Lead-based Perovskites Research Articles

Synthesis and resistive switching performance of lead-free double perovskite Cs2AgBiBr6 films

In recent years, the lead-free double perovskite Cs2AgBiBr6 has emerged as an appealing alternative to lead-based perovskites due to its nontoxicity and long-term stability. In this study, we employed methyl acetate as an antisolvent and prepared high-quality Cs2AgBiBr6 films by a facile one-step spin-coating method. The prepared films exhibited excellent crystallinity with densely packed crystal grains. The root mean square roughness and average roughness of the obtained Cs2AgBiBr6 perovskite films were 6.69 and 5.43 nm, respectively. Furthermore, the memory device based on the Cs2AgBiBr6 perovskite films exhibited uniform and repeatable bipolar resistive switching performance with an ON/OFF ratio of 15, an endurance of 80 cycles, and a retention time of 104 s. This work showcases a simple and convenient one-step spin-coating method for depositing high-quality Cs2AgBiBr6 thin films while highlighting their potential application in resistive switching memories based on lead-free double perovskites.

A Double Perovskite Single Crystal CsCuAgI3.

Eco-friendly halide double perovskites are attracting significant attention as potential substitutes for traditional lead-based halide perovskites. However, their typically wide or indirect band gap limits further technological advancement. This study presents a new, eco-friendly, all-inorganic millimeter-scale CsCuAgI3 single crystal (SC). The crystal exhibits a direct band gap of 2.02 eV at the G-point, markedly superior to that of traditional double perovskites. The absorption and photoluminescence spectra further corroborate its band gap attributes. Owing to the B-site Cu-Ag disorder, the crystal possesses a higher Urbach energy (119 meV), indicative of structural disorder. CsCuAgI3 exhibits a wide Stokes shift of 230 nm, a wide full width at half-maximum (fwhm) of 152 nm, a long fluorescence lifetime of 7.29 μs, and excellent stability. In addition, a photoelectric detection prototype was prepared using a CsCuAgI3 single crystal. Using a 375 nm laser as the excitation source, the device showed a very sensitive photoelectric response, clocking in at (0.37/0.21) seconds. This work offers new insights into developing novel lead-free double perovskite single crystals and exploring their potential applications.

Iso-BAI Guided Surface Recrystallization for Over 14% Tin Halide Perovskite Solar Cells.

Tin-based perovskite solar cells (PSCs) are promising environmentally friendly alternatives to their lead-based counterparts, yet they currently suffer from much lower device performance. Due to variations in the chemical properties of lead (II) and tin (II) ions, similar treatments may yield distinct effects resulting from differences in underlying mechanisms. In this work, a surface treatment on tin-based perovskite is conducted with a commonly employed ligand, iso-butylammonium iodide (iso-BAI). Unlike the passivation effects previously observed in lead-based perovskites, such treatment leads to the recrystallization of the surface, driven by the higher solubility of tin-based perovskite in common solvents. By carefully designing the solvent composition, the perovskite surface is effectively modified while preserving the integrity of the bulk. The treatment led to enhanced surface crystallinity, reduced surface strain and defects, and improved charge transport. Consequently, the best-performing power conversion efficiency of FASnI3 PSCs increases from 11.8% to 14.2%. This work not only distinguishes the mechanism of surface treatments in tin-based perovskites from that of lead-based counterparts, but also underscores the critical role in designing tailor-made strategies for fabricating efficient tin-based PSCs.

Advantageous occupation of Cu2+ in the B site of double-perovskite Rb2BB'Br6 (B = K; B′ = Bi) framework for white-light-emission

