Halide Perovskites for Photocatalytic CO2 Reduction.

It is still challenging to design and develop the state-of-the-art photocatalysts toward CO2 photoreduction. Enormous researchers have focused on the halide perovskites in the photocatalytic field for CO2 photoreduction, due to their excellent optical and physical properties. The toxicity of lead-based halide perovskites prevents their large-scale applications in photocatalytic fields. In consequence, lead-free halide perovskites (LFHPs) without the toxicity become the promising alternatives in the photocatalytic application for CO2 photoreduction. In recent years, the rapid advances of LFHPs have offer new chances for the photocatalytic CO2 reduction of LFHPs. In this review, we summarize not only the structures and properties of A2 BX6 , A2 B(I)B(III)X6 , and A3 B2 X9 -type LFHPs but also their recent progresses on the photocatalytic CO2 reduction. Furthermore, we also point out the opportunities and perspectives to research LFHPs photocatalysts for CO2 photoreduction in the future.

First-Principles Predictions of Structural, Mechanical, and Optoelectronic Properties of Se-Based Double Perovskites A2SeX6 (A = Rb, K; X = Cl, Br, I)

The toxicity of lead and the instability of lead-based perovskite materials in the air are two key challenges in emerging Pb-based inorganic perovskite solar cells. Thus, the development of lead-free and stabilized inorganic perovskite materials is of great interest. In this work, the structural, ductility, and optoelectronic properties of Se-based double perovskites A2SeX6 (A = Rb, K; X = Cl, Br, I) have been studied for the first time by first-principles calculations to determine their potential use in optoelectronic sectors. Results reveal that these new series of A2SeX6 (A = Rb, K; X = Cl, Br, I) double perovskites are structural and mechanical stability. Their ductility increases as the halogen atom goes from Cl to I. Especially, the K2SeI6 possesses better ductility than other double perovskites. Electronic structure calculations exhibit that these new perovskite compounds are indirect band gap semiconductors. The Rb2SeI6 and K2SeI6 have more suitable bandgaps (1.24 and 1.16 eV) and smaller carrier masses, which are suitable for absorber layers of solar cells, while A2SeCl6 and A2SeBr6 are suitable for fabricating the optoelectronic devices in the ultraviolet region due to the wide gap. Furthermore, all these A2SeX6 compounds exhibit excellent optical properties with light absorption coefficients over 105 cm–1. Especially, the Rb2SeI6 and K2SeI6 have more excellent absorption spectra throughout the whole visible region. These results show that both Rb2SeI6 and K2SeI6 are potential candidates for absorption layer materials of solar cells, and A2SeCl6 and A2SeBr6 are suitable for other optoelectronic devices, such as photodetectors, light-emitting diodes, and so on.

Organic Chain Length Effect on Trap States of Lead Halide Perovskite Scintillators

Scintillators fabricated from organic–inorganic layered perovskites have attracted wide attention due to their excellent properties, including fast decay times, superior light yield, and high exciton binding energy. In relation to their optoelectronic properties, hybrid organic–inorganic perovskites are known for their tunability, which could be manipulated by modifying the organic cations. In this study, we investigate the optical and scintillation properties of lead halide perovskites A2PbBr4, where A vary from amylammonium (AA), hexylammonium (HA), octylammonium (OA), and benzylammonium (BZA) organic ligands. Photoluminescence (PL) spectra display dual peaks due to surface and bulk trap states contributions, while fast average decay times from time-resolved photoluminescence (TRPL) for all samples are within the range of 0.69 ± 0.11–0.99 ± 0.13 ns. The optical band gap of these hybrid perovskites is within ∼3 eV range, which fulfill the criteria of promising scintillators. Radioluminescence (RL) spectra show negative thermal quenching behavior (NTQ) in all samples, with the AA2PbBr4 peak intensity appearing at relatively lower temperature compared to other samples. Thermoluminescence (TL) measurement reveals trap-free states in AA2PbBr4, while other samples possess shallow traps (<40 meV) as well as low trap density, which is beneficial for fast-decay scintillators, X-ray detection and energy conversion for solar cells. Overall, our results demonstrate that the extension of linear organic chains in lead-based perovskite is a deterministic strategy for a fast response hybrid-based scintillator to date.

