Lead-free Double Perovskites Research Articles

CsPbBr3 and Cs2AgBiBr6 Composite Thick Films with Potential Photodetector Applications

This paper investigates the optoelectronic properties of CsPbBr3, a lead-based perovskite, and Cs2AgBiBr6, a lead-free double perovskite, in composite thick films synthesized using mechanochemical and hot press methods, with poly(butyl methacrylate) as the matrix. Comprehensive characterization was conducted, including X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV–visible spectroscopy (UV–Vis), and photoluminescence (PL). Results indicate that the polymer matrix does not significantly impact the crystalline structure of the perovskites but has a direct impact on the grain size and surface area, enhancing the interfacial charge transfer of the composites. Optical characterization indicates minimal changes in bandgap energies across all different phases, with CsPbBr3 exhibiting higher photocurrent than Cs2AgBiBr6. This is attributed to the CsPbBr3 superior charge carrier mobility. Both composites showed photoconductive behavior, with Cs2AgBiBr6 also demonstrating higher-energy (X-ray) photon detection. These findings highlight the potential of both materials for advanced photodetector applications, with Cs2AgBiBr6 offering an environmentally Pb-free alternative.

Exploring optoelectronic, optical thin films, mechanical and thermal transport properties of bromide double perovskites Rb2Ag(Ga/In)Br6 for photovoltaic and thermoelectric applications

Lead-free double halide perovskites like Rb2Ag(Ga/In)Br6 have demonstrated themselves potential candidates in solar cell research owing to their environmental friendliness, stability, and exceptional performance. This study comprehensively analyzes the structural, mechanical, optoelectronic and optical coating features, as well as thermodynamic and thermoelectric properties of two Rb2AgGaBr6 and Rb2AgInBr6 compounds. Using the Wien2k code with GGA + mBJ exchange-correlation potentials, we confirm their structural stability in cubic phase Fm-3m and identifying them as direct band gap semiconductors (Γ → Γ) of 0.38 eV and 1.0644 eV, respectively. Then, optical analysis reveals broad absorption bands across visible and ultraviolet wavelengths, making them suitable for photovoltaic absorbers. Finally, the thermoelectric investigations under varying temperatures show favourable properties, such as a high Seebeck coefficient with poor electronic thermal conductivity. This also yields exceptional value (0.96 and 0.994 for Rb2AgGaBr6, Rb2AgInBr6, respectively) of figure of merit (ZT) at room temperature and chemical potential μ-μ0 = - 0.09eV near the Fermi energy level, enhancing their potential for thermoelectric applications. These findings underscore the versatility and promising future of Rb2Ag(Ga/In)Br6 as important semiconductors processing for optoelectronic, thermoelectric, and mechanical devices.

Evidence and engineering of x-ray luminescence in lead free perovskite Cs2AgInCl6 with Bi substitutions

Cs2AgInCl6 belongs to the family of lead-free halide double perovskites. Lead-free halide double perovskite appears as a viable contender for scintillator applications due to its inexpensive production costs, low intrinsic trap density, and nanosecond quick reaction. Perovskite crystals have a substantially lower trap density than lead halide and traditional oxide scintillator materials, according to thermo-luminescence measurements. Cs2AgInCl6 structure and dimensionality were engineered by Bi doping. Bi substitution reduces the bandgap, making it suited for scintillation applications. Bi substitution allows for easy tuning of Cs2AgIn(1−x)BixCl6 (0 ≤ x ≤ 50) due to its wide versatility in scintillation properties. For Cs2AgIn(1−x)BixCl6 (0 ≤ x ≤ 50), x-ray power dependent luminescence increases with increasing power. Because of their nontoxicity, sensitivity, reaction time, and stability, Cs2AgIn(1−x)BixCl6 (0 ≤ x ≤ 50) double perovskite crystals are promising for x-ray scintillation.

Investigation of structural, elastic, electronic, and optical properties of lead-free double perovskites Cs2XBeBr6 (X = Ge, Sn): a first-principles DFT study.