Research on lead-free double perovskite has demonstrated its potential as a solution to the stability and toxicity issues associated with lead-based inorganic perovskite white light-emitting diodes (WLED). This current investigation was designed to fabricate, examine, and compare the photoluminescence (PL) characteristics of Cu2+-activated Rb2BB'Br6 (B = K and B′ = Bi) double-perovskite (DP) [A2BB'Br6] luminous materials. Bi3+ ions are substituted with Cu2+ ions at their B′ sites. These ions are distributed to the equilibrium valence state and demonstrate minimal variation in ion radius. The microstructure and phase purity of Rb2BB'Br6:Cu2+ DP were assessed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The Rietveld refinement was also used to identify the crystal structures, and the resulting samples all exhibit cubic crystal structures. The Fm3m space group in Rb2BB'Br6 DP frameworks is significantly impacted by the B sites. The PL spectra were used to thoroughly examine the associated mechanism of the Cu2+ → Bi3+ energy-transfer process. Cu2+ ions can be successfully doped in the Rb2KBiBr6 host with an optical band gap (Eg) of 2.74 eV (RKBBr: 0.025Cu2+). The Rb2KBiBr6:Cu2+ phosphor exhibits distinct emission bands from 450 to 650 nm upon UV excitation at 366 nm. The Cu2+→ Bi3+ energy transfer design allows for systematic luminescence tuning from blue to white due to spectral overlap between the Cu2+ emission and Bi3+ excitation spectra. It has been established that Cu2+ → Bi3+ energy transfer significantly increases the white emission intensity of Bi3+, with an associated colour temperature of 7892 K and an outstanding colour rendering index of 88.8. As a down-conversion luminous material in solid-state illumination for the upcoming generation of display devices, the discovered Rb2KBiBr6: 0.025Cu2+ phosphor exhibits remarkable promise.

Mixed tin-lead perovskites with balanced crystallization and oxidation barrier for all-perovskite tandem solar cells

Mixed tin-lead perovskite solar cells have driven a lot of passion for research because of their vital role in all-perovskite tandem solar cells, which hold the potential for achieving higher efficiencies compared to single-junction counterparts. However, the pronounced disparity in crystallization processes between tin-based perovskites and lead-based perovskites, coupled with the easy Sn2+ oxidation, has long been a dominant factor contributing to high defect densities. In this study, we propose a multidimensional strategy to achieve efficient tin-lead perovskite solar cells by employing a functional N-(carboxypheny)guanidine hydrochloride molecule. The tailored N-(carboxypheny)guanidine hydrochloride molecule plays a pivotal role in manipulating the crystallization and grain growth of tin-lead perovskites, while also serving as a preservative to effectively inhibit Sn2+ oxidation, owing to the strong binding between N-(carboxypheny)guanidine hydrochloride and tin (II) iodide and the elevated energy barriers for oxidation. Consequently, single-junction tin-lead cells exhibit a stabilized power conversion efficiency of 23.11% and can maintain 97.45% of their initial value even after 3500 h of shelf storage in an inert atmosphere without encapsulation. We further integrate tin-lead perovskites into two-terminal monolithic all-perovskite tandem cells, delivering a certified efficiency of 27.35%.

Simulation and Optimization of Lead-Based Perovskite Solar Cells with Cuprous Oxide as a P-type Inorganic Layer

The hole transporting material (HTM) is responsible for selectively transporting holes and blocking electrons which also plays a crucial role in the efficiency and stability of perovskite solar cells (PSCs). Spiro-MeOTAD is the most popular material, which is expensive and can be easily affected by moisture content. There is a need to find an alternative HTM with sufficiently high resistance to moisture content. In this paper, the influence of some parameters with cuprous oxide (Cu2O) as HTM was investigated using a solar cell capacitance simulator (SCAPS). These include the influence of doping concentration and thickness of the absorber layer, the effect of thickness of ETM and HTM as well as electron affinities of ETM and HTM on the performance of the PSCs. From the obtained results, it was found that the concentration of dopant in the absorber layer, the thickness of ETM and HTM and the electron affinity of HTM and ETM affect the performance of the solar cell. The cell performance improves greatly with the reduction of ETM electron affinity and its thickness. Upon optimization of parameters, power conversion efficiency for this device was found to be 20.42% with a current density of 22.26 mAcm-2, voltage of 1.12 V, and fill factor of 82.20%. The optimized device demonstrates an enhancement of 58.80%, 2.25%, 20.40% and 30.23% in PCE, Jsc, FF, and Voc over the initial cell. The results show that Cu2O in lead-based PSC as HTM is an efficient system and an alternative to spiro-MeOTAD.