Lead-Free Perovskite Cs2 SnBr6 /rGO Composite for Photocatalytic Selective Oxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran.

Severe poisonousness and prolonged instability existing in organic-inorganic lead-based perovskite are two matters seriously hindering its potential future application in photocatalysis. Therefore, it is particularly important to explore ecology-friendly, air-stable and highly active metal-halide perovskites. Herein, a new and stable lead-free perovskite Cs2 SnBr6 decorated with reduced graphene oxide (rGO), is synthesized and employed in the photocatalytic organic conversion. The as-prepared Cs2 SnBr6 is ultrastable, exhibiting no clear changes after being placed in the air for six months. The Cs2 SnBr6 /rGO composite shows excellent photocatalytic activity in photo-driven-oxidation of 5-hydroxymethylfurfural (HMF) to high value enclosed 2,5-diformylfuran (DFF), achieving>99.5 % conversion of HMF and 88 % DFF selectivity in the presence of green oxidant O2 . Comprehensive characterizations disclose a multistep reaction mechanism, demonstrating that the molecular oxygen, photogenerated carriers, ⋅O2 - and 1 O2 altogether synergistically participate in the effective photo-driven conversion of HMF to DFF. This work expands the material gallery towards selective organic conversion and environmentally friendly perovskite options for photocatalytic application.

Facile preparation of highly efficient Te4+-doped Rb2SnCl6 perovskites for white light-emitting diodes

Lead-free vacancy‐ordered halide double perovskite microcrystals are new alternatives to lead-based halide perovskite materials for lighting applications; however, they are limited by harsh synthesis conditions and low quantum efficiency. Hence, a facile solution recrystallization method was used to synthesize Te4+-doped Rb2SnCl6 phosphors. Via Te4+ doping, the phosphors show a yellow–green emission at 550 nm and a broadband emission line width of approximately 97 nm, achieving a high photoluminescence quantum yield of 74.2%, arising from the Te4+ 1S0 →3P1 self-trapping exciton transition. The Te4+-doped Rb2SnCl6 microcrystals are subsequently used to fabricate a white light-emitting diode device, which shows a high color-rendering index of 97.1 and a correlated color temperature of 4739 K. This work reports a facile method to synthesize alloy double perovskite phosphors, opening up new avenues for the development of environment-friendly lighting applications.

Performance Improvement of Lead-Based Halide Perovskites through B-Site Ion-Doping Strategies.

Owing to their excellent properties, lead halide perovskites have attracted extensive attention in the photoelectric field. Presently, the certified power conversion efficiency of perovskite solar cells has reached 25.7%, the specific detectivity of perovskite photodetectors has exceeded 1014 Jones, and the external quantum efficiency of perovskite-based light-emitting diode has exceeded 26%. However, their practical applications are limited by the inherent instability induced by the perovskite structure due to moisture, heat, and light. Therefore, one of the widely used strategies to address the issue is to replace partial ions of the perovskites with ions of smaller radii to shorten the bond length between halides and metal cations, improving the bond energy and enhancing the perovskite stability. Particularly, the B-site cation in the perovskite structure can affect the size of eight cubic octahedrons and their gap. However, the X-site can only affect four such voids. This review comprehensively summarizes the recent progress in B-site ion-doping strategies for lead halide perovskites and provides some perspectives for further performance improvements.

Growth and Characterization of All-Inorganic Halide Perovskite CsPbF3 Single Crystals

Lead-based halide perovskite semiconductors have demonstrated considerable potential in optoelectronic applications. However, the lack of high-quality crystals suitable for research has led to rare reports on CsPbF3 single crystals. Good quality CsPbF3 single crystals were successfully grown using the Bridgman method. The structure, luminescence, and electrical properties of crystals were investigated. At room temperature, the crystal structure was determined to be cubic perovskite, with a calculated bandgap of 3.68 eV. The measured emission spectrum showed one broad emission peak at approximately 400 nm. Three decay time constants were obtained from a sum of exponential functions fit to the fluorescence decay curve: 0.4 ns, 2.4 ns, and 15.0 ns for fast, middle, and slow decay times, respectively. The decay times excited by pulsed X-ray were measured to be 2.2 ns and 10.2 ns, indicating that CsPbF3 is an ultrafast scintillator. Furthermore, the electrical properties demonstrated that CsPbF3 exhibits high ion mobility, which is approximately 20 times that of electron mobility.