In this study, the structural, elastic, electronic, and optical properties of Cs2GeBeBr6 and Cs2SnBeBr6 halide double perovskites (HDPs) were investigated using density functional theory (DFT) calculations. Notably, the Tran-Blaha modified Becke-Johnson (TB-mBJ) method was employed to predict indirect band gaps of 2.434 eV for Cs2GeBeBr6 and 2.855 eV for Cs2SnBeBr6. The stability of these compounds in a cubic (Fm-3m) structure was confirmed through formation energy, cohesive energy, tolerance factor, and elastic constants. Furthermore, the ductile nature of the materials was demonstrated through Poisson's and Pugh's ratios. Our optical property analysis, spanning the 0-13 eV energy range, revealed key insights into the dielectric functions, extinction coefficient, electron energy loss, refractive index, optical conductivity, reflectivity, and absorption coefficient. These results highlight the potential of Cs2GeBeBr6 and Cs2SnBeBr6 for future optoelectronic and photovoltaic applications. In this investigation, we employed density functional theory (DFT), implemented using the Wien2k package. The exchange and correlation potentials were treated using the generalized gradient approximation (GGA) and the Tran-Blaha modified Becke-Johnson (TB-mBJ) method. To evaluate dynamic stability, we analyzed the phonon band structures using the CASTEP code.

Synthesis, Structural, Morphological, and Optical Properties of Promising Lead-Free Double Perovskite Na2CuBiBr6: A Sustainable Material for Photovoltaic Applications

This work primarily focuses on synthesizing and evaluating the structure, morphology, and optical features of double perovskite Na2CuBiBr6 forphotovoltaic devices. In the present investigation, Na2CuBiBr6 is created by a solution-based antisolvent recrystallization approach. A comprehensive experimental investigation is conducted on the Na2CuBiBr6 double perovskite, encompassing its structural configuration, morphology, and optical features. X-ray diffraction analysis verifies the creation of Na2CuBiBr6 double perovskite and showcases its exceptional phasestability in the cubic phase. Scanning electron microscopy reveals the presence of multidirectional crystals ofNa2CuBiBr6crystals. The presence of polycrystalline cubic Na2CuBiBr6 is confirmed using transmission electron microscopy and electron diffraction investigation. In addition, energy-dispersive X-ray spectroscopy demonstrates the consistent distribution of elements within Na2CuBiBr6. UV–vis spectroscopy reveals a band gap of 1.37 eV. The optical characteristics demonstrate that Na2CuBiBr6 exhibits a greater absorbance level and a lower reflectivity level within the visible spectrum. The results of this study suggest that the Na2CuBiBr6 double perovskite, which is both lead-free and environmentally benign, has significant potential for applications in photovoltaic and thermoelectric devices.

Highly stable and self-powered ultraviolet photodetector based on Dion-Jacobson phase lead-free double perovskite

Metal halide perovskite materials present a wide array of opportunities for the development of high-performance optoelectronic devices, owing to their outstanding photoelectric properties. Compared with the lead-containing perovskites, stable and non-toxic organic-inorganic hybrid perovskites exhibit enhanced potential for future commercial applications. In this work, we developed a self-powered UV photodetector based on 2D Dion−Jacobson (DJ) phase lead-free double perovskite HAAg0.5Bi0.5Br4 (HA2+ = histammonium) perovskite with an on-off ratio up to 2.66 × 106, excellent specific detectivity of 6 × 1012 Jones, and response speed of 1.32 ms/118.4 μs. The light intensity related pyro-phototronic effect on 2D perovskite is thoroughly investigated. Temperature and light detection are realized through multi-energy coupling, which greatly improves the detection performance. Coupled pyro-phototronic current is calculated nearly 75 folds higher than that from the photoelectronic merely. As-prepared photodetector film shows excellent stability in normal environment, maintaining a value of 90 % to the initial performance after 500 cycles and 90 days. This work provides a new self-powered, stable and non-toxic candidate for the future UV photodetectors.

In Situ Fabrication of Highly Efficient and Stable Cs2NaInCl6: Sb3+@PVDF Composite Films for Optoelectronic Devices.