Few-mode metal-free perovskite optical fiber with second-order optical nonlinearity

Semiconductor core optical fibers are highly desirable for fiber-based photonic and optoelectronic applications as they can combine strong optical nonlinearities, tight light confinement, wide transmission bands, and electronic functionality within a single platform. Perovskites have emerged as particularly exciting materials for semiconductor photonics as they have strong optical nonlinearities and tunable optoelectronic bandgaps. However, lead-based perovskites contain toxic elements and are, therefore, not environmentally friendly. Furthermore, in fiber form, their core-size is prohibitively large, making them unsuitable for nonlinear optics and applications that require single-mode guidance, such as telecommunications. Here, we report a metal-free perovskite core optical fiber where lead has been substituted for an ammonium cation in the perovskite structure. The core material has a wide bandgap greater than 5 eV, a high laser damage threshold, and a core diameter that can be produced as small as 5 µm. At this core size, the fiber supports just six modes, and the fundamental mode can readily be excited and isolated. Moreover, the metal-free perovskite has a second-order susceptibility that is absent in the archetypal lead-based perovskites and many other semiconductor core materials, such as silicon and germanium. The second-order susceptibility is important for many nonlinear optics applications, such as second-harmonic generation and quantum optics.

Photoelectrochemical Sensor for H2S Based on a Lead-Free Perovskite/Metal-Organic Framework Composite.

Halide perovskites have emerged as a highly promising class of photoelectric materials. However, the application of lead-based perovskites has been hindered by their toxicity and relatively weak stability. In this work, a composite material comprising a lead-free perovskite cesium copper iodide (CsCu2I3) nanocrystal and a metal-organic framework (MOF-801) has been synthesized through an in situ growth approach. The resulting composite material, denoted as CsCu2I3/MOF-801, demonstrates outstanding stability and exceptional optoelectronic characteristics. MOF-801 may serve a dual role by acting as a protective barrier between CsCu2I3 nanocrystals and the external environment, as well as promoting the efficient transfer of photogenerated charge carriers, thereby mitigating their recombination. Consequently, CsCu2I3/MOF-801 demonstrates its utility by providing both stability and a notably high initial photocurrent. Leveraging the inherent reactivity between H2S and the composite material, which results in the formation of Cu2S and structural alteration, an exceptionally sensitive photoelectrochemical sensor for H2S detection has been designed. This sensor exhibits a linear detection range spanning from 0.005 to 100 μM with a remarkable detection limit of 1.67 nM, rendering it highly suitable for precise quantification of H2S in rat brains. This eco-friendly sensor significantly broadens the application horizon of perovskite materials and lays a robust foundation for their future commercialization.

Structural, optical, and electronic properties of single crystals of 4H lead-based hexagonal hybrid perovskite

Structural, optical, and electronic properties of single crystals of 4H lead-based hexagonal hybrid perovskite

Antimony-Based Halide Perovskite Nanoparticles as Lead-Free Photocatalysts for Controlled Radical Polymerization.

Metal halide perovskites have emerged as versatile photocatalysts to convert solar energy for chemical processes. Perovskite photocatalyzed polymerization draws special attention due to its straightforward synthesis process and the ability to create advanced perovskite-polymer nanocomposites. Herein, this work employs Cs3Sb2Br9 perovskite nanoparticles (NPs) as a lead-free photocatalyst for light-controlled atom transfer radical polymerization (ATRP). Cs3Sb2Br9 NPs exhibit high reduction potential and interact with electronegative bromide initiator with Lewis acid Sb sites, enabling efficient photoinduced reduction of initiators and controlled polymerization under blue light irradiation. Methacrylate monomers with various functional groups are successfully polymerized, and the resulting polymer showcased a dispersity (Đ) as small as 1.27. The living nature of polymerization is confirmed by high chain end fidelity and kinetic studies. Moreover, Cs3Sb2Br9 NPs serve as heterogeneous photocatalysts, demonstrating recyclability and reusability for up to four cycles. This work presents a promising approach to overcome the limitations of lead-based perovskites in photoinduced controlled radical polymerization, offering a sustainable and efficient alternative for the synthesis of well-defined polymeric materials.

