Lead-free Halide Double Perovskites Research Articles

Optoelectronic and thermoelectric response of lead free halide double perovskites Rb2AgPX6 (X = Cl, Br, I) for energy storage applications

Optoelectronic and thermoelectric response of lead free halide double perovskites Rb2AgPX6 (X = Cl, Br, I) for energy storage applications

First-principles study of Na2AgAsZ6 (Z = F, Cl, Br, I) of structural, elastic, optoelectronic, and transport properties of lead-free halide double perovskites for energy conversion applications

In this article, density functional theory (DFT) is used to investigate the physical aspects of the halide double perovskites Na2AgAsZ6 (Z = F, Cl, Br, I). These substances have a cubic arrangement and are classified under space group Fm3m (225) based on their octahedral and tolerance factors values. All the perovskites are determined to be thermodynamically stable, as indicated by their negative formation energy. These double perovskite materials are semiconductors based on their electronic band structure. The energy band gaps of Na2AgAsF6, Na2AgAsCl6, Na2AgAsBr6, and Na2AgAsI6 were determined to be 2.96 eV, 1.93 eV, 1.28 eV, and 0.68 eV, respectively. We also calculated and examined the optical properties of these substances in the photon energy range of 0–8 eV. Our results indicate that the majority of the absorption occurs in the visible-ultraviolet spectrum, which makes the materials well-suited for solar systems. We employed the BoltzTraP algorithm to compute the thermoelectric properties of the materials and establish their thermoelectric behavior. These materials demonstrated figures of merit values of 0.55, 0.71, 0.74, and 0.75, respectively. Thus, these materials are appropriate for application in photovoltaic and thermoelectric devices.

Tunable Multicolor-Emission in Eu3+ and Tb3+ Codoped Cs2NaInCl6:Sb3+ Double Perovskite Nanocrystals and its Dual-Model Anti-Counterfeiting and Temperature-Sensing Applications

Lead-free metal halide double perovskites with non-toxicity and stable self-trapped excitons (STEs) have received considerable attention in the field of photoelectric applications. However, it is difficult to achieve independent control of its photoluminescence performance to meet the requirements of multi-band emission. Herein, a doping strategy was employed to introduce lanthanide ions (Ln3+) into Cs2NaInCl6:Sb3+ nanocrystals (NCs), enabling the multicolor emission modulation ranging from blue to red and even white light. Benefiting from the efficient energy transfer from Sb-related self-trapped excitons to Ln3+ ions, green and red emissions originate from the 5D0→7FJ (J=1, 2, 3, 4) transition of Eu3+ ions and 5D4-7FJ (J = 6, 5, 4, 3) transition of Tb3+ ions, respectively. According to the tunable polychromatic photoluminescence characteristics of doped NCs, the dual-mode fluorescent anti-counterfeiting applications were exhibited. Furthermore, the distinct temperature sensitivities exhibited by blue (453 nm) and red (617 nm) emission in Cs2NaInCl6:Sb3+/Eu3+ NCs provide the opportunity for the optical thermometry, which demonstrates the maximum absolute and relative sensitivity are 0.0018 and 0.43% K−1, respectively. These results indicate that the synthesized codoped NCs have the potential applications in multifunctional fields, such as optical thermometer, fluorescence anti-counterfeiting, and multicolor-LEDs.

Fluorescence-enhanced Cs2Ag0.3-xNaxZn0.35In1-yCl6:yM double perovskites for multimodal optical anti-counterfeiting

The excellent optical properties of lead-free halide double perovskites (LHDPs) Cs2AgInCl6 are of great importance in the field of anti-counterfeiting encryption. However, the fluorescence quantum yield of the existing Cs2AgInCl6-based materials is relatively low, and the fluorescence color is monochromatic, making it difficult to use in advanced multi-mode anti-counterfeiting applications. In this study, we synthesized Cs2Ag0.3-xNaxZn0.35In1-yCl6:yM (M = Cr/Bi) series LHDPs using an anti-solvent assisted co-precipitation method, improving the optical properties of Cs2AgInCl6-based materials by optimizing their composition. The fluorescence quantum yield of Zn–Na substituted Cr-doped Cs2Ag0.3-xNaxZn0.35In1-yCl6 LHDPs increased from 1.53 % to 82.57 % on the basis of Cs2AgInCl6. The Zn–Na substituted Bi-doped Cs2Ag0.3-xNaxZn0.35In1-yCl6 LHDPs exhibited dual-wavelength fluorescence emission at 407 and 650 nm, and the relative intensity between the two emission wavelengths changed via a change in the Bi doping amount, resulting in a change in the material's luminescence color. The as-synthesized LHDPs could be applied to multi-mode anti-counterfeiting, optical coding information storage, and art decoration applications.

