First-Principles Calculations on Novel Rb-Based Halide Double Perovskites Alloys for Spintronics and Optoelectronic Applications

The outcomes of computational study of electronic, magnetic and optical spectra for A2BX6 (A = Rb;B = Tc, Pb, Pt, Sn, W, Ir, Ta, Sb, Te, Se, Mo, Mn, Ti, Zr and X = Cl, Br) materials have been proceeded utilizing Vanderbilt Ultra Soft Pseudo Potential (US-PP) process. The Rb2PbBr6 and Rb2PbCl6 are found to be a (Г-Г) semiconductors with energy gaps of 0.275 and 1.142 eV, respectively making them promising photovoltaic materials. The metallic behavior of the materials for Rb2BX6 (B = Tc, W, Ir, Ta, Mn, Sb, Mo) has been confirmed showing the attendance of conducting lineaments. The dielectric function is found to be large close to the ultraviolet districts (3.10 - 4.13 eV). The extinction coefficient of the Rb2BX6 has the ability to be used for implements. The band structures and density of states ensure the magnetic semiconductors’ nature of the Rb2Mn (Cl, Br)6 perovskites. The total calculated magnetic moment of Rb2MnCl6 and Rb2MnB6 is 3.00μβ. Advanced spintronic technology requires room-temperature ferromagnetism. The present work confirms that, bromine and chlorine-founded double perovskites are extremely attractive for photovoltaic and optoelectronic devices.

Stability and optoelectronic property of lead-free halide double perovskite Cs_(2)B′BiI_(6)(B′=Li,Na and K)

Although lead-based perovskite solar cells have achieved more than 25%power conversion efficiency,the toxicity of lead and instability are still urgent problems faced in industrial application.Lead-free halide double perovskite(DP)materials are promising candidates to resolve these issues.Based on the density functional theory,we explore the geometric stability,thermodynamic stability,mechanical stability,electronic structures,and optical properties of theCs_(2)B 0BiI_(6)(B 0=Li,Na and K)DP materials.By analyzing the tolerance factor and octahedral factor,we find the geometric stabilities ofCs_(2)NaBiI_(6) andCs_(2)KBiI_(6) DPs are better thanCs_(2)LiBiI_(6).By calculating the total energy,formation energy and decomposition energy,we propose that the most favorable structure ofCs_(2)B 0BiI_(6) is the orthorhombic phase,andCs_(2)LiBiI_(6) is less stable relative to the other two counterparts from an energetic viewpoint.Mechanical stability evaluations reveal that the orthorhombicCs_(2)LiBiI_(6) material is less stable relative to the isostructuralCs_(2)NaBiI_(6) andCs_(2)KBiI_(6) DPs.The mechanical property calculations indicate that theCs_(2)B 0BiI_(6) DPs possess good ductility,which can be used as flexible materials.Electronic structures and optical property calculations show that the orthorhombicCs_(2)B 0BiI_(6) DPs have suitable band gap values,weaker exciton binding energies,and excellent optical absorption performance in the visible-light range.Based on the above comprehensive assessments,we can conclude that the orthorhombic Cs_(2)NaBiI_(6) and Cs_(2)KBiI_(6) DPs with good stability are promising candidates for solar cell applications.

NH_(+)^(4)/K^(+)-substitution-induced C–F–K coordination bonds for designing the highest-temperature hybrid halide double perovskite ferroelastic

Ferroelastic materials with switchable spontaneous strain possess widely potential applications in the field of energy and information conversion.Recently,organic-inorganic hybrid halide double perovskites (OIHHDPs) have become a charming new platform for developing various functional materials,such as ferroelectrics,fluorescence and X–ray detection.Nevertheless,OIHHDP ferroelastic materials,especially high-temperature ones,are rare.Herein,we initially synthesized an OIHHDP ferroelastic,(2,2-difluoroethanamine)_(2)[(NH_(4))InCl_6](1),which possesses a ferroelastic phase transition at 407 K.Moreover,thanks to the flexible B-site for OIHHDPs,we replaced the NH_(4)^(+) ions within[(NH_(4))InCl_6]_n^(2n–)formworks with K^(+)ions,which endows with coordination bonds between 2,2-difluoroethanamine organic cations and[KInCl_6]_n^(2n–)formworks.Due to the existence of coordination bonds,the phase transition temperature of (2,2-difluoroethanamine)_(2)[KInCl_6](2) can reach 458 K.As far as we know,this value is the highest reported in OIHHDP ferroelastics.This work offers inspiration for the design of high-temperature OIHHDP phase transition materials including ferroelectrics and ferroelastics.