Pressure-induced DFT evaluation of MSnI3 (M = K, Rb) perovskites for electronic phase transition and enhanced optoelectronic utilization

In optoelectronic device applications, perovskite materials have overtaken other compounds because of their exceptional power conversion efficiencies. Lead-based perovskites have found extensive use; however, their widespread adoption is hindered by the inherent toxicity associated with lead content. In contrast, lead-free metal halide perovskites have taken the dominant position in the commercialization of optoelectronic devices by offering high efficiency, affordability, flexibility, tunability, and environmental benefits. To better understand the structural, electronic, bonding, optical, elastic, and mechanical properties of the non-toxic MSnI3 (M = K, Rb) metal halides under different hydrostatic pressures, a first-principles simulation has been carried out with the use of density functional theory (DFT). Lattice parameters and electronic band structures have been computed using both the Generalized Gradient Approximation (GGA) and the non-local hybrid sX (Hartree-Fock screened exchange) functional. Utilizing the sX method results in enhanced band gap values for MSnI3 (M = K, Rb) perovskite compounds. The application of pressure has led to a decrease in both lattice parameters and band gaps, marking a transition from a semiconductor to a metallic state. The projection of the density of states and their electronic orbital contributions are also explored to evaluate the band structure tuning of MSnI3 (M = K, Rb) under pressure. The bond length calculation and the charge density mapping confirm the existence of both the ionic and covalent bonds in MSnI3 (M = K, Rb). Additionally, the pressure-induced calculation suggests that the bonds between both compounds will be stronger at high pressure. Increasing hydrostatic pressure causes a dramatic movement of the absorption edge of MSnI3 (M = K, Rb) perovskites into the low energy region (a red shift), which is revealed by the analysis of optical functions. The optical functions’ investigation indicates that the hydrostatic pressure allows the compounds even better for a number of possible uses. The mechanical qualities are a direct reflection of the ductile and anisotropic nature of the compounds, both of which are significantly influenced by the external pressure.

An all-inorganic lead-free metal halide double perovskite for the highly selective detection of norfloxacin in aqueous solution.

Lead-based perovskites are highly susceptible to environmental influences, and their application in analytical chemistry, especially in aqueous solution, has been reported rarely. All-inorganic lead-free metal halide perovskites have been considered as a substitute for lead-based perovskites. Herein, a Cs2RbTbCl6 perovskite microcrystal (PMCs), which emits strong yellow-green fluorescence with a maximum emission wavelength at 547nm, was for the first time synthesized and characterized. The Cs2RbTbCl6 PMCs could be well dispersed in N,N-dimethylacetamide (DMF), and its fluorescence could be significantly enhanced by the addition of norfloxacin (NOR) in the aqueous solution. We found that the Cs2RbTbCl6 PMCs can be used as fluorescent probes (excitation, 365nm; emission, 547nm) to selectively detect NOR in a concentration range from 10.0 to 200.0μM with the limit of detection (LOD) being 0.04μM. The Cs2RbTbCl6 PMCs could also be adsorbed on filter paper to fabricate as a fluorescent test paper for visual detection of NOR under 365-nm ultraviolet (UV) lamp irradiation. The proposed method has the potential to establish a new analytical method to visualize the detection of NOR in aqueous environments and also promotes the application of all-inorganic lead-free perovskites for analytical detection in aqueous environments.

High performance CsBi3I10/PCBM bulk heterojunction perovskite photodetector.

Lead halide perovskites (LHPs) have been extensively studied due to their remarkable optoelectronic performance. However, the toxicity of a lead ion to humans and its instability under ambient conditions render lead-based halide perovskite an unsuitable material for commercialization. Meanwhile, lead-free halide perovskite (LFHP) devices generally exhibit poor performance. Therefore, enhancing photoelectric conversion capacity is the most important issue that needs to be addressed. Here, we propose a photodetector (PD) fabricated using C s B i 3 I 10/p h e n y l-C 61-butyric acid methyl ester (PCBM) bulk heterojunction as the active layer. The PD illuminated under 532nm can reach a high responsivity (1.54A/W) at -2V bias, while at 2V bias, the PD reaches a higher responsivity (224.40A/W). All of those results suggest that C s B i 3 I 10/P C B M bulk heterojunctions hold enormous potential in substituting for LHPs in optoelectronic devices.