Exploring the lead-free halide Cs2MGaBr6 (M = Li, Na) double perovskites for sustainable energy applications

In recent years, there has been a growing emphasis on the exploration of sustainable and eco-friendly materials well-suited for advanced applications in the realms of thermoelectrics and optoelectronics. Lead-free halide double perovskites have emerged as a compelling class of materials in this context. Nevertheless, despite their potential utility, thorough investigations into their thermal transport characteristics remain limited. In this systematic investigation, we employ density functional theory (DFT) and post-DFT techniques to elucidate the essential stability parameters, transport properties, and carrier-lattice interactions of the metal halide-based Cs2MGaBr6 (X = Li, Ga) double perovskites. Our assessment of structural stability involves a meticulous description of stability index parameters and the optimization of pristine structures using the GGA-PBE potential. Additionally, we calibrate the electronic structure while taking spin–orbit coupling (SOC) effects into consideration by using a combination of GGA and GGA + mBJ potentials. Our findings reveal that the TB-mBJ derived band gaps of 1.82 eV and 1.78 eV for Cs2LiGaBr6 and Cs2NaGaBr6 reside within the visible spectrum, prompting further investigation into their thermal transport characteristics. Moreover, we analyze the phonon characteristics and vibrational modes, extending our investigation to examine the electron–phonon coupling strength. The scrutiny of the Fröhlich coupling constant and the Feynman polaron radius unveils a stronger electron–phonon coupling strength. In the domain of thermoelectrics, the significant figure of merit (zT) values of 1.08 and 1.04 for Cs2LiGaBr6 and Cs2NaGaBr6, respectively, emphasize the considerable potential of these materials for deployment in renewable energy applications. Furthermore, our computational investigation into optical properties, including the dielectric constant, optical absorption, and refractive index, demonstrates optimal performance within the visible spectrum. Specifically, elevated absorption coefficient values of 30×10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$30\ imes 10$$\\end{document}4cm-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{cm}}}^{-1}$$\\end{document} for Cs2LiGaBr6 and 40×10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$40\ imes 10$$\\end{document}4cm-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{cm}}}^{-1}$$\\end{document} for Cs2NaGaBr6 are noted across visible and infrared spectra, highlighting their promising potential in optoelectronic and solar cell technologies.

Bandgap engineering of lead-free double perovskite Cs2NaBiCl6 through indium and silver alloying

In recent years, double perovskites (DPs) have received much attention due to their low toxicity and intrinsic thermodynamic stability. However, most pure phase DPs crystals have the problem of weak photoluminescence (PL) intensity. It has been proved that alloying through metal ion is an effective method to improve the PL intensity of DPs. We have successfully prepared a series of Cs2NaBi1-xInxCl6(0, 0.25, 0.5, 0.75, 1) crystals by a solvothermal method. By alloying Cs2NaBiCl6 crystals with In3+ to adjust the band gap, the optical band gap was increased from 3.06 eV (x = 0) to 3.66 eV (x = 1), and the PL emission spectra showed a broad emission peak. After further Ag+ alloying, the PL intensity was further improved, and the photoluminescence quantum yield (PLQY) was increased to 57.63%. It was confirmed by electronic structure calculation under the framework of density functional theory (DFT) that the composition of Bi-6p orbital near the conduction band minimum (CBM) and the bandgap can be efficiently tuned by introduction of Ag+. Both Bi3+ and Ag+ can locate at the edge of the band, effectively enhancing PL intensity through self-trapping excitons (STEs). The above research showed that the alloying of lead-free bismuth sodium halide double perovskites with other metals can provide a direction for non-toxic and high-performance light-emitting devices.

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.

