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Mixed-Cation Mixed-Metal Halide Perovskites for Photovoltaic Applications: A Theoretical Study
摘要： Perovskite solar cells based on multiple cations have shown excellent optoelectronic properties with high power conversion efficiency. Herein, the structural, electronic, and optical properties of mixed-cation mixed-metal perovskites MA1?xCsxPb0.25Sn0.75I3 were studied by employing the first-principles calculations for the first time. Our calculated results reveal that these perovskite materials possess direct band gaps in the range of 1.0?1.3 eV. Moreover, these compounds show excellent photovoltaic performance in terms of strong optical absorption coefficients compared with MAPbI3. Particularly, they also exhibit good structural stability and decrement of lead content. These results demonstrated that mixed-cation mixed-metal perovskites may be potential candidates for high-efficiency light-absorbing materials.
关键词： mixed-cation mixed-metal perovskites,electronic properties,optical properties,first-principles calculations,photovoltaic applications,structural stability
更新于2025-09-23 15:21:01
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Effect of Net Charge on the Relative Stability of 2D Boron Allotropes
摘要： We study the effect of electron doping on the bonding character and stability of two-dimensional (2D) structures of elemental boron, called borophene, which is known to form many stable allotropes. Our ab initio calculations for the neutral system reveal previously unknown stable 2D ε-B and ω-B structures. We find that the chemical bonding characteristic in this and other boron structures is strongly affected by extra charge. Beyond a critical degree of electron doping, the most stable allotrope changes from ε-B to a buckled honeycomb structure. Additional electron doping, mimicking a transformation of boron to carbon, causes a gradual decrease in the degree of buckling of the honeycomb lattice that can be interpreted as piezoelectric response. Net electron doping can be achieved by placing borophene in direct contact with layered electrides such as Ca2N. We find that electron doping can be doubled by changing from the B/Ca2N bilayer to the Ca2N/B/Ca2N sandwich geometry.
关键词： doping,boron,2D,ab initio calculation,structural stability,electronic structure
更新于2025-09-19 17:15:36
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Enhanced Moisture Stability of Cesium Lead Iodide Perovskite Solar Cells- A First-Principles Molecular Dynamics Study
摘要： An understanding of the interaction of water with perovskite is crucial in improving the structural stability of the perovskite. Hence, in this study, the structural and electronic properties of γ-CsPbI3 (220) perovskite surface upon the adsorption of water molecules have been investigated based on density functional theory calculations. Also, we perform the first-principles ab initio molecular dynamics simulations (AIMD) to explore the structural stability of the γ-CsPbI3 (220) perovskite surface in the presence of water molecules, and the results are compared with the conventional cubic CH3NH3PbI3 (100) perovskite surface. The water molecules show stronger interactions with the (220) surface of γ-CsPbI3 than the (100) of CH3NH3PbI3. However, AIMD results demonstrate that the former is much more stable, and no trace of surface degradation has observed upon the adsorption of water molecules.
关键词： water adsorption,density functional theory,perovskite,ab initio molecular dynamics,structural stability
更新于2025-09-19 17:13:59
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Superlattices are Greener on the Other Side: How Light Transforms Self-Assembled Mixed Halide Perovskite Nanocrystals
摘要： Perovskite nanocrystal superlattices (NC SLs) are the nearest real-world approximations to monodisperse NC ensembles. NC SLs thus represent ideal model systems for evaluating the optical and structural stability of CsPb(I1?xBrx)3 NCs at a macroscopic level. Here, photoinduced changes to CsPb(I1?xBrx)3 NC SLs (0 < x < 1.0) are probed via in situ photoluminescence, X-ray di?raction, and electron microscopy. We ?nd that prolonged (～10?20 h) ultraviolet?visible irradiation causes irreversible PL blueshifts, photobrightening, and crystal structure contractions. These changes stem from gradual photoinduced I2 sublimation, which transforms CsPb(I1?xBrx)3 into CsPbBr3. Despite eliminating half of the initial halides from individual CsPb(I0.53Br0.47)3 particles, NCs within SLs remarkably preserve their initial crystallinity, cuboidal shapes, edge lengths, and size distributions. This work illustrates compositional control toward generating precisely engineered perovskite NC SLs. It also highlights iodide photo-oxidation as a hurdle that must be overcome if mixed halide perovskite nanomaterials are to be applied beyond fundamental studies.