Lead-Free FACsSnI3 Based Perovskite Solar Cell: Designing Hole and Electron Transport Layer.

In recent years, lead-based perovskites solar cells have demonstrated excellent power-conversion efficiency. Despite their remarkable progress, the commercialization of lead-based perovskites is hampered by lead toxicity concerns. The recently discovered non-toxic FACsSnI3 perovskite has the potential to replace lead-based perovskites in solar cell applications. Since the perovskite material FACsSnI3 (FA0.85Cs0.15SnI3) is relatively new, there is a lack of information, particularly regarding the design features required for electron and hole-transport layers for efficient photovoltaic responses. The important variables, such as electron affinity, energy band gap, film thickness, and doping density of both electron and hole-transport layers, were simulated and modeled separately and iteratively in this study to achieve the most efficient photovoltaic response. Finally, the absorber layer thickness of FACsSnI3 perovskite is tuned to achieve a maximum power-conversion efficiency of slightly more than 24%. We hope that the findings of this study will serve as a strong guideline for future research and the design of lead-free perovskite solar cells for efficient photovoltaic responses.

Hole Transport Materials for Tin-Based Perovskite Solar Cells: Properties, Progress, Prospects.

The power conversion efficiency of modern perovskite solar cells has surpassed that of commercial photovoltaic technology, showing great potential for commercial applications. However, the current high-performance perovskite solar cells all contain toxic lead elements, blocking their progress toward industrialization. Lead-free tin-based perovskite solar cells have attracted tremendous research interest, and more than 14% power conversion efficiency has been achieved. In tin-based perovskite, Sn2+ is easily oxidized to Sn4+ in air. During this process, two additional electrons are introduced to form a heavy p-type doping perovskite layer, necessitating the production of hole transport materials different from that of lead-based perovskite devices or organic solar cells. In this review, for the first time, we summarize the hole transport materials used in the development of tin-based perovskite solar cells, describe the impact of different hole transport materials on the performance of tin-based perovskite solar cell devices, and summarize the recent progress of hole transport materials. Lastly, the development direction of lead-free tin-based perovskite devices in terms of hole transport materials is discussed based on their current development status. This comprehensive review contributes to the development of efficient, stable, and environmentally friendly tin-based perovskite devices and provides guidance for the hole transport layer material design.

Environmental lead-free Cs3Bi2I9 films deposited by vapor transport deposition for stable all-inorganic solar cells

The non-lead metal halides are of wide interest due to their low toxicity and good stability compared with lead-based perovskites. Among them, Cs3Bi2I9 is of interest because of its excellent electronic and optical properties. In this study, high-quality Cs3Bi2I9 films with large grains and good uniformity were deposited for the first time by a vapor transport deposition (VTD) approach using a mixture of CsI and BiI3 crystal powders as evaporation sources. The Cs3Bi2I9 film was then used as an absorber layer in the solar cell using a superstrate structure with FTO/TiO2/Cs3Bi2I9/CuI/Au. Due to the different melting points of CsI (626 °C) and BiI3 (408 °C), the CsI to BiI3 molar ratio can significantly affect the stoichiometry, structure, and optoelectronic properties of the prepared Cs3Bi2I9 films, which ultimately determine the performance of the Cs3Bi2I9 solar cells. The all-inorganic Cs3Bi2I9 solar cell can achieve a maximum PCE of 1.52% and remain at 80% of its initial value after one month of storage in the air without encapsulation. This work provides a new route to deposit inorganic perovskite films using evaporation sources with different melting points, which has promising applications in solar cells and photodetectors.

Uncovering the Role of Electronic Doping in Lead-free Perovskite (CH3 NH3 )2 CuCl4-x Brx and Solar Cells Fabrication.