Lead-free double perovskites (DPs) have superior phase stability and optical properties, which make them competitive for future applications in illumination and displays. However, the preparation of DPs was mainly based on high-temperature heating and hydrochloric acid as a solvent to form powders, which increased the risk and cost of the preparation process and limited its further application. In this study, the growth of Cs2NaInCl6: Sb3+ DPs in polyvinylidene difluoride (PVDF) films was achieved using an in situ fabrication strategy with DMSO as the solvent. The prepared Cs2NaInCl6: Sb3+@PVDF composite films (CFs) can achieve a bright blue emission under 302 nm irradiation. To achieve the optimal luminescent performance of CFs, the photoluminescence (PL) intensity of Cs2NaInCl6: Sb3+@PVDF CFs under various in situ preparation conditions was compared. In addition, the photoluminescence quantum yield (PLQY) of CFs was increased from 0.72% to 83.77% by adjusting the doping amount of Sb3+, and the fluorescence lifetimes t1 and t2 were 131.08 and 1048.52 ns, respectively. Temperature-dependent PL spectroscopy and density functional theory (DFT) calculations indicate that these excellent optical properties are derived from the self-trapped excitons (STEs) at the [SbCl6]3- octahedron and [InCl6]3- octahedron connected via Cl-Na-Cl. The CFs also demonstrated excellent environmental stability, maintaining a relatively stable PL intensity even under conditions of water immersion, high temperatures, and ultraviolet (UV) radiation. Finally, we used the CFs to assemble a blue light-emitting device (LED), which showed good and stable blue emission performance at different currents. This work can provide a new idea for preparing DPs, which is conducive to promoting their commercial application in high-performance optoelectronic devices.

Achieving Near-Infrared Highly Sensitive Temperature Sensing in Lanthanide-Doped Lead-Free Double Perovskite NaLaMgWO6 with Significant Thermal Enhancement.

The significant temperature response of lanthanide-doped up-conversion luminescent materials is typically characterized by a severe thermal quenching of the luminescence intensity at elevated ambient temperatures, which severely restricts materials' capability in temperature sensing. Herein, the influence of matrix phonon properties on the remarkable thermal enhancement effect in the thermosensitive material NaLaMgWO6:Yb3+/Nd3+ is reported. It is elucidated that achieving a significant thermal enhancement of Nd3+ with a higher phonon energy oxide matrix is easier than a halide matrix, which has lower phonon energy by comparison with previous findings. Interestingly, the emission of thermally related levels gets enhanced to various extents through phonon-assisted thermal population. In light of this, a three-model thermometer is constructed based on luminescence intensity ratio (LIR) technology. Given that Sr and ΔE possess a positive correlation, it is feasible to acquire greater temperature monitoring sensitivity Sr in Nd3+, which has a larger ΔE. At 313 K, this thermometry model may achieve a maximum sensitivity of 2.84%·K-1. This work not only provides guidance for the selection of efficient near-infrared up-conversion material but also opens up a prospect for the realization of ultrasensitive thermally coupled luminescent thermometers.

New semiconducting lead-free halide double perovskite Ag2LiGaF6 for optoelectronic and thermoelectric applications

A comprehensive study of lead-free halide double perovskite using density functional theory (DFT) including structural, electronic, dynamical, mechanical, optical, and thermoelectric properties has been carried out. The tolerance factor and the octahedral factor confirm that the compound belongs to face-centred-cubic structure with Fm-3m space group. The predicted band structure and DOS exhibit that the material is an indirect bandgap semiconductor. Our calculation reveals that material is dynamically stable because of no negative frequency found in phonon-dispersion curve. The material also possesses mechanical stability. The optical spectra of material show good absorbance and low reflectivity in ultraviolet region. The thermoelectric part discusses the Seebeck coefficient, thermal conductivity, electrical conductivity, power factor, and figure of merit (zT) at different chemical potential into temperature range 400–1200 K. The purpose of this investigation is to stimulate researchers to develop this kind of material and assess their potential for the advancement of contemporary thermoelectric and optoelectronic devices.