Obtaining and characterization of MAPbSnBr3 perovskite crystals trough AVC method

The obtaining tin-based perovskite from solution is challenging due to the rapid and uncontrollable crystallization of tin compared to lead-based perovskite. Another challenge is to reduce the use of lead to avoid poisoning. In this sense, Sn-based perovskite compounds such as CsSnBr3 have attracted great attention as an effective replacement, but current photovoltaic devices still problems of low efficiency and instability chemistry. The band gap of ASnX3 compounds is between 1.2 and 1.4 eV, being the ideal range for maximum theoretical efficiency in a solar cell. In contrast, APbX3 compounds have band gaps in the range of 1.45 to 1.6 eV. We synthesize MAPbSnBr3 perovskite crystals through the AVC method. The structural properties of the crystals were obtained by X-ray diffraction, Raman spectroscopy, these shown the presence of Sn and Pb in the crystals obtained, and the optical properties by UV-Vis absorption and photoluminescence spectroscopy obtaining the variation of the band gap in the perovskite.The results obtained from the MAPbSnBr3 perovskite (such as the band gap, absorption spectrum and crystal lattice) meet the necessary requirements for its possible application in photovoltaic devices. It is shown that it is possible to obtain MAPbSnBr3 crystals with a lower amount of Pb and how the bandgap is affected by varying these elements, for their possible application in solar cells.

Lead-Free Double Perovskites: A Review of the Structural, Optoelectronic, Mechanical, and Thermoelectric Properties Derived from First-Principles Calculations, and Materials Design Applicable for Pedagogical Purposes

Metal halide perovskite materials have shown significant advancements in their application as light absorbers in perovskite solar cells, with power conversion efficiencies reaching 27%. However, lead-based perovskites pose a concern due to their toxicity and stability issues in moisture, UV radiation, and heat. This has led to a pressing need to explore substitute materials that do not contain lead but maintain the remarkable characteristics of lead-based perovskites. This review article focuses on halide double perovskites characterised by the A2B’B”X6 composition, highlighting their structural, optical, thermoelectric, and mechanical capabilities. Additionally, the review evaluates several materials databases to investigate materials suitable for high-throughput first-principles calculations integrated inside density functional theory. The review aims to identify novel perovskite materials, offer a thorough evaluation of the potential benefits and drawbacks associated with this class of materials, and, from the pedagogical standpoint, discover effective instructional frameworks.

First-principles investigations on the structural, optoelectronic, mechanical and transport properties of new stable lead-free double perovskites Cs2BB′I6 (B = Ag/Rb, B′ = Bi/Ga) halides

Lead-free perovskite halides offer a promising alternative due to the successful replacement of lead-based perovskites in various applications. Density functional theory simulations have been utilized to ascertain the physical attributes of lead-free Cs2BB′I6 (B = Ag/Rb, B′=Bi/Ga) double perovskites in this work. The well-organized modified Becke-Johnson (mBJ) is employed to define exchange–correlation potential. The calculated negative formation energy values, structural optimization, along with evaluation of the tolerance factor support the stability of compounds. To judge the structural stability, several mechanical parameters are determined. For Cs2AgBiI6, a bandgap of 1.46 eV and 1.85 eV for Cs2RbGaI6 are achieved. The total and individual electronic states’ influence is also calculated. The optical absorption is prominent in the visible and UV regions for both perovskites depicting their potential use in optoelectronics. We also have an insight into the temperature-dependent transport characteristics of Cs2AgBiI6 and Cs2RbGaI6. The crucial ZT factor exhibits values of 0.78 and 0.75 for Cs2AgBiI6 and Cs2RbGaI6 at 800 K. The high Seebeck, ZT and electrical conductivity values also stand in the favor of their potential use in green technology.

