Composition engineering plays an important role in generating novel properties and decreasing the lead (Pb) toxicity for halide perovskite materials. To find out the modulation effect introduced by the composition engineering, namely, B -site co-metal ions, in (MA) 2 AgBi 1−x Sb x Br 6 systems with various Bi/Sb ratios of x = 0, 0.25, 0.75, 1.00, series of theoretical simulations and analyses are carried out. For the (MA) 2 AgBi 1−x Sb x Br 6 systems, the Goldschmidt tolerance factor t and the octahedral factor μ indicate that all samples are in a standard double perovskite structure with alternating AgBr 6 and Bi/SbBr 6 octahedra. The calculated electronic structures show that the band gap of (MA) 2 AgBi 1−x Sb x Br 6 decreases with the increase of Sb content, but the indirect band gaps are maintained for all samples. By analyses of the imaginary part ε 2 (ω) of dielectric function and the absorption spectra, we find that all (MA) 2 AgBi 1−x Sb x Br 6 systems show absorption in the visible-light region. All these results indicate that the composition engineering adopted in this paper is an effective strategy to modulate the optical properties of (MA) 2 AgBi 1−x Sb x Br 6 systems and may open a new way to put it into applications in the fields of solar cells and other optoelectronic devices.
The Cu-modulated lead-free double perovskite Cs 2 AgSbCl 6 shows excellent photoelectric performances. Thus the distribution of Cu dopants inside Cs 2 AgSbCl 6 and the influence induced by them are investigated thoroughly. The variation of charge distribution and then the electronic environment around the Cu dopant are simulated, which support the preferred formation of Cu Ag defect in Cs 2 AgSbCl 6 with a nominal monovalent state. Compared with other Cu-related defects, this configuration introduces the weakest tensile stress around the defects and the slightest distortion of the metal octahedron. Owing to the special Cu Ag defect, the electronic structures of Cs 2 AgSbCl 6 system change, e.g., the bandgap reduces manifestly, ascribing to the predominant contribution from Cu-3d orbitals to the band edges. With the increase of concentration of Cu dopants, the bandgap of Cs 2 AgSbCl 6 decreases further in a monotonic but gentle way, originating from the extra interactions between the Cu-3d orbitals. Therefore, the critical insight to understand the photoelectronic properties of Cs 2 AgSbCl 6 modulated by the Cu dopants is provided.
Cu-doped CsPbBr 3 with strong blue emissions is a potentially ideal material for high-quality light-emitting diode (LED) devices. This study thoroughly analyzes the influence of a Cu dopant on CsPbBr 3 materials through a series of theoretical investigations. Two artificial CsPbBr 3 supercells are constructed, and their electronic properties are analyzed. Additionally, the antibonding nature of the conduction band minimum (CBM) and valance band maximum (VBM) of CsPbBr 3 is elucidated. The results indicate that a Cu dopant can only alter the local lattice around it, not the entire lattice. Moreover, the CBM and VBM deformation potentials of CsPbBr 3 behave differently. Therefore, the energetic shift of VBM is more sensitive to the shrinkage of lattice due to the smaller energy difference between the constituent orbitals, leading to a bandgap reduction with the lattice contraction. This study reveals that the two critical reasons for the increase of bandgap are the contribution of Cu-3d orbitals to the VBM and the localized lattice distortion caused by Cu impurity. Therefore, this work clarifies how Cu impurities improve the blue light emitting performance of CsPbBr 3 systems.
Taking Cs2NaBiCl6, Cs2AgInCl6 and Cs2AgBiCl6 as examples of Lead-free double perovskites (DPs), we study the photoluminescence (PL) properties of Mn-doped DPs. The electron localization function (ELF) reveals the more ionic...
The correlation between the ferromagnetism and oxygen vacancy (VO) of Cu-implanted In2O3 nanowires was investigated. When annealed in vacuum, the saturation magnetization first increased to 0.71 Cu/μB for In2O3:Cu nanowires annealed at 800 °C, after which it rapidly decreased to 0.55 Cu/μB when annealed at 900 °C. However, the saturation magnetization showed a monotonously decreased trend when annealed in O2. The In2O3:Cu nanowires showed a direct relationship between the oxygen vacancy concentration and the degree of magnetization. The oxygen vacancies orbitals mediated indirect double-exchange model has been used to explain the ferromagnetism properties in Cu-doped In2O3 and a sufficient amount of both oxygen vacancies and Cu impurities is essential to the observed ferromagnetism.
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