Triple-mode fluorescent anti-counterfeiting and temperature sensing properties of lead-free double perovskites Cs2NaErCl6: Yb3+, Bi3+ microcrystals

In this paper, Cs2NaErCl6 double perovskites microcrystals (MCs) co-doped with Yb3+ and Bi3+ are successfully synthesized by a simple “dissolving-drying” method. When excited at 379 nm, 808 nm and 980 nm, the MCs show strong red, green and yellow light, respectively, which can be well distinguished by the naked eyes. On this basis, two kinds of systems are designed with doped/undoped MCs for triple-mode fluorescent anti-counterfeiting and information encryption of numbers and characters. The results indicate that our MCs are not only beneficial to the application of fluorescent anti-counterfeiting, but also greatly improve the security of anti-counterfeiting. In addition, we evaluate the temperature sensing performance of these MCs by fluorescence intensity ratio technique. The samples show a high relative sensitivity as 3.8 %/K at 243 K. The results show that the samples have multi-functional applications in the fields of fluorescent anti-counterfeiting and temperature sensing, and this work will broaden the application fields of lead-free double perovskites in fluorescent anti-counterfeiting and temperature sensing.

Disentangling the efficient photocatalytic reduction of CO2 by a stable UiO-66-NH2/Cs2AgBiBr6 catalyst

The compelling global warming crisis as well as extraterrestrial artificial light synthesis craves photocatalytic reduction of CO2 into fuels and value-added chemicals, for which efficient and robust catalysts with high selectivity and conversion rate is a prerequisite but hitherto a rarity. Herein we create a lead-free double metal perovskite of Cs2AgBiBr6, coupling with mesoporous/microporous UiO-66-NH2 MOF to form type-II heterojunctions for efficient photocatalytic reduction of CO2 with a high CO selectivity of 95 % at an electron consumption rate of 33 μmol g−1 h−1 (13.4 μmol g−1 h−1 for CO and 0.72 μmol g−1 h−1 for CH4). Multilayered mesoporous MOF particles manifest higher catalytic activity than their microporous counterparts due to the highly open mesoporous channels and larger pore volume of the former. Femtosecond transient absorption in combination with in situ infrared spectroscopic measurements disentangle the underlying mechanism accounting for the high product selectivity: the ultrafast electron transfer of 12.3 ps from Cs2AgBiBr6 to UiO-66-NH2-2 enables efficient charge separation; primary *COOH intermediates and rapid CO desorption from Bi-based photocatalyst lead to dominant CO product. Moreover, the MOF crystals maintain stability after γ-rays irradiation equivalent of over 45-year accumulation in a typical earth orbit, hinting their promising potential in extraterrestrial artificial light synthesis.

Impact of halogens modifications on physical characteristics of lead-free hybrid double perovskites compounds Cs2YCuX6 (X=Cl, Br, and I) for energy storage applications: First principles investigations

The purpose of this study is to examine the structural, electronic, optical, and thermoelectric features of novel double perovskite Cs2YCuX6 (X=Cl, Br, and I) for the first time in order to look for potential applications in solar power systems. Using first-principles calculations based on the widely recognized Density Functional Theory (DFT) and the PBE-Generalized Gradient Approximation (GGA) functional included in the WEIN2k package, the characteristics of the perovskites were determined. From the results of band structure and Total Density of States (TDOS) the energy band gap of Cs2YCuCl6, Cs2YCuBr6, and Cs2YCuI6 are observed 2.34 eV, 2.03 eV and 1.68 eV respectively. The PDOS outcomes shows that the formation of the valance and conduction bands is due to the hybridization of Cu-3d and halogen ions such that (X=Cl, Br, and I). The calculated values of goldsmith’s tolerance factor and formation energy reveal that the examined halide perovskites are structurally and thermodynamically stable. The electron localization function ELF and bader charge analysis show that the ionic nature between Cs and halogen ions X. Regarding the optical behavior, Cs2YCuI6has shown maximum absorption of electromagnetic radiation and conductivity in the ultraviolet and visible region i.e. (128–471 nm) which makes it a suitable candidate for optoelectronic and solar cell applications. The thermoelectric properties of the studied compounds have been calculated by means of the Boltztrap code. The presented findings unveil that amongst all studied compoundsCs2YCuI6 is best candidate for solar cell and thermoelectric applications due to higher conductivity, larger absorption range, significant Seebeck coefficient and higher Power factor.