Unravelling ultralow thermal conductivity in perovskite Cs2AgBiBr6: dominant wave-like phonon tunnelling and strong anharmonicity

Understanding the lattice dynamics and heat transport physics in the lead-free halide double perovskites remains an outstanding challenge due to their lattice dynamical instability and strong anharmonicity. In this work, we investigate the microscopic mechanisms of anharmonic lattice dynamics and thermal transport in lead-free halide double perovskite Cs2AgBiBr6 from first principles. We combine self-consistent phonon calculations with bubble diagram correction and a unified theory of lattice thermal transport that considers both the particle-like phonon propagation and wave-like tunnelling of phonons. An ultra-low thermal conductivity at room temperature (~0.21 Wm−1K−1) is predicted with weak temperature dependence( ~ T−0.34), in sharp contrast to the conventional ~T−1 dependence. Particularly, the vibrational properties of Cs2AgBiBr6 are featured by strong anharmonicity and wave-like tunnelling of phonons. Anharmonic phonon renormalization from both the cubic and quartic anharmonicities are found essential in precisely predicting the phase transition temperature in Cs2AgBiBr6 while the negative phonon energy shifts induced by cubic anharmonicity has a significant influence on particle-like phonon propagation. Further, the contribution of the wave-like tunnelling to the total thermal conductivity surpasses that of the particle-like propagation above around 310 K, indicating the breakdown of the phonon gas picture conventionally used in the Peierls-Boltzmann Transport Equation. Importantly, further including four-phonon scatterings is required in achieving the dominance of wave-like tunnelling, as compared to the dominant particle-like propagation channel when considering only three-phonon scatterings. Our work highlights the importance of lattice anharmonicity and wave-like tunnelling of phonons in the thermal transport in lead-free halide double perovskites.

Insights into optoelectronic behaviors of novel double halide perovskites Cs2KInX6 (X = Br, Cl, I) for energy harvesting: First principal calculation

One of the most important areas of materials science research is the creation of novel materials for energy conversion and storage. Computational simulations have become a potent tool for anticipating novel material characteristics and speeding up the discovery process in recent years. In this article, we present a computational investigation of the structural, electronic, and optical properties of double perovskites Cs2KInX6 (X = Br, Cl, and I), with a focus on their potential applications in energy conversion. The purpose of this work is to accomplish a comparative analysis of novel optoelectronic lead-free halide double perovskites. The Cs2KInX6 double perovskites compounds display direct semiconducting behavior with optical bandgap energies values of about 2.60, 3.60, and 1.67 eV for Cs2KInBr6, Cs2KInCl6, and Cs2KInI6, respectively. The results obtained underscore the remarkable characteristics of the studied compounds. Notably, a substantial absorption coefficient exceeding 106 cm−1 in the ultraviolet range and a notable absorption coefficient surpassing 105 cm−1 in the visible spectrum were observed. The obtained optoelectronic characteristics that have been indicate that Cs2KInX6 compounds hold great potential for usage in solar cell applications.

Mapping Uncharted Lead-Free Halide Perovskites and Related Low-Dimensional Structures.

Research on perovskites has grown exponentially in the past decade due to the potential of methyl ammonium lead iodide in photovoltaics. Although these devices have achieved remarkable and competitive power conversion efficiency, concerns have been raised regarding the toxicity of lead and its impact on scaling up the technology. Eliminating lead while conserving the performance of photovoltaic devices is a great challenge. To achieve this goal, the research has been expanded to thousands of compounds with similar or loosely related crystal structures and compositions. Some materials are "re-discovered", and some are yet unexplored, but predictions suggest that their potential applications may go beyond photovoltaics, for example, spintronics, photodetection, photocatalysis, and many other areas. This short review aims to present the classification, some current mapping strategies, and advances of lead-free halide double perovskites, their derivatives, lead-free perovskitoid, and low-dimensional related crystals.

Enhanced photocatalytic hydrogen evolution through suppressed electron–hole recombination in Cs2AgBiBr6-NC/g-C3N4 nanocomposites

One-pot in situ synthesis of 4–6 nm particles of Cs2AgBiBr6 on a g-C3N4 matrix gives a marginal enhancement in the HER from 44.9 μmol g−1 h−1 to 268 μmol g−1 h−1.

Bandgap reduction and efficiency enhancement in Cs2AgBiBr6 double perovskite solar cells through gallium substitution.