Impact of doping and hydrostatic pressure on structural, electronic, optical, and mechanical properties of novel double halide perovskite Cs_(2)LiGaBr_(6)

The emergence of lead-free halide double perovskites exhibiting bandgaps within the visible spectrum represents a substantial advancement in engineering environmentally benign perovskite solar cells.In this work,we investigated the structural,optical,electronic,and mechanical properties of Cs-based lead-free Cs2LiGaBr6 double halide perovskites with Mn and Cr doping under hydrostatic pressure ranging from 2 to 80 GPa using density functional theory(DFT).The introduction of dopants consistently alters the lattice parameters because of the mismatch in atomic radii,whereas increasing the pressure leads to a reduction in these constants.All the studied Cs2LiGaBr6 compounds exhibited direct band gaps,which increased slightly with doping.This is attributed to the modulation of electronic states by dopant-related defect levels.The bandgap variation under pressure is primarily attributed to changes in the quantum confinement effects induced by compressive strain.Analysis of the density of states and optical properties revealed enhanced absorption in the visible spectrum for the doped compositions,and in the UV spectrum under pressure.The study of mechanical stability confirms the ductile nature of both the doped and pristine compounds under pressure,underscoring their suitability for thin film production.This study contributes to the understanding of sustainable alternatives for perovskite optoelectronic applications,emphasizing Cs2LiGaBr6’s potential under diverse conditions and dopant influences.

High thermally stable deep red-emitting Sb^(3+),Ho^(3+)-codoped Cs_(2)NaScCl_(6) 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,Ho^(3+) was introduced into the thermally stable Cs_(2)NaScCl_(6)host,exhibiting a deep red emission of 660 nm.By constructing an energy transfer channel between Sb^(3+)and Ho^(3+),the photo luminescence quantum yield(PLQY) of Cs_(2)NaScCl_(6):1%Sb^(3+),40%Ho^(3+) rises up to53.8%,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 Cs_(2)NaScCl_(6):1%Sb^(3+),40%Ho^(3+) and Cs_(2)NaScCl_(6):1%Sb^(3+) with blue light emission were employed for fabricating a light-emitting diode(LED) device with a340 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.

Luminescent enhancement and multi-mode optical thermometry of erbium doped halide Cs_(2)(Na/Ag)BiCl_(6) microcrystals

Lanthanum-doped double halide perovskite has attracted increasing interest due to its distinctive upconversion and near-infrared(NIR) luminous characteristics.Here,erbium ion(Er^(3+)) doped Cs_(2)(Na/Ag)BiCl_(6) microcrystals(MCs) were synthesized and proved to be one of the most prospective candidates for optical thermometry.The enhancement of both white light from self-trapped exciton emission and NIR emission from Er^(3+) ion of Cs_(2)AgBiCl_(6) microcrystals is caused by lattice distortion due to Na^(+) ion doping.Fluorescence intensity ratio and lifetime methods provide self-referenced and sensitive thermometry under 405 and/or 980 nm laser excitation at the temperatures from 80 to 480 K.Besides,the maximum values of relative and absolute sensitivity of 3.62%/K and 27//K can be achieved in the low to high temperature range under 980 and 405 nm laser co-excitation.Through the experimental analysis,Er^(3+)doped Cs_(2)(Na/Ag)BiCl_(6) double perovskite is considered to be an ideal self-calibrating thermometric material due to its good long-term stability and multi-mode function of excitation and detection.