关键词： optical and structural stability,I2 sublimation,photoinduced changes,CsPb(I1?xBrx)3,Perovskite nanocrystal superlattices
更新于2025-09-19 17:13:59
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High Thermal Diffusivity in Thermally Treated Filamentous Virus-Based Assemblies with a Smectic Liquid Crystalline Orientation
摘要： Polymers are generally considered thermal insulators because the amorphous arrangement of the polymeric chains reduces the mean free path of heat-conducting phonons. Recent studies reveal that individual chains of polymers with oriented structures could have high thermal conductivity, because such stretched polymeric chains effectively conduct phonons through polymeric covalent bonds. Previously, we have found that the liquid crystalline assembly composed of one of the filamentous viruses, M13 bacteriophages (M13 phages), shows high thermal diffusivity even though the assembly is based on non-covalent bonds. Despite such potential applicability of biopolymeric assemblies as thermal conductive materials, stability against heating has rarely been investigated. Herein, we demonstrate the maintenance of high thermal diffusivity in smectic liquid crystalline-oriented M13 phage-based assemblies after high temperature (150 ?C) treatment. The liquid crystalline orientation of the M13 phage assemblies plays an important role in the stability against heating processes. Our results provide insight into the future use of biomolecular assemblies for reliable thermal conductive materials.
关键词： structural stability,self-assembly,thermophysical property,liquid crystal,filamentous virus
更新于2025-09-10 09:29:36
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Predicted semiconducting beryllium sulfides in 3D and 2D configurations: Insights from first-principles calculations
摘要： Light-metal sulfides have attracted great attention due to the technological application as energy storage devices. Combining first-principles calculations with structure searching, sulfur-rich compounds were explored theoretically in Be-S system. Interestingly, our results identify a hitherto unknown stoichiometry BeS2 in bulk and two-dimensional (2D) configuration. With the pressure increasing, BeS2 in bulk adopts P1(cid:2) structure at ambient pressure, C2 phase over 1.6GPa and then a cubic c-BeS2 with unique S2 2- dimmers up to 5.8GPa. The monolayer penta-BeS2 with Be2S3 pentagons and bilayer BeS structure are presented. Predicted c-BeS2, 2D BeS2 and BeS phases show a semiconducting character, interestingly, c-BeS2 is found to have a direct band gap of 1.52eV. The discovery of unknown beryllium sulfides and the understanding of electronic and chemical bonding properties will provide prerequisite for the potential application in electrochemistry.
关键词： Electronic property,First-principles calculations,Beryllium sulfides,Structural stability
更新于2025-09-10 09:29:36
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Mg-doping towards enhancing the composition-phase-structural stability of Li-La-zirconate based cubic garnet upon exposure to air
摘要： Mg, as a new dopant, has been found to stabilize the desired cubic garnet structure (Ia3d) of Li-La-zirconate (LLZO) and lead to Li-ion conductivities similar to those obtained with the same level of Al-doping. More importantly, Mg-doping, as opposed to Al-doping, suppresses the deleterious reactions with the atmospheric moisture/CO2, leading to stability in the composition-phase-structure upon exposure to air. Accordingly, when exposed to air, even though Al-doped LLZO pellets get spontaneously fractured/disintegrated, accompanied by reduction in ionic conductivity by ~3 orders of magnitude, Mg-doped LLZO shows no sign of cracking and almost retains the ionic conductivity measured prior to exposure.
关键词： Ionic conductivity,Mg-doping,Composition-phase-structural stability,Lithium garnet,Solid electrolyte
更新于2025-09-04 15:30:14
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Structural stability and electronic properties of XTO2 (X= Cu, Ag; T=Al, Cr): an ab initio study including X vacancies and Mg doping
摘要： Ab initio density functional theory-based calculations are used to study the structural and electronic properties of CuAlO2, AgAlO2, CuCrO2, and AgCrO2 transparent conducting oxides (TCOs). The hexagonal 2H delafossite polymorph is determined here to be one of the most stable polymorphs, by comparing total energies for different structural phases. The simple antiferromagnetic configuration is chosen to model magnetic effects in CuCrO2 and AgCrO2 due to it having one of the lowest ground state total energies and containing the most semiconductor like behavior of the magnetic configurations considered. Electronic structures of 2H CuAlO2 and AgAlO2 obtained from different approximations for the exchange-correlation functional, GGA (PBE), PBE+U, PBE+mBJ, PBE+mBJ+U, and the Hybrid HSE06 are compared. Supercells are employed to model 6.25% Cu and Ag vacancies, 3.13% O vacancies, and 6.25% Mg doping replacing Al and Cr, from which structural and electronic properties are obtained and used to predict on the effectiveness of these native defects and dopant on increasing the conductivity in all TCOs studied in this work. The obtained partial density of states for the pristine systems supports a model of hole conduction in the a – b plane, perpendicular to the O – X – O dumbbells of the delafossite structure. Additionally, the partial density of states of the defective and doped systems suggest a growth environment deficient in X and saturated in O may increase conductivity in these materials.
关键词： Delafossite,Density functional theory,Transparent conducting oxides,Mg doping,Structural stability,Ab initio,Vacancies,Electronic properties
更新于2025-09-04 15:30:14