Lead-free halide double perovskite (LFHDP) Cs2AgBiBr6 has emerged as a promising alternative to traditional lead-based perovskites (LBPs), offering notable advantages in terms of chemical stability and non-toxicity. However, the efficiency of Cs2AgBiBr6 solar cells faces challenges due to their wide bandgap (Eg). As a viable strategy to settle this problem, we consider optimization of the optical and photovoltaic properties of Cs2AgBiBr6 by Gallium (Ga) substitution. The synthesized Cs2Ag0.95Ga0.05BiBr6 is rigorously characterized by means of X-ray diffraction (XRD), UV-vis spectroscopy, and solar simulator measurements. XRD analysis reveals shifts in peak positions, indicating changes in the crystal lattice due to Ga substitution. The optical analysis demonstrates a reduction in the Eg, leading to improvement of the light absorption within the visible spectrum. Importantly, the Cs2Ag0.95Ga0.05BiBr6 solar cell exhibits enhanced performance, as evidenced by higher values of open circuit voltage (Voc), short-circuit current (Jsc), and fill factor (FF), which are 0.94 V, 6.01 mA cm-2, and 0.80, respectively: this results in an increased power conversion efficiency (PCE) from 3.51% to 4.52%. This research not only helps to overcome film formation challenges, but also enables stable Cs2Ag0.95Ga0.05BiBr6 to be established as a high-performance material for photovoltaic applications. Overall, our development contributes to the advancement of environmentally friendly solar technologies.

Tunable dual-emission of Sb3+, Ho3+ Co-doped Cs2NaScCl6 single crystals for light-emitting diodes

Lead-free halide double perovskites are considered as one of the most promising materials in optoelectronic devices, such as solar cells, photodetectors, and light-emitting diodes (LEDs), due to their environmental friendliness and chemical stability. However, the extremely low photoluminescence quantum yield (PLQY) of self-trapped excitons (STEs) emission from lead-free halide double perovskites impedes their applications. Herein, Sb3+ ions were doped into rare-earth-based double perovskite Cs2NaScCl6 single crystals (SCs), resulting in a large enhancement of PLQY from 12.57% to 87.37%. Moreover, by co-doping Sb3+ and Ho3+ into Cs2NaScCl6 SCs, the emission color can be tuned from blue to red, due to an efficient energy transfer from STEs to Ho3+ ions. Finally, the synthesized sample was used in multicolor LED, which exhibited excellent stability and optical properties. This work not only provides a new strategy for improving the optical properties of Cs2NaScCl6 SCs, but also suggests its potential application in multicolor LEDs.

Lanthanide/Bismuth-Codoped Lead-Free Halide Double Perovskite Nanocrystals with Upconversion and Short-Wave Infrared Luminescence

Lanthanide/Bismuth-Codoped Lead-Free Halide Double Perovskite Nanocrystals with Upconversion and Short-Wave Infrared Luminescence

Exploring magnetism of lead-free halide double perovskites: A high-throughput first-principles study

Exploring magnetism of lead-free halide double perovskites: A high-throughput first-principles study

Investigating the physical properties of lead-free halide double perovskites Cs2AgXBr6 (X = P, As, Sb) for photovoltaic and thermoelectric devices using the density functional theory

Lead-free halide double perovskites are promising materials for photovoltaic and thermoelectric applications due to their desirable functional features. In the present study, Wien2k ab-initio code based on the density functional theory (DFT) was employed to Cs2AgXBr6 (X = P, As, and Sb) to investigate their structural, electronic, mechanical, optical, and thermoelectric properties. The obtained results show that all compounds are mechanically stable. Both Cs2AgPBr6 and Cs2AgSbBr6 are ductile materials whereas Cs2AgAsBr6 is brittle. On the other hand, the atomic bonds of Cs2AgAsBr6 are stronger than those of the other two compounds, and its lattice structure is more rigid. Based on the hybrid functional (YS-PBE0) potential, the bandgap of Cs2AgXBr6 (X = P, As and Sb) was identified as indirect and have the values of 1.113, 1.517, and 1.672 eV, respectively. All compounds have high optical conductivity in the visible region and show the greatest absorption in the UV–visible region. Additionally, the positive values of Seebeck and Hall coefficients over the entire temperature range indicate the presence of hole-type charge carriers in these materials. The calculated thermoelectric Figure of Merit shows a broad plateau over the investigated temperature range which ensures stable efficiency over a wide operating temperature range. The present study demonstrates the potential of the investigated compounds to be utilized in photovoltaic and thermoelectric applications.

