Abstract Formamidine lead iodide chalcogenide (FAPbI3) is often used as a light-absorbing layer in solar cells to alleviate the energy crisis because of its own good photovoltaic properties.however, the lack of stability is also an obstacle to the current development. It has been found that doping with different kinds of elements at different sites can enhance its stability and improve the photoelectric conversion efficiency of solar cells. In this paper, the geometry, electronic structure and optical properties of FA1 − xCsxPbI3−yCly were calculated using Cs and Cl co-doped with FAPbI3 using the first nature principle. The analysis revealed that the Goldschmidt factors of the doped system were between 0.962 and 0.974, indicating that the system could maintain a stable chalcogenide structure, and the doped system had lower energy and more stable structure. By calculating the energy bands, it is found that the doped ions have a more pronounced effect on the increase of the dispersion at the bottom of the conduction band than the decrease of the dispersion at the top of the valence band of the system, and the reduction of the effective mass of carriers is more favorable for transport. As for the optical properties, the right amount of doping is favorable to the improvement of light absorption, while the excess doping shortens the light absorption range and weakens the light absorption effect, in which FA0.875Cs0.125PbI2.958Cl0.125 has the largest light absorption coefficient. It is shown that the photoelectric properties of chalcogenide FAPbI3 can be effectively modulated by the co-doping of Cs and Cl, which can provide theoretical reference for the precise preparation of more efficient solar cells experimentally.
The local structures of Cs3CoX5 (X = Cl, Br) were examined using nuclear magnetic resonance (NMR) and magic angle spinning (MAS) NMR experiments. The two inequivalent Cs(1) and Cs(2) sites in two compounds were clearly distinguished based on static NMR and MAS NMR spectra. We found that the structural geometry for Cs(2) changed more abruptly than that for Cs(1) with increasing temperature. The Cs(1) ions surrounded by 10X− ions exhibited long relaxation times, whereas the Cs(2) ions surrounded by 8X− ions exhibited short relaxation times. This is consistent with the bond lengths of Cs(1)-X and Cs(2)-X. The halogen species in Cs3CoX5 enabled an examination of the effect of Cl and Br ions, which was found to influence the quadrupole parameter but not the relaxation time.
With the determination of the crystal structure of (NH4)2TeI6 the list of the descriptions of A2TeX6 structures is further completed. At 293 K three structure types are observed with an antifluorite packing of cations and anions: The cubic K2PtCl6 type structure (space group Fm 3̄ m, Z = 4), the tetragonal Rb2TeI6 type structure (space group P4/mnc, Z = 2), and the monoclinic K2TeBr6 type structure (space group P21/n, Z = 2). The latter type was found for (NH4)2TeI6 with a = 8.0694(7), b = 8.0926(9), c = 11.7498(8) Å and β = 89.605(8)° and refined to a final Rw of 0.065. From ionic radii ratios the symmetry of the A2MX6 type structures can be predicted including a prediction of low temperature instability (soft mode condensation). Group-subgroup relationships connect the corresponding space groups and the space groups of the high/low temperature polymorphs.
AbstractTwo new members of a double salt containing halide supported zirconium octahedra were obtained from solid state reactions. Single‐crystal X‐ray data refinements established the isotypic compounds as Cs[ZrCl5]·Cs2[(Zr6B)Cl15] (I) (R3¯c, Z = 6, a = 12.765(2), c = 34.652(6)Å, R1(F) = 0.0339, wR2(F2) = 0.0770) and the mixed halide Cs[ZrCl5]·Cs2[(Zr6B)Cl14.57(2)I0.43] (II) (R3¯c, Z = 6, a = 12.777(2), c = 34.668(7)Å, R1(F) = 0.0459, wR2(F2) = 0.1279), respectively. The structure contains a network of boron centered [(Zr6B)Cli12] clusters interbridged three‐dimensionally by 6/2 Xa‐a atoms at all zirconium vertices (X = Cl, or Cl+I, respectively). Within voids of the cluster network [ZrCl5]— anions and Cs+ cations are located, allowing for the description as a double salt. The [ZrCl5]— anion (D3h‐symmetry) has been found so far only in this structure type. The space requirement of a variety of transition metal complexes is estimated and compared with the volume of the [ZrCl5]— anion in order to see if other double salts are geometrically possible. Besides the unusual [ZrCl5]— ion the mixed chloride‐iodide structure reveals another interesting feature. Contrary to many other structures an ordered chlorine atom substitution by iodine is observed on the cluster interconnecting site. The phase width for Cs[ZrCl5]·Cs2[(Zr6B)Cl15‐xIx] has been found to cover 0 ≤ x ≤ 1.
AbstractDas magnetische Verhalten von Cs2LiTmCl6, Cs2LiTmBr6, Cs2LiTmI6 und Cs2NaTmI6 wird im Temperaturbereich von 3,2 bis 251,3 K untersucht. Die magnetischen Daten werden mit einem früher entwickelten Modell interpretiert, bei dem der Einfluß des Kristallfeldes theoretisch durch das Angular‐Overlap‐Modell beschrieben ist. Die erhaltenen Werte des Angular‐Overlap‐Parameters eσ(R) für die einzelnen Verbindungen werden untereinander verglichen und diskutiert. Die Energiewerte der Kristallfeldniveaus des 3H6‐Grundzustands werden berechnet.
Abstract A pair of 35Cl NQR spin echo signals has been observed for the mixed valence complex Cs2 [AuICl2] [AuIIICl4] between 77 and 243 K. At 77 K, two resonance lines with the half widths ΔvQ ~ 50 kHz were located at vQ1 = 17.28 MHz for the AuI-Cl chlorine and at vQ2 = 27.10 MHz for the AuIII -Cl chlorine in accordance with the crystal structure. The chlorine ionic characters of the AuI-Cl and AuIII-Cl bonds are estimated as 0.63 and 0.42, respectively. The central gold atom carries a fractional protonic charge of 0.26 in [AuICl2]- and 0.68 in [AuIIICl4]-. The charge distributions in the complex anions differ insignificantly from those in the isolated [AuCl2]- and [AuCl4]- for ordinary complexes, indicating that the charge transfer interactions between the anions are weak in the mixed valence complex. The observed linear temperature dependencies of VQ and log TlQ are well explained by the lattice vibration. When the temperature was increased from 77 K, the resonance lines became gradually weak without changing ΔvQ and immeasurable above 215 K. ESR spectra taken at various temperatures revealed the presence of paramagnetic sites of ca. 5 x 1020 mol- 1 arising from Au(II). The small but finite concentration of Au(II) or some other reason should be responsible for the fade out phenomenon and the large ΔvQ observed.