Mechanism of Pressure-Modulated Self-Trapped Exciton Emission in Cs2TeCl6 Double Perovskite.

Pressure-modulated self-trapped exciton (STE) emission mechanism in all-inorganic lead-free metal halide double perovskites characterized by large Stokes-shifted broadband emission, has attracted much attention across various fields such as optics, optoelectronics, and biomedical sciences. Here, by employing the all-inorganic lead-free metal halide double perovskite Cs2TeCl6 as a paradigm, the authors elucidate that the performance of STE emission can be modulated by pressure, attributable to the pressure-induced evolution of the electronic state (ES). Two ES transitions happen at pressures of 1.6 and 5.8GPa, sequentially. The electronic behaviors of Cs2TeCl6 can be jointly modulated by both pressure and ES transitions. When the pressure reaches 1.6GPa, the Huang-Rhys factor S, indicative of the strength of electron-phonon coupling, attains an optimum value of ≈12.0, correlating with the pressure-induced photoluminescence (PL) intensity of Cs2TeCl6 is 4.8-fold that of its PL intensity under ambient pressure. Through analyzing the pressure-dependent STE dynamic behavioral changes, the authors have revealed the microphysical mechanism underlying the pressure-modulated enhancement and quenching of STE emission in Cs2TeCl6.

Facile synthesis, multimode and tunable luminescence, and multifunctional applications of rare earth ions activated lead-free double perovskite crystals

Lead-free double perovskites have gained recognition as top luminescent materials due to their environmental friendliness, high chemical stability, structural adjustability, and excellent photoelectric properties. However, the poor modulation of emission restricts their applications, and it is highly desirable to explore stable and efficient double perovskites with multimode luminescence and adjustable spectra for multifunctional photoelectric applications. Herein, the rare earth ions Ln3+ (Er3+ and Ho3+) doped Cs2NaYCl6:Sb3+ crystals were synthesized by a simple solvothermal route. The X-ray diffraction pattern (XRD), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and elemental mapping images demonstrate that the Sb3+, Er3+, and Ho3+ ions have been homogeneously incorporated into the Cs2NaYCl6 crystals. As anticipated, the emission spectra of Cs2NaYCl6:Sb3+/Ln3+ are composed of two bands. One broad blue band derives from self-trapped exciton (STE) in [SbCl6]3− octahedra while another group of emission peaks stems from the f-f transitions of Ln3+ ions. The emission colors of Cs2NaYCl6:Sb3+/Ln3+ phosphors can be tuned in a wide range by modulating the doping concentrations of Ln3+ ions. The efficient energy transfer from STE to Ln3+ is the key point to achieving the efficient and tunable emissions Cs2NaYCl6:Sb3+/Ln3+ samples. Interestingly, Cs2NaYCl6:Sb3+/Ln3+ can also exhibit characteristic up-conversion luminescence of Ln3+ under near-infrared (NIR) excitation besides the down-conversion luminescence, revealing that the materials may have potential applicability in multimode anti-counterfeiting and information encryption applications. Furthermore, the light emitting diodes (LEDs) assembled by Cs2NaYCl6:Sb3+ and Cs2NaYCl6:Sb3+/Ln3+ phosphors display dazzling blue, green, and red emissions under a forward bias current, which indicates that the as-obtained double perovskites materials may have great potential in solid-state lighting and optoelectronic devices.