Lead halide perovskites are attractive pigments to fabricate solar cells in the laboratory, owing to their high power conversion efficiency. However, given the presence of Pb, such materials also have a high level of toxicity and are carcinogenic for humans and aquatic life. Arguably, this hampers their acceptability for immediate commercialization. This study entails the synthesis, optoelectronic properties, and photovoltaic parameters of two-dimensional copper-based perovskites as an environmentally benign alternative to lead-based perovskites. The perovskites - (CH3 NH3 )2 CuCl4-x Brx with x=0.3 and 0.66 - are derivatives of the stable (CH3 NH3 )2 CuCl4 . The single crystals and powders diffractograms suggest compositions with variations in Cl/Br ratio and dissimilar bromine localization in the inorganic framework. The copper mixed halide perovskite exhibits a narrow absorption with a bandgap of 2.54-2.63 eV related to the halide ratio disparity (crystal color variation). These findings demonstrate the impact of halides to optimize the stability of methylammonium copper perovskites and provide an effective pathway to design eco-friendly perovskites for optoelectronic applications.

Quantum Chemical Modeling of CH3NH3MX3 (MAM*X3: M* = Sn, Si, Ge; X = Cl, Br, I) Lead-Free Perovskites in Comparison with Lead-Based Perovskite Materials

Quantum Chemical Modeling of CH3NH3MX3 (MAM*X3: M* = Sn, Si, Ge; X = Cl, Br, I) Lead-Free Perovskites in Comparison with Lead-Based Perovskite Materials

Numerical Investigation of Power Conversion Efficiency of Sustainable Perovskite Solar Cells

Perovskite solar cells have been researched for high efficiency only in the last few years. These cells could offer an efficiency increase of about 3% to more than 15%. However, lead-based perovskite materials are very harmful to the environment. So, it is imperative to find lead-free materials and use them in designing solar cells. This research investigates the potential for using a lead-free double-perovskite material, La2NiMnO6, as an absorbing layer in perovskite solar cells to enhance power conversion efficiency (PCE). Given the urgent need for environmentally friendly energy sources, the study addresses the problem of developing alternative materials to replace lead-based perovskite materials. Compared to single-perovskite materials, double perovskites offer several advantages, such as improved stability, higher efficiency, and broader absorption spectra. In this research work, we have simulated and analyzed a double-perovskite La2NiMnO6 as an absorbing material in a variety of electron transport layers (ETLs) and hole transport layers (HTLs) to maximize the capacity for high-efficiency power conversion (PCE). It has been observed that for a perovskite solar cells with La2NiMnO6 absorbing layer, C60 and Cu2O provide good ETLs and HTLs, respectively. Therefore, the achieved power conversion efficiency (PCE) is improved. The study demonstrates that La2NiMnO6, as a lead-free double-perovskite material can serve as an effective absorbing layer in perovskite solar cells. The findings of this study contribute to the growing body of research on developing high-efficiency, eco-friendly perovskite solar cell technologies and have important implications for the advancement of renewable energy production.

Room-temperature synthesis of lead-free copper(I)-antimony(III)-based double perovskite nanocrystals

In the field of perovskite solar cells, explorations of new lead-free all-inorganic perovskite materials are of great interest to address the instability and toxicity issues of lead-based hybrid perovskites. Recently, copper-antimony-based double perovskite materials have been reported with ideal band gaps, which possess great potential as absorbers for photovoltaic applications. Here, we synthesize Cs2CuSbCl6 double perovskite nanocrystals (DPNCs) at ambient conditions by a facile and fast synthesis method, namely, a modified ligand-assisted reprecipitation method. We choose methanol as a solvent for precursor salts as it is less toxic and easily removed in contrast to widely used dimethylformamide. Our computational structure search shows that the Cs2CuSbCl6 structure containing alternating [CuCl6]5− and [SbCl6]3− octahedral units is a metastable phase that is 30 meV/atom higher in energy compared to the ground state structure with [CuCl3]2− and [SbCl6]3− polyhedra. However, this metastable Cs2CuSbCl6 double perovskite structure can be stabilized through solution-based nanocrystal synthesis. Using an anion-exchange method, Cs2CuSbBr6 DPNCs are obtained for the first time, featuring a narrow bandgap of 0.9 eV. Finally, taking advantage of the solution processability of DPNCs, smooth and dense Cs2CuSbCl6 and Cs2CuSbBr6 DPNC films are successfully fabricated.