Simulation and numerical modeling of high performance CH3NH3SnI3 solar cell with cadmium sulfide as electron transport layer by SCAPS-1D

This work includes the numerical modeling (NM) of solar cells consisting of the active layer of CH3NH3SnI3 and electron transport layer of CdS, by employing a software SCAPS-1D. Organic-inorganic lead-based perovskites are superior in terms of power conversion efficiency. However, there are some serious drawbacks associated with them including poor stability, shorter life time and toxicity. Therefore, it is the demand of the hour to explore alternative materials to overcome these shortcomings. In this regard, tin is a competitive alternative to lead because it has similar electronic and chemical properties. Moreover, it is nontoxic, making it environmentally friendly. However, Sn based perovskite devices are reported with inferior power conversion efficacy, to date. In the present work, we have worked on a novel architecture of solar cells containing CH3NH3SnI3 as a light absorber layer and CdS as electron fetching layer. Optimization of the device was performed numerically by varying physical parameters related to the active layer such as thickness, defect density and shallow acceptor concentration. The proposed architecture of solar cells was proved as an efficient system with Jsc of 33.40 mA/cm2, Voc of 0.878 V, FF of 85.25 %, and PCE of 25.02 %. The temperature analysis has revealed that, temperature higher than 300 K increases the reverse saturation current, seriously degrading the structure of the device, hence limiting the power conversion performance of the solar cell. Furthermore, a rear electrode made of the high work function materials like Pt forms an ohmic junction at the HTL/anode interface, enhancing the performance of the device. Results of this study have paved the way for experimentalists to explore opportunities, to rationalize this architecture for real time applications such as inhouse lighting and laptop/smartphone charging.

Enhancing the Performance of 2D Tin-Based Pure Red Perovskite Light-Emitting Diodes through the Synergistic Effect of Natural Antioxidants and Cyclic Molecular Additives.

Tin (Sn)-based perovskites are being investigated in many optoelectronic applications given their similar valence electron configuration to that of lead-based perovskites and the potential environmental hazards of lead-based perovskites. However, the formation of high-quality Sn-based perovskite films faces several challenges, mainly due to the easy oxidation of Sn2+ to Sn4+ and the fast crystallization rate. Here, to develop an environmentally friendly process for Sn-based perovskite fabrication, a series of natural antioxidants are studied as additives and ascorbic acid (VitC) is found to have a superior ability to inhibit the oxidation problem. A common cyclic molecule, 18-Crown-6, is further added as a second additive, which synergizes with VitC to significantly reduce the nonradiative recombination pathways in the PEA2SnI4 film. This synergistic effect greatly improves the performance of 2D red Sn-based PeLED, with a maximum external quantum efficiency of 1.87% (≈9 times that of the pristine device), a purer color, and better bias stability. This work demonstrates the potential of the dual-additive approach in enhancing the performance of 2D Sn-based PeLEDs,while the use of these environmentally friendly additives contributes to their future sustainability.

Effect of Cu2+ doping on fluorescence of Cs2ZnCl4 powder prepared by solid-state synthesis

Recently Cu-doped all-inorganic zero-dimensional (0D) metal halides Cs2ZnX4 (X = Cl, Br) have attracted many researchers due to their excellent fluorescence (FL) performance and low toxicity compared to lead-based perovskites. Although these 0D metal halides nanocrystals or small-sized single crystals are prepared via solution methods in most of the reports, we used the solid-state synthesis method to get Cu-doped Cs2ZnCl4 powders and characterized their FL properties. The results and analysis indicate that Cu2+ can be doped in Cs2ZnCl4 up to 12 at.%, which enhances the FL of Cs2ZnCl4 powder. The photoluminescence quantum yield (PLQY) at 480 nm rises from 1.11 % (undoped) to 20.06 % (6 at.% Cu doping). A modified triplet self-trapped excitons mechanism is presented to explain the enhanced Cu−doped Cs2ZnCl4 powder.

Modulating luminescence properties of CsMnBr3-based lead-free single crystals by pseudohalide doping

Pseudohalide doping promoting luminescence properties of lead-free CsMnBr3-based crystals.