Study of promising lithium-based lead-free double perovskites Li2AuBiX6 (X = Cl, Br, and I) for optoelectronic and other renewable energy applications

The current study effort primarily focuses on the computational investigation of the physical properties of Li2AuBiX6 (X = Cl, Br, and I) double perovskites (DPs) utilizing the Density Functional Theory (DFT) framework. The structural and elastic characteristics have been evaluated to reveal phase and mechanical stability. The assessed formation energy and elasticity constants calculations validate that the examined DPs possess cubic phase, exhibit stability, and demonstrate ductility. The band structure analysis has been accomplished with a modified Becke-Johnson (mBJ) potential. Theband structure simulations reveal that Li2AuBiCl6, Li2AuBiBr6, and Li2AuBiI6 possess an indirect energy gap, with values of 1.12 eV, 0.77 eV, and 0.084 eV, respectively. We further examined the optical parameters in the spectrum of incoming photons from 0 to 4 eV. Considerable absorbance in the visible spectrum has been observed for Li2AuBiX6 (X = Cl, Br, and I), suggesting that these DPs are compatible with photovoltaics. Finally, we have computed thermoelectric (TE) characteristics in relation to temperatures within the range of 100 to 600 K. The investigated DPs might be suitable for thermoelectric systems, as indicated by the moderate values of the figure of merit, which needs to be improved. The obtained absorption and figure of merit values surpass similar perovskites Rb2AuBiX6. Hence, the current work might be advantageous for developing novel photovoltaic and TE systems.

Structural, electronic, optical, and thermoelectric features of Rb2XSbX’6 (X= Ag, Cu; X’= Cl, Br): Ab-initio calculations

This study investigates the electronic, optical, and thermoelectric properties of lead-free double halide perovskite materials, Rb2XSbX'6, through first-principles calculations employing Density Functional Theory (DFT) and the Wien2k code, complemented by Boltzmann transport theory. By substituting X with Ag or Cu and X’ with Cl or Br in Rb2XSbX’6, we uncover interesting properties. Rb2AgSbBr6, Rb2AgSbCl6, Rb2CuSbCl6, and Rb2CuSbBr6 exhibit low indirect band gaps of 1.18 eV, 2.17 eV, 1.22 eV, and 0.87 eV, respectively, alongside high absorption in the visible region. The studied compounds sustained a high level of structural and thermodynamic stability, which was confirmed by their high bulk modulus and negative formation energy. Furthermore, extensive values were observed for the figure of merit in the thermoelectric study. Given the strong agreement with previous research, these findings position the investigated materials as promising candidates for visible-light solar cell device applications.

Geometric and electronic structures of Cs2BB′X6 double perovskites: The importance of exact exchange

A widely adopted computational protocol in contemporary materials research is to first relax materials' geometries using semilocal density functional approximations (DFA), and then determining their electronic band structures using the more expensive hybrid functionals. This procedure often works well, as the popular semilocal DFAs, such as the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation, yield rather good geometries for a wide range of materials. However, here we show that, for some of the lead-free halide double perovskites (HDPs) Cs2BB′X6 (B=Ag+, Na+; B′=In3+, Bi3+; X=Cl−, Br−), the validity of this common practice is questionable. We find that, for these HDPs, the geometrical structures, in particular, the B(B′)−X bond lengths predicted by PBE show large deviations from the experimental values. Additionally, the band gaps of some of these materials (specifically, the In-based HDPs) are sensitive to the B(B′)−X bond lengths. As a consequence, the band gaps obtained using the hybrid functionals (such as the Heyd-Scuseria-Ernzerhof functional) based on the PBE geometries can still be quite off, in particular, for HDPs with B′=In3+. The situation is significantly improved by using hybrid functionals with tuned portion of exact exchange, based on the geometries determined consistently under the same level of theory. The successes and failures of several popular exchange-correlation (XC) functionals are traced back to the so-called delocalization error, and can be quantitatively analyzed and understood via a three-atom linear-chain B−X−B′ molecular model. Finally, our findings provide a practical guide for choosing appropriate XC functionals for describing HDPs and point to a promising path for band structure engineering via doping and alloying. Published by the American Physical Society 2024

(Invited) From PL-Inactive to PL-Active: Synthesis and Properties of Novel PL-Active 2D Lead-Free Double Perovskites Based on (PA)4AgInBr8