Physicochemical Properties of Organic Molecular Ferroelectric Diisopropylammonium Chloride Thin Films.

We fabricated ferroelectric films of the organic molecular diisopropylammonium chloride (DIPAC) using the dip-coating technique and characterized their properties using various methods. Fourier-transform infrared, scanning electron microscopy, and X-ray diffraction analysis revealed the structural features of the films. We also performed ab-initio calculations to investigate the electronic and polar properties of the DIPAC crystal, which were found to be consistent with the experimental results. In particular, the optical band gap of the DIPAC crystal was estimated to be around 4.5 eV from the band structure total density-of-states obtained by HSE06 hybrid functional methods, in good agreement with the value derived from the Tauc plot analysis (4.05 ± 0.16 eV). The films displayed an island-like morphology on the surface and showed increasing electrical conductivity with temperature, with a calculated thermal activation energy of 2.24 ± 0.03 eV. Our findings suggest that DIPAC films could be a promising alternative to lead-based perovskites for various applications such as piezoelectric devices, optoelectronics, sensors, data storage, and microelectromechanical systems.

Synthesis of cesium silver bismuth bromide double perovskite nanoparticles via a microwave-assisted solvothermal method

Bismuth-based perovskites have been widely investigated in recent years as an alternative candidate for resolving the toxicity of a high-performance lead-based perovskite. In this work, we present the synthesis of a cesium silver bismuth bromide (Cs2AgBiBr6) perovskite employing a microwave-assisted solvothermal method, which offers features for simple and minute-scale sample synthesis. The X-ray diffraction and Raman spectroscopy results reflected the high purity of bismuth-based perovskites synthesized at non-inert conditions. Field-emission scanning electron microscopy and energy-dispersive X-ray showed a particle size of 72 nm and Br-rich or Cs-deficient condition in the materials, respectively. The synthesized material also shows promising moisture and thermal stability. Ultraviolet–visible spectroscopy and temperature-dependent photoluminescence spectroscopy revealed the electronic structure and nature of the material, including low carrier localization and a strong electron-phonon effect. The time-resolved photoluminescence revealed a carrier lifetime of 921 ns, which is desired for an optoelectronic application. These findings point to a simple and rapid method for producing Cs2AgBiBr6 perovskite nanoparticles.

Neurotoxicity study of lead-based perovskite nanoparticles

Lead-based halide perovskite nanoparticles (Pb-PNPs) are promising alternatives for the next-generation of optoelectronic materials, while their nonnegligible biological behavior after exposure are still an enigma. Here, we clarify the translocation, biotransformation, and biodistribution related neurotoxicity of representative CsPbBr3 PNPs in C57BL/6J mice after intranasal administration through a combination of the feat of advanced synchrotron radiation (SR) and traditional analytical techniques. SR-based microscopic X-ray fluorescence scanning, inductively coupled plasma mass spectrometry and behavioral data demonstrate that CsPbBr3 PNPs can be transported and accumulated in the hippocampus, easily triggering Ca overload, causing severe damage of hippocampus-dependent learning, memory, and cognition behavior. Meanwhile, SR–based X-ray absorption near-edge spectroscopy analysis also reveals that CsPbBr3 PNPs can transform into soluble and insoluble lead compounds in different physiological environments. The toxicity of CsPbBr3 PNPs is higher than that of soluble Pb(Ac)2 due to the sustained release of Pb ions. The CsPbBr3 PNPs cause nerve cell apoptosis through triggering intracellular Ca2+ overload, upregulating reactive oxygen species production, while disordering the mitochondrial membrane potential. Our work provides significant insights into the neurological effects and mechanism of Pb-PNPs.