High thermally stable deep red-emitting Sb3+,Ho3+-codoped Cs2NaScCl6 double perovskite for plant lighting

Lead-free halide double perovskite has received widespread attention due to its excellent optical performance. However, the lack of deep red light and poor heat quenching resistance severely limit its application in plant lighting field. In this work, Ho3+ was introduced into the thermally stable Cs2NaScCl6 host, exhibiting a deep red emission of 660 nm. By constructing an energy transfer channel between Sb3+ and Ho3+, the photoluminescence quantum yield (PLQY) of Cs2NaScCl6:1%Sb3+,40%Ho3+ rises up to 53.8%, that is increased by 17 times, and its emission intensity can still be maintained by 80% at 423 K, exhibiting good heat quenching resistance. The obtained Cs2NaScCl6:1%Sb3+,40%Ho3+ and Cs2NaScCl6:1%Sb3+ with blue light emission were employed for fabricating a light-emitting diode (LED) device with a 340 nm UV chip, and its emission spectrum matches well the absorption spectra of chlorophyll A and chlorophyll B with the high resemblance of 70% and 75%, making it suitable for use as an artificial light source to control the growth process of plants in the field of plant lighting.

A2LiGaI6 (A = Cs, Rb): New lead-free and direct bandgap halide double perovskites for IR application

Recently, all inorganic double perovskites have drawn a lot of interest as promising solar materials. The optical, structural, thermoelectric, electronic, and mechanical properties of double halide perovskites A2LiGaI6 (A = Cs, Rb) are explored via first-principles calculations with the WIEN2k code, using GGA PBEsol and TB-mBJ potentials. The majority of perovskite materials utilized in the highest-performing solar cells have bandgaps ranging between 1.48 and 1.62 eV. The compounds A2LiGaI6 (A = Cs, Rb) have a direct bandgap of 1.51 eV and 1.55 eV, respectively, and are expected to be useful in solar cells. The optical study shows that there are large absorption bands in the visible region, as determined by the dielectric constant, absorption, and other dependent factors. Their potential for use in solar cells is increased by their absorption in the visible part. The BoltzTraP code has been used to perform thermoelectric studies to assess the electrical, thermal conductivities, and Seebeck coefficient. They are important for construction of thermoelectric generators that harvest heat energy because of their high figure of merit and incredibly low thermal conductivity of lattice at ambient temperature. Furthermore, by examining the spectroscopic limit maximum efficiency, up to 30 % efficiency is predicted for both compositions, which paves the way for the applicability of them in solar energy conversion.

Photoluminescence in rare-earth based halide double perovskite Cs2NaRECl6 (RE = Ce, Eu, Y, Lu) microcrystals

Lead-free halide double perovskites (DPs) with superior photoelectric performance are of great importance in perovskites materials family. In this paper, a series of rare-earth (RE) based Cs2NaRECl6 (RE = Y, Ce–Nd, Sm–Gd, Dy–Lu) DPs microcrystals (MCs) were prepared by convenient hydrothermal method. Cs2NaCeCl6 and Cs2NaEuCl6 MCs exhibit typical UV emission from the 5d→4f transition of Ce3+ and orange-red emission from characteristic 5D1 → 7F0, 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3, 5D0 → 7F4 transitions of Eu3+, respectively. The blue light emissions of Cs2NaYCl6 (300–650 nm) and Cs2NaLuCl6 (300–550 nm) are from the respective self-trapped exciton states (STEs). In addition, the bandgap and partial density of state (PDOS) of Cs2NaRECl6 (RE = Ce, Eu, Y, Lu) were calculated based on density functional theory (DFT) to have a further insight into the optical properties of the RE-DPs. The as-prepared RE based DPs have potential applications in advanced lighting, displaying and anti-counterfeiting, etc.

Composition Dependent Strain Engineering of Lead-Free Halide Double Perovskite: Computational Insights.

The critical photophysical properties of lead-free halide double perovskites (HDPs) must be substantially improved for various applications. In this regard, strain engineering is a powerful tool for enhancing optoelectronic performance with precise control. Here, we employ ab initio simulations to investigate the impact of mild compressive and tensile strains on the photophysics of Cs2AgB'X6 (B' = Sb, Bi; X = Cl, Br) perovskites. Depending on the pnictogen and halide atoms, the band gap and band edge positions of HDPs can be tuned to a significant extent by controlling the applied external strain. Cs2AgSbBr6 has the most substantial strain response under structural perturbations. The subtle electronic interactions among the participating orbitals and the band dispersion at the edge states are enhanced under compressive strain, reducing the carrier effective masses. The exciton binding energies for these Br-based HDPs are in the range 59-78 meV and weaken in the compressed lattices, suggesting improved free carrier generation. Overall, the study emphasizes the potential of lattice strain engineering to boost the photophysical properties of HDPs that can ultimately improve their optoelectronic performance.