In this work, novel two-dimensional lead-free double perovskites ((R)4MaMbMcX8, a+b+c=2) were synthesized to achieve novel compositional and dimensional tunability. Specifically, manganese (Mn2+) is incorporated into (PA)4AgInBr8 (PA = CH3(CH2)2NH3+) to form (PA)4Ag1-0.5xMnxIn1-0.5xBr8 (0 ≤ x ≤ 1). These samples were tuned to be PL-emissive under room temperature via this manganese alloying strategy. Three emission pathways can be investigated: band edge emission, emission stemming from self-trapped excitons, and the energy transfer processes associated with Mn2+ center energy levels. Temperature-dependent PL elucidates two emissive modes: self-trapped exciton emission as well as Mn-center emission based on analysis of the associated Huang-Rhys factors. Overall, this work informs the development of additional light-emissive 2D lead-free double perovskites.

Lead-Free Double Perovskites Rb2TlSbX6 (X=Cl, Br, and I) As an Emerging Aspirant for Solar Cells and Green Energy Applications

This study utilized the WIEN2k simulation program to examine the structural, mechanical, thermodynamic, optoelectronic, and thermoelectric characteristics of lead-free double perovskites Rb2TlSbX6 (X=Cl, Br, and I). The objective is to assess their potential contribution to next-generation photovoltaic and thermoelectric systems. The ab initio molecular dynamics (AIMD) has validated that materials are thermodynamically stable. Examining mechanical features confirms the mechanical stability and ductile characteristics of studied perovskites. Rb2TlSbCl6 exhibits superior flexibility and stiffness, whereas Rb2TlSbI6 demonstrates the highest level of anisotropy. The thermodynamic parameters confirm the thermal stability and stronger bonding at elevated pressure and temperature. The electronic features, determined by implementing the GGA-PBE and TB-mBJ functionals, indicate direct band gaps at the Γ- Γ position. The band gap ranges from 1.22 eV to 1.74 eV, 0.94 to 1.34 eV, and 0.81 eV to 1.15 eV for Rb2TlSbCl6, Rb2TlSbBr6, and Rb2TlSbI6, respectively. The analyzed optical characteristics reveal significant absorption and conductivity with decreased reflectance and optical loss between 0 and 6 eV. Rb2TlSbI6 has the greatest dielectric constant, which suggests a lower recombination rate of electron-hole pairs. The thermoelectric characteristics demonstrate a large figure of merit values of 0.78, 0.80, and 0.84 at room temperature. Therefore, these materials have the significant capability forsolar cell technology and may effectively convert thermal energy into usable electrical power.

Improving Cs2AgBiBr6 double perovskite solar cells through graphdiyne doping: A Stride towards enhanced performance

Lead-free halide double perovskites (LFHDPs) based on Cs2AgBiBr6 provide a promising replacement for conventional lead-based LBPs, offering significant benefits in terms of non-toxicity and chemical stability. Nevertheless, the efficiency of Cs2AgBiBr6 solar cells is restricted due to their significant bandgap (Eg). The proposed solution involves optimizing the optical and photovoltaic properties of Cs2AgBiBr6 through graphdiyne (GD) doping. The synthesized Cs2Ag0.95GD0.05BiBr6 is extensively characterized by means of X-ray diffraction (XRD), solar simulator studies, and UV–vis spectroscopy. XRD analysis reveals peak position shifts, indicating changes in the crystal structure caused by GD doping. Optical examination indicates a drop in Eg, this results in enhanced light absorption in the visible region. The increased performance of the Cs2Ag0.95GD0.05BiBr6 solar cell is demonstrated by its higher fill factor (FF), open-circuit voltage (Voc), and short-circuit current (Jsc), which are measured at 0.91 V, 5.58 mA-cm−2, and 0.75, respectively. As a result, the power conversion efficiency (PCE) increases to 3.74 % from 3.37 %. Our research not only tackles film formation issues but also develops stable Cs2Ag0.95GD0.05BiBr6 as a high-performance material for solar applications. All in all, our effort promotes solar technology that is environmentally benign. This work develops stable Cs2Ag0.95GD0.05BiBr6 as a high-performance substance that aids in overcoming film forming challenges in solar applications. Overall, our work advances ecologically friendly solar technology.