Modeling the Electronic and Optical Properties of Lead-Based Perovskite Materials: Insights from Density Functional Theory and Electrostatic Embedding

We present an investigation of the geometric, electronic, and optical properties of various bulk MAPbX3 (X = Cl, Br, and I) perovskite systems in different phases and of different heterointerface models built between MAPbI3 (hereafter MAPI) and TiO2, linked by a bifunctional para-benzoic acid derivative, in view of their importance as key components of perovskite solar cells. To this end, we combine periodic hybrid density functional theory (DFT) calculations, to model the geometric and electronic properties of these systems, with time-dependent DFT calculations (TD-DFT) carried out on non-periodic clusters, extracted from the periodic models, embedded in an array of point charges reproducing the periodic electrostatic environment, thus enabling the modeling of their optical properties in condensed phases. We found that all systems investigated present favorable key features for their use as building blocks for solar devices. Furthermore, the proposed computational approach, combining periodic and non-periodic calculations, appears as a reliable and effective tool to model both the electronic and the optical properties of various key components of materials related to photovoltaic applications at low computational cost.

A universal hydrochloric acid-assistant powder-to-powder strategy for quick and mass preparation of lead-free perovskite microcrystals

Lead-free halide perovskite materials possess low toxicity, broadband luminescence and robust stability compared with conventional lead-based perovskites, thus holding great promise for eyes-friendly white light LEDs. However, the traditionally used preparation methods with a long period and limited product yield have curtailed the commercialization of these materials. Here we introduce a universal hydrochloric acid-assistant powder-to-powder strategy which can accomplish the goals of thermal-, pressure-free, eco-friendliness, short time, low cost and high product yield, simultaneously. The obtained Cs2Na0.9Ag0.1In0.95Bi0.05Cl6 microcrystals exhibit bright self-trapped excitons emission with quantum yield of (98.3 ± 3.8)%, which could retain (90.5 ± 1.3)% and (96.8 ± 0.8)% after continuous heating or ultraviolet-irradiation for 1000 h, respectively. The phosphor converted-LED exhibited near-unity conversion efficiency from ultraviolet chip to self-trapped excitons emission at ~200 mA. Various ions doping (such as Cs2Na0.9Ag0.1InCl6:Ln3+) and other derived lead-free perovskite materials (such as Cs2ZrCl6 and Cs4MnBi2Cl12) with high luminous performance are all realized by our proposed strategy, which has shown excellent availability towards commercialization.

Effects of alkali-metals (X = Li, Na, K) doping on the electronic, optoelectronic, thermodynamic, and X-ray spectroscopic properties of X–SnI3 halide perovskites

The effect of alkali metals (Li, Na, K) doping at X sites in tin-based X–SnI3 halide perovskite on structural, electronic, phonon, thermodynamic, and X-ray core-level spectroscopic properties was investigated and correlated with optoelectronic efficiency in the development of a stable and environmentally friendly solar technology to replace toxic lead-based perovskite solar cells (PSCs). These calculations were carried out based on the density functional theory approach using the Quantum Espresso software with the generalized gradient approximation (GGA) exchange correlation Perdew Burke Ernzerhorf functional. In addition, the phonon frequency, thermodynamics, and X-ray spectroscopy calculations were completed in Materials Studio using the CASTEP code. Our results reveal that there is a clear correlation between the alkali metal's ionic radius, changes in the lattice structural parameters, and the electronic band gap, such that the lattice constants are 5.940, 5.868, and 5.897 Å and the band gaps are 1.20, 1.14, and 1.10 eV for LiSnI3, NaSnI3, and KSnI3, respectively. The highest lattice constant obtained for LiSnI3, indicates that Li atoms occupied interstitial positions in the perovskite crystal, whereas the direct band gap decreases as cationic size increases, with KSnI3 exhibiting the least band gap. Phonon calculations show that KSnI3 has the lowest negative vibration region in its phonon dispersion plot, indicating dynamic stability. Interestingly, all the structures are found to portray high optical absorption, high extinction coefficient, high polarizability. Additionally, the free energy computation of the perovskites shows a reduction with rising temperature, but enthalpy increases significantly with increasing temperature. Yet, due to phonon lattice vibrations, the heat capacity increased as the temperature rose. Although the XSnI3 (X = Li, Na, and K) perovskites under investigation will perform efficiently as semiconductors and can be used for optoelectronic applications, the KSnl3 perovskite material has the most desirable properties for the fabrication of solar cell devices.